CTC16 Flyback Cooling

[Arcanine]

So it looks like Tom (Electronic M) has brought life back to my CTC16 that I regretted buying. I was so mad about it I didn't even want to touch it. Long story there.

The one thing I noticed, and Tom did as well, is the flyback get's very hot after awhile and starts to drip wax. This is about after an hour on for him, and an hour on for me when I noticed it was hot. It's set correctly and Tom will chime in on that, or you can check the last parts of the CTC16 thread and see.

Do RCA Fly's just run really hot? And if so, would it hurt anything if I cut open the flyback box and installed a small computer fan to it externally, to suck cool air though the box so the Fly isn't sitting in there melting it self to death?

[Findm-Keepm]

Originally Posted by Arcanine

So it looks like Tom (Electronic M) has brought life back to my CTC16 that I regretted buying. I was so mad about it I didn't even want to touch it. Long story there.

The one thing I noticed, and Tom did as well, is the flyback get's very hot after awhile and starts to drip wax. This is about after an hour on for him, and an hour on for me when I noticed it was hot. It's set correctly and Tom will chime in on that, or you can check the last parts of the CTC16 thread and see.

Do RCA Fly's just run really hot? And if so, would it hurt anything if I cut open the flyback box and installed a small computer fan to it externally, to suck cool air though the box so the Fly isn't sitting in there melting it self to death?

They do run warm, but if you have melting/dripping wax, one of three problems come to mind:

1. Too much cathode current through the 6JE6/6LQ6 - should be less than 250mA, preferably the lowest the efficiency (linearity) coil will adjust to.

2. The horizontal drive signal is mis-shapen. Caps, out of tolerance resistors, or a weak 6CG7/6FQ7 can cause the "on" time to increase, which ups the current through the fly.

3. Too much load on the fly - bad/wrong boost rectifier (it requires a "fast" rectifier for Boosted B+, a typical silicon diode won't do), bad focus rectifier (my CTC16 has an R-2AV2 silicon replacement, eliminating the focus rectifier filament load from the fly), and even a shorted turn or two in the focus coil can increase the focus current, but still yield good focus range. You can also eliminate the filament load from the 3A3C by using a R-3A3/ECG508 silicon replacement.

Also, make sure the B+ is the correct level - today's higher line voltages increase all the voltages in vintage sets. A dropping resistor add (complicated) or running on a variac (easiest - set it for 110 VAC and you should be good) are suggested as fixes.

Cheers,

[Arcanine]

Originally Posted by Findm-Keepm

They do run warm, but if you have melting/dripping wax, one of three problems come to mind:

1. Too much cathode current through the 6JE6/6LQ6 - should be less than 250mA, preferably the lowest the efficiency (linearity) coil will adjust to.

2. The horizontal drive signal is mis-shapen. Caps, out of tolerance resistors, or a weak 6CG7/6FQ7 can cause the "on" time to increase, which ups the current through the fly.

3. Too much load on the fly - bad/wrong boost rectifier (it requires a "fast" rectifier for Boosted B+, a typical silicon diode won't do), bad focus rectifier (my CTC16 has an R-2AV2 silicon replacement, eliminating the focus rectifier filament load from the fly), and even a shorted turn or two in the focus coil can increase the focus current, but still yield good focus range. You can also eliminate the filament load from the 3A3C by using a R-3A3/ECG508 silicon replacement.

Also, make sure the B+ is the correct level - today's higher line voltages increase all the voltages in vintage sets. A dropping resistor add (complicated) or running on a variac (easiest - set it for 110 VAC and you should be good) are suggested as fixes.

Cheers,

Ah okay. Hopefully Tom sees this before he gets my CTC16 too far back together. I'd like to be able to use it and not worry about the flyback catching it self on fire.

[old_coot88]

Originally Posted by Findm-Keepm

1. Too much cathode current through the 6JE6/6LQ6 - should be less than 250mA

...250 ma? When we sold those sets new, 210 ma was the absolute limit for any hope of making it through warranty without killing the 6JE6.

200-205 ma was just about optimal.

...preferably the lowest the efficiency (linearity) coil will adjust to.

The factory manual tells you to adjust to the dip, then raise the current off-dip a bit. But that's nuts. It doesn't state any rationale for raising it. So just set it to the dip, period.

[dieseljeep]

Originally Posted by old_coot88

...250 ma? When we sold those sets new, 210 ma was the absolute limit for any hope of making it through warranty without killing the 6JE6.

200-205 ma was just about optimal.

The factory manual tells you to adjust to the dip, then raise the current off-dip a bit. But that's nuts. It doesn't state any rationale for raising it. So just set it to the dip, period.

I always followed the proceedure in the service manual regarding raising the current to slightly above dip.
Of coarse, if the fly failed, they had one on the shelf, at your distributor.
I went strickly with Thordarson later in the game.
BTW, did all you seasoned techs, check the efficiency coil with every 6JE6 replacement. I'm guilty for not!

[old_coot88]

Originally Posted by dieseljeep

...BTW, did all you seasoned techs, check the efficiency coil with every 6JE6 replacement. I'm guilty for not!

