Flyback temperature

[Tubejunke]

Originally Posted by Username1

If'n yer wanting to experiment on that Barkhausen thing..... I have 2 of the same model set
and they both have OEM Horizontal output tubes still in them, and they both have an ion
trap on them about midpoint on the tube. I got the Sams for the set, and they have the ion trap
on from the factory, and an explination as to why the trap is there.... and yes they
say it's the "B" Barkhausen.


Remember bias on G1 to a good degree dictates cathode current..... Is it runaway or not....?
Good thing to look into that screen grid cap as mentioned too....

I have heard of the ion trap used in this manner, but there is no reference to one recommended in my Sam's Set 722 Folder #4. My set's chassis is the 25LC30. I wonder if you have the older chassis, or maybe I should say the other chassis that some folks are talking about in another thread. It still may be worth a try.

I like the sound of the Chapstick idea for the slug as long as I can get the old one out. It seems to be disintegrating for whatever reason, so I keep thinking that I should get it out and put in the very much intact slug from the old unit that I removed with disintegrated plastic. On the flip, Old_coot88 suggests leaving it be as it would not be the problem if I had runaway current. It's only a fine tuning to my knowledge. Some earlier mentioned tube swapping caused and re-swapping rectified the runaway current which led me to discover the stuck slug trying to control it in a bit of haste. Right now she is holding a steady 210mA which is supposedly acceptable.

Now, to the G1 capacitor and biasing. I have not yet had time to check any voltages and it sounds like the right thing to do is simply replace such a critical cap. Looking at the schematic I see a .01mfd (C66) to pin 5 of the H.O. tube 6HF5 via a 100 ohm resistor. There is also a .001mfd @ 10% (C65) in parallel to that going through a 33K ohm resistor to ground. Admission of guilt on limited knowledge leads me to ask which of these is the right one. My bet is on the .01mfd going straight to G1, but I want to make sure along with getting a more firm understanding of these circuits.

This is great information once again folks! Thanks so much!

[jr_tech]

Originally Posted by Tubejunke

Now, to the G1 capacitor and biasing. I have not yet had time to check any voltages and it sounds like the right thing to do is simply replace such a critical cap. Looking at the schematic I see a .01mfd (C66) to pin 5 of the H.O. tube 6HF5 via a 100 ohm resistor. There is also a .001mfd @ 10% (C65) in parallel to that going through a 33K ohm resistor to ground. Admission of guilt on limited knowledge leads me to ask which of these is the right one. My bet is on the .01mfd going straight to G1, but I want to make sure along with

It is difficult to tell from the above description how the 2 caps are actually wired... if the .001/33k resistor combination connects to ground, it would seem to *not* be connected in parallel with the .01/100 ohm combo. The coupling cap would be located between the plate circuit of the horizontal oscillator and the grid of the horizontal output. If the other cap is also connected somewhere in the grid circuit of the horizontal output, I would replace it as well.

jr