Great advice on a Fender DRRI amp

[Stratman]

http://aga.rru.com/Events/MM-DRRI-rebuild/

This post contains a link to a great story on a rebuild of a DRRI amp.

That post is a great example of how to provide a story on amp modifications.

[ParaGuitarMedic]

Re: Great advice on a Fender DRRI amp

THanks, great for us DRRI owners. I am checking it out now!'

[Quencho092]

Re: Great advice on a Fender DRRI amp

so is the problem crappy power tubes, poor resistor tolerances, or excessive heat that leads to killing the resistor's value and throwing it off tolerance allowing it to get wiped out?

My guess is that it's the heat. After a year or so of playing (the DRRI gets scalding hot to the touch after about an hour of play) at these temperature levels, it is not a surprise that the piping hot PT may fail to deliver the proper amount of current or voltage ( i dont know crap about electronics, just from physics and such-but heat increases resistance, so an extremely hot tranny coil will have more resistance which would affect current and voltage?)

At the same time, the high heat could take its toll on the various resistors and capacitors on the board and the electrolytics. It wont happen overnight, but it will happen if you give it a year of heavy duty playing. My solution so far is having a computer fan blow air onto the power transformer. The heat level is significantly lower, now i can touch the PT without getting burnt.

I'll let you guys know if i have any problems in a few months. I've had it since june.

[Quencho092]

Re: Great advice on a Fender DRRI amp

somebody please chime in to correct me, or acknowledge this info. In the link, they mention failing power tubes-i'm guessing the stock EH tubes suck, as well as the older sovteks. I have the bigger bottle JJ's in there now.

That kind of heat could also warp the PCB over time (maybe?). I'm just trying to throw some stuff out there about the dangers of excessive heat in electrical equipment. The mikey dude talks about the 'undersized PT', then the PTP vs PCB tone myth, to which they seem to subscribe to. I think that the issue is crappy tubes, and heat damage to the components as a result of a slightly undersized PT that makes it run hot.