In the shop, yes, with a Pomona adapter and Simpson 260. But in the field and on the clock, it wasn't always practical to do so. But we did carry a couple of 'magic light bulbs' consisting of a #44 bulb adapter to put in the plate cap lead, to visually dip the eff.coil. One was for small top caps (6JE6 etc.), the other for big top caps (6JS6 etc.).
With a little practice, it was easy to gauge the current from the 'orangeness' of the bulb's glow.

[Findm-Keepm]

Originally Posted by old_coot88

In the shop, yes, with a Pomona adapter and Simpson 260. But in the field and on the clock, it wasn't always practical to do so. But we did carry a couple of 'magic light bulbs' consisting of a #44 bulb adapter to put in the plate cap lead, to visually dip the eff.coil. One was for small top caps (6JE6 etc.), the other for big top caps (6JS6 etc.).
With a little practice, it was easy to gauge the current from the 'orangeness' of the bulb's glow.

Ah, the old 44 bulb test - I saw another shop using one of those testers - had to have some dim lighting to use it, but it worked well. Eby made the one I have. As to the Pomona adapter, I have several, and one homemade one my dad used for years. I use a center-zero "save the flyback" meter - it doesn't care about polarity - just dip to the center...

[dieseljeep]

Originally Posted by old_coot88

In the shop, yes, with a Pomona adapter and Simpson 260. But in the field and on the clock, it wasn't always practical to do so. But we did carry a couple of 'magic light bulbs' consisting of a #44 bulb adapter to put in the plate cap lead, to visually dip the eff.coil. One was for small top caps (6JE6 etc.), the other for big top caps (6JS6 etc.).
With a little practice, it was easy to gauge the current from the 'orangeness' of the bulb's glow.

The HOT lamp was an RCA accesory, but IIRC it was a #39 lamp. The lamp got smashed in the bottom of the tube caddy and I had to order a box of them. Not a real common type. A small cap for the 6KM6 and a large cap for the 6JE6 et al.

[Findm-Keepm]

Originally Posted by old_coot88

...250 ma? When we sold those sets new, 210 ma was the absolute limit for any hope of making it through warranty without killing the 6JE6.

200-205 ma was just about optimal.

The factory manual tells you to adjust to the dip, then raise the current off-dip a bit. But that's nuts. It doesn't state any rationale for raising it. So just set it to the dip, period.

The raising above the dip is to bring the sweep into a linear region of the sweep - just watch the CRT with a cross-hatch and look for any non-linearity in the picture. If any, raise the dip. I've always gone for the dip, and never had a non-linear horizontal sweep after dipping. I have seen weak 6JE6's cause linearity problems.

We had a similar procedure in the world of Avionics - dipping current in driver and output tubes in VHF and UHF radios and one '50s TACAN unit. What fun - blade tracking and turn-loc coils, all one handed operation, as there was -900 volts on some coils.....

[old_coot88]

Originally Posted by Findm-Keepm

..I've always gone for the dip, and never had a non-linear horizontal sweep after dipping.

Same here.

[Username1]

Originally Posted by Findm-Keepm

They do run warm, but if you have melting/dripping wax, one of three problems come to mind:

1. Too much cathode current through the 6JE6/6LQ6 - should be less than 250mA, preferably the lowest the efficiency (linearity) coil will adjust to.

2. The horizontal drive signal is mis-shapen. Caps, out of tolerance resistors, or a weak 6CG7/6FQ7 can cause the "on" time to increase, which ups the current through the fly.

3. Too much load on the fly - bad/wrong boost rectifier (it requires a "fast" rectifier for Boosted B+, a typical silicon diode won't do), bad focus rectifier (my CTC16 has an R-2AV2 silicon replacement, eliminating the focus rectifier filament load from the fly), and even a shorted turn or two in the focus coil can increase the focus current, but still yield good focus range.

Also, make sure the B+ is the correct level - today's higher line voltages increase all the voltages in vintage sets. A dropping resistor add (complicated) or running on a variac (easiest - set it for 110 VAC and you should be good) are suggested as fixes.

Cheers,

These are probably the most important things you can do before you get
into modifying the circuit design.... But what if you wanted more protection?

Electrically transformers are made up of a pure inductance component and a
resistive component, It's the resistive component that ends up getting hot.
It's the inefficient part of the wire we can't do anything about inside the
flyback....

I'm wondering, If you wanted to shave an extra 20ma. off the current running
through the flyback, could ya do it be adding possibly 2 - 10 Ohm, @ 10 to 20
watt wire wound resistor to the horizontal output cathode circuit, and
possibly shift some of that heat to the resistor and away from the transformer....?

Anyone with one of these sets on the bench willing to test it ? Naturally,
you would have to be sure it didn't cause any width problems... Etc....

Not sure if it should be in the cathode circuit, or on the business winding
on the flyback supply, probably not too smart to put in in there on the plate
cap end.... Maybe on the other side of that..... I don't have a schematic
for that set, so can't come up with the exact point.....

