Fluke 8050A Voltage read issue. - Page 1
Forum section: electronics / repair

author: neo
author_rank: Super Contributor
timestamp: January 18, 2018, 11:38:06 pm
content: It will read resistance however it will not read voltage, constant over-range. Fresh tantalums, yes they are installed correctly, fresh batteries as well.13 is 14.46 is 6-5 is -5-15 is -10I think i am going to try new electrolytics, unless someone has a better idea?

author: Specmaster
author_rank: Super Contributor
timestamp: January 18, 2018, 11:46:43 pm
content: Have you got a LCR tester that shows the ESR of a cap?

author: neo
author_rank: Super Contributor
timestamp: January 19, 2018, 12:03:49 am
content: Chinese transistor tester, problem is i only know two scales by which to interpret ESR, under 1 OK and over 2 bad. That and if i de-solder then anyways might as well replace.

author: bd139
author_rank: Super Contributor
timestamp: January 19, 2018, 12:06:12 am
content: Posted this in other thread. Agree with replacing the filter caps after the rectifiers. They were dying on mine. Carefully inspect the board as sometimes they leak.If you have the battery option it’s different. Much harder.I think they are 220uF 25V ish. So cheap it’s not even worth testing them.

author: neo
author_rank: Super Contributor
timestamp: January 19, 2018, 12:10:23 am
content: Mine is the battery version.

author: bd139
author_rank: Super Contributor
timestamp: January 19, 2018, 12:16:56 am
content: Ah. Replace the big ass 2200uF one as well then.Worth checking the individual cell voltages as some of the power supply is referenced to it.

author: neo
author_rank: Super Contributor
timestamp: January 19, 2018, 12:22:23 am
content: Quote from: bd139 on January 19, 2018, 12:16:56 amOK, also when i replace caps i need a twenty dollar min order so i don't pick and choose which ones are the worst i just buy them all.Edit to add;I've yet to check the individual batteries but i know their fresh ones.

author: neo
author_rank: Super Contributor
timestamp: January 19, 2018, 04:44:01 am
content: Well the caps for the 8050A only cost 5 bucks but since of the minimum order thing i also bought a complete set for my 8000A and new electrolytic caps for my recently re-tanted 8010A. I tell ya, i'm not sure if i hate the min order for making me spend more or if i love it for keeping me pro-active on capacitors.

author: Ero-Shan
author_rank: Frequent Contributor
timestamp: January 19, 2018, 09:09:03 am
content: Quote from: neo on January 18, 2018, 11:38:06 pmJust checked: One of my 9 8050A seems to have the same problem: Resistance OK, but no voltage. Haven't opened it yet, though. Maybe I find the time to clean up enough desk space so I can have a look at the voltages.

author: bd139
author_rank: Super Contributor
timestamp: January 19, 2018, 09:11:32 am
content: Might be switches as well. They're notoriously unreliable.

author: Ero-Shan
author_rank: Frequent Contributor
timestamp: January 20, 2018, 03:33:34 pm
content: Quote from: neo on January 18, 2018, 11:38:06 pmAccording to the schematics in my 8050A manual, the voltages ought to be +10, +6, -5 and -10 Volts. With my non-Voltage reading 8050A, the +10 and -10 V rails are about +15 and -15 V. These voltages, however, are non-regulated and directly behind the rectifier, so they must be OK. Since mine doesn't have the battery option, there will be some differences. The manual suggests R2 (1 kOhm, 1 W), but that one is fine on mine. Didn't get farther than that, though.Your -10 Volts are a bit suspicious, the 14.4 can't be the result of bad caps, can they?

author: neo
author_rank: Super Contributor
timestamp: January 20, 2018, 05:50:34 pm
content: I have seen alot of weird things be the result of bad caps, as for the voltage levels i got the reference values from the troubleshooting guide in the manual.The one i am referencing is located here;http://manuals.chudov.com/Fluke-8050A.pdf

author: Specmaster
author_rank: Super Contributor
timestamp: January 20, 2018, 07:02:46 pm
content: Have you double checked the transformer connections against your local supply? Seeing as the 10 and 13v are unregulated and the two regulated supplies are both spot on, I'd be inclined to also double check the ground connections and the ground path for broken traces and or high resistance joints?

author: neo
author_rank: Super Contributor
timestamp: January 21, 2018, 03:14:27 am
content: Quote from: Specmaster on January 20, 2018, 07:02:46 pmI have yet to do it, next thing i am going to try after i get fresh caps.

