Hi Dallas So sorry. I understand how confusing it can be coming in part way through a repair. My apology. I have managed to implement your LEDs mod and I can see the LEDs light up but the voltage driving them, and the rest of the meter, is way too low.
The history of my 845 can be found here: http://www.eevblog.com/forum/metrology/teardown-fluke-845aabar-tweaks-and-mods-%28and-repairs%29/.You will need to scroll down somewhat. Briefly, When I first received the 845 it was not working and had nicad corrosion on the PS PCB. I have not really gotten it going properly yet. I then started on your LED mod hoping that would help, spurred on when I discovered the neons had turned black. So, I am now back to square one and working on getting a stable +-15v.I have managed to separate the PS and Main PCBs and will conduct experiments on the PS by emulating CR104/105, C117/118 off board. I live on the east coast of Australia, near Sydney. Regards, Lou On Thu, Jun 9, 2016 at 3:19 AM, Dallas Smith <[email protected]> wrote: > Hi Lou, > > I think we should talk to each other. Send me your phone number to > [email protected]. > > 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 -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts >> and follow the instructions there. >> >> >> > _______________________________________________ > volt-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
