Lynch Box - fired her up - hope I didn't break her

[yigba]

I fired up the Lynch Box combo I just bought and after playing a bit with the Blackface and Tweed modules - I am definitely a Tele with the Tweed module guy. I checked the bias for the EL34L's. They were at only 27.8. This seemed a wee bit too low.

I then tried to change the bias settings and pushed a bit too hard with the screwdriver. I actually forced the bias pot backwards, somehow turned it on it's side and the fuse on one of the tubes blew. Arrrgh!! The bias pot on my Fender RI Bassman is much sturdier.

I have now ordered fuses for it - I hope I didn't fry the tube or damage anything else. Pulled the chassis, unbent the bias pot - all looked fine. I just hope I didn't crack any of the soldering under the board - I imagine that would be a PITA to fix.

 

[JKD]

It sounds like you caused a short and probably hit maximum on the bias circuit...spiked the current draw and therefore popped the fuse...

The bias pot could be damaged, did you measure it was still variable after unbending it?

I'd keep an eye on those tubes when you next power on...start the bias from lowest possible and work up.

As for a repair, yes you have to pull the whole tube board...it's major surgery...so hope you didn't kill it.

 

[yigba]

Being that the fuses will take a few days I'll try and measure the pot tonight. One of the tubes did red plate when I screwed up the bias pot.

I am so pissed at myself for doing this. I didn't think the screwdriver I had originally inserted reached the bias screw as there was very little resistance, so I pushed in a bit further and voila - fried amp.

 

[Lution]

**** happens man. my guess is the fuse blew before any damage could be done.

 

[yigba]

OK - I checked the bias resistor and it is defintiely working. Just have to wait for the fuse, reinsert tubes and cross my fingers.

Thanks for that bias resistor heads up.

 

[Julia]

rule of thumb -- finger pressure only.

 

[yigba]

Pheeew. Everything works as it should. Thanks for all the input.

 

[m0jo]

rule of thumb -- finger pressure only.

Why don't they fix the pot on a metal part or something so it can't bend .. that would be roadworthy construction if you ask me.