02-11-2025, 01:26 PM
Well, here's a head scratcher. I had been using my 1077 while working on the Emerson and the last time I tried to use it, no video. I have sound, the RF out is working but the "test" light is on, which wasn't before. Upon lifting the cover I noted the CRT wasn't lit. All the tubes are lit. I double checked my settings, flipped switches, nothing. Sooo - dropped it down on the bench and began making some checks. I don't have the best schematic and the one I do have isn't the most descriptive thing. It lacks in the description of which switch is which, circuit description, etc, so it takes some detective work. If anyone has a good schemo I would be quite apprecative.
So, here's where I am. No HV, low (no) boost, B+ present and close to what it needs to be. No - on the H out grid, no signal, so the oscillator isn't running. It uses a 8CG7 dual triode. Tested good. Subbed the 33GY7 - no change. Yes, it is power transformer B+, series strung heaters. I have an older thread where this was recapped in 2000, but found my thread locked. Actually, found a lot of my threads locked. So, I noted the plate voltages on the osc tube were very low, which would make sense if it wasn't running and the tube was turned on all the way. It's suppose to have a - voltage on the grids too - nothing there. Ok, well, those plates are also run off the boost, and it is non existent. I saw a .1 cap off the boost source that looked like it had been desoldered previously, so I checked it - perfect, no leakage, so I ruled it out. I CAN hear the h-osc starting briefly when I flip the power switch on, but it just blips, then goes dead. I verified this with my scope.
This wasn't a good week for my test equipment, audio signal tracer quit (lead broke inside the probe - what a pain!), then my B&K, and I needed by sweep generator - and IT wouldn't work! Man, those e caps SHOULD last longer then 60 years - right? I mean seriously!
Ok, well, it needed fixed anyway. No sense having it if it doesn't work when I need it. It's like a tractor that won't start when my truck is stuck, and have to fix the battery charger so I can charge the battery on the tractor so I can start it and pull my truck out 
Alright, with that working now, I shoved a H drive signal into the output tube in the B&K and found everything was working from that point on. Have my screen lit with both V & H sweep and HV. Boost is also working. Still low plate voltage on the osc. should be 225v, sets about 25. Comes up briefly when the switch is flipped, but drops off, so again, osc isn't running. Now, here's where the confusion is coming in. The schematic shows 4 ICs right before the osc tube. Soooo - is what I thought is the osc tube actually just a driver? Then, are those 4 ICs actually the oscillator? FYI, on this one, the vert osc is a couple transistors that go to the triode driver then on to the output. That one's obvious. But, lack of information on the Horiz. No voltages listed on the schematic on the ICs, no description, no nothing. Do they just "kick start" the oscillator, then it is dying out, or are those ICs actually the oscillator and the 2 sections of the CG7 just drivers for the output? In looking at the schematic, it could be either. I'll post what I have a little later. Never had a moments trouble from this up until now. I have a smoked up one that I might be able to compare voltages, and yeah, maybe should go ahead and replace the larger value caps.
So, here's where I am. No HV, low (no) boost, B+ present and close to what it needs to be. No - on the H out grid, no signal, so the oscillator isn't running. It uses a 8CG7 dual triode. Tested good. Subbed the 33GY7 - no change. Yes, it is power transformer B+, series strung heaters. I have an older thread where this was recapped in 2000, but found my thread locked. Actually, found a lot of my threads locked. So, I noted the plate voltages on the osc tube were very low, which would make sense if it wasn't running and the tube was turned on all the way. It's suppose to have a - voltage on the grids too - nothing there. Ok, well, those plates are also run off the boost, and it is non existent. I saw a .1 cap off the boost source that looked like it had been desoldered previously, so I checked it - perfect, no leakage, so I ruled it out. I CAN hear the h-osc starting briefly when I flip the power switch on, but it just blips, then goes dead. I verified this with my scope.
This wasn't a good week for my test equipment, audio signal tracer quit (lead broke inside the probe - what a pain!), then my B&K, and I needed by sweep generator - and IT wouldn't work! Man, those e caps SHOULD last longer then 60 years - right? I mean seriously!
Ok, well, it needed fixed anyway. No sense having it if it doesn't work when I need it. It's like a tractor that won't start when my truck is stuck, and have to fix the battery charger so I can charge the battery on the tractor so I can start it and pull my truck out Alright, with that working now, I shoved a H drive signal into the output tube in the B&K and found everything was working from that point on. Have my screen lit with both V & H sweep and HV. Boost is also working. Still low plate voltage on the osc. should be 225v, sets about 25. Comes up briefly when the switch is flipped, but drops off, so again, osc isn't running. Now, here's where the confusion is coming in. The schematic shows 4 ICs right before the osc tube. Soooo - is what I thought is the osc tube actually just a driver? Then, are those 4 ICs actually the oscillator? FYI, on this one, the vert osc is a couple transistors that go to the triode driver then on to the output. That one's obvious. But, lack of information on the Horiz. No voltages listed on the schematic on the ICs, no description, no nothing. Do they just "kick start" the oscillator, then it is dying out, or are those ICs actually the oscillator and the 2 sections of the CG7 just drivers for the output? In looking at the schematic, it could be either. I'll post what I have a little later. Never had a moments trouble from this up until now. I have a smoked up one that I might be able to compare voltages, and yeah, maybe should go ahead and replace the larger value caps.
If I could find the place called "Somewhere", I could find "Anything"
Tim
Jesus cried out and said, "Whoever believes in me , believes not in me but in him who sent me" John 12:44
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