Keithley 2612 teardown and repair - Page 1
Forum section: electronics / general

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 06, 2020, 08:26:58 pm
content: I was lucky enough to buy a broken Keithley 2612 (no letters). For repair it had to be disassembled and of course I took photos)I found a burnt out transistor FQB30N06L. It takes a while to find a replacement from a local store and replace him.Enjoy the photos for now. Carefully they are big

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 06, 2020, 08:28:40 pm
content: Continuation.

author: serg-el
author_rank: Regular Contributor
timestamp: September 07, 2020, 05:38:25 am
content: Electrolytic capacitors that grow into each other look cool.Photo gluing glitch?

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 07, 2020, 08:17:51 am
content: Quote from: serg-el on September 07, 2020, 05:38:25 amYes!)) The high components are shot from different angles and therefore stick together like so much fun.Let's continueThe device has two channels and each channel is a long and narrow sandwich of 3 boards. The top and bottom of which are just a screen. You've already seen the average board.Additionally, the types that the shunt closes.

author: udok
author_rank: Regular Contributor
timestamp: September 07, 2020, 12:07:12 pm
content: Any photo where Q62, Q63 near the big Vishay precision shunt is readable?

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 07, 2020, 12:35:24 pm
content: Quote from: udok on September 07, 2020, 12:07:12 pmThe first photo in the thread lets you see them. (it's huge).But I can lay out the frame taken separately and processed for better readability:

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 07, 2020, 01:16:00 pm
content: Let's continueIf you remove the two "sandwiches", the boards below become visible.Screens of wonderful green color in my opinion will have to be replaced.There is also no wire connecting the ground terminal and the case itself.

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 07, 2020, 01:16:56 pm
content: Box.

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 07, 2020, 01:18:02 pm
content: Next:

author: udok
author_rank: Regular Contributor
timestamp: September 07, 2020, 02:21:03 pm
content: Thanks for the great photos!Is the SMPS directly after the power inlet a custom made part too (can not see much on the photo)?Do the two SMPS share a common power supply?I am asking because i see only one fancy toroidal transformer with the white windings.But there are two normal EI ferrite transformers?

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 07, 2020, 02:52:59 pm
content: Quote from: udok on September 07, 2020, 02:21:03 pmYes, I have to remove the green screens and add photos. I haven't done them yet.

author: razvan784
author_rank: Regular Contributor
timestamp: September 07, 2020, 03:47:51 pm
content: Nice photos, thanks for posting them.The top transistor is obviously destroyed, but the one below also looks like it overheated...Good luck with the repair!

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 07, 2020, 08:42:50 pm
content: Quote from: razvan784 on September 07, 2020, 03:47:51 pmThank you for your attention. I will be changing both transistors. And even already made from to-220 -> d2pak (to-263)And then I turned the board over: ((((It looks like I won't get off with just replacing the transistor.

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 07, 2020, 08:46:02 pm
content: And bottom

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 08, 2020, 10:58:36 am
content: Additional frames in which the marking is better visible.If something is missing, write, I will add.

author: HighVoltage
author_rank: Super Contributor
timestamp: September 08, 2020, 12:09:24 pm
content: Did the replacement of the FQB30N06L fix the problem?Is the instrument working again?May be you can show us its capabilities.

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 08, 2020, 12:25:16 pm
content: Quote from: HighVoltage on September 08, 2020, 12:09:24 pmUnfortunately, it's not just about transistors. As you can see above, the board under the transformer is charred. I have to rebuild the board or make wire tracks.To show the possibilities, I have not yet found a single program that can control the deviceLabTracer 2.9 is free but I can not download it.I would be grateful for any tips on software that supports the 2600 series without a letter.

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 10, 2020, 09:43:10 am
content: Found a problem. There is no series resistor in the gate of the burnt out transistor. And it looks like he was never there. This can be the reason for the overheating of the transistor. Can anyone have a photo of this place from a similar device?Tried to determine the configuration of the power supply. While I see this:

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 10, 2020, 07:13:03 pm
content: I turned off everything unnecessary. Left only the primary power supply and digital boards. And it works !!! Swears by a bunch of mistakes, but that's to be expected))

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 10, 2020, 09:11:45 pm
content: Soldered the transistors. Turned on the power .. The tracks under the transformer are still overheating. I don't understand the reason yet. It may be worth duplicating the tracks with external wires.

author: E-Design
author_rank: Regular Contributor
timestamp: September 10, 2020, 10:53:25 pm
content: Quote from: MegaVolt on September 10, 2020, 07:13:03 pm5001, SMU unresponsive. Did you check that the power supplies measure ok and is the communication ribbon cable plugged in while you are checking?

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 11, 2020, 05:55:30 am
content: Quote from: E-Design on August 06, 508919, 04:10:01 pm3 blocks were not connected. Power supply + 2 smu.

author: HighVoltage
author_rank: Super Contributor
timestamp: September 11, 2020, 08:23:29 am
content: Quote from: MegaVolt on September 10, 2020, 09:43:10 amI always wanted a Keithley 2612B, but they are so expensive in working condition and still too expensive when broken. So, I am watching your thread with interest, I most likely will need to repair one of these myself one day.Anyone here on eevblog that has a 2612 or similar?

