• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Found myself a Magnavox 9302-00

Got the whole console for $75 in very good shape. Bought from original owner. It's been sitting in the living room for 40+ years. Powers up and plays. :)

I'm thinking of transplanting it into a chassis and try to make it as small as I can.

Who has the schematic?

-and-

Anyone interested in two 15" woofers, two 6" midranges, and four tweeters? All paper with alnico magnets. They worth anything? I also have the turntable from it.

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That's a better amp than the unit in this thread. Notice the more massive O/P "iron", a B+ filter choke, and the properly sized 5U4 rectifier. Still, the family resemblance is quite obvious.

My remarks about 6EU7s in the linked thread also apply here.

There's LOTS to be said in favor of good sized sheet metal, starting with room to work. Consider casing up what you already have. The crappy OEM RCA jacks can be replaced by Neutrik NF2D parts that don't weaken the chassis, even though a good sized opening is made. Die cast metal helps. :)
 
The only concern I have with a small chassis is crosstalk and/or noise. Proper layout should help that. I planed on simple point-to-point wiring with it and a smaller layout makes that easier. Are there other issues I should know about?

Thanks for the link. I read about the 12AX7 conversion. I may do so because there's many substitutions to play with if I do.
 
Nice find. A wood chassis surround looks nice on those old Maggie's. The molex opening is good for a power switch. Don't forget to add a fuse. You can find schematics for all the maggies at the Friends of Magnavox yahoo user group. The speakers are a tough sell. I have found buyers on Craigslist for about $20.


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I figured the speakers weren't that sought after. I may use them for my guitar amp project and make a 2x15 cab with a pair of 6L6GT for outputs. I've been working on multi-stage distortion using 12ax7 tubes and think I have it figured out. Could be fun and I bet ~50w into 2 15s would fill a bar. :)
 
I'm not sure what happened to my amp but since I did the balance elimination I'm having bad crosstalk and I think phase cancellation. I took photos before and after and I'm positive I got it right.

What's happening is when the inputs to both channels are plugged in (stereo), the vocals are coming from the right speaker and the music from the left speaker seems out of phase. If I plug in only the left channel it plays (mostly) from the left. If I plug in the right channel it plays from both speakers equally.

I only had 330ohm resistors but I figure that would only reduce the amount of feedback.

Here's a pic.

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I found these yesterday and picked them up tonight for $25 with the Zenith Allegro console but the console was solid state so it got scrapped but I kept the drivers. Two Zenith 10" paper woofers, two small Philips dome horn tweeters, and two crossovers.

These remote speakers sound amazing with the Magnavox amp driving them. The bass shakes things in the room.


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I'm not sure what happened to my amp but since I did the balance elimination I'm having bad crosstalk and I think phase cancellation. I took photos before and after and I'm positive I got it right.

What's happening is when the inputs to both channels are plugged in (stereo), the vocals are coming from the right speaker and the music from the left speaker seems out of phase. If I plug in only the left channel it plays (mostly) from the left. If I plug in the right channel it plays from both speakers equally.

I only had 330ohm resistors but I figure that would only reduce the amount of feedback.

Here's a pic.

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You have it wired wrong , something is not grounded correctly .
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You have it wired wrong , something is not grounded correctly .

It was right. I just goofed the spade speaker connections. I have since added binding posts. That was all it that was wrong.

If your not using the tuner use 20- 22 k to keep the font end voltage the same

I swapped the 10k for a 22k. B+ to the opt is now sitting at 335v. 6EU7s are getting 292v. I separated the left and right output tube cathodes each pair with 220ohm+2.2kohm (200ohm total) with a 160uf cap in parallel. That was the only handy way to make 200ohms. My cathodes are at 13v though and I believe they should be closer to 10v. I need to find out why.

Any damage at 13v? Is that correct to say my output tubes are under biased?
 
There's something almost "dungeonesque" about them, if that's even a word. Maybe they remind me of my creepy aunt's house that was full of 60s-70s era wooden/iron furniture and chain-hung lighting that looked like small torture cages. Had I known then what I do now, I would have called dibs on the tubed Scott equipment that my uncle had built into the bookcase. The whole house was wired for sound. Speakers everywhere. I remember family reunions with "California Dreaming" playing on vinyl.

I found an ad for the speakers. "Tuned port"? More like a 3.5" hole in the back. No tube but it's amazing how deep the sound is. They play down in the 30s easily.

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I hope I can explain this correctly...

On the input of this amplifier (9302-00) it has 47k from input to grid and 470k from input to ground. This essentially makes a voltage divider for the input (to provide 470k input impedance and to reduce gain?) and 517k total resistance for the grid.

Could I simply use a .1uf cap from the input straight to the grid? This would leave the 517k grid resistance intact and capacitor couple my input. This should increase the sensitivity about 10% correct?
 
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