Fluke 335A repair / service manual - Page 1
Forum section: electronics / testgear

author: int2str
author_rank: Regular Contributor
timestamp: February 19, 2016, 06:53:34 pm
content: Just received a non-working Fluke 335A voltage standard from ebay.Since it was advertised as "turns on, doesn't produce output", I figured I might have a shotSure enough, that's what it does. Gave it a quick check of the voltages on one of the transformers and it's reading garbage voltages.One of the fuses (1/4A slow blow) had about 10ohm resistance which I found odd for a fuse, though I'm not sure about "slow blow" ones. Ordered new fuses anyway, just to be sure.However, I can't find a service manual anywhere so I'm not quite sure where to test more.Questions:1. Have you seen a fuse have such a high resistance?2. Anybody have a service manual for the Fluke 335A (found the normal manual, doesn't have enough info)?3. Any tips/tricks/insights?Thanks!

author: Dr. Frank
author_rank: Super Contributor
timestamp: February 19, 2016, 09:56:19 pm
content: Fluke has them online, but there's a whole bunch of different versions, like 332A, B, 335A, D of different vintage-Some key circuits (PCBs) differ, like the chopper OpAmp, the reference and the sample string.Most others are mostly always the same.There are some typical errors with these instruments; some can not be repaired, others are easy but maybe elaborate.Fuses do not belong to this category.I have four five different manuals for these mentioned differences.. before starting the search, you should take some photos of your unit, especially the chopper, the reference, the pre-regulator, the sample string and the front.Then it should be possible to determine the possible error.Frank

author: PaulAm
author_rank: Frequent Contributor
timestamp: February 20, 2016, 01:57:53 am
content: Make sure the controls are set properly . I got a 332b advertised as 'powers on, no output' and the only problem was the voltage trip control was completely counter clockwise on the minimum value.

author: int2str
author_rank: Regular Contributor
timestamp: February 21, 2016, 12:50:32 am
content: Yes, I was hoping that it was user error, but I don't think so...Pictures of some of the boards etc attached.

author: int2str
author_rank: Regular Contributor
timestamp: February 21, 2016, 12:56:06 am
content: More pictures

author: guido
author_rank: Regular Contributor
timestamp: February 21, 2016, 01:34:00 am
content: I have a D model. It has safety switches, won't turn the output on with the top or bottom cover removed. Not that it matters that much, the inner case is at output potential (1.1kV max). Be very careful.Do you have the extender board? If not i guess you need to make one to measure on the individual pcb's. There is another tread here with a information, search the forum. You will read i got the remains of a unit from Frank. Unfortunately i'm out of parts to make more extender pcbs (no more male pins). But i kept some parts.If you would find out it is the chopper pcb being broken, you can make a modern variant. It's in the other thread.

author: Dr. Frank
author_rank: Super Contributor
timestamp: February 21, 2016, 08:39:16 am
content: That unit looks very nice, i.e. LEDs on the front panel, the more modern MOSFET chopper version (not the mechanical one), and the better reference, containing the Reference Amplifier.I assume these two PCBs are ok.You now should check the power supplies, and especially the pre-regulator. You don't need an extender board for that:The transistors (in sockets) may have too low a beta, that's an indicator, or the power transistor and zener may be blown.This unit is from 1978, or earlier, so happy replacing all the dried out electrolytic caps.Frank

author: int2str
author_rank: Regular Contributor
timestamp: February 26, 2016, 09:55:06 pm
content: Do you have a service manual that would help me diagnose/measure the boards and the power transistors?

author: Dr. Frank
author_rank: Super Contributor
timestamp: February 27, 2016, 08:54:33 am
content: Quote from: int2str on February 26, 2016, 09:55:06 pmI could send you several manuals, which cover your instrument.These have 20MB each, so I hope that the email servers accept that size.The manuals do not contain error tracing descriptions, though.Please contact me via PM.PS: The 335D manual, May 1972, Rev 1 6/78 is a nice, tidy copy, and contains the more modern assemblies of your unit (chopper, reference), and has 13MB only.The sample string might be different in your unit, but that's not so important.Frank

author: Henrik_V
author_rank: Regular Contributor
timestamp: November 09, 2016, 03:20:44 pm
content: I just happened to get my hands on two 335A units , both missing the A5A2 SERIES PASS DRIVER .. (one even some more..)Also with the 'new' reference board and chopper.One with green PCBs one with brown...Looking at the manual from fluke (335A_D_imeng0000) I'm not shure to have the rigth schematics... but that missing board doesn't seem to contain any unoptainium ...I could harvest the connector from another board and migth be willing to rebuild that A5A2 board. A good picture of the A5A2 layout would be wellcome!

author: guido
author_rank: Regular Contributor
timestamp: November 11, 2016, 03:44:18 pm
content: i can take a picture, there is such a board in the scrap pile. Could also send it to you, so you can take the picture yourself.Or you can just use itIt is not complete, a number of parts are missing. But it is a start. Send me a pm.

author: Henrik_V
author_rank: Regular Contributor
timestamp: November 12, 2016, 10:03:28 pm
content: CoolYou have mail