Zenith 25EC58 Restoration Thread

[vol.2]

Originally Posted by TinCanAlley

Am I interpreting the correctly? Even in the SM, the crappy pic of the underside it appears that the positive side is down on the diode side.

Agree with BeamT about the cap.

However, 80% wouldn't generally cause a circuit to fail. It's an indication that it might be on the way out or that it was stressed (possibly from being in backwards), but it wouldn't generally be the actual cause of anything not working.

On the other hand, 80% and high ESR could cause something to fail if the ESR is high enough. You can imagine ESR as adding a resistor in the circuit across the capacitor, which will throw things off by creating voltage dividers and stuff.

Long story short, check ESR if you're troubleshooting. Capacitance is only telling you part of the story.

[TinCanAlley]

Okay, I managed to find an under chassis pic from when I first got the set, before any work. The cap is definitely installed positive side to the diode. In the second pic, it is after the recap. The recap was done for me by a family member as my soldering skills were pretty non-existent at that time. The cap was put in backwards as the negative stripe side is to the diode. The replacement cap was also quite a bit smaller. The replacement I have, that I just installed per schematics (positive to the diode) is quite a bit larger and near the size of the original. The new cap is the Sprauge part number in the SM.

I have been having issues with doing proper convergence, but the pot that was bad wasn't the one connected to this lead and the other one that I want to replace causes the screen to shimmy during adjustment and sometimes continue to shimmy afterwards. I'll just replace that one and give another cleaning to the rest and see if this reversed cap might be the issue with convergence.

[TinCanAlley]

Originally Posted by vol.2

Agree with BeamT about the cap.

However, 80% wouldn't generally cause a circuit to fail. It's an indication that it might be on the way out or that it was stressed (possibly from being in backwards), but it wouldn't generally be the actual cause of anything not working.

On the other hand, 80% and high ESR could cause something to fail if the ESR is high enough. You can imagine ESR as adding a resistor in the circuit across the capacitor, which will throw things off by creating voltage dividers and stuff.

Long story short, check ESR if you're troubleshooting. Capacitance is only telling you part of the story.

I have been checking ESR as well as value. The one I removed had an ESR of 540 milliohms with a 100K frequency.