Bonjour: See similar on many old HP LCR meters. Do you live in a very clean air location eg countryside or in a big city? Pollution oxidizes contact.

Typical for flaky PCB switch or relay contacts. Heat often affects such flaky contacts.

PCB card edge need to be pulled and cleaned off the board, just spraying cleaner everywhere is not enough as contact are oxidized.



Bon chance,

Jon
PS: the tiny bottles of DeOxit are a waste in my experience. High quality PCB cleaner, contact lube, with solvents or alcohol does just as well if not better at 10X lower cost.

I believe I located the source of the burn smell. A11A5 L5 and C9 were both charred (see attached image). C9 is a 2.2u 20V axial tantalum. These form a lowpass filter on the -10 V rail for the YTO sampler assembly. I could also clearly make out the smell I'd noticed when I opened this assembly. And, the capacitor in particular smelled really bad. I measured both on my low impedance meter. The cap got a reading of 1.93u (should be 2.2u) and 1.544ohm ESR at 100kHz. The capacitance is pretty close but the ESR seems high to me. Still, surprisingly close for something that looks as bad as it does. I didn't attempt a leakage test, though maybe that would be informative.

The inductor measured 0.267u (should be 1.2u) at 100kHz. My best guess for this drop in value is that the high current fused and thus shorted consecutive loops. Does that seem plausible?

I also pulled A11A4C3, which is the same part as A11A5C9, but on the YTO loop phase detector. I measured it to have about 1.5ohm ESR at 100 kHz out of circuit, which seems a bit high to me. Also, C28 is the same exact cap on that assembly and measured a fraction of an ohm in ESR.

Matt

Is it possible that you have a poor "ground" connection somewhere?

--
This email has been checked for viruses by AVG.

I have one of those, ie the 35660A. Let me check what I have for manuals.

The symptoms your unit shows point in fact to the O-ring problem. The rubber becomes hard and brittle over the time. I had a couple of attenuators showing the same an fixed them all with 2x1x0.5mm watch crown O-rings. They come from a 'RUIHUA No.4031' set off eBay (yellow-orange sticker on the box). Works perfectly. Just follow the instructions and be careful what you do.
Chris

At 08:20 PM 18/01/2022 -0800, you wrote:

The dbm readings are within specs as long as I use a multiple of 20 in
the attenuator setting. For example, -30,-50 attenuate the signal way more
than expected. I read about defective o rings that secure the
plugers/pustons to the solenoids. I even watched a video of someone
repjacing them.Would failed o rings cause this failure I am describing?

This video?


HP RF Attenuators: o-ring repair


'Failed o-rings' means stuck o-rings, that prevent some actuator plungers from moving.
Hence wrong attenuations.

Hi! In my quest to repair my SA, I am now facing a potential failed input attenuator.?

The dbm readings are within specs as long as I use a multiple of 20 in the attenuator setting. For example, -30,-50 attenuate the signal way more than expected. I read about defective o rings that secure the plugers/pustons to the solenoids. I even watched a video of someone repjacing them.

Would failed o rings cause this failure I am describing?

I tried cold spray and I did clean all of the edge connectors. I also went ahead and refreshed the solder joints on all edge connectors contact points where they are soldered in place.

Nothing about the symptoms changed. Cold doesn’t seem to influence the state of the machine, it can be off for several hours and behaves normally once tuned on, only to start the malfunction after up to 5 minutes.

Without more equipment suitable for diagnosis and testing this meter (I have a nice Tektronix scope and VOM but that’s just about what I do have), I fear making things worse. I found a repair depot for such things as this so unless a miracle happens I’ll probably end up sending it to them for repair.

Still looking :)

Even the adjustments section is missing!!!

?This unit is old enough that the card edge connectors may not be gold plated, they may be tinned connectors. If so, cleaning and a very thin coating of De-Oxit would be a very good idea on all of the edge brd. connectors on all of the circuit cards.
Simply pulling and reinserting the cards may cure the problem. Also your failure mode
indicates it is failing as it warms up, so cold spray and a hot air source (hair dryer or heat gun) can be your friends in isolating the problem.
Don Bitters

开云体育

Hi Tom:

I expect that a sorting machine, like that shown on my web page: would be setup to bin the diodes where each bin would be matched to some spec and there would be a number of adjacent bins.? I don't remember how many bins there were but about a dozen.

PS Note HP test equipment.

-- 
Have Fun,

Brooke Clarke

axioms:
1. The extent to which you can fix or improve something will be limited by how well you understand how it works.
2. Everybody, with no exceptions, holds false beliefs.

Other ideas appreciated.

Get a thermal camera. They are dirt cheap nowadays, considering what they can do for you.

-- john, KE5FX

"Harvey White" <madyn@...> writes:

A good place to check for burned smell would be the RIFA capacitors on
the power input.? They're filters, and fail (especially often) in 240
volt land.

The equipment will work without them, but they have a very distinctive
(and lingering) smell.

