First console pull, does this look worthwhile?

[downhiller20]

Its from a Zenith console, seller says it powers up but no sound. This would hypothetically be a fun little foray into tubes for me. The cost is pretty minimal, but its an hour drive each way. What is it? and is it worth my time?

 

[knockbill]

google the 4 digit # on teh amp (*H32),, should get you teh chassis schematic...I like Zenith,,,, a little unorthadox, sometimes,,, listening to teh little 3tube amp I just rebuilt now...
good luck with your project...

 

[gadget73]

Looks like it might be stereo single-ended 6BQ5, about 4 watts per channel. Probably not a bad performer but its not a powerhouse. It would be an easy restore though, not a lot of circuitry in a single ended amplifier. I do believe you'll find that it needs a pretty stout preamp to drive the power amp if its what I expect it is. No voltage amp stage on that chassis ahead of the output tubes.

 

[eddantes]

Looks like the amp section is just the power tubes and the rest is in the pre/tuner section - so this wouldn't be the easiest to make stand alone.... But I'm no expert. Still if it were me, I'd keep looking.

 

[RWood]

Eddantes is right, the preamp is on the tuner, and the whole thing is designed to work together. It is an MH2635, and maybe his comment is based on having seen one just like it! Amp is a 3H32, tuner is 12H26 (as in 12 tubes on the chassis).

The one in Marietta is certainly priced right, it just depends on how much your drive time is worth, in light of what you'd wind up doing with the console.

RWood

 

[downhiller20]

Yeah, the price is encouraging me. I should be able to bypass the tuner sextion and add a set of RCA inputs without to much hassle right? Or am I better off waiting for a console pull that would work independently?

 

[Trio]

But there is the educational factor to consider too. The main amp board is essentially a booster amp, and compact. 4 Watts as mentioned above may not sound like a great deal, but with the right speakers, it would be plenty loud enough. Plus, it exposes one to basic tube audio. You would learn a great deal of how to add preamp stages and tone and volume. If the cabinet is something you can work with, that is bonus material.

If you wanted immersion into tube amps, and fabrication- I can think of worse ways to start. It sounds like the cost is minimal, and if you are planning on going that direction on other business, you really not losing anything. Plus you will have some spare parts to work with as well. Those IF and oscillator cans will serve as spares for other tube tuners.

So if your goal is to learn, go get it. Don't worry if in the end you burn it up, you will hopefully learn what not to do in the future.

 

[derekva]

The amp is the gold in this system. The Zenith SE EL84 amps are what gave Steve Deckard his inspiration for his Decware amps.

-D

 

[gadget73]

Depending on how much room is on that amp chassis, its possible you could build the extra amp stage there and have yourself a proper stand-alone amp.

As for running the whole works, I wouldn't be too surprised if its got a tape or phono input that would work as a line-level input from a CD player or whatever you've got in mind.

 

[downhiller20]

Depending on how much room is on that amp chassis, its possible you could build the extra amp stage there and have yourself a proper stand-alone amp.

As for running the whole works, I wouldn't be too surprised if its got a tape or phono input that would work as a line-level input from a CD player or whatever you've got in mind.

I looked back at some of the pictures and I think there is one

 

[Trio]

It is certainly easy enough to replicate the amp if even building it from scratch.

 

[downhiller20]

I'm going to pick this up tomorrow for a cool hamilton, so not much cost at all. I'll probably save it as a fun little summer project.

 

[downhiller20]

Well here is what I ended up with for practically nothing but gas. All the tubes look to be original zeniths. Eventually would like to make this into a nice little standalone with RCA jacks and banana post and volume control, maybe even jumpers so I can use the pre and amp separately? Lots of learning ahead of me! Any details on tubes, what I have, schematics would be appreciated.

5u4gb I think?

No idea what these are

Wheres the preamp section?

 

[mibag6]

The 2 tall skinny tubes are el84s and with the seamed tops appear to be Mullards. If they are in good shape they're will worth your investment.
The tubes on the tuner/preamp that are next to the square transformers are the tuner tubes. Your preamp tubes are in the group of 4 towards the left, in the middle.

 

[s-petersen]

not positive,but the preamp looks like they are the 12Ax7's by the light bulbs and controls

 

[repair_guy]

I had one of these 10 years ago. I remember it being louder than the average 6bq5 single ended. The way to get sound into it is that little plug in the back corner (the red and white wires in the same jacket) for the phono, it's for a crystal cartridge, so you can hook this to any line level source, then set the selector to phono, you may have to put rca jacks on the wire. The best way would be the way you said, running it as a standalone amp, but you'd need 12 volts input for full power, so you'll need a preamp, one 12ax7 should work, 1/2 for each channel. You could use the 6eu7 from the tuner preamp, look up the pinout.

These amps have a cool feature, on the output transformers they ran an extra tap that goes to the power supply. They essentially put current going the other way on the outputs, this balances out the cores so they don't need an air gap, making the transformer work like a push pull transformer, big advantage, this makes it sound more dynamic with better bass. I have a slightly different model, but if I find the schematics I'll post them for you.

With some efficient speakers you'll think this thing is as loud as a 30 watt amp.


Good Luck,

Keith

 

[Dandy]

I've just recapped a similar British pull from an early stereo record player. Mine just has a single 12AX7 where your larger connection socket is. That power transformer and rectifier are clearly used to power up both amps. First item of business is likely to be replacement of the caps in the power section. The can cap there may be okay. Use a dim bulb tester when you first apply power.

 

[downhiller20]

I had one of these 10 years ago. I remember it being louder than the average 6bq5 single ended. The way to get sound into it is that little plug in the back corner (the red and white wires in the same jacket) for the phono, it's for a crystal cartridge, so you can hook this to any line level source, then set the selector to phono, you may have to put rca jacks on the wire. The best way would be the way you said, running it as a standalone amp, but you'd need 12 volts input for full power, so you'll need a preamp, one 12ax7 should work, 1/2 for each channel. You could use the 6eu7 from the tuner preamp, look up the pinout.

When I have the amp pulled up do I need to hook up the accessories, pilot light etc? As far as speakers, it has three connections, so I am assuming a left, right and common return?

 

[downhiller20]

Well I bit the bullet and fired her up tonight. Wired up some RCA's and hooked up an ipod and wow, the one channel thats working sounds amazing! not to fix this other channel. Where do I start looking on how to fix it? I know it is probably not my hookups, and one of the 6BQ5 tubes looks less bright than the other? If its in the preamp where should I look? Also, other than caps, what needs to be replaced?

 

[gadget73]

hard to guess on an unrestored piece. Clean the controls and check the cables between the preamp and power amp. Also might be worth switching tubes channel to channel to see if the problem moves. Honestly with half century old caps and resistors in there though, I can pretty well guarantee its got some parts out of tolerance so that may very well be the issue. If you think it sounds good now, wait till you hear it when its actually working all the way right.