Other ADA Gear > Step On It!

Broken MC-1 - Where to send for Repair?

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MarshallJMP:
Well i could fix it for you but then you'll have to ship it to belgium.Since you have the equipment that would be a bit stupid.Let's try to fix trough this topic or email.So first check the 5V,starting from the dc adaptor input trough a diode (1N400x),then a cap into a 7805 regulator.If you have 5V at the output of the 7805 then the next thing to check is if you have a clock signal on pin 6 of the Z80 µcontroller.I need to check it out but i think it works on 2MHz.I have the pcb of MC-1 here and it seems it has a 4MHz crystal (buffered by a 74HC04 (hex inverter) pin 1 and 2) going to pin 3 of a 74LS74 (D flip flop),there it will be devided by 2 so you will have 2MHz on pin 5 of the 74LS74 then it goes to pin 3 of the 74HC04 and pin  4  goes to pin 6 of the Z80.Also make sure sure pin 26 (reset) is high (5V).
I hope this makes sence,if not let me know.BTW the 74hc04 is on the right side of the crystal,the LS74 on the left side.

Dante:
MJMP to the rescue!!! (again)

rnolan:

--- Quote from: Dante on September 10, 2015, 04:12:45 PM ---MJMP to the rescue!!! (again)

--- End quote ---
+1  :thumb-up: :bow:

MarshallJMP:
 ::)

chrismilne:
Did you have any luck?  I just tried to fire mine up after many, many years and no power...

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