Cap job, besides filter caps.. Mark series

[McBarry]

I've done the filters on my Mk IIA, and am about to do the Mk IIB and the MkIII (the latter is sounding "lifeless" - I read "wet towel" here an it's a good analogy.)

Now, I've read some guys also do a few others while insode, eg: preamp board filter(s), bias ct filters etc etc.
I can't seem to find a consensus in the zillion of threads, so will ask the question..
Besides the PSU filter caps, what other electro's do guys replace/think seriously about as a matter of course?

Ideas?

 

[>Photi G<]

I've done the filters on my Mk IIA, and am about to do the Mk IIB and the MkIII (the latter is sounding "lifeless" - I read "wet towel" here an it's a good analogy.)

Now, I've read some guys also do a few others while insode, eg: preamp board filter(s), bias ct filters etc etc.
I can't seem to find a consensus in the zillion of threads, so will ask the question..
Besides the PSU filter caps, what other electro's do guys replace/think seriously about as a matter of course?

Ideas?

All of them. :lol: Seriously. The B+ supply is the most important though. So the 2 (or 4 for Simul Amps) 220's and the 4 (or 3 on a MK3) 30uF's are of utmost importance. The Bias/EQ/LDR, and Relay supplies aren't as important, but should be replaced while you have the amp on the bench. The thing is that the low-V supplies have some weird cap values that aren't easy to find. For the most part, the cathode bypass caps in the preamp are Wet Tantalum capacitors, and should not need replacement.

 

[stokes]

All the electro caps should be replaced.The lower voltage ones are not that difficult to find at all.Even tho the bias caps etc. are subjected to lower voltages and the sense is that they arent stressed as much as the high voltage supply caps,they are rated for lower voltages,so the stress factor is proportionate.They are also as old as the others and subject to the same "age causing them to dry out thing".Of course you can change just the power supply caps and see a big improvement that wont be any better if you also change the lower volt caps,but why wait for them to fail and possibly cause problems,they are fairly inexpensive and while you have the amp open you can do them and have peace of mind,knowing they arent likely to fail.

 

[McBarry]

Makes sense guys, ta!
The MkIIB will sound better anyway because it's gonna get a nice clean - there's 30yrs of dust/crud inside on the boards/components.. I'll bet there's stray little voltages all over the shop.
It's going to get some str415's too, and I'm hunting down some Tungsrams and RFT's to play with also, although to be honest I'm not sure my ear is finely tuned enough to pick little differences.
But hey, a digital recorder will help... will try post the results on a web page so all can hear for themselves..
I'm going to clean all the earth points (all mono sockets grounds, pot(s) grounds), tube socket tightening, check voltages as per schematics, but is there anything else U guys do as part of a biggish service?
Dave