Re: [time-nuts] HP 10544A Repair

On 3/1/2016 4:13 AM, Bob Camp wrote: Is it worth getting it super close? Probably not without a temperature test setup. Bob Right. It is entirely possible that if you did a temperature test in an environmental chamber, you would find that you could get a better tempco by adjusting oven

Re: [time-nuts] HP 10544A Repair

Hi As you do the tweaks, the frequency changes should go from parts in 10^8 to 10^9 to 10^10 per turn. A lot depends on the pot setup and the crystal in terms of how high it starts. The flip side to that is your counter and local reference standard need to be able to measure at least parts in

Re: [time-nuts] HP 10544A Repair

Been there and experienced it all to often. To tweak or not is the question. "Are you feeling lucky?" Regards Paul WB8TSL On Mon, Feb 29, 2016 at 1:50 PM, Mark Sims wrote: > Not to mention that a lot of pots that have been sitting at the same > setting for years tend to

Re: [time-nuts] HP 10544A Repair

Howdy All, This thread has split into a couple, but I’ll try to respond here to the various things. Based on how this crystal warms up, it does appear that it is a BT type crystal, as it warms up frequency goes up, and as it gets hotter eventually turns around and heads downhill again. I’ve

[time-nuts] HP 10544A Repair

Not to mention that a lot of pots that have been sitting at the same setting for years tend to distort the resistance element where the wiper has been making contact. Then when you make a small adjustment you cannot reach the value that you need. Ahhh, the subtle wonders of aligning old

Re: [time-nuts] HP 10544A Repair

Hi An SC cut OCXO stabilizes a bit faster from the temperature steps. The procedure Rick described is indeed the right way to do it for an SC. It takes less time and is reasonably accurate. For a super duper job you might come back a day later, but the pot its self (backlash etc) will probably

Re: [time-nuts] HP 10544A Repair

While in the navy, I had to repair a hp cesium standard. The control circuit had the oscillator slewed to one limit, I do not remember whether high or low. We had no spare parts to support this standard. The only option was to run the standard open loop. Over a period of two hours, I had the

Re: [time-nuts] HP 10544A Repair

Hi Except …. The big steps give you more “thermal shock” on a BT and that slows things down. Bob > On Feb 28, 2016, at 7:28 PM, Richard (Rick) Karlquist > wrote: > > > > On 2/28/2016 7:01 AM, Bob Camp wrote: >> Hi >> >> It’s not an electrical issue as much as a

Re: [time-nuts] HP 10544A Repair

On 2/28/2016 7:01 AM, Bob Camp wrote: Hi It’s not an electrical issue as much as a heat issue …. Before you start, consider that you will be doing something like: Move trimmer 1 turn CW Wait 10 minutes read frequency Move trimmer 1 turn CW wait / read Move trimer 1/2 turn CCW wait / read

Re: [time-nuts] HP 10544A Repair

Jim wrote: Can you tell what the cut is if you have the blank in front of you? You can do it directly with x-ray crystallography. Otherwise, you need to characterize multiple crystal parameters and infer the cut from those, which may not be particularly accurate. Best regards, Charles

[time-nuts] HP 10544A Repair

Hello Nigel , I already have done a similar repair on a 10811, described here: https://www.febo.com/pipermail/time-nuts/2012-January/062228.html A comparison of the 10811 manual, p. 8-16 and schematic, let me strongly assume, that the 10544 has exactly the same type of NTC inside. This NTC

Re: [time-nuts] HP 10544A Repair

Hi Ok a bit more of the story. It’s easy to simply turn on the device and see how it warms up. Back when it was made, the SC did not yet exist. The only thing it could be was a BT. With an X-ray setup you can absolutely tell it’s a BT. With the blank and a pair of calipers you can make a

Re: [time-nuts] HP 10544A Repair

Jim, Why cut it open? It is relatively easy to measure just by power the oscillator up. Just in this thread is an echo of a discussion we had many years ago that explains the method. The temperature curve for AT, BT and SC-cut is known and quite different, so just measure the heat-up curve

Re: [time-nuts] HP 10544A Repair

On 2/28/16 6:23 AM, Bob Camp wrote: Hi The whole “BT Cut” issue was a big top secret in HP. They spent a lot of time obscuring the fact that they used BT’s. The belief was that if any of the other outfits figured out that was what they were doing, the competition would have better OCXO’s.

