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    SCA 35. What update mods should be done?

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    poconoman

    Posts : 106
    Join date : 2013-01-17

    SCA 35. What update mods should be done?

    Post by poconoman on Fri Jul 26, 2013 6:27 am

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

    Thank you

    peterh

    Posts : 642
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: SCA 35. What update mods should be done?

    Post by peterh on Fri Jul 26, 2013 6:55 am

    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.


    poconoman

    Posts : 106
    Join date : 2013-01-17

    Re: SCA 35. What update mods should be done?

    Post by poconoman on Fri Jul 26, 2013 8:11 am

    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?

    peterh

    Posts : 642
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: SCA 35. What update mods should be done?

    Post by peterh on Fri Jul 26, 2013 9:16 am

    poconoman wrote:
    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?

    No, it's a replacement for the simple cathode bias , it reduces distortion and increases
    power ( yes it true )

    see http://www.tronola.com/html/dave_s_lab.html for description and ordering info.

    As it's mounted on a small board it also replaces the B+ capacitors


    tubes4hifi
    Admin

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    Join date : 2008-11-30

    Re: SCA 35. What update mods should be done?

    Post by tubes4hifi on Fri Jul 26, 2013 8:11 pm

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

    peterh

    Posts : 642
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: SCA 35. What update mods should be done?

    Post by peterh on Sat Jul 27, 2013 5:08 am

    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)

    poconoman

    Posts : 106
    Join date : 2013-01-17

    Re: SCA 35. What update mods should be done?

    Post by poconoman on Sat Jul 27, 2013 6:53 am

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

    Thank you Roy, ordered!

    poconoman

    Posts : 106
    Join date : 2013-01-17

    Re: SCA 35. What update mods should be done?

    Post by poconoman on Sat Jul 27, 2013 6:58 am

    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

    Posts : 642
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: SCA 35. What update mods should be done?

    Post by peterh on Sat Jul 27, 2013 9:46 am

    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.

    poconoman

    Posts : 106
    Join date : 2013-01-17

    Re: SCA 35. What update mods should be done?

    Post by poconoman on Sat Jul 27, 2013 6:42 pm

    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

    Posts : 106
    Join date : 2013-01-17

    Re: SCA 35. What update mods should be done?

    Post by poconoman on Sun Jul 28, 2013 11:31 am

    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

    Posts : 642
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: SCA 35. What update mods should be done?

    Post by peterh on Sun Jul 28, 2013 11:38 am

    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.


    poconoman

    Posts : 106
    Join date : 2013-01-17

    Re: SCA 35. What update mods should be done?

    Post by poconoman on Sun Jul 28, 2013 11:50 am

    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.

    sailor

    Posts : 269
    Join date : 2011-04-04

    Re: SCA 35. What update mods should be done?

    Post by sailor on Sun Jul 28, 2013 1:10 pm

    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.

    poconoman

    Posts : 106
    Join date : 2013-01-17

    Re: SCA 35. What update mods should be done?

    Post by poconoman on Sun Jul 28, 2013 3:06 pm

    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.

    poconoman

    Posts : 106
    Join date : 2013-01-17

    Re: SCA 35. What update mods should be done?

    Post by poconoman on Mon Jul 29, 2013 11:56 am

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

    tubes4hifi
    Admin

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    Join date : 2008-11-30

    Re: SCA 35. What update mods should be done?

    Post by tubes4hifi on Mon Jul 29, 2013 7:56 pm

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

    DarthBubba

    Posts : 81
    Join date : 2012-05-05

    Re: SCA 35. What update mods should be done?

    Post by DarthBubba on Mon Jul 29, 2013 10:41 pm

    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).  Twisted Evil

    poconoman

    Posts : 106
    Join date : 2013-01-17

    Re: SCA 35. What update mods should be done?

    Post by poconoman on Wed Jul 31, 2013 10:19 am

    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!

    sailor

    Posts : 269
    Join date : 2011-04-04

    Re: SCA 35. What update mods should be done?

    Post by sailor on Wed Jul 31, 2013 11:43 am

    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.

    poconoman

    Posts : 106
    Join date : 2013-01-17

    Re: SCA 35. What update mods should be done?

    Post by poconoman on Wed Jul 31, 2013 11:50 am

    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!

    poconoman

    Posts : 106
    Join date : 2013-01-17

    Re: SCA 35. What update mods should be done?

    Post by poconoman on Wed Jul 31, 2013 11:54 am

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

    sailor

    Posts : 269
    Join date : 2011-04-04

    Re: SCA 35. What update mods should be done?

    Post by sailor on Wed Jul 31, 2013 12:11 pm

    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.

    poconoman

    Posts : 106
    Join date : 2013-01-17

    Re: SCA 35. What update mods should be done?

    Post by poconoman on Wed Jul 31, 2013 12:50 pm

    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!

    DarthBubba

    Posts : 81
    Join date : 2012-05-05

    Re: SCA 35. What update mods should be done?

    Post by DarthBubba on Wed Jul 31, 2013 1:34 pm

    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.

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