Recapped the Avanti and....

[DaveWM]

the large oval shaped cap is part of the power supply voltage regulation system. if its not hot its OK. Its an oil filled 3.5uf cap, generally used for motor start caps on large AC motors. If the circuit breaker is not kicking out its prob ok.

50% out is not a problem with most eletrolytic caps of that era, I doubt that is causing the issue.

Older zeniths with jail bars would point towards blanking diodes in the video circuit. I would have to look at the schematic to see how blanking is accomplished here.

[DaveWM]

there is indeed a horz blanking diode and transistor that takes a pulse from the flyback to blank the video. You should scope there to see the blanking pulse check for correct amplitude, if incorrect then you could look for some componet (diode transistor resistor, there is not much too it).

[TinCanAlley]

The canister contains two 400uf 150V and two 500uf 35V caps. The cheapest 400uf I can find is a 200V for 23.89 on Mouser. That is for an axial. All other types are either too large or even more expensive. The 500ufs are much cheaper. So even if I wanted to rebuild the cap network on the bottom side of the board, I'm still looking at over 60.00 for a few caps.

As for checking the blanking pulse, would I use a scope for that? My brother has one and I'm sure I can get him to bring it over.

[DaveWM]

radials are much cheaper why are you replacing them anyway? are they bad?

[TinCanAlley]

Originally Posted by DaveWM

radials are much cheaper why are you replacing them anyway? are they bad?

I'm not replacing them (yet, if at all). I replaced all the exposed electrolytic caps based on age. I'm now tracking down the jail bar issue and someone mentioned the B+ voltage and a possible cap problem. Since I replaced all other caps, I asked if the B+ cap was inside the canister, if not I've already replaced it. If it is in the canister, I'd have to remove it, test it and replace if necessary.

I cannot find a radial cap that's 400uf 150V. I only find an axial 400uf 200V and I'm not giving them 23.89 for it.

[DaveWM]

http://www.mouser.com/ProductDetail/...hKIfMVcwrII%3d

[andy]

...

[TinCanAlley]

Okay, so a 470uf 20% wouldn't put it outside of the intended operating range? A 400 at 20% could be as low as 320 and as high as 480. The 470 could be as high as 517.

I'm not too up on tolerances and when it matter most/least.

[DaveWM]

the orig caps were prob -50% to +100% on the can caps.

generally speaking you can go up to the next common value.

[zeno]

The 2 400mfd caps are in the 125 scorce. Take a cap 100-200mfd
200V or more & hang it in parallel with the 400mfd section with
clip leads. Turn set on & see if it cures it. Do the same with
the other 400mfd.
The 500 is in the 24V. Do the same thing but BE SURE
you discharge the subbing cap first.

One other thing is lead dress be sure nothing like the yoke
wires are near the CRT harness.

Also looks like there is still an old 22-5001 cap on the flyback
board, change it !

73 Zeno

[TinCanAlley]

Originally Posted by zeno

The 2 400mfd caps are in the 125 scorce. Take a cap 100-200mfd
200V or more & hang it in parallel with the 400mfd section with
clip leads. Turn set on & see if it cures it. Do the same with
the other 400mfd.
The 500 is in the 24V. Do the same thing but BE SURE
you discharge the subbing cap first.

One other thing is lead dress be sure nothing like the yoke
wires are near the CRT harness.

Also looks like there is still an old 22-5001 cap on the flyback
board, change it !

73 Zeno

That pic is before the recap. All the safety caps have been changed to the orange drops (4 of them).

I think I have some caps to put in parallel. If not, my brother should. I'll let you know what happens.

As for the discharging, would leaving the set unplugged for a day do that? If not, which is the cap I should discharge? I think I have a high wattage ceramic resistor I could use.

[TinCanAlley]

Originally Posted by zeno

The 2 400mfd caps are in the 125 scorce. Take a cap 100-200mfd
200V or more & hang it in parallel with the 400mfd section with
clip leads. Turn set on & see if it cures it. Do the same with
the other 400mfd.
The 500 is in the 24V. Do the same thing but BE SURE
you discharge the subbing cap first.

One other thing is lead dress be sure nothing like the yoke
wires are near the CRT harness.

Also looks like there is still an old 22-5001 cap on the flyback
board, change it !

73 Zeno

I'm attaching a pic of the internals. I'm assuming the harnesses are in their factory positions, but if you notice something amiss, let me know.

Thanks

[zeno]

Originally Posted by TinCanAlley

That pic is before the recap. All the safety caps have been changed to the orange drops (4 of them).

I think I have some caps to put in parallel. If not, my brother should. I'll let you know what happens.

As for the discharging, would leaving the set unplugged for a day do that? If not, which is the cap I should discharge? I think I have a high wattage ceramic resistor I could use.

OK on cap, I tend to notice those things.

Discharge the cap that you use to sub. If you dont it can be charged
up to 125V when you move it to the 24V & bad things can happen.
In the all tube days we would just ground the neg of the
cap & touch the sections one at a time. Anything solid state
we would hang it in, turn on, see results. Then discharge
& do the next section. Gotta be more careful, transistors
are not forgiving like tubes.

BTW its good you had to readjust after the recap. It shows
you did have bad caps.

If you still have the jail bars after above I have the Sams out & me
& the other cats will try to help you along.....

73 Zeno

[TinCanAlley]

Originally Posted by zeno

OK on cap, I tend to notice those things.

Discharge the cap that you use to sub. If you dont it can be charged
up to 125V when you move it to the 24V & bad things can happen.
In the all tube days we would just ground the neg of the
cap & touch the sections one at a time. Anything solid state
we would hang it in, turn on, see results. Then discharge
& do the next section. Gotta be more careful, transistors
are not forgiving like tubes.

BTW its good you had to readjust after the recap. It shows
you did have bad caps.

If you still have the jail bars after above I have the Sams out & me
& the other cats will try to help you along.....

73 Zeno

Okay, hang in here with me. I just want to make sure this is as simple as I believe it is. I will take a clip-on lead from the ground point of the canister and then a clip-on lead from one of the 400uf legs of the canister. I will then take the other ends of the leads and clip them to a good cap and turn the set on. Is this correct? Also, if I'm reading the schematics correctly, the second 400uf cap is on the other side of the 16ohm filter that the first 400uf connects to. Should I do parallel both at the same time?

[TinCanAlley]

Okay, did some digging and found a couple 300uf 150V -10/+100% caps that measure out to roughly 415uf each. So it looks like I'm in good shape to test. Now all I need is confirmation if I should parallel both of the 400uf caps in the canister independently, or simultaneously.