Repair worklog : Old rusty HP 3458A

[TiN]

VK5RC

If you asking HPAK to repair your 3458A, you doing it wrong  .
Welcome to high-end gear. It's "normal" out there.

Macbeth
Yes, but no. We want perfect, right? How much perfect is only matter of disposable funds available...

Drift ain't there now  overnight span ~2.4ppm (temp change 26.1C to 30.3C), so that's OK.
I have wild theory now why it's not drifting now. No, A3 not changed, I did not even unscrew bottom cover yesterday. You guess?

[ManateeMafia]

Air filter?

[Macbeth]

I know, I know!!! That bloody cat is opening doors and letting the drafts in! 

[TiN]

No, not so obvious as air filter.
And no pets allowed in volt-nut house  .

Hint - it's not temperature or voltage related. 

[Vgkid]

Bad power connection/cable.

[TiN]

Nop. Nothing obvious, this one is tricky.

[crispy_tofu]

I was thinking something along the lines of a wobbly connection in the banana inputs, but it's not obvious...
Dodgy software? 

[VK5RC]

?Dissimilar metals of connection cable/connectors??

RE HP-A-KS just thought I would phone them to see how much in AUS, it is part of my tendency to "nuttery" voltage or time!!!!

Reminds me of the joke "a man with one clock knows the time, a man with two is not so sure" perhaps "a man with one DMM knows the voltage……. etc"

I have a slightly bulgy main 15000uF in the main PSU, a replacement is coming soon.

[deadlylover]

I have a slightly bulgy main 15000uF in the main PSU, a replacement is coming soon.

Hmm I might replace all electrolytics, because once you get it calibrated you don't want to ever open the thing up again until it requires repair.

Nop. Nothing obvious, this one is tricky.

Humidity/moisture in parts being released after a long cycle? 

[plesa]

My guess - thermal EMF

[TiN]

plesa is close, but no, not EMF Not related to thermals. 

[Monittosan]

?Dissimilar metals of connection cable/connectors??

RE HP-A-KS just thought I would phone them to see how much in AUS, it is part of my tendency to "nuttery" voltage or time!!!!

Reminds me of the joke "a man with one clock knows the time, a man with two is not so sure" perhaps "a man with one DMM knows the voltage……. etc"

I have a slightly bulgy main 15000uF in the main PSU, a replacement is coming soon.

If its ok by TiN pics pics pics! I had to stop my self from opening your 3458A soooo many times just to keep the cal seal intact and let the next owner have the satisfaction of cracking it open 

[Dr. Frank]

plesa is close, but no, not EMF Not related to thermals. 

Maybe, for this missing shorting jumper on jack P100, you used a TiNned one, instead of gold plated?
Oxydation might create unwanted chemical galvanic element in the signal path.

You know, P100 near the A9 PCB, which selects GND, +7V, or Normal, and which you might have used (and touched) for measuring A9 output.

Frank

[ManateeMafia]

Dr Frank,
 That would be a good catch even if it wasn't the main problem. At least TiN has a donor board to get a jumper.

[Dr. Frank]

Dr Frank,
 That would be a good catch even if it wasn't the main problem. At least TiN has a donor board to get a jumper.

That jumper already made me nervous when I have seen it for the first time.

On 2nd thought, it may be inside the AZERO circuit, and so any parasitic voltage would be eliminated.

Frank

[plesa]

plesa is close, but no, not EMF Not related to thermals. 

I must give up

[WN1X]

No, not so obvious as air filter.
And no pets allowed in volt-nut house  .

Hint - it's not temperature or voltage related. 

I am going to guess it is light leakage affecting some of the IC's.

[nfmax]

If all else fails, blame the software

[ManateeMafia]

Test gear or other device with fan blowing warm air into rear of meter.

[Zucca]

I must give up

You are not alone, my head is still smoking and nothing is coming out.

PS: I imagine TiN with a cold beer smiling on us 

[ManateeMafia]

I would be smiling too if I knew that A3 board was working! 

[Macbeth]

You are not alone, my head is still smoking and nothing is coming out.

PS: I imagine TiN with a cold beer smiling on us 

That's it! It's the bloody compressor cycling on his beer cooler! Should have got a peltier cooler instead.

[teksturi]

Power line frequency is not correct or stable or something similar.

[WN1X]

That's it! It's the bloody compressor cycling on his beer cooler! Should have got a peltier cooler instead.

The compressor is cycling too much because there is no thermal load for it after TiN drank all of the beer 

[Macbeth]

The compressor is cycling too much because there is no thermal load for it after TiN drank all of the beer 

I noticed a few bottles of India Pale Ale during his clean up operation. That Taiwanese IPA is nothing like the stuff over here, I mean 5-6% abv is normal, but 99%?