Hello everyone! back in '20 I built an amp which has served me well, I decided to add a volume pot. I added the pot as shown in this diagram and pictures. I connected only one channel at first, it seemed to be working fine, then my amp died!
The amp is this one: https://www.3e-audio.com/amplifier-kits/tpa3251-2ch-140w. The fault light is on now 100% of the time with nothing connected. I don't know if I shorted the input to the heatsink or overloaded it by only inputting one channel.
So, I had a little TPA3116 amp board, I took the time to set it all up as shown in the pictures. I turned it on, the light came on, no output. I had ANOTHER one of these TPA3116 boards, I eliminated the volume POT and hooked it up, and it works. I tried the first one, and nope, its dead.
Something about this pot circuit is killing my amps. I took the meter to it, there is no continuity between any leads ground/signal or L/R. Continuity is present between all grounds. When turned up all the way, there is continuity across the pot at 2.2 ohms on each channel, but not between them.
Are the caps in the right places? Previous advice was to have the input caps on both sides of the pot connected with the negatives to the pot, is that correct? Could a bad pot be causing my problems?
The amp is this one: https://www.3e-audio.com/amplifier-kits/tpa3251-2ch-140w. The fault light is on now 100% of the time with nothing connected. I don't know if I shorted the input to the heatsink or overloaded it by only inputting one channel.
So, I had a little TPA3116 amp board, I took the time to set it all up as shown in the pictures. I turned it on, the light came on, no output. I had ANOTHER one of these TPA3116 boards, I eliminated the volume POT and hooked it up, and it works. I tried the first one, and nope, its dead.
Something about this pot circuit is killing my amps. I took the meter to it, there is no continuity between any leads ground/signal or L/R. Continuity is present between all grounds. When turned up all the way, there is continuity across the pot at 2.2 ohms on each channel, but not between them.
Are the caps in the right places? Previous advice was to have the input caps on both sides of the pot connected with the negatives to the pot, is that correct? Could a bad pot be causing my problems?
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Sorry, I can't help, but can i ask what the pcb the pot is on?
I have a pot that I have bodged a perf board for, but it is a bit messy.
That looks tidy. What does one call it?
I have a pot that I have bodged a perf board for, but it is a bit messy.
That looks tidy. What does one call it?
It has spacing for ALPS R27 pots, no idea if it would fit the legs on others.
Strange note, after testing extensively with my meter, I decided to try again, hooked it up to the working TPA3116D2, and it works just fine.
HOW DID I KILL THESE OTHER TWO BOARDS!?!? Oh well.
Here is an eBay link that includes a probably fake ALPS, and an aliexpress link for just the boards. I recently used this aliexpress seller and received the boards within 12 days.
https://a.aliexpress.com/_mPKLxi6
https://www.ebay.com/itm/1335581965...0CFEdvPwR5u&var=&widget_ver=artemis&media=SMS
Stupid question, but yo checked the pcb for shorts before stuffing, right?
And thanks loads for those links.
Your timing was great. I knew there had to be a better way than what I did.
I have a tkd 2CP-601. I will look both of the specs up.
And thanks loads for those links.
Your timing was great. I knew there had to be a better way than what I did.
I have a tkd 2CP-601. I will look both of the specs up.
I've tested it and don't have any shorts to ground or between the channels, and it's working fine now. I think I killed m my God board either by overloading it by only hooking up one channel signal but both grounds or shorted something in the mess I had in the case. I think the first TPA3116D2 board was DOA ($10 EBAY special).
The only difference is there is no DC ground connection to the input of the amp.
That should be part of the amp and likely the blocking cap as well. I don't know
what killed the amp but I find it very hard to believe the volume pot did it. Are
you sure you made no changes to the ouput of the amps? I have some TPA3116
amps that do NOT have DC blocking caps to the speakers. Sonically this is of NO
consequence BUT it means there is 1/2 the supply voltage to the speakers. Since
it's balanced BOTH the + and - are at 1/2 supply so the net voltage to the speaker
is 0 with no signal. However, shorting either speaker lead to ground OR power
could damage it.
G²
Is the TPA3251 the same way with no blocking caps?
The "good" board I killed was the high regarded 3e Audio TP3251 based unit, very quiet, no hiss or other distortions. It's possible I shorted the outputs somehow during A/B testing. My binding posts are pretty close together.
The TPA3116 board I was extremely careful and the outputs are far from each other, so I really think that one was DOA.
If you have a 3251 that still works you can confirm with a Volt meter and verifying
the output DC value of the + & - relative to ground. I have no way of knowing how
it was designed without seeing the unit or the schematic. Output blocking caps are
at the discetion of the designer. They ARE necessary if attempting to reference to
ground. Output caps are NOT necessary if just using the + & - outputs to the
speaker.
G²
I have another board from the same manufacturer. I'm totally rewiring the amp and switching to banana plugs because I clearly can't be trusted with binding posts. Once that is done I'll test it as you indicate. Question, is the danger only when the unit is outputting, or anytime it's on?
The 1/2 power supply on is active all the time power is on. If you
measure 0 Volts then there is no issue directly IF there is no signal
playing. If shorting DC blocked outputs into a short it might fail
with signal. Bottom line ? Don't short speaker wires while running.
I've observed this rule for over 40 years and have not had a single
failure.
G²
I didn't do it on purpose! I'll just acknowledge my ham handedness and power all the way down before messing with things.
I KNOW you didn't. Nobody does but it happens to all. All I said was I stopped
messing with speaker wire while things are running and have had no more
problems. I used to repair things for a living and it seemed silly to cause MORE
work by being "ham handed".
G²