Re: [volt-nuts] Replace neons with LEDs in Fluke 845AB
Hi Lou, I think we should talk to each other. Send me your phone number to dosm...@outlook.com. I'm confused to the state your meter is in, you already made the mod and now you are having problems? Or it's not working before the mod? When I made my mod it pulled the rails to ±14 volts. It was a compromise between brightness and performance. I tried many LED's and the ones I selected were just right. The right brightness to current draw and the correct wavelength for the photo cells. My instructions are not as clear as it should be for the T202 move wire from pin 9 to 7. The high voltage winding are abandoned and the led's are powered by the winding that supply the ±15 volts. I may have to look at my meter to see better what was done. I work second shift, whats a good time to talk? I go to work at 3pm and return at midnight. Dallas On 6/8/2016 1:24 AM, Dallas Smith wrote: Hi Lou, I believe that the transistors are good. If they do not run to hot to hold on to. Yes CR105 feeds the negative supply. Did you check CR104 and CR105? Q203 and Q204 should also be check since they could shunt the transformer. Is transformer T202 and T203 hot. The high voltage windings on T202 could be leaky. Try taking out C119, did rails go to approximately 15 volts? Time to start isolating the supplies to various circuits to find the culprit by removing one leg of various resistors. You can deal with the carbon resistor accuracies later. I had all many issues with my meter, after all their very old. Dallas On 6/7/2016 11:09 PM, Lou Amadio wrote: Hi Dallas I set my DMM on Diode Check mode: Q201, PNP, no part number: EB/BE=0.23/Hi, CB/BC=0.21/Hi, EC/CE=Hi/Hi Q202, PNP, no part number: EB/BE=0.22/Hi, CB/BC=0.20/Hi, EC/CE=Hi/Hi Q111, NPN, 2N1304: EB/BE=Hi/0.28, CB/BC=Hi/0.26, EC/CE=Hi/Hi Q112, PNP, 2N1305: EB/BE=0.26/Hi, CB/BC=0.25/Hi, EC/CE=Hi/Hi The two 15v rails are down to about 5v each. The oscillator is working but fluctuating badly on frequency. Replaced all the electro caps. Have not replaced the resistors or diodes. Will check these next. CR105 feeds the neg 15v supply cap?? Regards Lou ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Replace neons with LEDs in Fluke 845AB
Hi Lou, I believe that the transistors are good. If they do not run to hot to hold on to. Yes CR105 feeds the negative supply. Did you check CR104 and CR105? Q203 and Q204 should also be check since they could shunt the transformer. Is transformer T202 and T203 hot. The high voltage windings on T202 could be leaky. Try taking out C119, did rails go to approximately 15 volts? Time to start isolating the supplies to various circuits to find the culprit by removing one leg of various resistors. You can deal with the carbon resistor accuracies later. I had all many issues with my meter, after all their very old. Dallas On 6/7/2016 11:09 PM, Lou Amadio wrote: Hi Dallas I set my DMM on Diode Check mode: Q201, PNP, no part number: EB/BE=0.23/Hi, CB/BC=0.21/Hi, EC/CE=Hi/Hi Q202, PNP, no part number: EB/BE=0.22/Hi, CB/BC=0.20/Hi, EC/CE=Hi/Hi Q111, NPN, 2N1304: EB/BE=Hi/0.28, CB/BC=Hi/0.26, EC/CE=Hi/Hi Q112, PNP, 2N1305: EB/BE=0.26/Hi, CB/BC=0.25/Hi, EC/CE=Hi/Hi The two 15v rails are down to about 5v each. The oscillator is working but fluctuating badly on frequency. Replaced all the electro caps. Have not replaced the resistors or diodes. Will check these next. CR105 feeds the neg 15v supply cap?? Regards Lou ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Replace neons with LEDs in Fluke 845AB
Hi David, That's just what I was thinking. As well I couldn't find any data on the GA2817's. Do you think the transistors are actually bad? What is the status of the new modern chopper design talked about in earlier post? Is there a PCB design now for it? Dallas > From: davidwh...