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TomWhitwell / Turing-Pulse-Expander

Rev 2 Turing Pulse Expander
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PULSES MKI output 4 not working, and 2+4 , 1+2 4+7 not working #7

Open antibiotico01 opened 1 year ago

antibiotico01 commented 1 year ago

Just bought a used Turing machine but it seems the PULSES module is not working very good,

outputs 1, 2, 7 and 1+2 are working, lights and pulses

but outputs 4 and 2+4 , 1+2 4+7 combinations are not working, no lights and no pulses

it seems the issue is around the 4 output?

any advice to fix it?

TomWhitwell commented 1 year ago

Hi, the schematic is here: https://www.musicthing.co.uk/Turing-Pulse-Expander/

There's not much to it, if 1+2 is working then the 4081 chip is at least partly alive + damaged 4081 couldn't explain why 4 is dead.

Check:

antibiotico01 commented 1 year ago

Dear Tom thanks a lot for the advice, I will review it !

antibiotico01 commented 1 year ago

well it seems that the soldering and the cable are ok, I´ve checked with a multimeter and everything is fine is a through hole pcb (version I) so it is not complicated, no smd components so I think it is the chip maybe

antibiotico01 commented 1 year ago

I attach a video of the behavior, 4 and 2+4 , 1+2 4+7 combinations are not working oly 1, 2, 7 and 1+2 are working although 7 seems a little bit dimmer than the others

https://user-images.githubusercontent.com/122239826/211676463-29b67d52-d481-4c8e-bb8b-814b5fdc5b01.mov

nickolaytsirkunov commented 1 year ago

I had the same problem with PULSES: outputs "1+2" and "1+2+4+7" were not working and some of the other outputs were dimmer. IC cd4081 was fault. Everything begins to work properly after I've changed IC.

antibiotico01 commented 1 year ago

THAKS A LOT! must be the chip I´ll try to change it thanks for the advice [nickolaytsirkunov]