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is my A-160/161 broken?
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author is my A-160/161 broken?
justin3am
...and if so can I fix it myself?

Basically, the reset input on my A-160 does not work. It hasn't since I owned it but I didn't know it wasn't working until recently because... well honestly, I didn't know how to use it.

When I send the output of a step on the 161 to the reset input on the 160 it does not reset. Nor does the 160 reset when I send the any other gate or trigger to it. Anyway, I'm pretty sure it's not functioning how it's supposed to.

If it is broken, I'd like to try my hand at fixing it myself. I have a fair amount of experience with small electronic projects (CGS kits, Thingamagoops, some circuit bending) and I have a nice volt meter and oscilloscope to help me troubleshoot the problem. I'm just not sure if this is a great place to start learning how to repair electronics.

Any thoughts?
Tim Stinchcombe
justin3am wrote:
If it is broken, I'd like to try my hand at fixing it myself. I have a fair amount of experience with small electronic projects (CGS kits, Thingamagoops, some circuit bending) and I have a nice volt meter and oscilloscope to help me troubleshoot the problem. I'm just not sure if this is a great place to start learning how to repair electronics.
Well modules don't come much simpler than the 160/161, so I'd say it was an excellent place to start learning! And that you have a scope will make it even easier.

The reset input passes through two NPN transistors before reaching the 'reset' pin of the 4024 chip, so is inverted twice. It is a simple matter to trace that part of the circuit, and with an input square wave, probe the collectors of the transistors and see if the (inverted) signal makes it through. If not, then you've probably found a dead transistor. The only other thing you will need is to Google a little for the pin-out of the transistors, and a little patience! Oh, and I'd also suggest that the 'music tech DIY' sub-forum is a better place for your post! (But I'm not sure of you can change it yourself, or if you'll have to alert a moderator.)

Tim
justin3am
Thanks a bunch for the input Tim! I wasn't sure which would be the best subforum to post in. I can't move the thread now but if a mod wouldn't mind, it would be much appreciated.
sandyb
moved smile
good luck fixing your module.
justin3am
Well, I think I've tracked down the problem. The C547C NPN transistor which is fed from the reset input is not passing any voltage to it's output pin.

My problem now is finding a part to replace it. When I search for "C547C" on the Mouser site, I'm presented with a lot of options, which has me a bit overwhelmed. Perhaps this is a question for the Doepfer list?
meridic
it is probably a BC547

http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/BC547C/?qs =sGAEpiMZZMuDHCWHhuFg%252baPN204G4fBcB%2f1orK9WJoY%3d

that should do you.
justin3am
Awesome, you guys rule!
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