@gmail.com > To: volt-nuts@febo.com > Date: Tue, 7 Jun 2016 11:18:56 -0500 > Subject: Re: [volt-nuts] Replace neons with LEDs in Fluke 845AB > > Silicon replacements should work fine; I would try the TIP30 or other > low current and slow power transistors like the BD234/BD236/BD238. The > only thing I would worry about is oscillation during switching if the > replacements are too fast and that is something I would check with an > oscilloscope by monitoring the collector waveform. > > The transistors operate in saturation so the bias change will be > insignificant; the higher Vbe of silicon will lower the frequency by > about 3%. > > I could not find any data on the GA2817 shown in the parts list. The > minimum Vce in the circuit is double the supply voltage. I think Ic > is below 100 milliamps. > > On Mon, 6 Jun 2016 12:25:32 -0400, you wrote: > > >Hi Lou, > > > >It's normal for some leakage in germanium transistors. Do you have a > >curve tracer? > >If you change them to Si you will have to re-bias them (i.e. R207_8). > >The 84 Hz may change also, might have to adjust C203. > >But should be possible. > > > >Dallas > > > > > >On 6/6/2016 7:33 AM, Lou Amadio wrote: > >> For Dallas Smith > >> Thanks for the info. It is in keeping with the original design. > >> My 845AB 15v supplies are currently down and I suspect the germanium > >> transistors around T202 may be leaky?. > >> Am thinking of replacing them with Si transistors. Your thoughts? > >> Regards, Lou > ___ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Replace neons with LEDs in Fluke 845AB
Hi Lou, It's normal for some leakage in germanium transistors. Do you have a curve tracer? If you change them to Si you will have to re-bias them (i.e. R207_8). The 84 Hz may change also, might have to adjust C203. But should be possible. Dallas On 6/6/2016 7:33 AM, Lou Amadio wrote: For Dallas Smith Thanks for the info. It is in keeping with the original design. My 845AB 15v supplies are currently down and I suspect the germanium transistors around T202 may be leaky?. Am thinking of replacing them with Si transistors. Your thoughts? Regards, Lou On Mon, Jun 6, 2016 at 12:35 PM, Dallas Smith <dosm...@outlook.com> wrote: Hi Lou, Its been awhile since I made this mod, but I had the foresight to save the project to K04BB's site. K04BB /Fluke/Fluke 845A AB < http://www.ko4bb.com/getsimple/index.php?id=manuals=Fluke/Fluke_845A_AB Still works great, hope you have the same results. Dallas ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Replace neons with LEDs in Fluke 845AB
Hi Lou, Its been awhile since I made this mod, but I had the foresight to save the project to K04BB's site. K04BB /Fluke/Fluke 845A AB <http://www.ko4bb.com/getsimple/index.php?id=manuals=Fluke/Fluke_845A_AB> Still works great, hope you have the same results. Dallas On 6/5/2016 9:51 PM, Lou Amadio wrote: Question for Dallas Smith: I want to replace neons with LEDs in my Fluke 845AB. Following your instructions below, did you mount the LEDs where the neons were on the PCB and use the plastic light tubes or did you mount the LEDs hard up against the LDRs in the yellow foam block? Thanks, Lou Quote Dallas Smith, 2 years ago Permalink <http://narkive.com/bdOZWNXt.1> Raw Message Report “Finally got around to modify my Fluke 845ab with LED 's for the chopper circuit. Used the 17 volt windings for LED's (Mouser 941-C513AMSNCW0Y0511 Warm White Round LED) instead of the 130 volt, move red wire on transformer pin 9 to pin 7.This winding is 180 degrees out of phase, so I reversed the steering diodes (CR106 & CR107) I left in to help make sure the phase was correct for the LED's when connecting. Change R154 to 6K to set the brightness, selected for good operation of the zero control. Then install jumper to replace C119. Also changed the filter integration response caps C111 to .022uF and C116 to 47uF, this stabilized the jitter to a manageable mode of operation. Meter now works as well or better when the original neon's worked.” Lamp Blocks ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Oven thermal insulation
