SCA 35. What update mods should be done?

Getting a SCA 35 and wondering what basic 'musts' be done to bring it back to glory.

Thank you

peterh wrote:

poconoman wrote:Getting a SCA 35 and wondering what basic 'musts' be done to bring it back to glory.

Thank you

Nothing really if it sounds good.

What may be done :
- verify that all el84 is good and that they work as a matched quad.
- check voltages inside ( consult the sca-35 manual for details)

- installation of EFB board ( that also replaces some of the electrolyte caps) is the single thing that
does most to the amp.Everything else is just a lot of work for no real effects in my opinion.

EFB board. Is that the pre amp board?

Dave sells the EFB bare board only, I have assembled boards here:  http://tubes4hifi.com/sca35.htm

tubes4hifi wrote:Dave sells the EFB bare board only, I have assembled boards here:  http://tubes4hifi.com/sca35.htm

Thank you Roy, ordered!

peterh wrote:

tubes4hifi wrote:Dave sells the EFB bare board only, I have assembled boards here:  http://tubes4hifi.com/sca35.htm

That was good news ( for everyone else as i already have one in my sca35)

Thank you for all your help. BTW, once the EFB is in, do I still need to use a variac? Because according to the previous owner, it hasn't lit up in five years. But he assured me that everything works.

peterh wrote:

poconoman wrote:

peterh wrote:

tubes4hifi wrote:Dave sells the EFB bare board only, I have assembled boards here:  http://tubes4hifi.com/sca35.htm

That was good news ( for everyone else as i already have one in my sca35)

Thank you for all your help. BTW, once the EFB is in, do I still need to use a variac? Because according to the previous owner, it hasn't lit up in five years. But he assured me that everything works.

personally i would fire it up "as is" first and get a first impression. This way you assure that
everything works ( or not), this is important if you  get any problems during the rebuild.
Varic for start ? nice to have but not necessary.

Ok, thank you. I'll turn it on and see what happens. Good, I hope.

poconoman wrote:

peterh wrote:

poconoman wrote:

peterh wrote:

tubes4hifi wrote:Dave sells the EFB bare board only, I have assembled boards here:  http://tubes4hifi.com/sca35.htm

That was good news ( for everyone else as i already have one in my sca35)

Thank you for all your help. BTW, once the EFB is in, do I still need to use a variac? Because according to the previous owner, it hasn't lit up in five years. But he assured me that everything works.

personally i would fire it up "as is" first and get a first impression. This way you assure that
everything works ( or not), this is important if you  get any problems during the rebuild.
Varic for start ? nice to have but not necessary.

Ok, thank you. I'll turn it on and see what happens. Good, I hope.

I forgot to mention. I'd like to recap. I'm using the SCA 35 for digital sources. No phono. Recap the 12AX7 and 7199 boards and what values are suggested? Parts list?

Thank you

peterh wrote:

poconoman wrote:

poconoman wrote:

peterh wrote:

poconoman wrote:

peterh wrote:

tubes4hifi wrote:Dave sells the EFB bare board only, I have assembled boards here:  http://tubes4hifi.com/sca35.htm

That was good news ( for everyone else as i already have one in my sca35)

Thank you for all your help. BTW, once the EFB is in, do I still need to use a variac? Because according to the previous owner, it hasn't lit up in five years. But he assured me that everything works.

personally i would fire it up "as is" first and get a first impression. This way you assure that
everything works ( or not), this is important if you  get any problems during the rebuild.
Varic for start ? nice to have but not necessary.

Ok, thank you. I'll turn it on and see what happens. Good, I hope.

I forgot to mention. I'd like to recap. I'm using the SCA 35 for digital sources. No phono. Recap the 12AX7 and 7199 boards and what values are suggested? Parts list?

Thank you

Start with using it "as is" to get a ground feeling.  When your ears have got used start thinking about
mods. EFB is as i said the single thing that get's most ( but matched el84 is a prereq for any mod)
If you don't use phono now, why don't let it be there ? Who knows when you get a TT ?
I also suggest one mod at a time, thus you will be able to know what really mattered and what did not.

Very good advice Peter. I didn't have any intentions of removing the phono section. I figured to recap the line stage. But like you said, HEAR first and then mod if necessary. I did get the EFB from Roy though. I heard these amps run very HOT.

