RCA sp-20

Endspec · Jul 10, 2008

RCA sp-20 updated, got inside the house.

Picked this up today with some other stuff, am going back saterday to look at more stuff too.

1 RCA SP-20 amp 6v6 pp quad output tubes

1 Heath singnal tracer

1 knight signal tracer

1 EMC model 801 resistance capacitor testerr comparitor bridge in curcuit cap tester

1 bk 238 digital volt meter

1 Eco model 232 vtvm

1 heath model IM-38 vtvm

Also have more stuff in the storadge jeep that I will get some pics of later.:thmbsp:

update got inside and got a tube caddy and three boxes of tubes i need to go through + a nri profeshinal model 71 tube tester some more vom' and vtom's and a few other things, pic's to come soon.

jaymanaa · Jul 10, 2008

Wow, nice hit, and more to come.:thmbsp:

Endspec · Jul 10, 2008

This is from a old mans house that past on about 4 years ago and his nef is haveing a friend and myself clean it out, this stuff was in a some sheds outback and saterday we start on the inside of the house and he has a shop in there I can't wait to see the stuff that might be in there.

Now all I need to do is find some space to store it here lol.
The rca amp is complete and looks to be in good shape, just want to find a schematic for it before I start a rebuild on it.

Oh and when I find out what all I got some of the stuff will go up for sale on the ak sale area too.

Endspec · Jul 10, 2008

here are some more rca amp picks, bottomless too. I need to find the info on reading the bumble bee caps again as there are 5 in here I will replace and the three can caps will be replaced too. This is the first amp I have seen with a input voltage adjustment on it too. Also there is a flat thing in the upper right corner in the bottom pics that I don't know what is, hope some one can identify it for me please. And all the tubes look origanal too.

radioactive · Jul 11, 2008

the square thing your referring to is a capacitor. btw thats a nice amp ,i particulary like the quad 6v6 for outputs.:yes:

Tom Bavis · Jul 11, 2008

Service info is in Sams folder 253-11 - I'll see if I have it.

soundmotor · Jul 11, 2008

Endspec said:
Picked this up today with some other stuff, am going back saterday to look at more stuff too.

1 RCA SP-20 amp 6v6 pp quad output tubes

I truly hate you!

Rare and virtually unknown.

You'll need this -

SP-20 Manual

Endspec · Jul 11, 2008

Thank you very much soundmotor, that is what I needed to start on this. now do mica caps need to be replaced too?

gadget73 · Jul 11, 2008

Mica caps are usually pretty stable.

dshoaf · Jul 11, 2008

Never did know much about the RCA stuff but I've been inside some of the old RCA radio broadcast mixing boards. The workmanship of that RCA amp looks like it may have been built for that sort of environment - 24x7 operation. I wonder if the recently pased gentleman was in that industry?

Cheers,

David

PakProtector · Jul 11, 2008

hey-Hey!!!,
That RCA amp is one sweeeeet thang!. There is also a single PP pair version. Last pair of either I saw was at the Mill in PA. I join soundmotor in his jealous feelings...

That amp is the best sounding commercial amp I have ever heard. I wish you much luck in finding a second.
cheers,
Douglas

cademan · Jul 11, 2008

Hi endspec, this is for you (if you need it) and for anyone else who needs it.

Endspec · Jul 11, 2008

cool thanks cademan.

soundmotor · Jul 11, 2008

Endspec said:
Thank you very much soundmotor, that is what I needed to start on this.

You are welcome. Put it in your keep pile and start looking for a second. There is one for sale from an infamous character out there in the net. It would be worth paying the price to get into a set of these.

This may be apocryphal hooey, but I have heard from different and varied sources over the years that these where Harry Olson's babies at RCA. You don't get many chances to own a product designed by an icon such as he.

Now all you'll need is a set of LC1A's to go with them. Here's one in the RCA studio cabinet. No need for me to comment on how truly cool I think that is.

Lastly, it is truly great to see that there are still some undiscovered gems out there waiting to reward the dilligent. Great score, congratulations. That RCA is a beaut, dirt & all!

(image taken from online source)

Endspec · Jul 11, 2008

Well I picked up some caps for it this afternoon, the only problem is two of them are polyester caps .047 at 400 the rest are better caps and the power caps are
sgi 47mf at 450 and nte 100uf at 150 the 47's are takeing place of 40's and the rest are the same specks.
Will the polyesters work till I can order better ones? they are going in c4 and c5 in the schematic posted earlyer in the post.

update.
Well all the coupling and input caps are replaced and working on the power caps, might have it up and running tonight if my eyes hold out.

Endspec · Jul 11, 2008

Well got the recap done, but have not fired it up yet, will do that saterday some time. wish me luck lol. here are two pics of the underside with the new caps, kept the top looking stock.
The resistors I tested were good too.

joshuahhhhhhh · Jul 12, 2008

hope u have a variac if not a light bulb setup should do it http://antiqueradio.org/dimbulb.htm polyesters will do the job If they are of the same voltage rating as what was in there. Most people recommend polypropylene or my favorite polystyrene. I'm only 30 and have seen the guts of maybe 40 or so amps and I have yet to come across a bad mica mold capacitor. Most of the time on some of the older stuff I have tinkerd with I end up putting the old caps back in there lol.
From my experience and experimentation the old mica molds tend to have a more defined and articulate midrange. So now instead of totally going nuts on a piece of gear I try and fire it up and listen to it the way it is before I start replacing stuff.

jaymanaa · Jul 12, 2008

Or do what I used to do; just turn your head and plug her in.

That's some damn fine looking work Steve, I can't wait to hear what you think of the tone. :music:

joshuahhhhhhh · Jul 12, 2008

yer nuts you have any idea how much paper is inside them lil silver cans

Endspec · Jul 12, 2008

I have had those little siver cans granade on me before, confettie everywhere!!!! and can hear a thing for a bit lol. I do have three veriacs in the house and now 5 o scopes and some other vtvm's and signal tracers too. now all I needis to get my shop done to realy set up the bench, the kitchen table is getting old.

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