Anyway, my thinking is, if the resistive component in the flyback "primary"
is say 20 Ohms, and you add a 5 Ohm resistor, will you shift enough heat
off the transformer to have it not melt the wax....? And still not effect
the rest of the set materially.....?

.

[Findm-Keepm]

Originally Posted by Username1

These are probably the most important things you can do before you get
into modifying the circuit design.... But what if you wanted more protection?

Electrically transformers are made up of a pure inductance component and a
resistive component, It's the resistive component that ends up getting hot.
It's the inefficient part of the wire we can't do anything about inside the
flyback....

I'm wondering, If you wanted to shave an extra 20ma. off the current running
through the flyback, could ya do it be adding possibly 2 - 10 Ohm, @ 10 to 20
watt wire wound resistor to the horizontal output cathode circuit, and
possibly shift some of that heat to the resistor and away from the transformer....?

Anyone with one of these sets on the bench willing to test it ? Naturally,
you would have to be sure it didn't cause any width problems... Etc....

Not sure if it should be in the cathode circuit, or on the business winding
on the flyback supply, probably not too smart to put in in there on the plate
cap end.... Maybe on the other side of that..... I don't have a schematic
for that set, so can't come up with the exact point.....

Anyway, my thinking is, if the resistive component in the flyback "primary"
is say 20 Ohms, and you add a 5 Ohm resistor, will you shift enough heat
off the transformer to have it not melt the wax....? And still not effect
the rest of the set materially.....?

.

No effect at all. Think about it, when you put a milliammeter in the circuit to check the current, you are adding the DC resistance of the meter, which is several hundred ohms, and you still have 200 mA in the circuit.

[Username1]

Originally Posted by Findm-Keepm

No effect at all. Think about it, when you put a milliammeter in the circuit to check the current, you are adding the DC resistance of the meter, which is several hundred ohms, and you still have 200 mA in the circuit.

I don't think this is true at all.... Resistance of 1 - 4 Ohms max,
Several Hundred Ohms and you strongly change what the meter is actually
reading. Most good meter movements are Micro-Ampers full scale, so reading
200Ma, the current handling resistor should be pretty small.

For a current reading meter to be highest in accuracy, it would have to present
as close to zero resistance to the circuit as possible..... Just as in measuring
voltage, the meter should present as close as possible to infinite resistance
as possible to the circuit.... That is why VTVM's and digital's are choice for
a lot of really accurate DC voltage use especially, because of high resistance
on input...

.

[Electronic M]

Originally Posted by Findm-Keepm

They do run warm, but if you have melting/dripping wax, one of three problems come to mind:

1. Too much cathode current through the 6JE6/6LQ6 - should be less than 250mA, preferably the lowest the efficiency (linearity) coil will adjust to.

2. The horizontal drive signal is mis-shapen. Caps, out of tolerance resistors, or a weak 6CG7/6FQ7 can cause the "on" time to increase, which ups the current through the fly.

3. Too much load on the fly - bad/wrong boost rectifier (it requires a "fast" rectifier for Boosted B+, a typical silicon diode won't do), bad focus rectifier (my CTC16 has an R-2AV2 silicon replacement, eliminating the focus rectifier filament load from the fly), and even a shorted turn or two in the focus coil can increase the focus current, but still yield good focus range. You can also eliminate the filament load from the 3A3C by using a R-3A3/ECG508 silicon replacement.

Also, make sure the B+ is the correct level - today's higher line voltages increase all the voltages in vintage sets. A dropping resistor add (complicated) or running on a variac (easiest - set it for 110 VAC and you should be good) are suggested as fixes.

Cheers,

It is running slightly less than 200mA, on the 6LQ6. I have not checked parts in the horizontal osc/drive system (aside from the 6CG7 which is quite strong) or the waveform. Don't know if my boost rect is silicon or what, I'd have to check that.....If it ain't then the only way I can put a 'fast' diode in is if I happen to have one in the parts I've scrapped off BPC sets. I don't stock any other new diodes that can take the voltage and current, and I don't buy parts online. I don't have any SS 3A3 or 2AV2 substitutes either.

AC at the outlet the set plugs into here with it on is 117VAC. I will look for a high line voltage primary tap on the transformer.

My thoughts on adding a fan are that one should add a Heppa filter in the air intake to limit dust intake.

[Arcanine]

Originally Posted by Electronic M

It is running slightly less than 200mA, on the 6LQ6. I have not checked parts in the horizontal osc/drive system (aside from the 6CG7 which is quite strong) or the waveform. Don't know if my boost rect is silicon or what, I'd have to check that.....If it ain't then the only way I can put a 'fast' diode in is if I happen to have one in the parts I've scrapped off BPC sets. I don't stock any other new diodes that can take the voltage and current, and I don't buy parts online. I don't have any SS 3A3 or 2AV2 substitutes either.

AC at the outlet the set plugs into here with it on is 117VAC. I will look for a high line voltage primary tap on the transformer.

My thoughts on adding a fan are that one should add a Heppa filter in the air intake to limit dust intake.

The flyback was getting really really hot even before he changed out the diodes. Even before the set was working even half way correct, the fly kept getting really hot on me.