Opened up my Studio Pre...a few questions for the savvy...

[JT_Marshmallow]

Ok, I have some electronics/soldering experience but I would still consider myself a newbie.

- First of all, I know that when you work on amps you're supposed to drain the stored voltages. Does this apply to rack preamps? There are some big capacitors on this board so I'm curious if I have to be careful with stored voltages in preamps too.

- As for the reverb tube, it looks like the previous owner put a regular Groove Tubes 12ax7 in there, though the schematic says it should be a 12at7. Are these types always interchangable?

- If I were to try the proverbial "C+ Mod", how much of a hassle would it be to get to the bottom of the board? I see the plastic clips connecting it to the chassis, but I also see dozens and dozens of wires connected to the board. This makes me think it would be hard to turn it over to solder/de-solder. If anyone has worked on their Studio Pre, does the board turn over easily?

 

[nomad100hd]

YES Anytime high voltages are being used you need to drain the caps.

 

[ytse_jam]

YES Anytime high voltages are being used you need to drain the caps.

Yes. When I opened my Studio Pre last week I heard a loud pop when I drained one of the big blue caps... that's because I did it in the wrong way, but that also means that there was still charge in there. And I hadn't been using it for weeks.

 

[nomad100hd]

I hadn't touched my mesa in over a month once because it was acting up. I took it apart to check it out and still had 300V+ one of the filter caps!!!!!!!!

 

[joe web]

don´t change the 12aT7 to a 12aX7!
the AT can handle more voltages as the AX7, so if you still have an AX for the reverb tube, change it to an AT7.
the AX will not last long in this position.

 

[hengushrh]

a) drain it!
b) go change the reverb tube back to an 12AT7
c) get a recomended engineer do the mod for you, then you can smile when it works instead of screwing when you fluff it -not saying you will, but if you do... :0(