Randy, hi again, My idea sounds crude but it worked very well. The outer box was made out of small squares of aluminum drilled and taped with small aluminum angle pieces. I have two references in this oven, a fluke circuit based on the 731b, and one of Doug’s 10 volt references. I run the oven at 45°C. The gray board for the inner cover is ‘GATOR Board’ used to mount prints, it has a foam core. You should also have a guarded transformer, got mine from scrape fluke 510, Dallas On 7/6/2015 10:09 PM, Dallas Smith wrote: Hi Randy, I used a box in a box then shot yellow window or gap fill insulation from your hardware store, use minimal expanding type. Fill around the spaces between the boxes with the tube but very slowly. You will get this on your hands so use your gloves because you will have to hold the boxes in place as it expands. After it dries cut the top off with a bread knife. May take a couple of tries to get what you want. Dallas Date: Mon, 6 Jul 2015 17:43:45 -0700 From: randyevans2...@gmail.com To: volt-nuts@febo.com Subject: [volt-nuts] Oven thermal insulation I am working on a voltage reference deisgn that will go into an oven for the highest stability. I am looking for a good insulation material that can stand high temperatures safely (up to 80C). Looking at some HP frequency standard ovens I see a hard, light-weight insulation material of some type that looks like it would work really well, but I have no idea what it is. Does anyone have any suggestions? Thanks, Randy Evans AE6YG ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
[volt-nuts] Fluke 720a Switching Center
To volt-nuts, I uploaded my metrology switching center project for my Fluke 720a to ko4bb's. (ftp://ftp.ko4bb.com/) in windows explorer. Fluke_720a_Switching_Center_Other-MetSwitchingCenter.pdf This simplifies the different wiring configurations that the Fluke 720a is used for. Dallas ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] HP-419 and Fluke 845 Modifications
Randy, I'm glad to see that you completed your design, This could be the ultimate permanent solution for these meters. My LED mod is still working very well, but I think the zero of your design will solve the offset drift problem. My led mod has a drift about ±100nv's over a day or so, not perfect but better than the original specs. I changed the value of C116 to 22uf tantalum, the response was a little to slow for overloads. Your design may eliminate the need for the zero control entirely. Do the light pipes contribute to the high isolation resistance that the Fluke 845 has? Will your modifications improve this spec? I may consider your mod as a improved version, after your testing. Since the mod, I was able to complete the self calibration of my Fluke 720 from beginning to end without the need to re-adjust the null meters zero. This was the driving source for my mod, Dallas Randy Evans wrote: I finished the H-419A/Fluke 845A design modifications but I am still trying to decide on the preferred power supply design. The basic meter circuit uses the LTC2054 and LTC6255 with two CR123 Li-Ion 3 V batteries. The basic meter circuit draws less than 0.2 mA and with 1500 mAH CR123A batteries should be able to go several thousand hours on a set of batteries. For the meter circuit, it is always battery powered and doesn't have to be plugged into the mains. I also added a TI AMC1100 isolation amplifier for recording output but it needs a 3.3 VDC isolated supply and a 5VDC output supply. The current design uses separate isolation power supplies using LT8300 ICs that work off the mains transformer so there would be no worry about failing batteries. Therefore, to use the recorder, the unit would have to be plugged in. I am trying to decide if it would be simpler to use batteries for the isolation circuit as well. If I use batteries, do I use rechargeables or non-rechargeable batteries such as the CR123s? The circuit would need one set for the input isolated circuit side and another set for the recorder output side and the batteries would not last as long as the meter circuit since the isolation circuits draw about 12 milliamps. They would still work about one hundred hours most likely and would not draw any current unless the isolation circuit is turned on (with a separate toggle switch). My preference is to stay with the LT8300 power supplies but I thought I would query the group. Any thoughts on what would be your preferences? Thanks, __ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] HP-419 and Fluke 845 Modifications
