Speaker Terminal Arcing

thunderchicken · 30th March 2015, 04:40 AM

Yeah, that's not supposed to happen. Was looking for DC offset on my 2nd board- source connected but not playing. No load. I put the black probe on the black speaker terminal and the red probe on the red speaker terminal. Couldn't get a stable reading, which I thought was odd. I pulled the probes to change the scale on my DMM, and when I placed the black probe on the second time it arced. Now my DMM probe is black and pitted.

What went wrong and how can I fix it?

gmphadte · 30th March 2015, 08:12 AM

The amp could be oscillating or you set the scale to Amps on your meter.

Gajanan Phadte

thunderchicken · 30th March 2015, 11:01 PM

I think it's a ground (earth) issue, but I don't know what I should be looking for/fixing/replacing. Could the chip have a short? I know my transformer is (slightly- 28 vs 25) over the recommended range, but the first channel worked right away. I guess I have a different question now.

Is it worth connecting the tested power supply to the oscillating amp? That one step will tell me if it's the power supply causing the issue and it doesn't risk frying the good amp board. If the amp has the same issue with the good power supply, then it's definitely the amp. I think I just talked myself into it. Probably could have checked this last night.

thunderchicken · 31st March 2015, 01:39 AM

The bad amp board is behaving the same on the verified/working PS. I didn't probe the speaker terminals again, but I hooked up my test speakers and got the same noises.

thunderchicken · 31st March 2015, 01:43 AM

Measuring amps on my meter means changing the probe to a different socket, so it wasn't that.

rayma · 02:32 AM

Quote:

Originally Posted by thunderchicken

Measuring amps on my meter means changing the probe to a different socket, so it wasn't that.

Use caution, this could even be AC line voltage. At any rate, don't connect your speakers until it's fixed.
Voltmeters don't normally cause arcing like that, whether DC or AC.

thunderchicken · 31st March 2015, 02:40 AM

Totally agree, I disconnected the faulty board, took reference photos, and posted them in my build thread. Also got in touch with chipamps.com. The other channel of this dual mono kit works fine. Still not sure what the issue is, hopefully I'll have some answers soon.

rayma · 31st March 2015, 02:54 AM

Quote:

Originally Posted by thunderchicken

The other channel of this dual mono kit works fine.

Can you measure the power supply directly normally, without these symptoms, on the bad channel?

thunderchicken · 31st March 2015, 03:11 AM

Which specifically? Am I checking between PG+ and V+ or am I probing V+ and V-?

rayma · 03:26 AM

Quote:

Originally Posted by thunderchicken

Which specifically? Am I checking between PG+ and V+ or am I probing V+ and V-?

Try all the combinations, though none should spark.
Also, try borrowing another meter just to be sure.

30th March 2015, 04:40 AM	#1
thunderchicken diyAudio Member Join Date: Mar 2015	Speaker Terminal Arcing Yeah, that's not supposed to happen. Was looking for DC offset on my 2nd board- source connected but not playing. No load. I put the black probe on the black speaker terminal and the red probe on the red speaker terminal. Couldn't get a stable reading, which I thought was odd. I pulled the probes to change the scale on my DMM, and when I placed the black probe on the second time it arced. Now my DMM probe is black and pitted. What went wrong and how can I fix it?

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30th March 2015, 08:12 AM	#2
gmphadte diyAudio Member Join Date: Jul 2003 Location: Dona paula, Goa	The amp could be oscillating or you set the scale to Amps on your meter. Gajanan Phadte

30th March 2015, 11:01 PM	#3
thunderchicken diyAudio Member Join Date: Mar 2015	I think it's a ground (earth) issue, but I don't know what I should be looking for/fixing/replacing. Could the chip have a short? I know my transformer is (slightly- 28 vs 25) over the recommended range, but the first channel worked right away. I guess I have a different question now. Is it worth connecting the tested power supply to the oscillating amp? That one step will tell me if it's the power supply causing the issue and it doesn't risk frying the good amp board. If the amp has the same issue with the good power supply, then it's definitely the amp. I think I just talked myself into it. Probably could have checked this last night.

31st March 2015, 01:39 AM	#4
thunderchicken diyAudio Member Join Date: Mar 2015	The bad amp board is behaving the same on the verified/working PS. I didn't probe the speaker terminals again, but I hooked up my test speakers and got the same noises.

31st March 2015, 01:43 AM	#5
thunderchicken diyAudio Member Join Date: Mar 2015	Measuring amps on my meter means changing the probe to a different socket, so it wasn't that.

31st March 2015, 02:40 AM	#7
thunderchicken diyAudio Member Join Date: Mar 2015	Totally agree, I disconnected the faulty board, took reference photos, and posted them in my build thread. Also got in touch with chipamps.com. The other channel of this dual mono kit works fine. Still not sure what the issue is, hopefully I'll have some answers soon.

31st March 2015, 03:11 AM	#9
thunderchicken diyAudio Member Join Date: Mar 2015	Which specifically? Am I checking between PG+ and V+ or am I probing V+ and V-?