Concert lead cap questions-pictures inside

[shibbz]

I'm almost certain my red faced concert lead is due for a cap job. It has a slight hum that does not get louder with the volume of the amp, only noticeable a bed room volumes. Lately though it makes a louder sound right when I turn it on and off, so I figure, while it does sound wonderful as is, it needs to be recapped within the next couple months. I opened it up out of curiosity and noticed some things.
These kinda look sweaty, leaky?

I noticed there's a little snap pin with nothing going to it?

Also, I'd never noticed this, is that a little trim pot?
What does it control? I didn't mess with it, just curious.

[mckinnon audio]

Hi there,those "sweaty" things are resistors and it looks like flux residue on them,they're ok,nothing to worry about. The empty snap pin,unless you can find a wire without the pin on the end,I wouldn't worry too much about it,could have been put on without the wire,maybe someone did a mod,hard to say,check the schematic,all those pins should have a number on the schematic and pc board.I believe the trim pot is your bias adjust.Hope this is of some help,good luck,Mel.

[george]

I'd check those resistors on the PA board - I bet they've drifted. Not sure why there would be flux residue on the topside of these single sided boards - I'm going with bubbles from over heating. The red front panel Sunn were supposed to be able to drive 2 ohm loads - good luck with that.

[shibbz]

Awesome, thanks for the input. I have driven 2 ohms with this amp but very rarely, before I knew it was a bad idea.
Are the symptoms I described pretty certainly a cap thing?

[shibbz]

So today I went to turn on my head and there was no cracking sound that has been happening the past couple months when turning it on, and the cap hum was slightly quieter. I'm not positive but the amp itself may have seemed a little quieter as well, just barely, if at all. It also didn't make the cracking sound as I turned if off. What could this mean? The caps are getting worse and effecting the output? A cold solder that fixed itself? Any ideas?

[george]

Hard to say what's going on there? A bad solder joint will not heal itself. Probably should have a tech check out the amp the next time it acts up.

[Walt-Dogg]

As has been said before by many here, a tech knows what he's doing better than oneself, these amps can kill you. In short if you don't know what's wrong, don't make guesses, take it to a reliable tech rather than risk hurting or killing yourself.

[shibbz]

Yea, I just dropped it off at the shop. Should have it back in a week!

On a separate note, other folks with the redfaced concert lead, I have a question.
When plugged into the normal input, with all the switches off, turn the distortion knob to 10.
Do you get a sort of bass boost, and slight loss of volume?
I do and have always preferred the tone this way, but was just curious if they all did this.

[Walt-Dogg]

Yeah the same thing happens to me with my '76 Concert Lead. I actually leave the distort switch in the off position and turn the boost on with the distort knob at 3.5 and the boost cancels out the bassyness and volume loss of the distort knob being turned at all past 0 (switch on OR off) and adds a nice grit on top of my RAT.

[shibbz]

Awesome, thanks!
I've always been curious about that but I've never had a chance to play anyones but mine.
Mine's a 77'.