Re: [time-nuts] HP 10544A Repair

Hi It’s not an electrical issue as much as a heat issue …. Before you start, consider that you will be doing something like: Move trimmer 1 turn CW Wait 10 minutes read frequency Move trimmer 1 turn CW wait / read Move trimer 1/2 turn CCW wait / read Move trimmer 1/4 turn CW wait / read Move

Re: [time-nuts] HP 10544A Repair

Hi The whole “BT Cut” issue was a big top secret in HP. They spent a lot of time obscuring the fact that they used BT’s. The belief was that if any of the other outfits figured out that was what they were doing, the competition would have better OCXO’s. Watch the frequency as it turns on. An

Re: [time-nuts] HP 10544A Repair

Hal, It depends a lot on the thermistor. As with any component, there are higher precision models that would be pretty repeatable within a model number, and cheaper ones that will be somewhat less repeatable. In this case I didn’t have a specific model number, nor specific nominal/beta values,

Re: [time-nuts] HP 10544A Repair

Mark, I don’t see that referenced in the documentation, and the frequency adjustment pot appears to be plastic, but I will compare a non-conductive tool, to a conductive one to see if it makes a difference. Nigel > On Feb 27, 2016, at 19:11, Mark Sims wrote: > > Also,

[time-nuts] HP 10544A Repair

Also, when messing with a 10544A be aware that that the frequency tuning adjustment must be made with an insulated tool. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to

Re: [time-nuts] HP 10544A Repair

rich...@karlquist.com said: > If you replaced the thermistor with an exact replacement, then you shouldn't > need to change the pot. ... How repeatable are thermistors? How close do you need/want to get the temperature? -- These are my opinions. I hate spam.

Re: [time-nuts] HP 10544A Repair

Bob, I’m not sure what type is in it. It *is* a 10544A, not one of the 10811 devices. The references I’ve found indicate the 10544A being an AT type. If it’s of any use, the date codes on the parts in the oven control circuit indicate it was built in the latter part of ’77. I can’t say I’ve

Re: [time-nuts] HP 10544A Repair

If you replaced the thermistor with an exact replacement, then you shouldn't need to change the pot. If you didn't replace the thermistor with an exact replacement, then you should carefully measure the resistance of the pot as you found it. (I hope you did not fool with it already.) From the

Re: [time-nuts] HP 10544A Repair

Hi The key bit of missing info: You likely have a BT cut crystal in that OCXO. If it was an AT, you wold look for a minimum frequency. With the BT, you look for a maximum. Bob > On Feb 27, 2016, at 9:48 PM, Nigel Vander Houwen > wrote: > > Hello All, > >

[time-nuts] HP 10544A Repair

Hello All, Relatively new to the group, but thought I’d ask for a bit of advice. I have an old HP 10544A ovenized oscillator that was pull from some equipment some time ago because it got too far off frequency to phase lock with the external reference. It looks like the thermistor in the oven

Re: [time-nuts] HP 10544A repair

The quarantine is officially over (for this week :) Thanks for the uploads Didier KO4BB PS: I am now trying to move the manuals and equipment specific docs out of the GPS Timing folder into the manufacturer's folders. I realize it may be less convenient for those who are only interested in

Re: [time-nuts] HP 10544A repair

Thank you very much Didier for your wonderful site and thank you again Charles for your precious schematic. Finally i'm able to understand something more! Ciao! Luca iw2lje Milano Italy Il domenica 3 maggio 2015, Didier Juges shali...@gmail.com ha scritto: The quarantine is officially over

Re: [time-nuts] HP 10544A repair

Ok, very good, many thanks Gianni, Corby, Charly, for your suggestions and hints! I will be here again if there will be interesting topics related with this item. Cheers Luca iw2lje Milano - Italy Il lunedì 27 aprile 2015, Charles Steinmetz csteinm...@yandex.com ha scritto: That reminds me --

Re: [time-nuts] HP 10544A repair

That reminds me -- years ago I cleaned up, corrected, and annotated a copy of the HP 10544 schematic. I dug it up and just posted it to Didier's site (http://www.ko4bb.com/manuals/). When it comes off quarantine, you can find it by searching for HP 10544A schematic corrected and annotated.

[time-nuts] Hp 10544A repair

Hi all, Have anyone some experience about 10544A repair? I've recently fixed a 10811A, and it is relatively easy to disassemble, but 10544 has not screws and the manual does not deal about servicing. Can i try to open the box by removing the white plastic tips without demage something? And

Re: [time-nuts] Hp 10544A repair

Hi all, Sorry for bad english The transistor Q4 has the emitter and the collector reversed; R12 is connected to the collector and the waveform is square wave with duty cycle that depends on the oven temperature; supply voltage = cold, minimun duty cycle = warm. It is relatively easy to extract

[time-nuts] Hp 10544A repair

Luca, You can pry out the plastic pins easily. Then remove the thin foam piece. Then if I remember correctly you will have to diagram where each color of wire goes to the edge connector and then unsolder them. Now you can remove the guts, some pressure on the tuning capacitor thru the hole