Randy, You can access the files by entering 'ftp://ftp.ko4bb.com/' in windows explorer ( not IE), then supply the user name password. username: manuals password: ko4bb2014 Dallas On 11/26/2014 12:18 PM, Randy Evans wrote: I have finished the design and analysis (LTSpice) and I am preparing the BOM and doing a PCB layout now (ExpressPCB). I am hoping to finish the work over the Thanksgiving holidays but I wanted to see Dallas's 845A modifications before ordering parts and pulling the plug on PCB fab first but it hasn't shown up on K04BB's site yet (still in the upload section). Randy On Wed, Nov 26, 2014 at 4:06 AM, ludger.len...@gmx.de wrote: ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] HP-419 and Fluke 845 Modifications
The current version has been updated, also is in a word document. Dallas On 11/26/2014 12:45 PM, Todd Micallef wrote: Randy, I sent you a copy of the file to your email address. Todd On Wed, Nov 26, 2014 at 12:18 PM, Randy Evans randyevans2...@gmail.com wrote: ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] HP-419 and Fluke 845 Modifications
Anyone making this mod, be sure to use the Mouser LED's listed in the schematic. Dallas Date: Wed, 26 Nov 2014 12:53:55 -0500 From: dosm...@outlook.com To: volt-nuts@febo.com Subject: Re: [volt-nuts] HP-419 and Fluke 845 Modifications The current version has been updated, also is in a word document. Dallas On 11/26/2014 12:45 PM, Todd Micallef wrote: Randy, I sent you a copy of the file to your email address. Todd On Wed, Nov 26, 2014 at 12:18 PM, Randy Evans randyevans2...@gmail.com wrote: ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
[volt-nuts] Completion of LED Mod's for the Fluke 845AB 845AR Null Meter.
To All, The final modification of the Fluke null meters with LED's is completed. The results is impressive, keeping the basic original circuit of the meters. My rev 8 AR version has a double diode in the output stage which seems to remove the zeroing hysteresis around a zero reading was also made to my 845AB. Implementing two 1.2v reference diodes in the zeroing circuit greatly improved the zero drift for the zeroing control. There were also changes to the feedback response by changing two capacitors. If anyone is interested, please E-mail me at my personal address. dosm...@outlook.com Dallas ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Completion of LED Mod's for the Fluke 845AB 845AR Null Meter.
Please send me an email so I can put you in my special address book for the info. Date: Sun, 23 Nov 2014 12:51:32 -0700 From: n...@npgcable.com To: volt-nuts@febo.com Subject: Re: [volt-nuts] Completion of LED Mod's for the Fluke 845AB 845AR Null Meter. Dallas, I have a noisy 845AR, so I am keenly interested in your modifications. Thank you, Joe Hobart Flagstaff, Arizona On 11/23/2014 11:29 AM, Dallas Smith wrote: To All, The final modification of the Fluke null meters with LED's is completed. The results is impressive, keeping the basic original circuit of the meters. My rev 8 AR version has a double diode in the output stage which seems to remove the zeroing hysteresis around a zero reading was also made to my 845AB. Implementing two 1.2v reference diodes in the zeroing circuit greatly improved the zero drift for the zeroing control. There were also changes to the feedback response by changing two capacitors. If anyone is interested, please E-mail me at my personal address. dosm...@outlook.com Dallas ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Completion of LED Mod's for the Fluke 845AB 845AR Null Meter.
How do I make my RTF attachment available to Volt-nuts? I do not trust cloud servers and the like. Dallas On 11/23/2014 1:29 PM, Dallas Smith wrote: To All, The final modification of the Fluke null meters with LED's is completed. The results is impressive, keeping the basic original circuit of the meters. My rev 8 AR version has a double diode in the output stage which seems to remove the zeroing hysteresis around a zero reading was also made to my 845AB. Implementing two 1.2v reference diodes in the zeroing circuit greatly improved the zero drift for the zeroing control. There were also changes to the feedback response by changing two capacitors. If anyone is interested, please E-mail me at my personal address. dosm...@outlook.com Dallas ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Completion of LED Mod's for the Fluke 845AB 845AR Null Meter.
