Fluke 343A repair

[Rax]

For the top one you need to pull op from the middle. It will fold a bit and come loose. It has slots on the sides.
The bottom one i think is the same.

I have a very early one. Serial# 183
I don't know if later units are build the same.

I wasn't clear enough in my request, sorry. I believe that, in order to access that switch - STANDBY/ON - I need to remove the cover(s) that are further to the front of the unit (see pic below). It inserts in side channels (see arrows) and it won't just come off if the screws are removed. Unless I'm missing something obvious, it looks like the handles have to at least be loosened to allow for the cover to no longer be captive to those two side channels.

[70bytes]

Ok.
I opened mine to check. No problem. Just needed to tilt. See photo.

[Rax]

Ok.
I opened mine to check. No problem. Just needed to tilt. See photo.

Interesting. Mine won't release even with some force applied (as much as I feel I can before I bend it out of shape or break it). It's captive under the side channels, and it's pretty clear to me it's not intended to just come off by tilting. It may be a later redesign or something like that.

Thank you very much for going into your unit and trying this out.

[Rax]

Well, stop press... I pushed my luck and tried harder and it very reluctantly came off. I think there was some possibly conformal residue that was petrified in place holding it in, and it was also probably never removed since coming out of the factory. It looks like it needs to slide in a bit, so I may need to remove that residue to make room on that narrow transversal channel it needs to lock onto.

I just conditioned the STANDBY/ON switch with some Deoxit D5 - being the exact same symptom as in your case, 70bytes - and I'll let it cure for a few minutes and retest... crossing fingers.

[Rax]

The limit LED turned off and immediate turned on again. This time the needle wanted to go to the other site over its max limit. I measured 200V+ at the outputs in the 10V range.
The cause of this problem in my unit was a dirty standby/On switch. After cleaning the switch the problem was solved.

Regards,
Maurice

Maurice - that was just spot on. Brilliant, and thank you. Once I conditioned that switch, the unit seems to be working again with no hitch. I should probably say "we'll see," as it seems these may be a bit cranky until several issues (probably all related to age) are resolved.

[70bytes]

Nice to hear.
I replaced all the electrolytic capacitors. Most of them measured still fine. The oldest component i could find was from week 18 1968.
2 of the big capacitors were bad. 1 was replaced earlier. I read somewhere that the sprague capacitors mostly are bad.

 

[bastl_r]

Hi
Unfortunately I don't look in here every day...
I could have told you about the flap.
There is a 1Ohm resistor behind the lower flap which burns out if the connections are short-circuited at a high output voltage or if the overvoltage arrester of a measuring device responds. Then the protective circuit is activated immediately when the power is switched on. Please don't ask how I know this.

I have now also received my "new" Fluke343. As it looks inside, it is still in its original and very clean condition. So it still has the original capacitors.

Unfortunately, of course, it has a small problem...
The zero points are shifted. However, the deviation matches the range.
7.998mV in the 10V; 79.97mV in the 100V; and ~800mV in the 1000V range so I suspect a common error. The offset then also runs through all stages with the same deviation.
The respective settings seem to fit exactly so that I don't want to adjust anything for the time being, although I'm sure from my 341 that I couldn't adjust that much with the zero adjustment.
Should I start a new thread for this? I think so. Or what do you say?

@Maurice: How did you cleaned the switch contacts?

bastl_r

[coromonadalix]

deoxit should clean correctly  the switches,  and do verify the shafts  extenders  they crack  and become loose

[Rax]

How did you cleaned the switch contacts?

bastl_r

I also used Deoxit (D5), though I'd recommend holding off from using it on any of the output adjustment switches. For those, I'd just use IPA to clean them, and if I'd conclude they need conditioning (mine don't seem to), I'd very parsimoniously apply a bit of Deoxit on the copper contact surfaces only. I'd be very careful not to spill any on the substrate of the switch. But I'd leave them alone if they operate OK.

Another contact conditioner I came to like is MG Chemicals 801B. Very expensive, but seems to work very well. It helped me bring back to life a few DM501As that otherwise have been very reluctant to work reliably.

[bastl_r]

Sometime, it is a good recommendation to read the ****ng manual! 
On page 35 ist the solution for my problem, i think.

