need help identifying these units

G

gerjamr

Member
I picked these up at a sale, they have no markings anywhere.

1 = mullard 12ax7, mullard el84/6bq5, mullard 6x4

2 = mullard 12ax7, 448?, sylvania 6x4

Would these be decent mono amps to rebuild for a beginner?

Thanks.
Dan
 

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Those look like they would be the perfect vehicle for the audio experimenter to learn about tube audio amplifiers. They appear to be single ended 6BQ5 amplifiers and you have two for stereo. They should put out several watts, but you will have to be willing to experiment. You will need basic tools like a soldering iron and multi meter. Maybe this article will inspire you: A Beginner 6BQ5 SE Amp.
 
Thank you all for the replies! I would like to have 2 amps, use as much of whats there as possible. I would like to make new chassis for them so I can arrange things to be more pleasing to the eye. If someone has done something similar with pics that would be great!

Palustris, thank you for the link! I will be reading up on this.

Thanks
Dan
 
gerjamr said:
I picked these up at a sale, they have no markings anywhere.

1 = mullard 12ax7, mullard el84/6bq5, mullard 6x4

2 = mullard 12ax7, 448?, sylvania 6x4

Would these be decent mono amps to rebuild for a beginner?

Thanks.
Dan
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Sorry, i can not help you with the id'ing of these little amps, but i do know that they can be very good sounding ones after rebuilding, and well worth the effort and expense. I don't know if you have any experience doing that but if you have high efficiency speakers, like Altec or Klipsch, of around 100db, the sound from little single ended el84 amps can blow you away. It would be great to get them singing again. About the hardest thing to deal with is the plug in octal based can caps. No one makes them anymore and i am not sure if you can get them rebuilt. Perhaps, they can be but i don't recall anyone rebuilding that type. But it is not a big deal removing the socket and using a JJ multi value cap. cheers.
 
I'd probably give some consideration to turning these into a DGSE1. The tube lineup is suitable if you plan to rebuild these on another chassis.
 
+1... I would want to get them working as original first, tho,,, just to make sure the components(tubes, TX etc) were working... May just need a few caps, or resistors, and a variac to bring em up slow ...
 
Thanks everyone!
I have a pair of heresy's so I have that covered, I also have a variac and thought about turning them on but someone cut one side of the resistors in the back of each one, hard to tell in the pic but it's a large light green one and a smaller brownish one in the same spot on the other amp so I sure about turning them on.
Could I remove all the tone control stuff and replace the cap cans with some different type and keep everything else in its place for now to test? It looks like with the controls gone it would be a bit less " scary " under there!

Thanks
Dan
 
I wouldn't modify them before getting them running, it would make things more complicated to figure out, weather a problem is old, or new.
Looking at the pic, it looks like the first resistor powering the unit is disconnected, the can caps may be shorted, or something, it looks like the HV is disconnected. A better pic of the area would help. The large greenish Tru-Ohm and the brown resistor on the other amp, are disconnected Correct?
The brown wires out of the back are the speaker wires.The RCA jack is the input.
If you have a variac, or DBT it would be a good thing to use.
 
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!! The one on the left in your 1st picture has a simply epic 'Tested' stamp on it.

That is far + away the largest one I have ever seen outside of a beef aging cooler!

Fun project!
 
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