Old Muntz TV for sale Locally to me, Should I pick it up?

[vortalexfan]

Originally Posted by Kevin Kuehn

So what did you find out when you followed Electronic M's below procedure?

I haven't had a chance to try it yet.

I'm actually kind of afraid to disconnect the wires from the rectifier tube socket because I'm afraid I might accidentally reconnect them wrong and screw things up even more than they already are, especially since I don't which wires are the wires that Electronic M is talking about.

I did post a schematic of the power supply for this TV on here, if someone could mark on the power supply which wires are the ones I need to disconnect and test I can get a better idea of which wires to disconnect and test without risking disconnecting more wires than need to be.

[Kevin Kuehn]

Originally Posted by vortalexfan

I haven't had a chance to try it yet.

I'm actually kind of afraid to disconnect the wires from the rectifier tube socket because I'm afraid I might accidentally reconnect them wrong and screw things up even more than they already are, especially since I don't which wires are the wires that Electronic M is talking about.

I did post a schematic of the power supply for this TV on here, if someone could mark on the power supply which wires are the ones I need to disconnect and test I can get a better idea of which wires to disconnect and test without risking disconnecting more wires than need to be.

Can you take a picture before you disconnect the wires so you'll have a reference to get them back to original? Not trying to be rude, but you need to take the initiative to follow directions and report back if you expect folks to help you troubleshoot this. If I can get the picture to load I drew a red line thought the connections you'll need to open.

[Tube TV]

How many ohms is there between the ground and the white wire you unsoldered?

[vortalexfan]

Originally Posted by Tube TV

How many ohms is there between the ground and the white wire you unsoldered?

There is 256.6 Ohms between ground and the white wire that I unsoldered from pin 2 of the 5U4 tube socket.

[Kevin Kuehn]

Originally Posted by vortalexfan

There is 256.6 Ohms between ground and the white wire that I unsoldered from pin 2 of the 5U4 tube socket.

Is that white wire connected to the same point as the negative side of C1A & B as it appears in your picture? If so it needs to be moved to the plus end of C1A. Also check to see if R93 is in fact still 15 ohms.

[vortalexfan]

Originally Posted by Kevin Kuehn

Is that white wire connected to the same point as the negative side of C1A & B as it appears in your picture? If so it needs to be moved to the plus end of C1A. Also check to see if R93 is in fact still 15 ohms.

It was but then I switched it around once I realized it was hooked up wrong.

I powered it up with that white wire disconnected from the 5U4 tube and it didn't arc anymore.

I'm guessing that means that the Filter Choke may be bad? How hard is it to replace those and how expensive are they to buy? Also how necessary is it to have that filter choke in the circuit? Can the set be ran without it in circuit?

[Kevin Kuehn]

Originally Posted by vortalexfan

It was but then I switched it around once I realized it was hooked up wrong.

OK, so you switched it around. Have you powered up the set with the white wire connected back to pin 2 of the 5U4 since you switched it? If you previously had that white wire going to the negative side of the C1A, & B caps, that alone explains why the set was drawing excessive current, because that point connects to the center tap of the high voltage windings. Normally there would be 15 ohms from that point to chassis ground, which is why I suggested you also measure the resistance of R93(should be 15 ohms)

Originally Posted by vortalexfan

I powered it up with that white wire disconnected from the 5U4 tube and it didn't arc anymore.

I'm guessing that means that the Filter Choke may be bad? How hard is it to replace those and how expensive are they to buy? Also how necessary is it to have that filter choke in the circuit? Can the set be ran without it in circuit?

[Tube TV]

That seems quite low, some of that could be the electrolytics loading the circuit down as they charge. To me it looks like its ahead of the transformer and rectifier.
You could power it up and watch the rectifier tube for arcing, and red plating.

[vortalexfan]

Originally Posted by Tube TV

That seems quite low, some of that could be the electrolytics loading the circuit down as they charge. To me it looks like its ahead of the transformer and rectifier.
You could power it up and watch the rectifier tube for arcing, and red plating.

without that white wire attached to the 5U4 tube socket the tube doesn't arc anymore which I'm guessing means that the filter choke is bad.

[Electronic M]

Originally Posted by vortalexfan

without that white wire attached to the 5U4 tube socket the tube doesn't arc anymore which I'm guessing means that the filter choke is bad.

All it means is that the power transformer and tube, and tube socket are good (and that the short is inor down stream of L1). You need to confirm L1 is bad by unhooking both leads on the choke and measure resistance of both to ground and confirm it is a measurable/low resistance to confirm L1 is bad. If L1 is infinite resistance to ground then it is good and you still need to find the actual short.

Gotta keep dividing and conquering... you've cleared some of the more important parts, and found a a direction to follow to find the short. Keep at it.
Don't let yourself get lazy or confused.

[vortalexfan]

Originally Posted by Electronic M

All it means is that the power transformer and tube, and tube socket are good (and that the short is inor down stream of L1). You need to confirm L1 is bad by unhooking both leads on the choke and measure resistance of both to ground and confirm it is a measurable/low resistance to confirm L1 is bad. If L1 is infinite resistance to ground then it is good and you still need to find the actual short.

Gotta keep dividing and conquering... you've cleared some of the more important parts, and found a a direction to follow to find the short. Keep at it.
Don't let yourself get lazy or confused.

Ok. Just curious but can a filter choke be wired up backwards, or does it not matter which way it's wired up?

[Tube TV]

Don't worry about replacing the choke until you know it's bad.
Heres how to test it.

There' a black wire that is connected to the filter choke that leads to the lower end of the terminal strip where the electrlyics are connected.
I can't see the other wire that come from the choke, but it too should be at the terminal strip. Mark these so that you can connect them back in the same places.
Unsolder these wires and and see if you can get any resistance between it and the chassis.
The reading with both wires off the choke should be infinity or at least in the several megohm range between the chassis and one of the choke leads
The reading between the 2 leads off the choke should be low. Somewhere around 3 to 20 ohms for example.

[vortalexfan]

Originally Posted by Tube TV

Don't worry about replacing the choke until you know it's bad.
Heres how to test it.

There' a black wire that is connected to the filter choke that leads to the lower end of the terminal strip where the electrlyics are connected.
I can't see the other wire that come from the choke, but it too should be at the terminal strip. Mark these so that you can connect them back in the same places.
Unsolder these wires and and see if you can get any resistance between it and the chassis.
The reading with both wires off the choke should be infinity or at least in the several megohm range between the chassis and one of the choke leads
The reading between the 2 leads off the choke should be low. Somewhere around 3 to 20 ohms for example.

OK thanks, I was just getting ready to do that.

[Tom9589]

The filter choke is definitely necessary for proper power supply operation. It’s easy to install - there are only two leads. The bigger problem would be finding a replacement.

[Tube TV]

Also wiggle the wires on L1 while rechecking for the short to ground to rule out a possible intermitent short . To be at infinity on one side of the choke is not possible.
The choke is simply one long run of wire on a transformer core.
Edit: also make sure that when testing one lead on L1 that the other lead is not touching the chassis or other parts in the circuit.