Starting a Stromberg Carlson ASR-444 amp build

So..., I'm in the winter amp building mood again. I had a pretty beat up Stromberg Carlson Stereo 60 (ASR-444) and wanted to build a straight amp from it. This is how far it has progressed tonight.
The Chassis is a blemished SS Dynaco 70 chassis that is sometimes offered on the auction site.
I already had the cage, but it may not be used.The tube sockets on the front will likely go away, as they are completely useless.
I will have to make some resistance changes because the 2 6AV6's are gone. The amp will use 6L6GC output tubes
The speaker terminals are not the best, but they are better than the screws that were used in the Dynaco's
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Schematic updated 2/15
 
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Nice looking chassis, and iron! Seems you have another winner on your bench...

I kinda like those spring lock speaker terminals,,, I first saw them on my Sansui 800, and have used them on a Maggy rebuild, have you had any problems with them? I tin the speaker cable so there aren't any stray wires missing the holes, but they seem to work fine...
 
Cool. It looks reasonably close to an ST-70 too, any plans for what to do with the second cap opening ?
 
Nice looking chassis, and iron! Seems you have another winner on your bench...

I kinda like those spring lock speaker terminals,,, I first saw them on my Sansui 800, and have used them on a Maggy rebuild, have you had any problems with them? I tin the speaker cable so there aren't any stray wires missing the holes, but they seem to work fine...
I haven't had much trouble with spring terminals, I've had more trouble with the screw terminals, with wire hairs bridging adjacent terminals.
I had to modify the blocks slightly, because the holes were supposed to be 55mm apart, but came 60mm instead.
Cool. It looks reasonably close to an ST-70 too, any plans for what to do with the second cap opening ?
I plan to plug it with a dummy cap, Hayseed Hamfest sent me a couple of rejects, and I am using them on a pair of mark IV conversions, also in process(Scott 290 schematic,with tweaks), but they gave me an idea to try for this one.
They can be used as bias probe points, and Dynakit Parts makes a nice bias balance kit that fits there.
This amp uses cathode bias, I am thinking of mounting level controls in them.

One mistake I made was ordering the black fiberglass without copper on one side, it would have been better shielding, now I will have to use some aluminum sheet instead.
 
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I never ever use bare wires going to a terminal strip. Always crimp or solder on ring or spade lugs. Bare wire just mashes out from under the screw and invites trouble. Besides, ring and spade lugs have been in use in industrial control wiring for about a century and have very few failures it done correctly. It also makes for the best low resistance connection by far.

BillWojo
 
I put a vintage pilot light in a can cap hole on a Maggy chassis, its set back kinda like yours... Used an off whitish lens on it with a dim (12V on 6V supply) bulb,,, glows about the same as the tubes...
Save those cans to restuff!!!!
 
I bought ~8 NOS can caps from the 80's that I can restuff, if I get brave. The crimp terminal are a good idea, but I am constantly connecting / disconnecting the speakers, It would be inconvenient to unscrew the screws all the time.
The spring terminals seem to be fine for modern equipment, unless it is very high wattage.I have several Mcintosh SS amps with spring terminals, albeit better quality.
 
Good ideas Scott. I built a 6U8-frontend amp a while back but I used 7868 outputs. I had two issues on mine: 1) finicky 6U8's required DC on the heaters, 2) AC coupling between gain and phase inverter stages added an extra R/C time constant that therefore required careful sizing of the screen bypass cap. If you build the 444 schematic as shown with DC coupling I think you can probably avoid this issue.
 
I have always picked up 30+ watt amps , what bothers me, about 5 years ago I threw out about 300 pounds of tube iron while cleaning out storage, that's a major regret I have.
 
Well,,, I understand... I grabbed a huge hoard of NOS Zenith PTs a few years ago at a hamfest, and made a friend along with it!!! PM if you ever need any, I have more then my lifetimes worth!!
 
Careful.. I may take you up on that, I have a Churchill amp with a marginal PT (wires are crispy at the transformer) and a Heathkit SA2 with rust in an untested transformer, What do they drive?
I regretted getting rid of them almost as soon as they were gone, many of them were Lafayette, Knight, Scott, Sansui and Fisher I parted many mid level integrated amps that had some major defect. Lafayette and Knight for the bad PC boards, some Scott's and Fisher's for a bad PT
 
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