Thank you, that will be fine. I'm getting swamped with request. could you start a volt-nuts thead to its location? Date: Sun, 23 Nov 2014 22:20:17 -0500 From: tmical...@gmail.com To: volt-nuts@febo.com Subject: Re: [volt-nuts] Completion of LED Mod's for the Fluke 845AB 845AR Null Meter. Dallas, Thanks for the information. Would you be opposed to uploading it to the KO4BB website? I think Didier could place it in a Fluke 845AB/AR folder. I could upload it with a copy of the manuals and send him an email. Todd On Sun, Nov 23, 2014 at 10:02 PM, Dallas Smith dosm...@outlook.com wrote: How do I make my RTF attachment available to Volt-nuts? I do not trust cloud servers and the like. Dallas On 11/23/2014 1:29 PM, Dallas Smith wrote: To All, The final modification of the Fluke null meters with LED's is completed. The results is impressive, keeping the basic original circuit of the meters. My rev 8 AR version has a double diode in the output stage which seems to remove the zeroing hysteresis around a zero reading was also made to my 845AB. Implementing two 1.2v reference diodes in the zeroing circuit greatly improved the zero drift for the zeroing control. There were also changes to the feedback response by changing two capacitors. If anyone is interested, please E-mail me at my personal address. dosm...@outlook.com Dallas ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Completion of LED Mod's for the Fluke 845AB 845AR Null Meter.
Thank you Todd Dallas Date: Sun, 23 Nov 2014 23:13:11 -0500 From: tmical...@gmail.com To: volt-nuts@febo.com Subject: Re: [volt-nuts] Completion of LED Mod's for the Fluke 845AB 845AR Null Meter. I have uploaded the mod file to the ko4bb ftp server. I could not find the AR or AB manuals so I also added them. Right now they are sitting in the Recent Uploads directory. Todd On Sun, Nov 23, 2014 at 10:31 PM, Dallas Smith dosm...@outlook.com wrote: Thank you, that will be fine. I'm getting swamped with request. could you start a volt-nuts thead to its location? Date: Sun, 23 Nov 2014 22:20:17 -0500 From: tmical...@gmail.com To: volt-nuts@febo.com Subject: Re: [volt-nuts] Completion of LED Mod's for the Fluke 845AB 845AR Null Meter. Dallas, Thanks for the information. Would you be opposed to uploading it to the KO4BB website? I think Didier could place it in a Fluke 845AB/AR folder. I could upload it with a copy of the manuals and send him an email. Todd On Sun, Nov 23, 2014 at 10:02 PM, Dallas Smith dosm...@outlook.com wrote: How do I make my RTF attachment available to Volt-nuts? I do not trust cloud servers and the like. Dallas On 11/23/2014 1:29 PM, Dallas Smith wrote: To All, The final modification of the Fluke null meters with LED's is completed. The results is impressive, keeping the basic original circuit of the meters. My rev 8 AR version has a double diode in the output stage which seems to remove the zeroing hysteresis around a zero reading was also made to my 845AB. Implementing two 1.2v reference diodes in the zeroing circuit greatly improved the zero drift for the zeroing control. There were also changes to the feedback response by changing two capacitors. If anyone is interested, please E-mail me at my personal address. dosm...@outlook.com Dallas ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Fluke 845AB 1993 Modification Schematic
On 9/25/2014 12:01 PM, starb...@uplink.net wrote: I not sure this was ever used for production, no known schematic. I'm going to use the LTC1150 for my other null meter 845ar. It would be a better choice then the fet chopper you are referring to. I'll use the LTC1150 for the first stage with the over all feedback and stage two op amp to control the feedback for the switch 101b which controls the gain from 300 to 9000. will scale this gain between the two op amps. Look at the May and August threads. Randy Evans is currently designing a new chopper for his HP419. Dallas Need the schematic of the Fluke 845AB 1993 modification. Thanks, John ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
[volt-nuts] 845ab Led Mod Update
