SCA-35

[K-MAN]

I'm tempted to get a ST70 one day, it looks like it's better for listening to your favorite rock song on a nice set of big speakers in the living room Yellow_Light_Colorz_PDT_06

[Slartibartfast]

I'm tempted to get a ST70 one day, it looks like it's better for listening to your favorite rock song on a nice set of big speakers in the living room Yellow_Light_Colorz_PDT_06

It is also good for listening to Classical and Jazz. In fact I just finished listening to a Dave Brubeck LP. Yellow_Light_Colorz_PDT_11

[sorenj07]

quick check: what's the best way to clean out questionable switches/pots in a SCA-35? I'm considering doing a straight up restoration with the exception of a tone control bypass switch...

[K-MAN]

Ok my friend has restored dozens of vintage radios and this is how he does it and it worked great on mine. You use a contact cleaner that doesn't have any lube so I use one with alcohol. Now the most important part is to flush out the old lube and dirt in the pots/switches and don't move the pot at all since there's no lube now and it might scratch the contacts. Then you use a contact cleaner with a lubricant like silicone or one that says it lubricates controls and put just a quick squirt into the control and work the switch/pot back and forth a bit. Allot of people make the mistake of using a contact cleaner with no lube in it and this actually makes it worse in the long run since the delicate contact strip inside is getting worn away.

[sorenj07]

One quick question. Assuming I felt like blowing the cash for a new PSU and circuit, how does a triode-mode 6L6GC PP setup sound to you? TDSL quotes an operating point of around 13W dissipation per tube but into an 8K a-a impedance. This only nets 6W, but could upping the B+ to 360V, running fixed bias, and feeding 60mA into each tube work? That ought to net around 11W of pure triode glory. If I get tired of that, I suppose I could always drop in 6V6's, and run UL with cathode bias... 340V 35mA nets 12W of dissipation, which should be reasonable with good 6V6's, right?

This is just idle fancy because I have respect for the sanctity of the working amp, especially if it's as pristine as this one. And there's no reason I couldn't do the above with Edcor iron if I sell the recapped, choked SCA..

[mesherm]

I have an amp that is running winged-C 6L6Cs in triode mode biased at 60ma each and it runs just fine. It runs in the neighborhood of 360v and cranks out some sound. It runs Hammond 1650Gs (no UL taps).

[mesherm]

quick check: what's the best way to clean out questionable switches/pots in a SCA-35? I'm considering doing a straight up restoration with the exception of a tone control bypass switch...

http://store.caig.com/s.nl;jsessionid=a ... tegory=188

This is the best stuff for contacts and pots I have ever found. I use the bottle with a metal pin point tube. On pots I put a drop or so on the openings and then use canned air to blow it inside at the parts I cant reach with the tip. I used it on all the original pots and switches on my two PAS 3xs and I have never had a problem since.

[sorenj07]

all right, cool. I finally got the thing and it's looking pretty great. My idea is to cut out the can cap that's closest to the Z565 and put in a small 5H 200mA 65 ohm choke to replace R41, the first resistor in the PSU which is 50 ohms 5 watts. I can arrange electrolytics below using terminal strips to bypass the other can cap, though I'll leave it in for show :)

The boards themselves are very dark and seem a little fragile. is it worth it to try and etch my own (i have the files somewhere) or is a simple check of the resistors and caps, and replacement of the tube sockets OK? it also came with some "west-germany" 12AX7's with little diamonds on the underside. they might find themselves on an auction block in order to finance the rest of the rebuilding...

[sorenj07]

Unfortunately, it turns out the files I had were for the ST-35 boards. Does anyone have high-quality scans for the original SCA-35 amplifier modules, and maybe the phono board as well? I still haven't decided what I want to do, but it can't hurt to have them I guess.

[K-MAN]

I ordered new boards for mine from this guy http://www.dslextreme.com/users/triman/triman.html

They were great quality but I'm sure you could get the scans for it to build your own if you email him.

[sorenj07]

I'll ask but I'm not too hopeful, since he is offering the finished product for sale... ideally I'd just put some aluminum plate over the holes and go point-to-point, but with a phono stage, that might get dicey (but fun!)...

[sorenj07]

I want to try a little shuffling with the PSU, since I'll only really have room for one can cap if I put in the choke I want to. How about a 100+100uF JJ? One part forms the last CLC with the new choke, that feeds B+. The next 100uF goes to the stage right before the EL84's, with a 4.7K 3W instead of the two RC's of 2.2K/1W? If it's really necessary I can use exactly 4.4K. After that, one loose 22uF 450V under the hood will make the last RC that feeds the 12AX7's. Does this sound reasonable? I'd draw it out but it's pretty simple. I figure that it's all right to cut out one RC stage since the choke will kill ripple so much better than the resistor. 100uF for the output stage still seems a little wimpy, but it's still an improvement..

[wiredbecker]

quick check: what's the best way to clean out questionable switches/pots in a SCA-35? I'm considering doing a straight up restoration with the exception of a tone control bypass switch...

http://store.caig.com/s.nl;jsessionid=a ... tegory=188

This is the best stuff for contacts and pots I have ever found. I use the bottle with a metal pin point tube. On pots I put a drop or so on the openings and then use canned air to blow it inside at the parts I cant reach with the tip. I used it on all the original pots and switches on my two PAS 3xs and I have never had a problem since.

Great trick. I've foolishly soaked the pot, inevitably allowing fluid to needlessly drip into the amp. Thanks for the suggestion.

[K-MAN]

The fluid wont hurt anything in the amp it drips on, just clean it off with some alcohol.

[EWBrown]

Let me dig through my stash 0' stuff, I may have a set of ready-to-go fiberglass SCA-35 replacement (clone) boards that I can let go for cheap. These would be the two amp boards, though I may also have a phono board as well, though I can't guarantee that... Yellow_Light_Colorz_PDT_11

/ed B in NH