| Electronics > Repair |
| (FIXED) Keithley 225 (current source) repair |
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| Vgkid:
Good job :-+ |
| motocoder:
--- Quote from: cncjerry on June 08, 2015, 03:56:26 am ---https://www.westfloridacomponents. They had the mosfets I needed for my 228. I only dealt with them that one time. I'm thinking I'll just buy another 228 though Keithley made a lot of current and voltage sources. Glad tee someone other than me stick with a difficult restoration. --- End quote --- They do have some interesting, older, parts, but I don't see any match for the challenging parts in that 225. I did find that Central Semiconductor has a part, 2N3585, which is pretty much an exact match for the output transistors. Mouser carries those if you need them, although I think the NTE parts I'm using are fine. It's really just Q104 that is a challenge. Even now that I have it working, it is the one part that heats up quite a bit under operation - up to 80C when I was watching it, and that was with the case open. I don't think I'll be buying anything else from Keithley. This thing is a somewhat fragile design. Compared to the HP precision and Power Designs power supplies, it doesn't stack up very well. |
| motocoder:
I've scanned in the main schematic page with my annotations. I also added some notes and a list of replacement parts that I found to work. Hopefully this will save someone some time. I have a higher res version in Photoshop format, with the annotations on separate layers. However, it is too big to upload here. PM me if you want a copy. |
| TiN:
I would be happy to rehost it on my site in Keithley section, if you may upload here. :-+ |
| motocoder:
--- Quote from: TiN on June 09, 2015, 12:29:37 pm ---I would be happy to rehost it on my site in Keithley section, if you may upload here. :-+ --- End quote --- Thanks. They are in a folder called Keithley_225. |
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