Well I finally got the 615nm Led's installed and the results seem so so. The zero drifted was significantly on the 1uV range. So I used two LT1634 1.25 Volt references with the current set by two 43k resistors from the ±15 volt supplies. The previous reference used came from the -0.4 volts at TP1 and +0.6 volts at TP8. Removed the 150k resistor at the positive end of the zero control and lifted the negative end from the circuit board the connected the ±1.25 ref to the zero pot. Much better stability, drifts by noise about ±.1 to ±.2uv now on 1uv range. Is this normal now? Never used a new Fluke 845ab before. The white led's seemed to filter the noise better with its persistent, may go back. The zero seems stable with ±2 F change in room temperature now. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Finally got around to modifying my Fluke 845ab with LED's
Thank you Robert for you experience, My white LED's did have a persistence to them, so I'm going to change them to ORG/RED (615nm). I've temporarily using some low output amber LED's and determined that the caps I changed needed to be changed back to original values. I also modified the zero control circuit with a 1.25 volt reference centered at zero with two switching diodes to base the offset at zero for less drift. I,m considering using the Linear chopper amp Randy's using. But I'm not sure how to incorporate the gain control at S101B? The over all feedback should be no problem. Dallas On 9/15/2014 3:57 PM, George Atkinson wrote: Hi, I'm late to this thread, but have some experience. Several years ago I did some research on replacing xenon flashlamps in a high speed fluorescence instrument application. As the white LED candidates had phosphor coatings I assumed (don't assume - guess ;-) that they would be too slow. It turned out that they were significantly faster than the xenon lamps, with sharp turn-off rather than the tail of the flashlamp. So don't dismiss white LEDs for modulated applications. Robert G8RPI. On 11 September 2014 13:14, Chuck Harris cfhar...@erols.com wrote: Hi Dallas, Let us know if it helps. Neons are very fast light sources, and can switch way faster than the CdS photo resistors can respond. A nice red/orange LED should work well with the original CdS photo resistors. -Chuck Harris Dallas Smith wrote: Chuck, After searching for the wave length of NE2 neon bulbs, I found that the spectrum is between 600-650nm. So I ordered red-org at 615nm. The white LED's I've have do have the characteristics you mentioned, Thank you for all your input, maybe the results will show some improvement. Dallas ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Finally got around to modifying my Fluke 845ab with LED's
Chuck, After searching for the wave length of NE2 neon bulbs, I found that the spectrum is between 600-650nm. So I ordered red-org at 615nm. The white LED's I've have do have the characteristics you mentioned, Thank you for all your input, maybe the results will show some improvement. Dallas ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Finally got around to modifying my Fluke 845ab with LED's
Hi Chuck, Its only 84Hz, It had the offset problem long before I made this mod. The new meter at work many decades ago also had this problem. I pick white so the full spectrum would be covered by the Csd's. Checked waveforms with scope, has sharp rising and falling edges. This mod may not be as elegant as a Linear Devices copper mod, but at lest I will not have to mess with the shielded front end. The offset may be due to the bias current in the front end reacting with the different polarities. Dallas Date: Tue, 9 Sep 2014 15:48:01 -0400 From: cfhar...@erols.com To: volt-nuts@febo.com Subject: Re: [volt-nuts] Finally got around to modifying my Fluke 845ab with LED's One thing that might be hosing things up a bit is white led's don't switch quickly. They are really UV LED's with a bit of fluorescent material between the LED and the world. The fluorescent material will also luminesce for hours after the LED is turned off. Perhaps because the led never shuts off completely, it is biasing the meter up a few tens of microvolts? -Chuck Harris Dallas Smith wrote: Finally got around to modify my Fluke 845ab with LED 's for the chopper circuit. Used the 17 volt windings for LED's (Mouser 941-C513AMSNCW0Y0511 Warm White Round LED) instead of the 130 volt, move red wire on transformer pin 9 to pin 7.This winding is 180 degrees out of phase, so I reversed the steering diodes (CR106 CR107) I left in to help make sure the phase was correct for the LED's when connecting. Change R154 to 6K to set the brightness, selected for good operation of the zero control. Then install jumper to replace C119. Also changed the filter integration response caps C111 to .022uF and C116 to 47uF, this stabilized the jitter to a manageable mode of operation. Meter now works as well or better when the original neon's worked. As the meter originally had this problem, why is the offset reading different when polarity is reversed at the meter input? About 10uV's. Lamp Blocks. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Finally got around to modifying my Fluke 845ab with LED's
