1962 Magnavox Imperial Wiring Question

[dstroup]

I recently purchased a 1962 Magnavox Imperial console (Danish Modern). The model number is 1-ST657.

The previous owner did some rewiring including cutting 2 wires (1 from each side mounted woofer: Green and Blue as indicated on the schematic detail photo below) which led to the “Speaker Switch”. I have managed to rewire everything back to what is indicated on the schematic, but the 2 cut wires will require some soldering.

My question:
Do I really need to reconnect these 2 wires? In other words, does the “Speaker Switch” default to “Internal” speakers (speakers in the console). I only plan on using the “Internal” speakers.

I don’t really understand how this stuff works, but I want to make sure I don’t do something that causes damage to this super nice console which I hope to get working again.

I have included some photos below to illustrate my dilemma.

Please Note: The wide shot with the back open was taken before I rewired everything (although I haven’t done any of the rewiring for the turntable yet).

Thanks!

 

[thorpej]

Uh... it kind of looks to me like maybe you do need to reconnect them, although it's kind of hard to tell without seeing the diagram for the switch itself.

Did the previous owner use it with only external speakers or something?

As an aside, that's a fine looking piece of furniture and it looks like a unit that has a 930x amplifier! Very nice. Probably the best of the Magnavox console amps. It will probably sound great in it's native environment after being electrically restored (even just to stock form), but also has serious potential with some modification (though that may not be suitable for use in the console with the pre-amp and stock loudspeakers).

 

[dstroup]

Thanks for your advice! I will try to come up with a diagram for the switch.

The previous owner appears to have rewired the turntable so he could connect it to another piece of equipment and could run power to it directly. He also rewired the speakers to connect to an external piece of equipment. I hope this doesn't indicate there's something wrong with the tuner for the amplifier?

Thanks for the compliment, yes it's in super nice condition. It is a 9304 amp.

 

[gadget73]

yeah, they need to be re-connected. It appears that the + output from the amp goes to the selector via the orange and brown wires. It comes back out to the speakers on the blue and green wires.


Bypassing the guts could mean they don't work, or maybe he just wanted to use something else. Just beware, this thing is old, and old tube gear that has not run in a long time needs to be re-powered with care or its liable to let the smoke out. Check out the sticky at the top for information on how to safely bring up a tube amp after a long hibernation. For long term reliability, this will need some parts replaced too.

 

[RJolly87]

I suspect the switch was pulled for a reason. If I am guessing right, the wiring goes from the amp output, and should go to the speaker selector switch, then the crossover network. If I was using my brain, I would connect straight from the amp output to the crossover network.

I also think the amp has been spun around, because I would think they would normally try and mount them in a manner that points the power cord to the back panel.

 

[larryderouin]

The way it's wired up from the factory, it does not default to the internal speakers. You CAN however disconnect the switch from between the amp and the speakers, then wire the speakers directly to the amp, OR solder the green and blue wires back. (historically accurate would be solder them back together, and leave the switch on Internal. Once ot twice a year exercise the switch about 20-30 times to break up corrosion.

Orange and brown are your Ch1 and Ch2 output's from the AMP. The go directly to the speaker switch. The speaker switch only switches the HOT or + side of the speakers. Grounds are all in BLACK!

If you want to run INTERNAL SPEAKERS ONLY and BYPASS the switch, disconnect each of the following in turn, replacing with new wire to the new connection. NOTE: If the cut Green and Blue wires from the speakers are long enough to run from the speaker to the amp, connect them directly to the amplifier CH1 and CH2 terminals.

Some time in the future you may want to hook up external speakers, so try and not cut, or otherwise disrupt the original wiring, except where cut. that's why I suggested using new wire , but if the Loose (cut) GREEN and BLUE wires are long enough to reach the amp without stretching them, go ahead and use them to go directly to the amp. Roll up the rest fo the loose wiring and tuck it away somewhere internal that won;t be too affected by the tube heat.

