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Workshop Anyone ever had a leaky styro cap?

 
In The Workshop
Last Post by Nuvistor 4 weeks ago
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Forum 136
 irob2345
(@irob2345)
Posts: 624
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On the weekend I was helping a friend out with his T21 chassis Pye Pedigree from 1967.

The Pye Pedigree is one of the more desirable TVs with collectors.

After attending to the immediate fault we suddenly had no sound - or at least, very weak sound.

Measuring voltages around the 6DT6 Syntector, I found only 7 volts on the anode, with or without the valve in its socket (no series heaters here!)

220k load resistor was immediate suspect but it was OK.

What I did measure was 30k to ground.

The only component in that path was a 470pf 630 volt styro cap.

"No, it won't be that!"

So I scraped the solder mask away between the track and ground, expecting to remove the 30k ohms.

Nup.

So I pulled the styro. And that was it, it had become a 30k resistor!

Now I've been working with styros since they first appeared in the late 50's and I have NEVER seen this happen!

Styros are known for open circuits in line oscillators that fix themselves when touched with a meter probe, but never leakage.

Anyone else seen this?

 

 
Posted : 09/09/2024 11:02 am
Nuvistor
 Nuvistor
(@nuvistor)
Posts: 4650
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@irob2345 No only shorts or O/C, I also had the intermittent O/C ones in line oscillators, I replaced them with silver mica.

Frank

 
Posted : 09/09/2024 11:33 am
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