I thought that might be the case, the scope waveform shows no problem. The white LED has multiple spectra output, thought it might have a better chance having the right wave length, the extra brightness seems to help with the deficiencies. From: hol...@hotmail.com To: volt-nuts@febo.com Date: Tue, 9 Sep 2014 22:33:45 + Subject: [volt-nuts] Finally got around to modifying my Fluke 845ab with LED's I would probably use green or yellow LEDs, but the white ones should not be a problem. I built an LED analyzer/integrating sphere and one of the features is a circuit that optically measures the LED driver PWM frequency. It can also detect the minute variance in LED intensity from an LED driven by a 950 kHz boost converter. It also had no problems with a white LED driven at 4 MHz from a signal generator. You see the long persistence phosphors mainly in large lighting LEDs and not in small indicator LEDs. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Finally got around to modifying my Fluke 845ab with LED's
Thank you Chuck, I think you have something there, that is probably driving the choppers. The meter had a little more jitter than before after the mod, that is why I modified the integration filter caps. I like the slower response anyway. When I have time I'll share my mods for the Fluke 540b, Much better than before, can transfer at lightning speed. The suggestion of using a voltage regulator (LM1117) for the 1.35v mercury battery from the EEV Blogs Didn’t pan out. Its not a reference, it’s a voltage regulator. You don't need accuracy but stability. Dallas Date: Tue, 9 Sep 2014 20:30:30 -0400 From: cfhar...@erols.com To: volt-nuts@febo.com Subject: Re: [volt-nuts] Finally got around to modifying my Fluke 845ab with LED's Hi Mark, I have an itty bitty white led, probably called a T-1 size, and it glows dimly for a long time after you shut it down. They all pretty well have to. I think what you are seeing with your analyzer is the blue/UV component that drives the phosphor element. It will run just as fast as any old style LED. I also think that the blue/UV component, which is very bright, is what is driving Dallas's chopper. But enough on that. I wasn't trying to criticize, just make mention of something I noticed in my own work. Where I got to thinking of this is when I burned out the strobe tube in my G-R strobotach. Replacement tubes were in the $300 range, so I knew that would never happen, so I was thinking of making a solid state replacement using a handful of those wonderful little white LED's. They would certainly be bright enough, but I'm pretty sure the phosphor hang would make them unsuitable for stopping motion... your eye would see a blur instead of the razor sharp image you get with the strobe tube. -Chuck Harris Mark Sims wrote: I would probably use green or yellow LEDs, but the white ones should not be a problem. I built an LED analyzer/integrating sphere and one of the features is a circuit that optically measures the LED driver PWM frequency. It can also detect the minute variance in LED intensity from an LED driven by a 950 kHz boost converter. It also had no problems with a white LED driven at 4 MHz from a signal generator. You see the long persistence phosphors mainly in large lighting LEDs and not in small indicator LEDs. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Stuff for free and for sale
Hi Joe, Whats the frequency of the Fluke 510A? Dallas On 5/11/2014 10:31 PM, Joseph Gray wrote: Fluke 510A AC reference standard. Has original NiCad pack, but I removed it to prevent corrosion. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Newer Fluke 845ab manual with chopper mod?
