Mystery Sylvania Console 7868 PP Amp

just got this :D and i am wondering if it has 8 or 4 ohm transformers.
mine is kind of low on its output with 8ohm speakers comparing to about the same wattage ss pioneer receiver.
 
Well, I went and ordered the SAM's schematic, so hopefully I can get into it a bit this winter with Kegger. If I can rough it out, he can finesse it.
 
Sam's showed up yesterday and this amp has been "worked". The 12AT7s should be 12AX7s, so I'll see if they just plugged them in or if there was circuit changes made.

He's the info for posterity. PM me for full sized pics.

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Just chiming in on an old, old thread to say that I too have one of these Sylvania SC591W2's. It is a terrific sounding amp, that (in totally stock form) got me to sell off all of the Stereo 70s I had spent 20+ years messing with. Then 4 years ago it died, got a hum on it. I got the schematic from Andyman (thanks much), and FINALLY found the time to dive in. After creating a whole host of other problems and fixing them, I got new filter caps in it and used 1 of the filament windings to buck the voltages into spec, and it is dead quiet and punchy and sounds bloody marvelous. This amp is not a sleeper, it's a giant killer. Thanks to Andyman and Audiokarma!
 
Hy i have very similar amp , 6an8s for the small tubes it was 6L6 out puts but some one converted it to 6bg6ga out put tubes ----amp works and has great sound when it warms up , very warm , very pleased but amp has a small back ground hum when idle , and i would like to fix this , but not sure what to do , mabey increase a cap value , but would like input on this ---------not much or many on line , for this one , uses 5u4 rectify too . has run light , on /off switch and speaker jacks - this amp has way better sound then my maggies it has mcintosh type sound , and i do have a pair of MC30s - but it has this hum issue that i need help with , its not a lot , not real bad , but its there and you really only hear it a quite times in music or at idle with no input signal , ive tried ground ing chassy and reversing the power plug , no go ! --- could it be because of the out put tube switch ? should i put it back to 6L6 ? please help ! have another sylvania console tube amp that i use on my multi tube amp system just to power my jbl 2404h tweeters its a el84 amp similar to a maggie it works great to power the compression tweeters in my four way system , the mcintosh mc 30s power just the jbl 2012h ten inch lower mids , a maggie 8802 powers the jbl midrange 2445 horns with 2380 lens --- if i can get that hum out of the sylvania it could be a back up to power my lower mids or a replacement for my maggie 8802 to get a bit moor power to the mid range horns ---------electronic crossover is a sony tad888 , all thanks to my late uncle watts ------------a solid state amp powers the 15 inch 16 ohm JBL woofers
 

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Hy i have very similar amp , 6an8s for the small tubes it was 6L6 out puts but some one converted it to 6bg6ga out put tubes ----amp works and has great sound when it warms up , very warm , very pleased but amp has a small back ground hum when idle , and i would like to fix this , but not sure what to do , mabey increase a cap value , but would like input on this ---------not much or many on line , for this one , uses 5u4 rectify too . has run light , on /off switch and speaker jacks - this amp has way better sound then my maggies it has mcintosh type sound , and i do have a pair of MC30s - but it has this hum issue that i need help with , its not a lot , not real bad , but its there and you really only hear it a quite times in music or at idle with no input signal , ive tried ground ing chassy and reversing the power plug , no go ! --- could it be because of the out put tube switch ? should i put it back to 6L6 ? please help ! have another sylvania console tube amp that i use on my multi tube amp system just to power my jbl 2404h tweeters its a el84 amp similar to a maggie it works great to power the compression tweeters in my four way system , the mcintosh mc 30s power just the jbl 2012h ten inch lower mids , a maggie 8802 powers the jbl midrange 2445 horns with 2380 lens --- if i can get that hum out of the sylvania it could be a back up to power my lower mids or a replacement for my maggie 8802 to get a bit moor power to the mid range horns ---------electronic crossover is a sony tad888 , all thanks to my late uncle watts ------------a solid state amp powers the 15 inch 16 ohm JBL woofers
Welcome to AK!

