changing out caps.... advice..opinions..what ever

[cromag]

so, how difficult is it to change out caps in a second gen model T?  i would take it to my local guy,but...   i had taken it to him before to change tubes and re-bias.  he told me the output tranny was bad.  AFTER he changed out some resistors that had blown (leading him to believe the op tranny blew as well.).  but, he changed the value of the resistors.  why, i don't know.  so my good friend joearthur walked me through (via emails and photos) changing the resistors back to proper value and correctly biasing the amp.  turns out the output tranny was fine (at least to my ears.  have been playing this amp off and on for almost two years since fixing it myself with the original op tranny).  joearthur isn't around anymore for me to ask.  would i be able to change caps just by unsoldering the old one, wiring it up, and re-soldering the new one?  would i need to check any values with a multi-meter before / afterwards?  any help, opinions or general comments would be greatly appreciated.  thanks everyone.

[mckinnon audio]

  Hi there,it's a pretty simple task,just resolder in the new ones.The only thing to be careful about is to make sure you have the polarity correct.You can mark the chassis before you take out the old caps.I prefer to "ramp up" the AC voltage on the new caps.By this I mean that I plug the amp into an AC Variac,(variable auto transformer),turn the power and stnby sw.'s on and ease the AC up to 40 volts,leave it there for about a minute,then back to zero and ease it up to 80 volts,repeating the procedure till you get to 120 volts.Hope this helps,be careful Mel.

[cromag]

hey mel, what does this do, the "ramping up"?  kind of break in the new caps?   also, which kind would you recommend for this amp.   i have heard of a few different types.  the copper tubes and the blue bplastic ones as well.  which is better / not as good, etc...?  will this change the tone at all?

[mckinnon audio]

  Hi there,rather than put the AC full rail on the caps,I've always done it this way.You'll get people who will say there is no benefit to this and it is a waste of time,but I've always done this.Standard procedure in electronics class in the 70's !!
  As far as caps go,I've used a lot of different brands and had sucess with all of them.
  The only things I'm really concerned about are the volts,(I try to get 600 volt rated) for electrolytics,and the temp. rating.Standard rating is 85* Celcius,but you can get most of the same values at 105* Celcius,so you have some headroom in temp. Hope this is of some help,good luck Mel.