Zenith 25EC58 poor focus

[Electronic M]

Originally Posted by Carmine

After having my capacitor order canceled twice (Elliot Electronics) and EBay seller (Chinese gibberish) can anyone suggest a reputable place to purchase quality .0018uf 1.6KV capacitors for this TV?!

https://www.digikey.com/en/products/...CUApANRAF0BfIA

I only order new caps from digikey or mouser (and on rare occasions some of the antique radio specialty suppliers). They're professional suppliers for companies that build their own electronic products, and they confirm their products aren't counterfeit.

So basically they won't give of the troublesome BS that eBay and Amazon electronic components often do.

[BeamT]

I've not seen Octopart, good to know, interesting they are a secondary seller.

Mouser Part # 667-ECW-HA3C182H4 Panasonic .0018uf (1800pf) 1.6kv 3%
600+ In-Stock, $.46 each with a Qty. of 10. They do advise:

"A tariff of 44 % may be applied if shipping to the United States."

[Carmine]

Oh frustration...

The new caps have been installed. HV is down where it should be (as is focus voltage per the "corrected" Sam's). Focus is now worse than ever. Best focus is now at the extreme clockwise (it was almost perfectly centered earlier). Whereas before, the picture was "watchable" it's now a blurry mess. Although, as before, lower brightness does improve the focus, but anything approaching normal requires an almost invisible picture.

Photos show a dark and "normal" screen HV readings





Beyond the safety caps, I did notice a 10mfd @300v cap right next to one of the "middle chassis" safety caps that had to be open, it pretty much fell apart in my hands. Luckily I have a decent electronics store at literal walking distance, so I was able to buy this cap in a 350v rating. I don't have my laptop/Sams nearby, so I'm not sure which circuit this involves.





I'd be inclined to think I really screwed something up except that by "specifications", (HV and focus V readings), I'm better than before. What gives?!

[zeno]

If it uses a focus divider start with that. They usually crack, bulge, change color or melt. There may be a kit ( 800-616 ) but you need to up sub
from the OEM 63-#### I can help you with that.

If no divider the tripler just has focus out ( to CRT ) and control lines.

The cap was probably the boost cap. It would get too much DC on it
if the HV goes high & it brews up. Keep it in mind. It is one of the most
common fail on ALL brands from apx 1978 til the end of TV. It can
cause MANY different symptoms.

C U Later
Zeno
LFOD !

[damen]

Use the high voltage meter to check and see if you get any voltage on the focus pin of the CRT with the socket unplugged. If there's leakage from the anode connector to the focus pin inside the CRT it can cause the focus voltage not to track with the high voltage. If you measure voltage, use a grounded clip lead and touch the focus pin, if it "pops", like discharging the anode, it may correct the problem.

[Carmine]

Originally Posted by damen

Use the high voltage meter to check and see if you get any voltage on the focus pin of the CRT with the socket unplugged. If there's leakage from the anode connector to the focus pin inside the CRT it can cause the focus voltage not to track with the high voltage. If you measure voltage, use a grounded clip lead and touch the focus pin, if it "pops", like discharging the anode, it may correct the problem.

I'll try this in the morning. You're suggesting discharging the focus pin like a 2nd anode if I read this correctly?

[Carmine]

The cap I replaced is number 270 in the schematic. 10 mfd @ 300v



It's an electrolytic, but I'm still not sure of the circuit yet.

I was always taught to trouble shoot by first looking at what has changed... I changed caps that tune the HV circuit, it brought down my HV and focus voltage. Now the picture looks worse than before when there were open caps. Seems to me the issue has to be related to that, not a coincidental new failure?! I will give that focus pin discharge a shot in the morning.