[Vertamps]

Hello, i had made these Fluke 343A high voltage capacitor mod boards (a few months ago). Iv intended to use solid copper wire to solder the mod capacitor to the the Fluke PCB, either bend the leads or use cheap  spacers i bought off Amazon. I will solder one in this week to show you it installed and see if i need a minor tweak to the pcb. I did think of adding holes for a few plastic snap in spacers as there is room on the board, standing off is doable a few ways. I can put the Gerber files up on my drop box so you can order your own, or PM and i can email but wait till my install test. I paid $8.16 total for 20 of these boards shipped to me.

[bastl_r]

Hi
I am very interestet on the gerberfiles.
Can you send me a link for Download?

Thank you

[daisizhou]

Hello, i had made these Fluke 343A high voltage capacitor mod boards (a few months ago). Iv intended to use solid copper wire to solder the mod capacitor to the the Fluke PCB, either bend the leads or use cheap  spacers i bought off Amazon. I will solder one in this week to show you it installed and see if i need a minor tweak to the pcb. I did think of adding holes for a few plastic snap in spacers as there is room on the board, standing off is doable a few ways. I can put the Gerber files up on my drop box so you can order your own, or PM and i can email but wait till my install test. I paid $8.16 total for 20 of these boards shipped to me.

You choose to replace the original capacitor with a smaller capacitor.
Although their capacitance and withstand voltage meet the requirements, large capacitors have high power, while small capacitors usually have low power.
In other words, the redundancy performance has become weaker

[Vertamps]

You choose to replace the original capacitor with a smaller capacitor.
Although their capacitance and withstand voltage meet the requirements, large capacitors have high power, while small capacitors usually have low power.
In other words, the redundancy performance has become weaker

Well, i suppose if you wanted to pick out 3 skinny/tall capacitors you could parallel them for lower ESR than the original capacitor and fit them on the pcb size.
But I went with a single United Chemi-Con and assuming it will be ok. With 3 filter caps i would add thermal relief on pads for quicker install. I think my initial design will have
good contact area with the capacitor leads.

[Vertamps]

Hi
I am very interestet on the gerberfiles.
Can you send me a link for Download?

Thank you

Hello, let me install one first so im not sending out files with an issue. Ill try to tonight after work (sorry wait one more day ). Worse case my spacing measurements are off by a mm. Mating hole size board to board are 1.2mm to fit 1mm/18 gauge solid
core copper wire.

[Rax]

You choose to replace the original capacitor with a smaller capacitor.
Although their capacitance and withstand voltage meet the requirements, large capacitors have high power, while small capacitors usually have low power.
In other words, the redundancy performance has become weaker

If you mean smaller physically, things are nowhere near that simple. Manufacturing of electrolytics capacitors has come a very long way since the late '60s, and using 105C 5k+ hrs life capacitors of equal or higher capacitance and voltage from a reputable manufacturer should provide a very high reliability from the unit (in addition to a much smaller size). I am using 12k duty caps for my recapping and am not concerned with their reliability. I also don't think ripple current handling in this application is very demanding.

[Rax]

Hello, let me install one first so im not sending out files with an issue. Ill try to tonight after work (sorry wait one more day ). Worse case my spacing measurements are off by a mm. Mating hole size board to board are 1.2mm to fit 1mm/18 gauge solid
core copper wire.

Assuming you get the spacing right, what do you plan to use for the five leads going to the unit's board? Is that the 18 gauge solid core wire? If yes, I wonder if you've figured a convenient way to attach them to the adapter PCB for soldering. Unless you're using some PCB mount header pin type that snaps onto the board or something similar, I assume keeping attached for soldering five terminals to each of the boards makes the recapping very laborious.

[Vertamps]

Hello, let me install one first so im not sending out files with an issue. Ill try to tonight after work (sorry wait one more day ). Worse case my spacing measurements are off by a mm. Mating hole size board to board are 1.2mm to fit 1mm/18 gauge solid
core copper wire.

Assuming you get the spacing right, what do you plan to use for the five leads going to the unit's board? Is that the 18 gauge solid core wire? If yes, I wonder if you've figured a convenient way to attach them to the adapter PCB for soldering. Unless you're using some PCB mount header pin type that snaps onto the board or something similar, I assume keeping attached for soldering five terminals to each of the boards makes the recapping very laborious.

