Lafayette Comstat 23 Mark V

[danmcclain]

I have a Lafayette Comstat 23 Mark V that powers up, the panel light comes and but the tubes don't light up.
Where would I start to look for a problem? I can't remember if I posted this someplace else so I apologize if I did.

 

[TM86]

I'll preface this with the fact that I have zero knowledge of the radio in question. I do have Sams CB-23, but that will only go so far.

I'm looking at the schematic and it shows that the tube filaments should be on the same circuit as the panel lamps. If the panel lamps are coming on, are they full intensity? No could mean there's not enough voltage to get the tube filaments to light up. Yes could mean multiple tubes with bad filaments. Multiple tubes all dying at the same time is unlikely, however, if this radio was somebody's parts queen they could have been swapped out over time. Someone with more tube experience will hopefully chime in on whether it's worth it to just do a continuity check on the filaments. I suspect it is and should probably be done out of circuit.

Another thing to look for is bad soldering or a wire put in the wrong place during a previous repair attempt. I'm working strictly from pictures but it appears that this uses point to point wiring and not a circuit board. So putting a wire on the point next to the one you wanted is a little easier to do, especially if you're distracted or in a hurry.

Anyways, that's what I can think of to start looking at. No idea if any of it is actually helpful. Whatever you do, be careful. There may still be high voltage lurking about on tube pins even if the filaments are dark.

 

[nomadradio]

Doesn't the heater circuit pass through two pins on the power cord's socket?

Might be worth popping the cover off the socket to see that the jumper wire is intact.

73

 

[danmcclain]

I'll preface this with the fact that I have zero knowledge of the radio in question. I do have Sams CB-23, but that will only go so far.

I'm looking at the schematic and it shows that the tube filaments should be on the same circuit as the panel lamps. If the panel lamps are coming on, are they full intensity? No could mean there's not enough voltage to get the tube filaments to light up. Yes could mean multiple tubes with bad filaments. Multiple tubes all dying at the same time is unlikely, however, if this radio was somebody's parts queen they could have been swapped out over time. Someone with more tube experience will hopefully chime in on whether it's worth it to just do a continuity check on the filaments. I suspect it is and should probably be done out of circuit.

Another thing to look for is bad soldering or a wire put in the wrong place during a previous repair attempt. I'm working strictly from pictures but it appears that this uses point to point wiring and not a circuit board. So putting a wire on the point next to the one you wanted is a little easier to do, especially if you're distracted or in a hurry.

Anyways, that's what I can think of to start looking at. No idea if any of it is actually helpful. Whatever you do, be careful. There may still be high voltage lurking about on tube pins even if the filaments are dark.

I'll preface this with the fact that I have zero knowledge of the radio in question. I do have Sams CB-23, but that will only go so far.

I'm looking at the schematic and it shows that the tube filaments should be on the same circuit as the panel lamps. If the panel lamps are coming on, are they full intensity? No could mean there's not enough voltage to get the tube filaments to light up. Yes could mean multiple tubes with bad filaments. Multiple tubes all dying at the same time is unlikely, however, if this radio was somebody's parts queen they could have been swapped out over time. Someone with more tube experience will hopefully chime in on whether it's worth it to just do a continuity check on the filaments. I suspect it is and should probably be done out of circuit.

Another thing to look for is bad soldering or a wire put in the wrong place during a previous repair attempt. I'm working strictly from pictures but it appears that this uses point to point wiring and not a circuit board. So putting a wire on the point next to the one you wanted is a little easier to do, especially if you're distracted or in a hurry.

Anyways, that's what I can think of to start looking at. No idea if any of it is actually helpful. Whatever you do, be careful. There may still be high voltage lurking about on tube pins even if the filaments are dark.

Thanks again TM86, the panel light looks to be at full strength. As far as the tubes go, I have a tube tester and will check every one of them. I noticed a toggle switch on the front panel that looks like it doesn't belong there. I'll see where the wiring goes too. Always careful to let the radio set unplug for a few hours before I delve into it.

 

[danmcclain]

Thanks again TM86, the panel light looks to be at full strength. As far as the tubes go, I have a tube tester and will check every one of them. I noticed a toggle switch on the front panel that looks like it doesn't belong there. I'll see where the wiring goes too. Always careful to let the radio set unplug for a few hours before I delve into it.

Sorry, got my radios mixed up...

 

[danmcclain]

Doesn't the heater circuit pass through two pins on the power cord's socket?

Might be worth popping the cover off the socket to see that the jumper wire is intact.

73

I wired the plug myself according to Sams PhotoFact CB-23, the 2 jumpers are intact.

 

[danmcclain]

I wired the plug myself according to Sams PhotoFact CB-23, the 2 jumpers are intact.

Began checking the tubes, 1st one I checked 6GH8 was bad, so I checked the other 2 6GH8 tubes and found a different tube in both spots, a 8H8. Doesn't show on the sub list. It shows a 6HL8 but not a 8H8. Taking a break since I can't do any ordering till the 1st of next month.

 

[danmcclain]

I'll preface this with the fact that I have zero knowledge of the radio in question. I do have Sams CB-23, but that will only go so far.

I'm looking at the schematic and it shows that the tube filaments should be on the same circuit as the panel lamps. If the panel lamps are coming on, are they full intensity? No could mean there's not enough voltage to get the tube filaments to light up. Yes could mean multiple tubes with bad filaments. Multiple tubes all dying at the same time is unlikely, however, if this radio was somebody's parts queen they could have been swapped out over time. Someone with more tube experience will hopefully chime in on whether it's worth it to just do a continuity check on the filaments. I suspect it is and should probably be done out of circuit.

Another thing to look for is bad soldering or a wire put in the wrong place during a previous repair attempt. I'm working strictly from pictures but it appears that this uses point to point wiring and not a circuit board. So putting a wire on the point next to the one you wanted is a little easier to do, especially if you're distracted or in a hurry.

Anyways, that's what I can think of to start looking at. No idea if any of it is actually helpful. Whatever you do, be careful. There may still be high voltage lurking about on tube pins even if the filaments are dark.

Just got through checking the rest of the tubes. Believe it or not all were bad except one, an original Lafayette tube 6BJ6. I hope this is all thats wrong with it. Time will tell. Thank you all for your help. I'll give an update once I get the tubes installed.