High DC Offset in Primare A30.2 Power Amp

gradovn

Member
2016-01-28 4:08 pm
Hello,

I won a Primare A30.2 in eBay, but there is problem. When I first power it on, there is long noisy (about 30 second 3 months ago, but now about 5 minutes), then the noise stopped. Then, when there is the signal from the preamplifier, it need about 10 second for the right channel to get full power as in the left one.

I take some measurements and found that the DC at the input always very high, about 5V DC.

Attached is the service manuals of that power amp.

Please someone help me to fix the problem.

Thanks in advanced!
 

Attachments

  • Primare-A30.2 pwramp.pdf
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Ian Finch

Member
Paid Member
2010-04-11 4:22 am
Coffs Harbour, NSW
I have no experience to offer with this particular design but are you saying there is 5V DC at the input socket (either XLR or RCA socket) or do you mean the output terminals? Assuming the Jumpers JP1,5,9 & JP105,7,9 are configured for 2 channel stereo mode and you do mean the input, then specifically where on the schematic (eg sockets J1, J101, J2, J102) are you measuring this voltage?

Generally, a fault that clears over time will be related to heat (warming up) or a failing electrolytic capacitor as the increasing length of time required to turn on suggests. This is often associated with the operation of output protection or even standby circuits but a persistent 5V DC offset anywhere is a serious problem.

Ebay is a dumping ground for other people's problems so you need to be skilled in repairs or have friends who are, when you buy used equipment based on seller's claims that they work. The questions to ask first are; just how well does it work and what was the real problem that caused someone to sell it.