02-08-2014, 08:25 PM
OK, I eventually took over that thing as even when Tim and I called each other on Skype it proved to be too much to do remotely.
It came in the mail today and in two hrs after that (well, about 1hr work) it sang just fine.
Then there were additional problem the last of which I just fixed.
Most problems initially occured due to the PCB being phenolic paper (FR2) and the traces on those do not adhere to the board well. So when a heavy part is soldered and then subjected to vibration the solder joint will unglue and then the trace will eventually snap and the solder joint will be separate from the trace.
So, in the order of having been discovered:
1. A black wire (-3V) came off. But that could be a result of troubleshooting.
2. A trasnsformer pin's solder joint got separated from the trace.
3. A large resistor 's pin did the same.
4. -3V pin (the one with the wire broken) did the same.
5. The electrolytic cap's minus pin did the same (could be the result of troubleshooting).
All was fixed by ceaning the soldermask off the traces and then flooding it with solder to join with the pin.
I also soldered over a couple of suspicious places.
6. Most wires coming to the board were on the verge of breaking off, so I cut them off, stripped and re-soldered.
7. So was one of the battery holder contacts, same thing done.
Others:
8. The speed pot did not regulate speed, it would be either maximum or none. Upon closer look the pot was exactly that - either close (in the max speed position) or fully open. Surprisingly, the opposite pin (unused to that point) behaved fine and smoothly regulated the resistance fro 0 to 100 Ohm as it should. This made me suspect the other pin separate from the resistive element.
I simply resoldered the wire to the unused pin, and now it regulates speed fine, only in the opposite direction from what"s written, "slow" is not fast and "fast" is slow.
9. The volume pot was scratchy, opened it, cleaned the element, put some deoxit in and a dab of deoxit plus lithium grease. Works fine now.
10. After I thought I was done a couple of times the motor barely moved and the amp buzzed unhappily. I suspected the power switch. I took off the disk, and it was very dirty and when pressed in a bit the symptom disappeared. Cleaned it with alcohol, then applied Deoxit; works fine now.
11. The last one, once in a while the volume disapeared, the amp only playing a little at the maximum volume. Looked at it, saw the quick connect tht goes to the adapter move a lot. First thought the whole pin moves but then realized that luckily it was just a quick connect - when touched, the symptom appeared or disapeared; so I took it off, compressed it a bit, pushed it on again. Plays fine now.
So if no other surprises show up, it is ready to ship back.
PS. I think the motor, from the way it looks (there are some thin wires separating together with someone'os hair.....) is on its last leg.
Tim,
I need you to get me a shipping label and for the box twice the size you used - I cannot risk sending it back in it. We got lucky once...the second time it might not work so well.
Whew!
It came in the mail today and in two hrs after that (well, about 1hr work) it sang just fine.
Then there were additional problem the last of which I just fixed.
Most problems initially occured due to the PCB being phenolic paper (FR2) and the traces on those do not adhere to the board well. So when a heavy part is soldered and then subjected to vibration the solder joint will unglue and then the trace will eventually snap and the solder joint will be separate from the trace.
So, in the order of having been discovered:
1. A black wire (-3V) came off. But that could be a result of troubleshooting.
2. A trasnsformer pin's solder joint got separated from the trace.
3. A large resistor 's pin did the same.
4. -3V pin (the one with the wire broken) did the same.
5. The electrolytic cap's minus pin did the same (could be the result of troubleshooting).
All was fixed by ceaning the soldermask off the traces and then flooding it with solder to join with the pin.
I also soldered over a couple of suspicious places.
6. Most wires coming to the board were on the verge of breaking off, so I cut them off, stripped and re-soldered.
7. So was one of the battery holder contacts, same thing done.
Others:
8. The speed pot did not regulate speed, it would be either maximum or none. Upon closer look the pot was exactly that - either close (in the max speed position) or fully open. Surprisingly, the opposite pin (unused to that point) behaved fine and smoothly regulated the resistance fro 0 to 100 Ohm as it should. This made me suspect the other pin separate from the resistive element.
I simply resoldered the wire to the unused pin, and now it regulates speed fine, only in the opposite direction from what"s written, "slow" is not fast and "fast" is slow.
9. The volume pot was scratchy, opened it, cleaned the element, put some deoxit in and a dab of deoxit plus lithium grease. Works fine now.
10. After I thought I was done a couple of times the motor barely moved and the amp buzzed unhappily. I suspected the power switch. I took off the disk, and it was very dirty and when pressed in a bit the symptom disappeared. Cleaned it with alcohol, then applied Deoxit; works fine now.
11. The last one, once in a while the volume disapeared, the amp only playing a little at the maximum volume. Looked at it, saw the quick connect tht goes to the adapter move a lot. First thought the whole pin moves but then realized that luckily it was just a quick connect - when touched, the symptom appeared or disapeared; so I took it off, compressed it a bit, pushed it on again. Plays fine now.
So if no other surprises show up, it is ready to ship back.
PS. I think the motor, from the way it looks (there are some thin wires separating together with someone'os hair.....) is on its last leg.
Tim,
I need you to get me a shipping label and for the box twice the size you used - I cannot risk sending it back in it. We got lucky once...the second time it might not work so well.
Whew!