author: Specmaster
author_rank: Super Contributor
timestamp: January 21, 2018, 12:06:57 pm
content: Quote from: neo on January 21, 2018, 03:14:27 amTBH thats what I'd have checked first before doing the caps because I've never heard of a voltage gain due to caps, especially in this type of circuit as you only have single caps on these rails and the kind of fault that caps would present you with is a reduction in voltage due to them being leaky to ground.

author: neo
author_rank: Super Contributor
timestamp: January 21, 2018, 07:16:29 pm
content: I had an 8800A, may it rest in pieces, who had a tantalum short. The -18V rail went away and -13 became +5. At 5 bucks the caps are cheap and need replaced anyways.

author: neo
author_rank: Super Contributor
timestamp: January 22, 2018, 11:09:12 pm
content: We have.... progress.But not much13V is 14V-10V is -10V- 5V is - 5V6V is 6VIf the values barely moved how can i call that progress? Because, before the fresh caps it constantly went over range, displaying HV, even without input now it only does it with input. I missed a couple but i have those on order now as well.Also i have no idea when i got the -15V from, re-reading the manual it clearly says -10V which it is. I apologize if my blunder caused any confusion.

author: neo
author_rank: Super Contributor
timestamp: January 22, 2018, 11:46:43 pm
content: Cell voltage:1.28351.27501.26801.2682

author: Specmaster
author_rank: Super Contributor
timestamp: January 23, 2018, 12:48:27 am
content: Quote from: neo on January 22, 2018, 11:09:12 pmWell that is progress, 3 out of 4 are spot on and TBH I doubt if the extra 1V is going to make that much difference, but if all you've done so far is replace caps, where did the 1v drop from 15 to 14 come from. strange but when you said -15v, I also looked at the manual somehow I also substituted the -10 for -15v strange how we fell into the same trap, in my defence I can claim it was very early in the morning and I ought to have been bed getting some zzzzzzzzzzzz's

author: neo
author_rank: Super Contributor
timestamp: January 23, 2018, 02:22:39 am
content: So then the question is why is it that it reacts the way it does with voltage input? Something screwy is going on.

author: neo
author_rank: Super Contributor
timestamp: January 23, 2018, 05:21:03 am
content: nothing on TP 650mV square wave of varying frequency on TP 7and then this, whatever this is, on TP 8https://youtu.be/1I5YdFEWiJUI don't know how to interpret these readings except i know there should be something on TP 6, and 50 mV don't seem like much. I tried to measure voltage on the tants I installed and that is completely absent as well.

author: Specmaster
author_rank: Super Contributor
timestamp: January 23, 2018, 09:22:58 am
content: Quote from: neo on January 23, 2018, 05:21:03 amThe link is not working

author: neo
author_rank: Super Contributor
timestamp: January 23, 2018, 06:57:01 pm
content: Apologies, i set it to private instead of unlisted. It should work now.

author: Specmaster
author_rank: Super Contributor
timestamp: January 23, 2018, 07:50:41 pm
content: Yes, its working now, but that signal puzzles me. I'd be inclined to work backwards from the first tant you replaced which has 0v on it and then look closely at whatever is between it and the incoming supply line.

author: neo
author_rank: Super Contributor
timestamp: January 24, 2018, 06:26:40 am
content: This thing is a royal PITA to fix, look for the proper waveform on (insert location here), but then it never tells you the proper waveform. Not to mention the two versions, battery and not, are jumbled together into one manual, which wouldn't be so annoying if they did a better job or organizing them.Honestly i think Fluke designed this to where service would only be possible by Fluke, my disdain for them increases with everything of theirs i open.

author: neo
author_rank: Super Contributor
timestamp: January 24, 2018, 07:52:23 am
content: A few tenuous days later and give or take a bit of hair that i ripped out while reading their manual, i figured it out i think.I think it was one bad solder joint on the new tants. I say that because i redid them and suddenly, IT LIVES!All was not in vain however, that big 2200u was well on it's way to going bang.

author: Specmaster
author_rank: Super Contributor
timestamp: January 24, 2018, 10:13:50 am
content: Yep, thought it would be a bad connection somewhere pissing about with the supply rails with volts being higher on unregulated ones at least than what the manual states usually is because the loading has been removed and a bad joint can do that. Well done