The variac is only necessary if you don't change out the old can caps which you are doing. Not sure why but the old can caps fail more often on the Stereo70 than on the ST or SCA not sure why. As far as the caps on the board if you wish to change them out the .1 caps to the output tubes can stay the same or be increased to .22 any larger will not be of any benefit. Remember they have to be small caps to fit on SCA board. The 1 cap should be replaced with the same value.
I would download the manual for the SCA35 and go to the last pages and check to make sure the knobs for the tone controls are properly set per the manual. many were not correctly set by the builders. Once you install the new power supply and check the tone controls I would listen to the SCA for a few months before making any more changes. It's a great little amp. I don't use the phono section either.

sailor wrote:The variac is only necessary if you don't change out the old can caps which you are doing. Not sure why but the old can caps fail  more often on the Stereo70 than on the ST or SCA not sure why. As far as the  caps on the board if you wish to change them out the .1 caps to the output tubes can stay the same or be increased to .22 any larger will not be of any benefit.  Remember they have to be small caps to fit on SCA board. The 1 cap should be replaced with the same value.
I would download the manual for the SCA35 and go to the last pages and check to make sure the knobs for the tone controls are properly set per the manual. many were not correctly set by the builders. Once you install the new power supply and check the tone controls I would listen to the SCA for a few months before making any more changes. It's a great little amp. I don't use the phono section either.

Thank you for your input Sailor. Greatly appreciated.

On the stock rear RCA inputs, which is best for CD and other digital sources?

the 3 line inputs are identical, download the manual and look at it

peterh wrote:

tubes4hifi wrote:
Start with using it "as is" to get a ground feeling.  When your ears have got used start thinking about
mods. EFB is as i said the single thing that get's most ( but matched el84 is a prereq for any mod)
If you don't use phono now, why don't let it be there ? Who knows when you get a TT ?
I also suggest one mod at a time, thus you will be able to know what really mattered and what did not.

Very good advice Peter. I didn't have any intentions of removing the phono section. I figured to recap the line stage. But like you said, HEAR first and then mod if necessary. I did get the EFB from Roy though. I heard these amps run very HOT.

It will run cooler, and therefore longer, with the EFB mod.  Cap mods are like food seasoning, they should be done "to taste."  I would also mount any plastic caps UNDER the circuit boards (if they'll fit, and with proper insulation) to reduce the effects of tube heat on the caps.  Some plastic caps WILL melt a bit.  An extra cool-air vent hole or two, judiciously placed, will help somewhat.  Obviously, you don't want to go drilling lots of holes in the chassis if the unit is for restoration and resale.  I have two SCA-35s; one stock and almost new, the other was always destined for Dr. BubbaStein's Laboratory (TM) (R) (C).  

The EFB arrived and it's well put together. The instructions are very clear and laid out. Very easy. Can't wait to install it!

A couple of things. The caps can not be mounted under the board. There is not enough clearance in the SCA35.
Second, If you are only hooking up a CD player and nothing else plug it into the {to tape recorder} the RCA closes to the output. This will completely bypass the selector switch and 50 years of dust and grime on it's contacts and connect it to the volume control. Again, this can only be used if you are not using the phono section or any other inputs. This is what I use as I only have a CD player and it is does sound better.

sailor wrote:A couple of things. The caps can not be mounted under the board. There is not enough clearance in the SCA35.
Second, If you are only hooking up a CD player and nothing else plug it into the {to tape recorder} the RCA closes to the output. This will completely bypass the selector switch and 50 years of dust and grime on it's contacts and connect it to the volume control. Again, this can only be used if you are not using the phono section or any other inputs. This is what I use as I only have a CD player and it is does sound better.

Thanks Sailor for that. I'm only going to install the EFB. And for CD, I'll use the RCA tape recorder. Thank you again!

Sailor, isn't the To Tape Recorder an output or did you mean FROM?

Yes, the tape out. If you follow the wire from that RCA you will see that it is soldered directly to the wire going to the volume control which bypasses the selector switch. Once you have done this set the selector switch on radio so you don't pick up any noise from the phono section.

sailor wrote:Yes, the tape out. If you follow the wire from that RCA you will see that it is soldered directly to the wire going to the volume control which bypasses the selector switch. Once you have done this set the selector switch on radio so you don't pick up any noise from the phono section.

You're awesome. Thank you!

poconoman wrote:A couple of things. The caps can not be mounted under the board. There is not enough clearance in the SCA35.

I wasn't completely clear; I was referring to the audio coupling caps on the SCA-35's circuit boards, not the caps on the EFB.  The some plastic caps are heat sensitive, and since some of the "audiophile" caps are largish it's even worse.

Sorry about the lack of clarity.