Standby

[tazelikechickn]

Hey Guys,

I am repairing a AWA DSA-510 amp. I  have it up and running, but it won't switch off! The standby light stays on (which I thought only stayed on when the amp is off??) The amp works fine, but as I said, it won't switch off.

Yes, I checked the switch and that works fine. It's a momentary switch, but I am unsure of what it activates further down the track. I can't find a schematic for it but I guess it may switch off the main relay. I guess...

I assume that most systems may work similarly in this area, so I would appreciate any help I can get.

Cheers

[Mr. OBrien]

can we see some pictures of the inside?

[tazelikechickn]

Here are a few photos. I'm not sure what can be determined from them, but I do have others if necessary.

Thanks for your help

[Shock]

Trace where the switch goes and check the relay, then test the relay itself with your lab supply. It looks like it's switching mains so perhaps it's stuck on.  One hint would be when you plug in the amp and switch it on at the mains, does it power up by itself? That could suggest the same component is faulty.  You can also simulate what the relay is doing manually with it out of circuit, as well as measure that the low voltage side is working.

BE SAFE, keep in mind I have not seen the schematic so have no idea what the relay is switching.

[tazelikechickn]

Thanks for your reply.

The relay clicks on when I plug the unit in. I will check the coil side of the relay to see if it is powered all the time & see if I can trace it backwards.

Just finding some time - that's the problem!!

[Cyberdragon]

Amplifier with a relay you say?

Might be a speaker protector, they are usually near the power supply and are just current sensing. If it is then that's not your problem (red herring). It's just switching on as a result of the amp being on. It is connected to the power leads but it's basically just functioning as a circuit breaker so it's supposed to be always on.

EDIT: Always on when the amp is on that is. It definitely shouldn't turn on just plugging it in. However, since speaker protectors do switch power it may be controlled and on current sense. But these usually switch on only the power to the main amplifier chips.

[tazelikechickn]

Thanks for your reply.

It is a relay (part Number MI-SS-212LM, and as I said, it does click in and out when the unit is turned on at the power point. I just can't get it to change at the switch. The switch is ok and doing it's job, but I'm not exactly sure of what the standby circuit is and how it activates.

I have downloaded the IC's where the switch goes to, but can't see a standby pin attached.

Any thoughts???

[tautech]

Normally these are some sort of toggling latching switch. When used to switch a relay, commonly a bipolar with back emf protection is used. Away from my PC but somebody might put up a link to that concept.

[simingx]

The contacts may be welded already, in that case the relay will sound normal but the armature will not actually be moving the contacts

[tazelikechickn]

Thanks guys,

I am yet to trace the circuit back, but it is probably a latching system. Will have to scratch my head a little more and give it some thought.