Panasonic RE-784A Radio Speaker/Transformer Wiring

[willemv]

Hi folks,

I recently got myself a Panasonic RE-784A Radio from a yard sale. I think these date back to the 1950s, if I'm not mistaken. I would love to get it going, but it has a problem. The radio switches on and off nicely. The tubes light up. There are no wierd sounds like humming or buzzing. As a matter of fact, there is no sound at all... ;-)

The wiring between the speaker and its transformer is partially disconnected, as is the wiring between these items and the external speaker jack, and the rest of the radio. I have no clue how to reconnect the wiring and don't want to go at it on a wing and a prayer. The wiring diagram on the bottom of the unit is very small and means as much to me as abracadabra.

The transformer is marked 48E53W16I on the metal bridge and ETK-131Z on the winding. If I keep it horizontal with the markings readable, it has two connection points on the top side (I'll call these 1 and 2, left to right) and three on the bottom (I'll call these 3, 4, and 5, left to right). Points 3 and 4 are bridged with one of those brown, flat disc thingies (005MF P TDK). There is also a thin, bare wire sticking out from the bottom of the transformer.

From the main electronics block that holds the tubes four wires protrude that were apparently all involved with the speaker and/or transformer at one point: red and blue coming from one hole, white and black from another.

Currently...

- the red wire goes nowhere.
- the black wire goes nowhere.
- the blue wire connects to transformer point 4.
- The white wire connects to transformer point 2.

From the speaker comes a black and a white wire that go nowhere.

From the external speaker jack comes a black and a green wire that go nowhere.

Is there anyone out there who can tell me how to put these connections together again?

Alternately, if there is anyone out there with the same model and willing to share a picture of its inside, that would be very helpful, too.

Thanks in advance,

- Willem Vandenberg

[Reece]

See if you can scan and maybe blow up the schematic so it is readable. The brown disk is a capacitor. Take clear pictures of the transformer. Take out the chassis and note where the disconnected colored wires go: for example, red wire goes to terminal (number) of the (number) tube.

Does this radio have any external speaker jacks or terminals and are they involved in this?

[tgunner]

I was able to find this, but not a bigger resolution. The same site has a schematic, but I can't figure out how to view it in full.

[Reece]

That site won't let you see anything unless you are a member, and I'm not. You can be a member by paying a fee or by sending them a picture of some radio they don't have, etc. Maybe someone will chime in here that has a schematic for this radio and will post it.

[tgunner]

Originally Posted by Reece

That site won't let you see anything unless you are a member, and I'm not. You can be a member by paying a fee or by sending them a picture of some radio they don't have, etc. Maybe someone will chime in here that has a schematic for this radio and will post it.

Hmm, interesting. With 120+ radios, I'm sure I have seomthing that they don't.

[Reece]

Can you take a good closeup digital pic of the schematic on the bottom of the radio and post it? I've got a pretty good idea how to connect this up but the diagram would help. I believe the white and black wires disappearing mysteriously into the radio are part of a feedback circuit, looking at the pictures on "that" site.

Does the speaker jack have two or three terminals on it?

[tgunner]

Originally Posted by Reece

Can you take a good closeup digital pic of the schematic on the bottom of the radio and post it? I've got a pretty good idea how to connect this up but the diagram would help. I believe the white and black wires disappearing mysteriously into the radio are part of a feedback circuit, looking at the pictures on "that" site.

Does the speaker jack have two or three terminals on it?

Looking at the picture I posted, you can see the speaker jack has a white wire going to the speaker, and a green and black wire going to the transformer. Whoever cut this up really made it hard for us, eh?

[Reece]

If the speaker jack has three terminals, it's a closed-circuit jack which cuts off the radio's speaker when an external speaker or headset is plugged in. The wiring for that is easy. The red and blue wires coming from the chassis are the usual colors going to the primary of the output transformer. The black and white wires going back into the chassis are throwing me off and why I would like to see the section of the schematic around the speaker and output tube. I wouldn't want to recommend a hookup without seeing the diagram. If it didn't have the black and white wires I'd jump in feet first! Maybe someone reading this has a similar Panasonic radio and can post the schematic or scope out the wiring.