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UPDATED Fluke 8508A repair Ep01 (Patreon)

Published:
2024-07-17 05:29:47
Imported:
2026-06
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Content

One of the most reluctant patients I have ever treated!

Files

Previews only

Hardest Repair Ever! Fluke 8508A 8.5 Digit Reference Multimeter

Boost your electronics business or hobby https://www.welectron.com/Lab-Equipment Pics, FW, RE stuff: https://github.com/marcoreps/fluke-8508A More from Reps via channel membership or https://www.patreon.com/marcoreps 00:00 Intro 02:02 Anamnesis 02:45 Disassembly 05:40 DC Board repairs 09:21 Ω Board repairs 16:32 Ω Board descriptions 20:46 AC Board 27:49 Success? 29:27 DC Board details 32:51 Tests 33:59 Noise spectral density 35:17 Integral nonlinearity 36:35 Thermals 36:57 Common mode leakage 37:46 Transformer isolation 38:55 Conclusions & comparisons #repair #electronicengineering #metrology

Comments

Martin Sona

Breakfast with Ruehrei, mushrooms, springonion, fresh Break and a 33 minute video about putting the nanovolts back a Fluke. Yummy!

Michael Johnson

That's a truly heroic repair Marco! It was very interesting to see how similar and yet how different this machine is from the Datron 1281.

Rick Mann

I think it might be time to invest in equipment racks.

Andreas Happel

A very informative and exciting video, thank you very much. The only thing on the internet that gave me the opportunity to begin to prepare myself for the fact that today I want to look at an 8508A, which singe yesterday suddenly no longer wanted to measure AC voltage for no apparent reason. At least I Hope I can find out the trace the Signal takes from Front to ACV-Pre-Amp, to get the broken Relais/IC. All selftests are passed. On Test 81/ P016 (179mV after pre-amp Output) on the green Cable ist a 1,79V Output - so everything after the pre-amp works. But it makes no difference if I measure from the Input-Terminals to the black cable (you identified as AC-Voltage Input to the AC-Board, or I put the Signal (100 mV 60 Hz) onto the black cable to measure some Output on the green cable: no Signal is measured.... It seem there are several ways not switched?! But as I said: it happend from one Minute to another during low Voltage AC measurements...Are at the Any suggestions?

marcoreps
>>155844117

hm interesting! did you try to find continuity from a front binding post to the AC board yet? if you have that, you could check the relays and relay driving op amps on the AC board. if not, the same on the analog main board, where front / rear inputs are selected and routed to the selected module

Andreas Happel
>>155844117

Thanks for reply... for the Moment: I've checked direct Connection from the front binding posts to the AC-Board without success. But what is strange that there is also no measured DC-Voltage from the the AC-Board back to Mainboard (Green wire) when I inject the AC-Signal into AC-Board Input (black wire). So at at least to "stations" have a misbehaviour (Front Post to AC-Input and AC-Input to AC-Stage Output). I Must also confess: I am not experienced in repairing DMMs. And bevor I forstet to mention: I have referenced all Signals / Measurements Input/as Output to Chassis Ground of the Mainboard. I haven't removed the Board(s) from the Chassis to track the Traces from/to Relais But as I speculated bevor: more than one path seem Not be switched right - what looks like a more "centralized" Problem? I don't have a clue what drives the Input-Stage/switch.