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The circuit is described here: https://forum.vcfed.org/index.php?threads/next-400dpi-laser-printer-restoration.1242501/page-4#post-1316015 How is the voltage on C156? Do you have the real fuser lamp connected and does it turn on (and does the temperature sensor report the rise in temperature)...

Interesting project @JimDrew , I hope you succeed. My KIM-1's current draw was about 500-700 mA with all the ICs in. The large ICs U1-U3 and the display do consume a bit of power

You're right, but it's also like finding a needle in a haystack. Which part of the circuit (on this board alone) could cause issues with blanking? I removed the board and will try to find bad switches or solder cracks

I don't get it, this is with both horizontal sweep settings at the same position, IC 505 pins 15 + 12 bad board good board why does it look so different? I think I'll quit here... it's taking away too much time from other projects and also above my capabilities

The ZAmp deviates by ~100mV on the faulty board, where as it stays fairly close to 0.63 V when switching from A / INTEN Since the fault follows the board I can probably eliminate the PEF-560 board (I hope). I also noticed that my 5 V supply is off on both scopes. On the good one it's around...

You have to measure the supply voltage of the ICs on the board.. There's a difference between TTL and CMOS logic levels. https://learn.sparkfun.com/tutorials/logic-levels/all

/FSRD is an active low signal... if never goes low there is a problem on the logic board

Does your lamp get hot then when you plug it in? Are you sure it's the full AC current you're seeing and not some measuring quirk? https://forum.vcfed.org/index.php?attachments/1683839618898-png.1257321/ From what I understand RL101 is normally closed but Q101 outputs the AC current based...

It does work correctly if it twist it on power up. So either the spindle circuitry has become weak (if such a thing even exists) or it developed stiction. If it's an proprietary part problem or stiction it's end of the line, I guess

Making a note here that this thing I already repaired twice refuses to work AGAIN, flashing code E "no hall transitions during spin-up" and now needs a twist to spin up. Whoever thinks of seriously using one in their vintage systems better stick with Seagates or NEC drives

This was (or is) an additional issue. The problem I described where it would execute the debug board code even though DB was off, eventually went away while handling and flexing the board, or taking an IC in and out of its socket, not sure what did it in the end. I made a mental note about it...

Sorry, pin 13 of the CPU (AB4) Tests 0, 1, 2 (2 only showing the blinking LED of course) run fine without the -002 chip, they run also run fine with the -003 inserted in any position and they don't run anymore with the -002 in any position U2 or U3 I think it has had its last hurrah in the...

U1-U3 were socketed from factory on my board. I haven't found the issue yet. I don't understand it, with U2 inserted there is AB4, pin 8 of 6502 with too low signal levels. If it has a signal resembling data or not is random on each RS press (sometimes it's just a flat line at 1.5-ish Volts)...

Unfortunately I don't have any devices with a 20mA current loop terminal interface... It's getting worse again. I checked the first page of each listing, where the addresses from U3 are as attached and U2 was completely fine. I then moved on to the EPROM location 0C00 and 0E00. Apart from the...

Excuse, but how to attach a video output to the KIM-1? Is this a serial terminal type application or analog video? I've never used a KIM-1 before this thread... If possible, you could give some pointers I could try to figure out how to adapt the code? I saw that there is a white ceramic...

Without U2, U3 the switches do what I would expect them to do. On test 2, I had a blinking LED indicating the test is running so I think there is still something wrong, either with the ICs in U2 or U3 or with the logic managing it

In this case it's not necessary, because I managed to punch in the example code from the manual and run it (I think.. still not too sure.. got 05 and FE from page 12). The keyboard and display look ok to me. In its basic functions it appears to work. But I still can't get the other tests...

The increased current draw seems to be normal, it's just the LED display. If I turn off the debug board and insert U2 and U3 I get numbers on the display and can type in stuff, but can't run the the other tests on the board. I'll study the manual to see if I can manually run something or if it...

I found out that КР565РУ2 / KR565RU2 are Intel 2102 pin compatible 1Kx1 SRAM ICs and they're still cheaply available. I ordered some from Germany and had a friend deliver them to me :) After replacing an additional IC (U11) the RAM test now completes, it looks like the soviet equivalent works...

I asked for support in the German neighbour forum, it took a while to find the problem but the drive is fixed now. Summary: - absolutely no signals from the amplifier when reading as written before - eventually, we found out that one of the input voltages (pin 1 of LM733) was too low, where it...