The solder holes on the fluke are larger to accompany the original caps, if i remember not all of the ground lugs are connected to ground so its universal to keep all the mounting holes filled or not. For a one and done project the extra time to install is fine, i will try 1mm headers and show if it works. After thinking about it I will also make a spacer pcb file with no copper layer, just the drill holes. Could just remove the layer files and reorder but it won't take long, ill add some overlay info. You could stack the pcb standoffs and solder the mounting leads if using solid wire to keep em more straight. Copper is flexible and im sure there's a way to pinch them in or just clip extra lead length after install. Ill really try to reply tonight with an update, maybe quick video. I found some 3mm adhesive trips at work im gonna use as a spacer for now.

[Rax]

The solder holes on the fluke are larger to accompany the original caps, if i remember not all of the ground lugs are connected to ground so its universal to keep all the mounting holes filled or not.

That's right - see pic below - and to me using a bit of insulated wire to connect the ones needing it is fine. What's a bit more messy is cleaning the board after soldering, given the conformal coating which gets charred by the soldering iron. But I feel the work is good and will be long lasting.

[bastl_r]

Well, i suppose if you wanted to pick out 3 skinny/tall capacitors you could parallel them for lower ESR than the original capacitor and fit them on the pcb size.

The ESR will only play a subordinate role here. I therefore see no need to use special electrolytic capacitors. At most some with a view to a longer service life.

bastl_r

[Vertamps]

*New PCB links Below

[Vertamps]

Here i have uploaded pcb mod files of your choosing. Both 1mm and 1.2mm mating holes, a Wide hole cutout spacer that clears all solder pads, one tight fit spacer board with 1.2mm holes.
I am fine with sticky pad spacers i used in trial, however i will tack on each of my boards for my next order. If using JLC PCB just drop the selected zip file, select 10 board qty and your good to go.
Let me know of any issue with the link. -William
https://www.dropbox.com/scl/fo/nz4almtqw9p33j7ymv4mh/ADGSwEl5e5UdivuPPLuvtyQ?rlkey=6nn4h3je2gnniqhheckspqx6j&st=61lgvxhj&dl=0

[bastl_r]

Oh man  "head --> table"

The zero points are shifted. However, the deviation matches the range.
7.998mV in the 10V; 79.97mV in the 100V; and ~800mV in the 1000V range so I suspect a common error. The offset then also runs through all stages with the same deviation.

Wen i was looking for a video disassembling the switches i found the repair of defpom where he repaired a switch shaft.
Later in bed I remembered what else can happen with a broken switch shaft 
And yes the shaft of the 4th digit ist totally destroyed.
Unfortunately, the latching mechanism is firmly screwed to the device housing and suggests a correctly functioning switch, whereby the contacts set to 8 do not move any further...
Defpom has uploaded a print file for a new shaft piece to thingiverse, but unfortunately it doesn't quite work with our printer. But that's not a problem. At least the error has been found.
I will now replace all the shafts because they are all cracked
Now I'll solder the old UA709 and the old Q39 back in and see if I can manage without recalibration. I didn't have to replace the electrolytic capacitors I've replaced so far. They were all still within the specified capacitance range, even though some of them were a bit high-impedance.

Regards

[TheDefpom]

Oh man  "head --> table"

The zero points are shifted. However, the deviation matches the range.
7.998mV in the 10V; 79.97mV in the 100V; and ~800mV in the 1000V range so I suspect a common error. The offset then also runs through all stages with the same deviation.

Wen i was looking for a video disassembling the switches i found the repair of defpom where he repaired a switch shaft.
Later in bed I remembered what else can happen with a broken switch shaft 
And yes the shaft of the 4th digit ist totally destroyed.
Unfortunately, the latching mechanism is firmly screwed to the device housing and suggests a correctly functioning switch, whereby the contacts set to 8 do not move any further...
Defpom has uploaded a print file for a new shaft piece to thingiverse, but unfortunately it doesn't quite work with our printer. But that's not a problem. At least the error has been found.
I will now replace all the shafts because they are all cracked
Now I'll solder the old UA709 and the old Q39 back in and see if I can manage without recalibration. I didn't have to replace the electrolytic capacitors I've replaced so far. They were all still within the specified capacitance range, even though some of them were a bit high-impedance.

Regards

The downloadable file is an STL, which you can drag into Cura for example and have it use your normal print settings and chosen material configuration, so you should be able to print it out like anything else you normally do, I do recommend something like PLA+ rather than just PLA as it will be stronger, unless you have something else that performs well.