That's obviously a different amp - different output tubes and tube rectified. Similar layout, though. Is it a Sylvania or do you even know the brand?

I'm not really familiar with the 6AN8 but it's a triode / pentode kind of like the 7199 and others. The 7199 is often run at operating points that eventually results in heater to cathode leakage, the symptom of which is hum that increases as it gets worse.

First thing I'd try is putting some NOS 6AN8s in, especially since they're not a rare and expensive tube.
 
Thanks been wanting to join AK for many years now . Yes i believe it to be a sylvania amp , it was sold to me as one and it looks enough like that other one to confirm that it must be , its just a bit different year or model --------the 6an8s tubes are nos and ive tried others , but thanks --------i can only guess but thinking maybe the power supply , if i could maybe install a choke and or bias adjuster , but would need some help on that one , i can do the work if i new what to do and where , i do have xtra tubes for this and when i swap out put tubes around the hum gets slightly better or slightly worse , wish this amp had a bias adjuster , can some one talk me threw the install , i may even have xtra pots around here or ill order one
 
Transformer numbers can confirm the maker, maybe date it too. Sometimes that's enough to find a schematic. Power supply hum should mostly cancel in a push-pull output stage, so bias trimming or tube matching can help... but first, what condition are the power supply capacitors in? You can be sure it didn't hum noticeably when it was new, but component deterioration and the mods in the meantime could change that. Gotta know what you have before you think about changing it!
 
i can only guess but thinking maybe the power supply , if i could maybe install a choke . . . wish this amp had a bias adjuster , can some one talk me threw the install , i may even have xtra pots around here or ill order one
As Tom said, you really should try to figure out what it is first.

It looks like the PS caps and coupling caps have already been replaced but that doesn't mean there are no issues with them or other mods that were done. Did you replace them or did you get the amp like that?

A choke might help and it seems to have enough space to mount it but if there's some other problem that's causing hum a choke probably won't fix it.

As for a bias control, you can't just add a pot. The amp likely has a cathode bias scheme which in not adjustable. Adjustable bias is, ironically, referred to as "fixed bias" and it requires a negative voltage supply, not just a pot.
 
Thank you for all this and i do sort of understand ---there are no numbers on out put transformers but on power transformer there is TR-205 and a 798 6025 --Some of the mods where done when i bought it off e-bay years ago and i had to do moor , i recall checking and replacing resistors and that one diode and the input wires from rca jacks and i added the basic thermister by the fuss holder ,[ its a CL-70 ] and i can say that all the power caps are good and not that far from what was factory , so where it called for a 40 uf , it now runs a 47 , where it called for a 5uf it now runs a 6.8 uf --ive even replaced the power caps once again with 105 degree rated capacitors about a year ago but it has the same back ground hum issue -- the coupling caps have been changed and maybe the spec on those went up , like you would do on a maggie rebuild but im thinking that this is not the issue
 
The latest theory is that radio frequency buzz or hum may be getting into threw the over head , high voltage , beam power , tube wire set up ,--the fix maybe to add some kind of ten ohm resistor to each one and some kind of a coil , but need help in finding the rite parts , if this is really the issue , what kind of a ten ohm resistor can with stand that voltage , how high of voltage could it be ? - this sounds crazy but after lots of reading on line , this is what i came up with
 
The heater wires aren't twisted. I'd start there before going crazy with the high-voltage side of things.
 
The issues seems to be in the drive 6an8 tubes , when i unplug them , the hum is gone , so the out put is dead quite , but with them in , it has that 60 hz filament hum , --all so if i unplug a rca input jack a high pitched scream happens , grounding amp to pre amp is no help , tube shields no help , swapping 6an8 tubes , no help , -----------i think that there used to be a film type capacitor on the rca wire input , near the input resistors , would this help to put those back ?
 
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