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Old Fluke Multimeters
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DC1MC:
I have a Fluke 8800A waiting for reanimation (initial symptoms: faint red range LED, no reaction to buttons, former owner broke the the green paddle and put acetone to glue it back managing to melt it on the case  :palm: ).
Because I was felling in need of (relatively) instant gratification, I've open it, changed the usual basterds (see the picture, trifecta, Sprague, Phillips and and MEPCO, this one on the 5V being actually 16pF !!!) and the old girl sprang to live, the initial readings had some offset but were stable enough, except for the high voltages ranges, where it was a real noise +/- 15%, egal what voltage was applied.
After cleaning all the contacts, carefully marking the position of the trimmer potentiates and exercising them few times, everything stabilized nicely EXCEPT for the bloody zero on short, this was moving in between +70 and+ 20 on the ends of the front panel zero trimmer  :scared:, I was preparing to replace the main adjustment resistor, as the manual suggest, realized that I have none :( and staring to feel bad, but while moving the device on the table the zero offset I've seen some mechanical variation on the reading with the input shorted.

 Long story short, the bloody range relay it's a POS, I've clean it as good as I could, put it back and I've got a minimum value of +14 and stable, exercising it by putting on and off a 150V to switch the relays reduced it to 6 and that was it, no way to go lower, but at least now it's really rock stable, the 10V in the picture are staying like this for 2Hrs and I'll let it run over night, so mission (almost) accomplished  ;D.

Now I have a couple of questions for the Fluke gang:

- Any NOS or other replacement for the ranging relay available somewhere  ?

- Anybody in DE/EU has a donor unit and willing to send me the green (or any paddle) to replace the power supply Pfu­sche­rei ?

- Any ideas for the zero adjustment WITHOUT replacing the main calibration resistor if I can't get a new relay ?

 Finally after almost 2 1/2h it started to blink 10.0000/9.9999, I'm taking bets for tomorrow for the drift  :-DD.

 Cheers,
 DC1MC

Obligatory pictures attached  8).
GregDunn:
Same caps I replaced on mine and it was resurrected almost immediately.  That, plus a couple of nasty solder joints on the Ω board, were all that was keeping it from its full glory.  Well, that and dirty switch contacts.

I have cleaned the big relay on mine as well, and it seems to be stable.  I haven't seen any option for replacement, unlike the little reed relays.

The previous owner broke the power switch on mine as well, but he did a superb job of repairing it.  Perhaps we should keep an eye out for 88xx front panels on the Bay, and accumulate a small stock of spares?
DC1MC:

--- Quote from: GregDunn on December 02, 2018, 02:50:06 am ---Same caps I replaced on mine and it was resurrected almost immediately.  That, plus a couple of nasty solder joints on the Ω board, were all that was keeping it from its full glory.  Well, that and dirty switch contacts.

I have cleaned the big relay on mine as well, and it seems to be stable.  I haven't seen any option for replacement, unlike the little reed relays.

The previous owner broke the power switch on mine as well, but he did a superb job of repairing it.  Perhaps we should keep an eye out for 88xx front panels on the Bay, and accumulate a small stock of spares?

--- End quote ---

The ironic part is that 30yrs ago I was working with similar relays like the big one, they were crappy then as well, I can't imagine why Fluke has chosen it, maybe a cost reduction measure  :-//
Anyways it looks like gold coating on it, but it's just yellow metal (bronze-beryllium ?), it was some oxidation on the contacts that it polished off, so far I'm extremely pleased with the stability, it didn't drifted at all on 10V, tomorrow I'll put my 1,10 and 100K resistors to test the ohms board, the soldering was looking OK, but who knows.
If I could get rid of this miserable zero offset shift then can calibrate it properly.

Speaking of spare parts, chances are slim in DE/EU, the US seem to be awash in 88xx, as usually, I've seen two of them on this strange site that  I was asking before, I'll give it a try to the 8810 with the PayPal.
If you get some, we can split the parts, I also need one of the rubber feets, but at lest the handle is perfect  :-+.
I'm still amazed that is almost 40years and still works nicely, and it come really cheap (for DE).

 Cheers,
 DC1MC

 
GregDunn:
I'll probably be picking up another 1 or 2 8800A units as soon as I get the current queue shortened a bit.   ;D  If they're cheap enough I'll probably do what I've been doing with the 8600A - picking up broken units for repair or possibly just spares.  If that happens I'll surely have some pieces to split off.  I'm not too bothered by having handles on my equipment, but without feet it's a pain to get them to sit stably on the shelf...

The goal is just to have 2 each 8600A and 8800A running eventually, with enough spares to make sure they stay that way.   :-DD 
DC1MC:
I hammered the bloody big relay until I got some +1 count for zero, but this thing is ridiculous, such a nice and stable instrument hindered by this crappy thing, now I've seen that somehow the moving part dig a small trench in the support and with the plastic cover on, it never settles in the right position, I discarded the plastic crap, but still I have to find a long term solution to this.

Any advice is welcome, my idea is to get a modern 4,5V relay, throw away the old one and the socket and solder it on a small board or with flying wires.

Any other ideas and replacement solutions are welcome.

 Cheers,
 DC1MC
 
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