Old St-35 board.

[Blooze]

I got a Rev.B board last year that had been populated in 2003 I believe. Never been powered up, and I've had it sitting for nearly a year as I can't decide if I want to build it or go to a SS power amp with a tube pre. Anyway, what's your opinion of powering this board up as far as the electrolytics are concerned? Swap them out at this point? FWIW, I don't have a variac so that's not an option.

[Shannon Parks]

It will be A-OK. The Nichicons in Rev B are very, very stout electrolytics with low leakage current.

Shannon

[Blooze]

Thanks Shannon. I wasn't sure given that the 8 PS capacitors are probably going on 9-10 years old now. I need to decide if I'm going to buy iron and build this thing or not.

[EWBrown]

I can "second" that those 220 uF 250V nichicon caps are really good, they aren't yet so old that they would require re-forming - maybe in another 40 or 50 years I still have a LOT of these caps in my parts stash, they have come in handy for several other projects, as well.

FWIW I have one of the original "green board" DIY35 boards, that I got from Gary Kaufman a couple years ago. I'll have to check, if it is a "Rev A" or "No Rev" board.

I'm sure that there are not too many of these boards in circulation. The main difference from the "B" board, is that it does not have the 10 ohm "measuring" resistors in series with the cathode resistor networks, so setting the 35 mA cathode current becomes a bit more of a complex and iterative procedure, so I just set them to 400 ohms and called that" good enough". That works very well with most new "matched quad" J/J EL84s.


/ed B

[Shannon Parks]

I forget the quantities of the Rev - and Rev A boards. Maybe three of each? I used the 3 (up to 6) for $33 proto boards from Advanced Circuits for the Rev A. I think the Rev Dash was another proto deal from another company.

I'm finally dusting off the diytube ST35 folder and *might* do a Rev E.

Shannon

[EWBrown]

I'm finally dusting off the diytube ST35 folder and *might* do a Rev E.

Interesting.... what new circuit changes are you thinking of?

I was thinking that the old "green board" might be a good candidate for Dave Gillespie's EFB mod, just remove the adjustable RK networks, tie all four of the cathode pin 3's together and let the EFB handle the current control duties.

/ed B