It’s not a MMU problem. To be precise i installed new ram on bank 2. The diag cartridge shows 1MB, all connections fine but when testing i have these errors. So (because perhaps some chip were solded with too hot air) i’m quite sure I destroyed one of them. Because soldering there SOJ ram are really...

Hi there.
I have a bad ram ship on my ATARI STF motherboard C103414-001 REV 1 When I use the test cartridge here is the screen Do you know how to detect the faulty RAM ?

Any help welcome.

I finally found the culprit : the 1uF tantal cap was dead

Very interesting, but still stuck ...

I tested all resistors R10, R11, R12, R13, R14 et R15 and they are fine.
Q3 is also fine.

Output voltages are still 6.28V and 14.23V

So the only differences are Q1 and Q2 ...

What if I try to change values R13 and R14 to bring 5v back ? (newbee idea)

Slight variations in part number may have different current gains. In fact I replaced original Q2 C3040 by BU508A (ref given on the schematic) and original Q1 C2236 by 2SC1384 (ref given on the schematic) Here are the datasheets. Can you get some differencies that would make higher output voltages ...

This is odd and a difficult one. It might be because you changed the transistors. Slight variations in part number may have different current gains. Or it may be you 5v load isn't connecting properly causing the PSU to overvolt. I usually use this load board to test PSU and it is the first time I h...

Hi. I just recap an ASP34-4 power supply for my Atari 1040 STF (also found on some STEs). I followed the Exxos page and Exxos values for improvment https://exxosforum.co.uk/atari/last/psu/#ASP34 C5, C4 : 47uF 350V (33uF 350v replacement) C15, C14, C7 : 680uF 35V (330uF 35v replacement) C13 : 4700uF ...

Interesting...

Just a question...
Before the fix and after too, I still have an error playing the Printer/Joystick Port Test using the diagnostic cartridge.
Could somebody explain why as the STE now works perfectly ?

Hooray it's fixed!

The problem came from a trace probably cut (impossible to see with the naked eye) between the WD1772 and the 7406 (U305) on inverter D. Everything is back to normal.
Thank you all for your help which re-energized me and gave me some clues on how to detect this error.