DC-3 what would cause this?

[rightback]

Hi, the pilot light was on and one tube lit up but none of the others. I took it in to be repaired and the culprit is in the picture. Any idea what would cause this? I was using the recording out and speaker mute switch when it happened, any chance there could be something wrong there or was it just a coincidence?

Thanks.

 

[user 41014]

Ouch, that can't smell good, and that doesn't look like coincidence. Fuse still good and right amperage?

I can't see what that is but what is pin 3 and pin 4? And if you took it in to get repaired and they found that, what did they say? Dollars to donuts there is a short somewhere- caps ok?

 

[rightback]

Ouch, that can't smell good, and that doesn't look like coincidence. Fuse still good and right amperage?

I can't see what that is but what is pin 3 and pin 4? And if you took it in to get repaired and they found that, what did they say? Dollars to donuts there is a short somewhere- caps ok?

Thanks, the repair note didn't provide any detail but it sounds good through the speaker...I'll give them a call on Monday. I'm no technician so I don't go testing caps or anything

 

[Monsta-Tone]

I've seen a couple of those connectors fail just like this.
If it were my amp, or in my shop, this is what I would do.

Replace all filter caps
Replace bias filter caps
Remove the plastic connector and solder the wires directly to the pins that come out of the circuit board
- Make sure that the wires are staggered in height so that they don't touch each other
- I strip about 3/8" of the wire, and then "Tin" the ends, then I wrap each wire around it's pin and squeeze it with needle nose pliers before soldering

Hope this helps!

On a side note, while the tech is in there.....
You might think about having him replace the 4N33 opto isolators that control all of the switching in the amp.
I have had several of these go bad, which causes odd sounds or no channel switching.
They are super cheap and easy to replace.
I look at it like I'm changing the old belts and hoses in a used vehicle when I get it......just good maintenance.

 

[robert swartz]

Monsta-tone, thank you for getting back to me! You just made my day!! I hope l can be of service to this forum in the future... Thanx again! Rob Swartz

 

[rightback]

I've seen a couple of those connectors fail just like this.
If it were my amp, or in my shop, this is what I would do.

Replace all filter caps
Replace bias filter caps
Remove the plastic connector and solder the wires directly to the pins that come out of the circuit board
- Make sure that the wires are staggered in height so that they don't touch each other
- I strip about 3/8" of the wire, and then "Tin" the ends, then I wrap each wire around it's pin and squeeze it with needle nose pliers before soldering

Hope this helps!

On a side note, while the tech is in there.....
You might think about having him replace the 4N33 opto isolators that control all of the switching in the amp.
I have had several of these go bad, which causes odd sounds or no channel switching.
They are super cheap and easy to replace.
I look at it like I'm changing the old belts and hoses in a used vehicle when I get it......just good maintenance.

Thanks for your response. I called and the tech had soldered the wires directly (I think he said at the suggestion of Mesa) as you suggested above. He said it's just one of those things that happen and nothing to worry about. I'll keep in mind your suggestion about the opto isolators for next time I need the amp looked at.

 

[rightback]

Thanks, the repair note didn't provide any detail but it sounds good through the speaker...I'll give them a call on Monday. I'm no technician so I don't go testing caps or anything

I did follow up as mentioned above. Thanks for your response.