Oh so close, but now what (new problem)

[DaveWM]

I would not recommend re-engineering the use of the mica sheets. Make sure you examine parts closely to make sure where mica is present or not present.

[TinCanAlley]

Originally Posted by DaveWM

I would not recommend re-engineering the use of the mica sheets. Make sure you examine parts closely to make sure where mica is present or not present.

Have the chassis out and found that there are three pieces of mica on the HOT and the screws never touch the chassis. The go through a bigger hole and the threads are actually on the isolated board.

One of the mica pieces came apart trying to remove, but the other two are in good shape. I'm actually going to try the NTE Thermopads. They take the place of the mica and compound.

[DaveWM]

that ringing is coming from the tripler ref post, did you ever get a chance to check the damper diode? not sure how well a reg diode check would work (unless its completely open) since its a pretty high power diode).

[TinCanAlley]

Originally Posted by DaveWM

that ringing is coming from the tripler ref post, did you ever get a chance to check the damper diode? not sure how well a reg diode check would work (unless its completely open) since its a pretty high power diode).

I have an NOS replacement for the damper diode. I can test the original and compare it to the new. Should just put the new one in since it's an important component.

What is the tripler "ref post"?

Speaking of triplers....a bad tripler wouldn't cause the problem I'm having, could it? If so, I do have the new tripler with built-in focus. Was keeping it more as a spare since I have the new focus divider installed.

[DaveWM]

I assume its just a low voltage tap off the tripler.

I don't like to replace a lot of parts an one time, unless its clearly bad. So if the diode checks ok then I would leave it for now. You have spent a lot of time on this set, I want you to find the EXACT problem. With the scope hopefully you can narrow down the issue (lets hope that ringing in the brightness is it) and then checking/replacing one part at a time in the effected area and checking the scope each time will get it fixed. I know you would prob rather just get it done once to avoid all the chassis pulling, but for your own education process I think its better to see the effects of each part (I don't know for sure if the damper has this effect, so its not just for your education ).

good luck, your doing well. The scope is a real asset, but only to a point.

[TinCanAlley]

Originally Posted by DaveWM

I assume its just a low voltage tap off the tripler.

I don't like to replace a lot of parts an one time, unless its clearly bad. So if the diode checks ok then I would leave it for now. You have spent a lot of time on this set, I want you to find the EXACT problem. With the scope hopefully you can narrow down the issue (lets hope that ringing in the brightness is it) and then checking/replacing one part at a time in the effected area and checking the scope each time will get it fixed. I know you would prob rather just get it done once to avoid all the chassis pulling, but for your own education process I think its better to see the effects of each part (I don't know for sure if the damper has this effect, so its not just for your education ).

good luck, your doing well. The scope is a real asset, but only to a point.

The diode checked out okay and was in the same range as the new one and the other two that are installed in the set. So I'll leave it.

I'm still going to take out and test the low voltage regulator as it is one of the pieces that can kill the HOT. It will allow me to clean up the transistor, mount and socket. I really hate it when they put a ton of the thermal compound on and it oozes out all over the place. Not only does it look bad, it really doesn't help much in the thermal coupling.

[TinCanAlley]

Originally Posted by DaveWM

I assume its just a low voltage tap off the tripler.

This tripler has the input, ground and anode. No other connections/taps on it.

[DaveWM]

interesting, my zenith manual show input, ref, HV anode. I just assumed it was a low volt tap. the triplers I am used to generally have a input, focus, and the HV lead.

the ref goes thru a couple resistors, the pot to ground and has a zener diode. Perhaps that is the same as the ground lead on yours?

[zeno]

Originally Posted by TinCanAlley

I have an NOS replacement for the damper diode. I can test the original and compare it to the new. Should just put the new one in since it's an important component.

What is the tripler "ref post"?

Speaking of triplers....a bad tripler wouldn't cause the problem I'm having, could it? If so, I do have the new tripler with built-in focus. Was keeping it more as a spare since I have the new focus divider installed.

A tripler will cause it. So can yoke, HOT bias, the white caps, FBT or any
heavy load or mismatch on the FBT. The ref. is the ABL terminal. If you
dont do the bulb at least do the heat check. But if its really loaded
down the HOT will INSTANT death. We used the variac to bring
them up slowly & watch the current but ive used the bulb also.
It will protect the HOT & save $$.

73 Zeno

[TinCanAlley]

Originally Posted by zeno

A tripler will cause it. So can yoke, HOT bias, the white caps, FBT or any
heavy load or mismatch on the FBT. The ref. is the ABL terminal. If you
dont do the bulb at least do the heat check. But if its really loaded
down the HOT will INSTANT death. We used the variac to bring
them up slowly & watch the current but ive used the bulb also.
It will protect the HOT & save $$.

73 Zeno

My brother has a variac. Guess I should borrow it.

[TinCanAlley]

Some pics of the HOT diode, HOT cap and resistor and ABL cap and resistors. The ABL is the one with the bright blue cap that has 021 K0 written on it).

[zeno]

This is worth reading.
http://www.repairfaq.org/sam/reppic/horiz-tv.pdf

If its a simple variac add an AC ampmeter to the set-up.
The set will usually start running about 75V but the regulator
will kick in soon & bring the 125V up almost instantly. Keep your
amps under 1 amp. A normal running set will draw abt
.75 amps at 120 VAC, .5 for the HV. With this type regulation you may
have to do the bulb trick. IIRC they start to work but
pulsate then as you go up kick in 100% quickly.

BTW the variac we used was a Sencore power right or the B&K
equivalent. They have a variac, isolation, metering for volts
& amps & leakage test. A must have for any newer sets or
working on hot chassii.

73 Zeno