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ultratone SE 6bq5 stereo amp - mystery guy

Jcricket

Jcricket

not someday, but today
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Hey folks,
I just aquaried this little SE el84 stereo amp. It is quite a simple looking amp. The tubes in it are RCA manufactured for ultratone. The driver is a 6eu7. It takes a 6ca4 rectifier.

I have done a fair amount of googling and have not found the schematic.

Something interesting to me, the output transformers have different taps than I am used to seeing. There are 4 primary taps. One is b+, one connects to pin 7 of the el84. On the other two, one connects to the el84 after it goes through a resistor, and the last tap goes through a resistor and then connects to the 6eu7.

That make sense? ANyone seen a schematic like this? Anyone understand what is happening here?
 

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When I saw that pictures, it reminds me of my 2 monoblocks that came from the classroom record players. They're identical. :banana: Looks alot like your amp except the power transformer since they're separate. They were tossed to the garbage at my work. Each use one 6x4 rectifier, one 6av6, and one EL84 (one amp have what is made in Holland and other amp have what is made in Britain). They sound pretty good through my headphones along with the loading resistors.
 
ccheath said:
When I saw that pictures, it reminds me of my 2 monoblocks that came from the classroom record players. They're identical. :banana: Looks alot like your amp except the power transformer since they're separate. They were tossed to the garbage at my work. Each use one 6x4 rectifier, one 6av6, and one EL84 (one amp have what is made in Holland and other amp have what is made in Britain). They sound pretty good through my headphones along with the loading resistors.
Click to expand...

Yep, I have a pair of RCA 6AQ5 amps that look VERY similar, from record players. Actually, are you sure those drivers are 6AV6? Mine use 6AU6s. ;) Sorry, I don't understand those resistors, but I bet someone here does.
 
Jcricket said:
Something interesting to me, the output transformers have different taps than I am used to seeing. There are 4 primary taps. One is b+, one connects to pin 7 of the el84. On the other two, one connects to the el84 after it goes through a resistor, and the last tap goes through a resistor and then connects to the 6eu7.
Click to expand...

That's the feedback circuit if the wires are connected to the secondary side of the transformers. Some output transformers are wired internally from the secondary side to the feedback loop. A Packard-Bell amplifier I own has the outputs wired this way.
 
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spaceman said:
Yep, I have a pair of RCA 6AQ5 amps that look VERY similar, from record players. Actually, are you sure those drivers are 6AV6? Mine use 6AU6s. ;) Sorry, I don't understand those resistors, but I bet someone here does.
Click to expand...

Yes, 6av6 with a "V". It's like 1/2 of 12ax7 (or you could say 1/2 of 6eu6 ;)). And they're tested strong on both amps.
 
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Feedback, got it. I should have caught that. Now it makes sense.

I thought this might have been a packard bell. Anyone else care to try and identifiy this little critter.
 
ccheath said:
Yes, 6av6 with a "V". It's like 1/2 of 12ax7 (or you could say 1/2 of 6eu6 ;)). And they're tested strong on both amps.
Click to expand...

Those sound like.. I cant remember the name now. Ive got 5 left but Ive thrown the cases away. :scratch2: starts with an "N" Noresco?

School AV department record players from the 60's

They make nice little guitar amps.

Cricket, I havent seen one like that before. ~ kinda like one of the similiar Maggy's in the looks dept.

..
 
resound said:
Those sound like.. I cant remember the name now. Ive got 5 left but Ive thrown the cases away. :scratch2: starts with an "N" Noresco?

School AV department record players from the 60's

They make nice little guitar amps.

Cricket, I havent seen one like that before. ~ kinda like one of the similiar Maggy's in the looks dept.

..
Click to expand...

You mean Newcomb? Mine's model R-124 or R-124V. I threw the cases away too. I saved the schematic though.
 
Ultratone was a firm in Michigan City, In., that built private label audio pruducts. The ones I worked on were well performing units. A lot better than some of the competition.
 
ccheath said:
You mean Newcomb? Mine's model R-124 or R-124V. I threw the cases away too. I saved the schematic though.
Click to expand...

Thats right, Newcomb. I saved the red & blue "N" plates but couldnt remember the name.
Let that be a lesson to all you whippersnappers about the dangers of fast women. :D
Its one of those amps in the little lunch box guitar amp I show'd off here last month.
Which reminds me that I need to get hot on those.


..
 
Tom,

There is a stamp in ink on the chassis that is a circle with a "14/A" in it. The output and power trannies have the same number on them - 9496123. THe ouputs also have the number 1217c on them. That is it, that is all that is on the chassis anywhere.

Thanks!
Mark
 
Transformers are Apex Coil & Transformer, 1961, week 23. There's an Ultratone model 14 listed, Sams 618-8, 1963. Possible... but not in my files. I wouldn't buy it without verifying that it matches...
 
Thanks Tom!

Apex Coil and Transformer - know if it is any good? Is it worth putting a little effort into this to make it a stand alone unit? Any thoughts?
 
Jcricket said:
Hey folks,
There are 4 primary taps. One is b+, one connects to pin 7 of the el84. On the other two, one connects to the el84 after it goes through a resistor, and the last tap goes through a resistor and then connects to the 6eu7.
Anyone understand what is happening here?
Click to expand...


yes, the one connecting to pin 7 is the "plate" lead, the other lead connects (through a resistor) to the screen grid of the EL84. the last one connecting to the 6EU7 through a resistor is a feedback supply.
 
Jcricket said:
Thanks Tom!

Apex Coil and Transformer - know if it is any good? Is it worth putting a little effort into this to make it a stand alone unit? Any thoughts?
Click to expand...


yes, it is a nice little amp using the williamson design. you will need to replace them white ceramic capacitors, & check all of the 220kohm resistors under the 6EU7 socket.
 
:thmbsp:
Already planned on it. I even have the multi can cap to replace the PS cap - kinda like this amp was meant for me. I didn't have to order thing. Maybe I am just too deep into this now that my shelves look like warehouse of caps and resistors. :no:

I'll post more when I get to it.
 
robert1 said:
you would not by chance happened to save the plug-in needles when you scrapped them?
Click to expand...

:no:Sorry, no I didn't. One of the player I scrapped was pretty busted. The other player was playable but looks like the needle needed to be replaced. Had one monoblock and wanted another since they're identical so scrap the player. It was already hard to dismantle it since it was a pretty decent classroom record player.
 
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