Remove each channel in turn and repair before going on to the next channel.
1.) BROWN wire from Amp CH1 connection. Loose GREEN Wire from Woofer on LEFT (CH 1) . Install new wire between amplifier Ch1 connection to the speaker terminal where you just disconnected the loose green wire from. See note above for green and blue wires. This is the black line from Ch1 to
2.) ORANGE wire from Amp CH2 connection. Loose BLUE Wire from Woofer on RIGHT (CH 2) . Install new wire between amplifier Ch2 connection to the speaker terminal where you just disconnected the loose blue wire from. See above note for green and blue wires


You are done. The internal speakers will work as designed, the speaker switch is bypassed, and you can solder the blue and green wires back at your convenience, and it's totally reversible.

The black lines are new leads to the speakers vice the blue and green if not long enough. For illustrative purposes only. I inadvertantly reversed them at the amp connections. Otherwise it's correct.

 

[dstroup]

Thanks for feedback / advise. Would it be possible acceptable to splice wires to the blue and green leads that were cut coming from the speaker selector switch? I would prefer to do this over having to solder ( something I have little experience with). Of course, I would wrap the splices with electrical tape.

 

[thorpej]

Thanks for your advice! I will try to come up with a diagram for the switch.

The previous owner appears to have rewired the turntable so he could connect it to another piece of equipment and could run power to it directly. He also rewired the speakers to connect to an external piece of equipment. I hope this doesn't indicate there's something wrong with the tuner for the amplifier?

Thanks for the compliment, yes it's in super nice condition. It is a 9304 amp.

Tube equipment is extremely fixable. You're really only out of luck if the transformers are bad. But even in that case, for a 930x, there are options.

This is a really nice unit. If this is your first vintage tube unit, there are some things you're going to want to do first... cap job, for example. Not hard at all if you're handy with a soldering iron.

Agree with @larryderouin, you could just bypass that speaker switch altogether.

 

[larryderouin]

Thanks for feedback / advise. Would it be possible acceptable to splice wires to the blue and green leads that were cut coming from the speaker selector switch? I would prefer to do this over having to solder ( something I have little experience with). Of course, I would wrap the splices with electrical tape.

Yes. splice green to green and blue to blue. Get a couple Wire nuts (caps) like those used by electricians in boxes. Trim back about 1/4 to 3/8" insulation on each end and twist the ends tightly. Then wire nut them. Fold over about 1" so the nut is laying on the wires. Wrap with electrical tape from 1" from the end you to 1" past the end. Fold over the tape end that doesn't have wire in it, and wrap tightly to the end. Now it's sealed and insulated.

DO NOT AUTOMATICALLY PLUG IN AND POWER UP! There are things you need to check for and repair/replace before powering up the 1st time. A Dim Bulb Tester(DBT) needs to be made, (google it), and a variac should be used in conjunction with the DBT. These two will help prevent you from literally burning down your house (worst case) if something is drastically wrong on the amp or tuner. I haven't got anymore time, as I have to go baby sit grandkids, so I'll leave it to thorpej and others to handle the startup.

 

[dstroup]

Thank you everyone for your assistance with this! It has been a very good learning experience for me.

I decided to stop by my local electronics supply store this morning and discuss the problem with them as well. I ended up buying some 18 gauge wire, butt connectors, female quick disconnects, and a crimping tool and connected some new wire to the Green and Blue leads.

After the wiring was complete I powered her back up (sorry, larryderouin - I hadn't read your post yet) and she works great!

EXCEPT...

The tuner string appears to be malfunctioning because it's stuck on one station and turning the tuning dial does nothing. This would explain why the previous owner had done the rewiring (use an external receiver with the magnavox speakers and turntable).

So next up is researching how to repair / replace a tuner string on the tuner.

Thanks again!

 

[larryderouin]

Restringing a maggie is fairly easy. Get the model # off the tuner chassis, and look up the sams photofact on it. It'll probably have the amp chassis schematics on it also. But they usually have the tuner stringing info.

 

[gadget73]

String broke. Not a big deal, just mildly frustrating. Hopefully its still basically in the right place so you have a reference. Scotch tape will help hold things in place for you. I've used a number of things to re-string before but you want something close to the original thickness or its probably not going to lay properly. High test braided fishing line, commercial sewing machine line, actual dial cord, it all will get the job done. The really slick stuff might be prone to slipping on the tuning shaft but if you rub it with a candle to put a bit of wax on it, it'll drive better.