They fail, but less often, in 120 volt land.

I did check these, however, I couldn't discern any smell coming from the
RIFA or the input filter, so I think they're probably not the
source. I'll probably replace them anyway, given the horror stories I've
heard. Though I'm in the US, so doing so is likely a bit less urgent.

This reminds me of another question I had recently. I noticed the one
standalone RIFA was wrapped in black heat shrink. I don't have the unit
open at the moment, but I can send a picture when I open it up again. I
haven't seen this before and was wondering why. Is it intended to act as
an additional seal against moisture?

Back to troubleshooting: although the unit continues to work
consistently, the smell reappears every time I turn the unit on. It's
strong enough that it concerns me, so I'm thinking of ways to localize
it.

Some general thoughts:

It's not clear whether the fact that the smell occurs when the unit is
powered on is because current is burning an already burned part, or if
it's existing smell that is now entering the surrounding room because
the fans are blowing air into the room.

To determine this, I may very temporarily disable the fans.

If the smell is occuring because the fans are blowing air, then maybe I
don't have an active problem to worry about. On the other hand, if it's
not the fans, then I can probably resume the test of pulling the
assemblies until the smell goes away.

The fact that the smell has probably distributed through the instrument
makes it harder to locate. So I may try to blow the smell out of the
instrument with compressed air and then try again.

I liked Bill's idea of the straw; will give this a go.

If my nose fails me, I have a cheap air particulate matter detector that
might have better luck. I'll use the straw trick here as well.

Other ideas appreciated.

Matt

I came across an old HP price list from 1971 where HP was asking a whopping $8.55 for the 5082-2308 matched pair.? The matched quad was $27.15.? At that time HP was also offering the individual 5082-2303 (1N5157) diode for $3.30.

?

While looking around I recently noticed a single diode on ePay offered by a chap in Britain for around $24.00

?

Given the meticulous testing of devices by HP I am sure that they thought of nearly every factor, both electrical and environmental, that would affect the results.

?

Greg

Here is a video of the malfunction. Typically on first start up in the morning it runs normally and then slowly drifts into this state you see.

The capacitor being attached is a brand new mica 820pF.



73s
geo VE3GZB?

On Mon, Jan 17, 2022 at 06:07 PM, Matt Huszagh wrote:

Interesting. Why wouldn't the designers use a fuse closer to the max
current draw? FYI it is the right fuse, I'm just taking the value from
the manual.

------
I think your question is if -10V is supplying 1.5A from your measurement why a 5A fuse. ?Fuse in -10V section carries current of -5.2V supply in addition to -10V. The fuses are there in case current limit circuit fails, otherwise current limit of each section looks comparable to fuse rating and they will act faster than the fuse. Foldback current limiting is used which reduces current limit when there is a short so the fuse doesn't even see the peak current for long during a short, probably the reason why you were measuring low current out of -10V supply when there was a short, i.e. it was doing its job.?

Ozan

Yes, indeed, matching to that level in general requires not insignificant effort, hence the reference to cost. However, if the diodes aren't from a random collection, but rather from the same general region of a wafer, the matching should be pretty good, even for Schottkys. And in the old days, HP made their own Schottkys, so that option would've been readily available to them. I do not know, however, if they took advantage of that option, but if they had to crank out other than a small number of matched quads, I bet they did something like that.

-- Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070

On Sun, Jan 16, 2022 at 07:29 AM, David wrote:

Hi,
I am trying to test my HP8563E A6 power supply with a Tenma 72-13210 DC electronic load. Could anyone tell me what is the MAXIMUM current that the power supply SHOULD be able to supply per voltage rail (+15v,-15v,+5v,-5v,+28v,-12.6v). So far the +15v rail holds a stable voltage up to 4 amps but the -15v rail's voltage starts to drop at 3.2 amps. Where can I find out what the maximum currents should be? Thanks.

----------
Easier to guess for the supplies with IC regulators but a back of the envelope guess:
+28V -> 1.5A
-12.6 -> 1A
+15V -> 3.7A
-15V -> 3.1A
+5V -> 7.8A
-5V -> 1.4A

These estimates depend on actual supply voltages, sense resistor value, simplifications, etc. so at best +/- 20% accurate.?

If you are seeing very different values I can look at it again.?

Ozan

Tom,

Thanks for pointing this out.I was on the way out the door when I wrote the post and overlooked some details.

From what I can gather from the scatty information I have it appears that they are trying to match the diodes with a maximum delta V_f of 20 mV and a maximum delta C_o of 0.2 pF.It doesn’t appear that there are actual hard values for both of those parameters but, instead simply trying to match the two diodes as close as possible to each other no matter where the values fall.

What bothers me a bit is that the probe schematic shows a quad set of diodes.A pair would only serve to replace half of the quad.HP did sell a matched quad set of this particular diode under part number 5082-2370.Any thoughts on this one?

Greg

The problem with matching to that sort of level means that matching and operating temperature has to be very accurate.

Craig