Alpine 3545 blows all fuses after 5 seconds of power

[bmore5077]

4.8mv,,5.8mv,,7.1mv since there is 3 sets on the good channel.

 

[bmore5077]

I don't know if that's bad or good

 

[Perry Babin]

Is the bias increasing as you go through the tests or do you get the same readings for the various test points if you check them repeatedly?

 

[bmore5077]

If I hold the probes it clims like .1mv every 2 seconds. So it does rise

 

[Perry Babin]

Back the bias back to 1mv and let it stabilize. Keep adjusting to get it to 1mv when stable. Do all test points read the same after stable?

 

[bmore5077]

It went from .7,,,.9mv. To .8,,,1 after 10 sec. Then to 1,,1.1 after another 10 seconds. So it raises like .1mv every few seconds. Steadily climbs slow.

 

[bmore5077]

Is it safe to leave it turned on a few minutes. Don't want to burn something up. Thanks

 

[Perry Babin]

If you don't have an amp meter on your 12v power supply, you'll have to watch the bias to make sure it doesn't go too high. 7mv was very high.

 

[bmore5077]

Ok after 5 min . First pair 1.2mv second pair 1.3. Those controllers seem to get pretty hot on the heatsink

 

[Perry Babin]

What about the other channel?

The heating is likely OK.

 

[bmore5077]

I readjusted the idle bias to 1 and it runs 1st pair 1mv,,2nd 1.3,,3rd 1.5mv.thanks

 

[bmore5077]

I guess you adjust it when it's warm because it seems to climb

 

[bmore5077]

After 5 min good channel 1.4,,2nd pair 1.6,,,3rd pair 1.8mv. Definitely changes each time I check it and as it heats up.

 

[Perry Babin]

Keep reducing the bias to keep it at about 1mv until the bias stabilizes.

 

[bmore5077]

Also the one side with only 2 transistors plays lower than the other side about 1/2 volume. Gains set the same. Is that normal

 

[Perry Babin]

No. There is likely a dirty switch or pot or a broken connection somewhere.

 

[bmore5077]

After 20 min 2 transducer side 1st pair 1.7 second pair 2.0mv. Good side 1st pair 1.0 2nd pair 1.1..3rd pair 1.3mv.

 

[bmore5077]

Thanks again. Calling it a night. Think I bit off more than I can chew...ha

 

[Perry Babin]

What I wanted to see was that all of the outputs were sharing current evenly. When the bias was drifting, you could not get usable readings. I think it's OK.The only thing that you cannot determine is where the emitter resistors for the missing transistors are within tolerance. If they read the same as the other emitter resistors with your meter, they're likely OK.

 

[bmore5077]

So when I read from the leg 3 npn to pnp pairs,,,how close should the pairs match. None in this amp match...somewhat close but didn't know what the tolerance is. Also is it normal for them to raise as it warms up.