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 Zenith A730 rectifier replaced and installed diode wrong (oops)

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Bill n



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Join date : 2010-10-12

PostSubject: Zenith A730 rectifier replaced and installed diode wrong (oops)   Sun Oct 17, 2010 8:25 pm

Not sure what damage I've done here.
The 22 ohm 5 w resistor was replaced at this time with a 100 ohm 6.5w resistor.The electrolytics were also replaced. I disconnected power when resistor started heating up. I checked the resistor, it's good and the lytic's test good with a R.S. cap tester. Radio just hums with diode hooked up right. Do I need to replace these caps again and and what else might have been damaged?
Bill
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Johnnysan



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PostSubject: Re: Zenith A730 rectifier replaced and installed diode wrong (oops)   Sun Oct 17, 2010 8:36 pm

It may have damaged the electrolytics.
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Chas

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Location : S. Dartmouth MA 02748-1225 ------------ Avatar: Uncle Tony's Shack

PostSubject: Re: Zenith A730 rectifier replaced and installed diode wrong (oops)   Sun Oct 17, 2010 8:54 pm

Replace the diode too, because of the high current stress and any other electrolytics in the B+ string.
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smeezekitty

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PostSubject: Re: Zenith A730 rectifier replaced and installed diode wrong (oops)   Mon Oct 18, 2010 1:29 am

Test the electrolytics and diode with an ohm meter.
The diode should not conduct both ways.
Also the electrolytics should be in the kilo-ohms after a few minits of having it on the ohm meter.
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Reece

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Location : Cleona, PA

PostSubject: Re: Zenith A730 rectifier replaced and installed diode wrong (oops)   Mon Oct 18, 2010 7:22 am

Remember the painted band (cathode) on the diode "gives" the B+ to the radio, goes "towards the radio" not the line.
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Bill n



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PostSubject: Re: Zenith A730 rectifier replaced and installed diode wrong (oops)   Mon Oct 18, 2010 9:22 am

Thanks for your help.
I am going to replace the caps and diode. I had read an earlier post on the forum that described the proper direction for the diode but got it wrong.
Bill
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Randy Bassham



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PostSubject: Re: Zenith A730 rectifier replaced and installed diode wrong (oops)   Mon Oct 18, 2010 10:04 pm

Back in the 1970's I was replacing all 4 diodes in the bridge rectifier circuit on a Magnavox Tube type color TV that had taken a lightning strike. One of the 1N4007's I put in had the stripe painted on the wrong end. It tripped the breaker instantly, I must have checked them with the Simpson 260 at least 4 times before I realized one was checking backwards to the other 3.... Rolling Eyes
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dberman51



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Join date : 2010-10-13

PostSubject: Re: Zenith A730 rectifier replaced and installed diode wrong (oops)   Tue Oct 19, 2010 12:28 pm

It probably didn't help that IIRC the Simpson 260 tests them "backwards."

-David
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