Electronics > Repair

AWA DSA-510 Amp

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tazelikechickn:
Hey Guys,

I am trying to repair a AWA DSA-510 Amp. I have a standby light on, but will not fire up when I press the switch. The switch etc is ok, but I would like to check out a schematic to see how it works.

Does anyone have access to a Schematic? I have tried all the sites that I know, but no luck.

Thanks for your help.

David_AVD:
Does it use a switchmode or conventional transformer power supply?

tazelikechickn:
Hey Dave,

It is just a standard transformer. It has power coming out (13 V & 6 V) and fuses are OK. No AC power to the bridge rectifier. The relay is not clicking on.

David_AVD:
Check for open-circuit relay coil (it happens!) first.

Then move onto the relay drive transistor circuit.  Some amplifiers have a small value electrolytic capacitor that is charged via a separate diode off the power transformer.  If that cap dies, the relay won't kick in.

Other than that, check for cracked solder joints and any sign of overheated resistors (check their value).  That should get you started.

EDIT: Oh, so no AC into the bridge?  I missed that at first read.  Does it have another smaller power transformer?

tazelikechickn:
No smaller transformer that I can see. I haven't really traced or done a lot of checks at the relay. I see a diode, a few caps and transistor nearby and will check that tomorrow.

Also haven't checked the relay coil or switch operation, but can't hear it click when the button is pressed. I gather it is not being switched. Another job for tomorrow.....

IDIOT ALERT!! I just realised that I was testing the bridge rectifier incorrectly. Damn you AC/DC! Once I checked the right terminals I got 29.7 Volts AC & 35.5 Volts DC - all good. I think I will have to check the relay next. I checked for continuity on the coil, but might have the wrong side. I will desolder it and check it off the board and it should power up with a 9 Volt battery I think?

I have included a photo that should make it easier to understand

BTW thanks for the help - it is greatly appreciated  8)

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