| previous by date | index | next by date |
| previous in topic | topic list | next in topic |
Very good advice as usual, Bob, thanks. Will do that right after the current KLM-367 INH/DATA/P2x check and I am also trying to fit a jumper/socket for the large GND cable, because it is a lot of trouble to desolder and re-solder that cable when troubleshooting. If that works, I'll put some pics in the files section.
I checked ∗all∗ the IC18 connections after building the matrix of Pots vs Opamp Pin for the CVs as shown in the document I linked to earlier based on Johannes's instructions - no issue, no apparent short (pin 7 & 8 or 6 & 8 do show some resistance values), removed the chip, cleaned the area around and the socket and reflowed the latter.
This implies a faulty 4501 @ IC18? Will have to try.
I did try a swap of the 4501s int he front panel, and reverted back until I can pinpoint rationally and understand myself where the issue is since I've got only two new ones. I do have 2 old stock ones too, but if I make sure the lines are fine first, then I'll be more confident to make proper swaps, knowing if I'm swapping a good one for a faulty one.
Examining KLM-367 again yesterday, guess what? Greenish residue on all the 6 electrolyticcaps on the left side of the board.... Either the caps themselves leaked or the battery alkali attacked them. The caps on the right seem fine as I examined everything with Macro photos and zooming in.
Couldn't find enough proper caps in my Grade A salvage box, so had to dive into the salvage circuits. Found some great Elna and Nichicon caps in DVD players that people threw away next to my door. The Elna didn't fit cap-wise, so the Nichicon were usable.
Re-capped using 4 Nichicons and 2 caps from a previous salvaging operation, of a more dubious brand. Was happy to have the Nichicons for the crystal and near the Opamps, and used the other ones for the power rails.
Tested continuity for ∗all∗ of these connections and ensured they were all good. It looks to me that this is a must-do because on following the lines, these caps deal with a lots of the important chips and traces, including CPU-P1, etc... If these caps are mis-behaving, then a lot of issues can occur on the board. I have hope here.
Thanks a lot for all the valuable advice, it helps a lot.
Breakfast, then more troubleshooting/hacking.
Yash