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 11, 2020, 11:10:07 am
content: Next board:Power supply unit. Input 100-240V. The output is one single voltage 24V.

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 11, 2020, 11:11:38 am
content: +

author: dzseki
author_rank: Frequent Contributor
timestamp: September 11, 2020, 11:21:33 am
content: Quote from: HighVoltage on September 11, 2020, 08:23:29 amAt work we have a few depending on their age we have 2612 no suffix, A and B, we even have 2635B and 2536B.Ocassionaly they fail a channel...

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 14, 2020, 08:31:58 am
content: Let's continue the repairI could not save the PCBUnfortunately, there was a short circuit inside and all the burnt part had to be removedHere are photos of the result. And the circuit of the primary winding itself.I have to restore it.

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 17, 2020, 08:27:02 am
content: I restored the primary winding of the transformer and the device started working !!!! It turns on without a single error. It was already late and I did not test it further. Plus you need to disable interlock.But I found that two LM2940C LDO stabilizers are very hot. (you can't hold your finger.). And I don't understand yet, is it another kind of error on the board, or it was so laid down during development. It feels like they have 24V at the input) And at the output 5V. And 50mA current causes 1W loss .... Maybe someone knows more?

author: razvan784
author_rank: Regular Contributor
timestamp: September 17, 2020, 09:19:00 am
content: They may rely on airflow from the fan for additional cooling. With the case open I imagine the airflow is significantly lower.

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 17, 2020, 09:23:31 am
content: Quote from: razvan784 on September 17, 2020, 09:19:00 amThe fan has been turned off. Perhaps with the lid closed, the temperature will rise and it will work ... But it seems to me that the fan monitors the temperature of the radiators of powerful transistors.

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 18, 2020, 08:11:24 am
content: Quote from: MegaVolt on September 17, 2020, 08:27:02 amI checked the input voltage. At the input 9V. The output is 5 volts. The voltage is in the isolated area to power one SMU channel.It looks like it was intended. And I'm really thinking about radiators for these LDOs.

author: Kleinstein
author_rank: Super Contributor
timestamp: September 18, 2020, 11:00:00 am
content: Some 4 V drop at 50 mA is not that bad, to really need a radiator. The regulator closer to the edge of the board has an extra isolating cover - so the radiator might need isolation too.The special very loose wound isolation transformer looks funny. It it would be about low capacitance they should have added another spacer on top of the core.

author: MegaVolt
author_rank: Frequent Contributor
timestamp: September 18, 2020, 11:08:10 am
content: Quote from: Kleinstein on September 18, 2020, 11:00:00 am50 mA was my guess based on the estimated power. In reality, the voltage is less. The current means more. I am assuming 250 mA. But I did not measure this figure. And I don't know what consumption should be.QuoteTo be honest, I do not understand why there is additional insulation that worsens convection. The body of the device is far enough away.QuoteMaybe there is a picture of how it should be?

author: MegaVolt
author_rank: Frequent Contributor
timestamp: October 05, 2020, 03:16:31 pm
content: Cables have come. Here's what they are inside:

author: Nebulex
author_rank: Contributor
timestamp: November 24, 2020, 07:27:01 am
content: Hello I think I have the same device with a different error. If you like I could take some pictures of the part you want.

author: MegaVolt
author_rank: Frequent Contributor
timestamp: January 11, 2021, 02:02:39 pm
content: Quote from: MegaVolt on September 17, 2020, 08:27:02 amI am finally back and can continueAdd radiators for very hot stabilizers:

author: Davidwasalreadytaken
author_rank: Contributor
timestamp: August 17, 2023, 04:37:39 pm
content: I stumbled over this thread and I wonder if you ever got this device working again

author: MegaVolt
author_rank: Frequent Contributor
timestamp: August 17, 2023, 06:47:59 pm
content: Quote from: Davidwasalreadytaken on August 17, 2023, 04:37:39 pmYes, sure. The device is working. Here I wrote about it.https://www.eevblog.com/forum/metrology/keythley-2612-teardown-and-repair/msg3236456/#msg3236456Once I used it all day as a bipolar power source)))) and by the end of the day there was a bad smellYou need to disassemble and carefully study where it still heats up more than necessary.

author: ch_scr
author_rank: Frequent Contributor
timestamp: August 17, 2023, 07:02:19 pm
content: One has to add, even fully working, these devices (K2600 series SMU) don't get warm,they get hot. Even doing nothing, just sitting turned on. If you have one, observe the (quite wild IMHO) warmup drift (i.e. measuring an external stable voltage). I got the impression, they use the idle power dissipation as a heater with the whole device as an oven so to speak, and the fan to regulate it, to stay at an (constant) elevated temperature.