Did Fluke ever make the 845ab Null Meter with the optically-isolated Bilateral Analog FET chopper? Is so where's the schematic? The 335D is not optically isolated. Will not having this isolation effect the leakage? What is the part number of the optical-isolated Bi-FET? My Fluke null meter new neon's are now starting to flicker with unstable zero again. I modified the meter to use curve tracer selected INS-1 Russian neon dots. Selected for equal break down voltage and brightness. Worked well for about two years. The NE2? with the isotope in it is impossible to find. Has anyone used some type of circuit modification for this meter? Dallas On 5/3/2014 12:18 PM, Dallas Smith wrote: Does anyone have the schematic for the Fluke 845 chopper modification as stated in front of manual to be released approximately Dec 1993? Manual statement: 'The new circuit now employs optically-isolated Bilateral Analog FETs, and is fabricated on an additional circuit board.' Frank, from Volt-Nuts 21 Mar 2010, suggested that: The 335A_D manual contains the coil chopper for the calibrator circuitry, (page 119/120) and the opto chopper version for the included Null volt meter, same circuitry as of the 845A/B. Compare this with the 335_D manual,(page 169) where you can find the MOS FET version for the calibrator amplifier. Has anyone tried this circuit for the Fluke 845ab? ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
[volt-nuts] Economical Standard Calibration
Hi nuts, This is my first post. The knowledge from contributors is amazing. Was wondering where one could economically get our voltage standards calibrated to some traceable standard since Joe Gellar suspended operations for his SVR-T? voltagestandard.com doesn't sell a 10v references and two of his 5v Vref5-002 are costly. Dallas ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Economical Standard Calibration
Good point, not a meter a Fluke 731b transfer standard. no access to local labs. On 3/8/2014 4:54 PM, Dr. David Kirkby wrote: On 8 March 2014 21:44, Dallas Smith dosm...@outlook.com wrote: Hi nuts, This is my first post. The knowledge from contributors is amazing. Was wondering where one could economically get our_voltage standards calibrated_ to some traceable standard since Joe Gellar suspended operations for his SVR-T? voltagestandard.com doesn't sell a 10v references and two of his 5v Vref5-002 are costly. Dallas It would be worth stating what meter you have. Clearly what is going to be useful for a 3.5 digit meter, will not be for an 8.5 digit one. Dave ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Economical Standard Calibration
Hi Bob, I also heard about this technique, probably on 'volt-nuts'. They connected 16 LM199's summed together isolated with about 500 ohms each. This averaged the voltage and reduced the noise. But not knowing the absolute voltage will not calibrated my Fluke 731b. It appears if I want a calibration, I'll have to play with the big boys and spend the bucks. Dallas On 3/8/2014 10:05 PM, Bob Albert wrote: I have five AD587 switch selected, powered by a wall wart. They seem to be very good, but of course not in the league of the units discussed here. In any case, they are 10V and all within about a millivolt. If I average them I should get a statistically valid accuracy improvement, neglecting any systematic errors in their manufacture. While watching the display on my HP 3456A I begin to realize that my need for 'exact' voltage isn't really so great. Certainly what I have is more accurate than anything I will ever really need. But it's fun to see the variation and watch the drift and compare my other high class voltmeters. The 3456A manual says to wait an hour for it to warm up and that seems reasonable; nearly all the drift is gone by about 45 minutes. Bob On Saturday, March 8, 2014 5:34 PM, Dallas Smith dosm...@outlook.com wrote: I'm in west Michigan, Holland. As far as accuracy the manual states ±10ppm for 30 day or ±30ppm per year for the 10v output . I need it to calibrate my (modified with reference oven) EDC (Electronic Development Corp.) model 520a. Which I calibrate my Fluke 510a with a Fluke 720 voltage divider. I use the 510a to calibrate DB voltage for my audio test equipment. I also have a Fluke 8505, Fluke 8800 and Data Precision Model 2500. So if I can achieve ±50ppm per year this would be sufficient, but better would be nice since they may not be calibrated every year. I’m just a hobbies audio engineer that designs audiophile equipment and other interesting projects not related. So sending it to fluke is not economical for me. Since Joe suspended operations for his SVR-T with low cost calibration. I purchased one and put it in a 35°C oven and it seems to outperform the Fluke 731b as compared to my 8505 for drift. I will have three 10 volt references in my lab to track uncertainty. So are there any calibration labs that will calibrate my 731a and my home brew reference’s? Date: Sat, 8 Mar 2014 16:00:41 -0700 From: n...@npgcable.com To: volt-nuts@febo.com Subject: Re: [volt-nuts] Economical Standard Calibration Dallas, How accurately do you need the 731B set? Where are you located? I am in Flagstaff, Arizona I have four 731s, and I know how to calibrate them. I also have a 3458A and a Fluke 7001 that goes to Fluke for calibration soon. I do not know the turnaround time. Joe ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
