ACA v1.6 problems.
Hello everybody. Tim in Denver. I just finished building the ACA v1.6 after it plays for a few minutes starts turning off then after a couple seconds back on then off again repeat. Is there anybody in Denver area that would be willing to look at it, help me out. I am not a tech just like good sound.
Hello everybody. Tim in Denver. I just finished building the ACA v1.6 after it plays for a few minutes starts turning off then after a couple seconds back on then off again repeat. Is there anybody in Denver area that would be willing to look at it, help me out. I am not a tech just like good sound.
Quick thought... are you using the correct power supply?
What you describe could be a symptom of the power cycling on and off.
Bring it by, we'll figure it out. 
Sorry for the wait, I've got a pretty busy week !
Here what I got :
Unsolder one end of R7, measure its resistance. (Should be 10k) : 10K
Next unsolder one end of R5, measure its resistance. (Should be 100r) : 100r
Leave them out of circuit for the next test.
Now put the Black meter lead on the ground wire.
Measure the resistance from ground to S : 520r
then from ground to G : 0r
and again from ground to D of Q2 : 520r
I will admit I am still having some difficulty reconciling some of the measurements. I expect it will become clear once we know what the fault is...
That is a very odd result.
There should be no connection from ground to Q2 G with R5 lifted. Only explanation is a solder blob or wire strand shorting to the heatsink?
There is little point trying anything else, It Is time to take it apart and inspect the rear of the board. Then do some out of circuit checks on the 'transistors'.
Alan
That is a very odd result.
There should be no connection from ground to Q2 G with R5 lifted. Only explanation is a solder blob or wire strand shorting to the heatsink?
There is little point trying anything else, It Is time to take it apart and inspect the rear of the board. Then do some out of circuit checks on the 'transistors'.
Alan
Hi,
I'm a first-time builder and have a question I'm hoping can be answered here. Has anyone had an issue where a potentiometer will not bias? One of the potentiometers displays on my dmm as 25.5v no matter where I set it. The other one behaves as expected. Needless to say, the amp isn't working. Powers up, leds light but no audio output. Not a surprise given my lack of soldering skills.
Thanks,
Gary
I'm a first-time builder and have a question I'm hoping can be answered here. Has anyone had an issue where a potentiometer will not bias? One of the potentiometers displays on my dmm as 25.5v no matter where I set it. The other one behaves as expected. Needless to say, the amp isn't working. Powers up, leds light but no audio output. Not a surprise given my lack of soldering skills.
Thanks,
Gary
You could check that the pot is adjusting resistance with power off and your DMM probing the relevant connections. That should rule in/out whether you've flowed solder on to the pot's connections satisfactorily.
Gary,
You have probably answered your own question, 90% chance it is a poor solder connection.
First make sure all the components are in their correct place, easy to mix up some resistors. Make sure that Q3 and Q4 are the right way round and that the capacitors are the right way round too.
If you post some good pictures we can take a look as well.
Alan
Edit, where do you get 25.5 volts from? What power supply are you using? Please measure the voltage at the V+ pad on the board to the GND pad.
You have probably answered your own question, 90% chance it is a poor solder connection.
First make sure all the components are in their correct place, easy to mix up some resistors. Make sure that Q3 and Q4 are the right way round and that the capacitors are the right way round too.
If you post some good pictures we can take a look as well.
Alan
Edit, where do you get 25.5 volts from? What power supply are you using? Please measure the voltage at the V+ pad on the board to the GND pad.
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I'll check all that you mention. The voltage measured is actually 20.5. I should also mention that I did search the thread before posting. I found that someone else had the same problem. What resolved the issue for him was not applicable to my amp. I'm sure I soldered something badly. In addition to what you suggest I'm going to try reflowing anything that looks suspicious. I have to say, this feels like a short somewhere. It's definitely down to something I've done wrong. Thanks for the response.
Thanks to the help here I've discovered the problem with that potentiometer. Somehow one of the legs got broken off after insertion. The leg is completely missing in action. Careless handling on my part, no doubt. It wouldn't surprise if I've inadvertently caused other damage as well. I'm considering simply purchasing another parts kit. Thanks again to all who responded.