CTC16 Flyback Cooling

[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...

.