Keithley 2410 repair - Page 1
Forum section: electronics / repair

author: johnbaker26
author_rank: Contributor
timestamp: April 06, 2025, 12:02:32 pm
content: Hello, does anyone have the schematics for a Keithley 2410? I seen in an old postherea partial schematic that I didn't see in the service manual.The problem I'm troubleshooting only presents itself when I switch to the highest KV range when sourcing voltage. When I enable the output, my trusty Fluke 289B shows about 5V high. So I source something like 250V and I show about 255V on the Fluke. The meter shows way less on the VFD like 235. And when I disable the output, I have a residual 5V present even though the output is disabled. If I change the range selection back down to anything smaller than the highest range, the residual 5V without the output enabled goes away.I'm guessing an opamp like a DG444DY does the range switching? Just a ton of them and not sure which one. I tried heating up various op amps when the residual 5V is present. The only change on the Fluke doing the output measurement was U234. I believe looking at the AD795JR (U234) datasheet this is normal reaction since it seems to be quite temperature dependant. Out of desperation I did replace it and the DG444DY (U406) next to it. Problem persists. The incorrect reading at higher voltages I think might be the TF-245 resistor network. I did remove it and tested it. Its strange all the readings on the TF-245 are right on except for the last four pins which are open. Looking at the PCB board with it removed it seems only one of the last 4 are used? The pins in question (last 4) are 7,8 and 15,16. They read open if I use the Keithley 2000 schematic values. I ordered a new one from Tektronix USA, though it will be a few weeks before it gets all the way to me on the other side of the world. I believe this only is for the measurement side and isn't used for generating precise voltages?Ohh I did check the voltage rails per the service manual. They seem to all be fine. I also replaced all the electrolytic caps though there was no sign of leakage.Video of issuehttps://youtu.be/lAzk5JPkYhs?feature=sharedThanks for any help!

author: johnbaker26
author_rank: Contributor
timestamp: April 07, 2025, 03:00:40 am
content: A bit more testing seems the voltage output and measurement both get stuck when changing with output enabled sometimes. This clears with a power cycle. Now suspecting the AD7489 DACs might be a fault here.

author: marcumr
author_rank: Contributor
timestamp: April 07, 2025, 05:25:48 am
content: Hi.Have you had any problems ordering the TF-245 from Tektronis/Kitheliy, I have been trying to get one to repair my K2000 for many years.thanks in advance.

author: johnbaker26
author_rank: Contributor
timestamp: April 07, 2025, 03:40:41 pm
content: Yes but because I live in Asia. I believe you can only get them Tektronix USA now. I had to have a friend take shipment and forward to me. There is a bit of a process with setting up an account using my best American accent but what's the alternative?

author: marcumr
author_rank: Contributor
timestamp: April 08, 2025, 06:43:03 am
content: OK, thanks I will try to place the order from Tektronix USA

author: johnbaker26
author_rank: Contributor
timestamp: April 23, 2025, 05:09:57 am
content: Well turns out the problem was me the user haha. There is a setting inside the config for output off. On the 2400 it's default is normal but on the 2410 it's default is guard. I had done a reset of the unit to put everything into default to rule this out but didn't realize the 2410 is different. Once I put it back to normal and calibrated it everything is fine.

author: picburner
author_rank: Frequent Contributor
timestamp: April 23, 2025, 07:20:20 am
content: @ marcumrIf you live in Italy, for Tektronix/Keithley spare parts, you have to gohere.At least until a few years ago when I also bought the TF-245 and other things.At first I went to Tektronix UK and Tektronix DE but they no longer sold to private individuals and they gave me the address of their distributor in the link.P.S. you have to be very precise in your request: they want all the component ID /device name /serial codes etc.

author: johnbaker26
author_rank: Contributor
timestamp: April 24, 2025, 05:13:16 am
content: I have a spare TF-245 unused now. 40 dollars shipped. It will be from Thailand so please be patient.

author: marcumr
author_rank: Contributor
timestamp: April 24, 2025, 04:42:47 pm
content: #Johnbaker26I'll take it very gladly thank you.#PicburnerThanks for the information I will try to order the ‘Display lens’ from them.