petehall347
the brandy coffee man
you might have connected the supply the wrong way round and burnt the diodes
http://uk.rs-online.com/web/p/bridge-rectifiers/6290322/If u know of one or find one let me know
you might have connected the supply the wrong way round and burnt the diodes
Ok I did as you suggested. I bought a power supply and set it at 12V 40mA and both of those relays kicked in. I also went through and VERY carefully checked all the inputs into the board for AC voltage (Red, blue, orange and brown). They all tested working. I also tested (again) the bridge rectifier coming off the blue connector which puts out 12V DC. I put my multi meter to the + and -- terminals coming off it while the amp was powered up and got no voltage coming off it. I think I may now know why the amp isn't working properly and the speaker relays were not working.
There isn't any 12V power to the board due the bridge rectifier being stuffed (I'm pretty sure).
On a scarier note.....I had my power supply set to 12V 40mA to test the relays and then upped the amperage to 950mA to test elsewhere. For some reason I went to double check the relays again and when I put the leads on the circuit to test they didn't click and I saw some smoke! I turned the power supply off immediately and wept (well felt like crying) as I thought I'd now stuffed the amp up due not turning the amperage down (Although won't the circuit only take the amperage required? I wasn't forcing amps through it?)
So I can't see and damaged parts and I have no idea where the very small amount of whispy smoke came from...only the general area. I hope I haven't stuffed something else up
Anyhow... I just shouldn't have mucked around putting voltage through parts of the 12V circuit just because I thought I knew what the problem was. I tested the small diodes in blue and the relays I've circled in Red.
The suspect Bridge Rectifier is D519 part number S1NB60-4062
http://au.mouser.com/ProductDetail/Shindengen/S1NB60-4062/?qs=/ha2pyFaduhQpnubSiXYNQT21Sy4XtCsah0%2b%2bxP96emZJvwlDhAcfg==
Of course it's not available
It's rely hard to hurt a scope just make shure to grind it to the chassis are far a vertical sencativaty try about 5 volts per cenameter
You can, but are you sure the fault is powered by the 5V rail?Can I power the 5V only with a power supply and test that way?
Since the fault is on this circuit?
This doesn't guarantee that the power amplifier circuitry is working, because the headphones are driven by the output of the preamplifier, before the power amplifier.It works fine with the 5v unplugged through headphones. All tone controls work perfectly ok and the volume works as it should.
When I plug the 5V blue connection in to the board that's when it turns on and the relays click and then the amp goes into standby with the volume knob flashing red.
I'd first check for a square wave at the gates of Q521 and Q523.So how can I test what is the problem?
Get you a good function generator (audio range sine/square) and a scope and the schematic, start chasing it down one section at a time.