41hz Amp10 Basic Setup Issues

raromachine · 15th March 2008, 06:01 PM

Apologies for posting here and not on the 41hz forum - I can't seem to register there and I know folk here are pretty knowledgable.

I've soldered up an amp10 - which apart from a small short in the PCB at one edge (which I've now fixed) - seems to be running, but not quite right.

My 5V+ gives exactly 5V+, my 18VAC feeds become about 2x25.5V which is right as far as I can see.

The LED which signal whether the AMP is muted or un-muted glows very dimly sometimes just after switching on or off. The other LED that shows whether the speaker-relay is open or closed seems to work perfectly. I've checked all the of the R values around the LEDs and these seem fine - though it appears the muting LED/control is driven from the Tripath chip.

The speaker terminals have a DC offset of 2.5v when measured on my autoranging meter - which is crazy high in my estimation.

No input signal or output driver is connected - and I've checked the board from shorts repeatedly!

Any ideas what could be going awry?

Cheers,
raro

raromachine · 15th March 2008, 06:24 PM

Pics:

nicoch58 · 15th March 2008, 08:40 PM

short the input and try trimmer for dc offset .... max 70mv if not chip are burn , put a 1000uf to work around dc offset but......recheck all

mazdapowered · 15th March 2008, 09:08 PM

I don't have the BOM to double check but there is a resistor missing, right next to "41hz" written on the board, which I have seen fitted on another AMP10 basic.

raromachine · 15th March 2008, 09:25 PM

Quote:

Originally posted by mazdapowered
I don't have the BOM to double check but there is a resistor missing, right next to "41hz" written on the board, which I have seen fitted on another AMP10 basic.

It's on the bottom - the holes deformed after I removed the resister for the 3rd time - took me a while to realised the BOM for Amp10 and Amp10 Basic were different.

If it wasn't there neither of the LEDs would work.

I've actually found a post on the 41hz forums that practically duplicates my issues:

http://www.41hz.com/forums/topic.asp?TOPIC_ID=1763

I think I'll give this a whirl

raromachine · 15th March 2008, 10:59 PM

A bit of desoldering, the destruction of another via and a 1.5K resistor (I had no 1K) later and I'm in business - offset trimmed to a 1mV and stable. Now I just need to buy some speakers to test the amp with

15th March 2008, 06:01 PM	#1
raromachine diyAudio Member Join Date: Jun 2006	41hz Amp10 Basic Setup Issues Apologies for posting here and not on the 41hz forum - I can't seem to register there and I know folk here are pretty knowledgable. I've soldered up an amp10 - which apart from a small short in the PCB at one edge (which I've now fixed) - seems to be running, but not quite right. My 5V+ gives exactly 5V+, my 18VAC feeds become about 2x25.5V which is right as far as I can see. The LED which signal whether the AMP is muted or un-muted glows very dimly sometimes just after switching on or off. The other LED that shows whether the speaker-relay is open or closed seems to work perfectly. I've checked all the of the R values around the LEDs and these seem fine - though it appears the muting LED/control is driven from the Tripath chip. The speaker terminals have a DC offset of 2.5v when measured on my autoranging meter - which is crazy high in my estimation. No input signal or output driver is connected - and I've checked the board from shorts repeatedly! Any ideas what could be going awry? Cheers, raro

15th March 2008, 08:40 PM	#3
nicoch58 diyAudio Member Join Date: Oct 2004	short the input and try trimmer for dc offset .... max 70mv if not chip are burn , put a 1000uf to work around dc offset but......recheck all __________________ Sic58

15th March 2008, 09:08 PM	#4
mazdapowered diyAudio Member Join Date: Jan 2006 Location: UK	I don't have the BOM to double check but there is a resistor missing, right next to "41hz" written on the board, which I have seen fitted on another AMP10 basic. __________________ Richard

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15th March 2008, 06:24 PM	#2
raromachine diyAudio Member Join Date: Jun 2006	Pics:

15th March 2008, 10:59 PM	#6
raromachine diyAudio Member Join Date: Jun 2006	A bit of desoldering, the destruction of another via and a 1.5K resistor (I had no 1K) later and I'm in business - offset trimmed to a 1mV and stable. Now I just need to buy some speakers to test the amp with

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