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  #1  
Old 11-17-2018, 04:05 AM
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radiodayz radiodayz is offline
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Zenith Royal 755 battery leak

I'm a bit embarrassed to admit this in a public forum, but I need some help...
I have a Zenith Royal 755 large AM portable that I've had for a year or two. It always worked fine, but I noticed a few days ago that the batteries were getting weak. This morning, I put six fresh C cells in it, turned it on, nothing. I had to leave for work, but I resolved to check on it later. When I returned a few hours later, the battery tube was warm to the touch and fluid was sizzling and oozing out. I quickly removed the batteries. I probably had installed them with the wrong orientation, I guess; they're supposed to be loaded with four facing one direction and two the other, but I must have screwed up somehow. Anyway, what should I do know? Is there any hope it can be restored to operating condition? I don't think any critical components were damaged.
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Old 11-17-2018, 12:03 PM
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What probably happened is you got a bad batch from the store.. lots of counterfeit Chinese batteries have came in to the country... sometimes the do that in the package in the store.... I've had remotes pee acid into my hand while I was using them and they were still working.

If half were backwards there should not be any voltage across the output terminals of the pack and no current should flow so that should not have caused your issue...

Get them out clean the acid off and assess the condition of the terminals... you may have to replace the springs if they rotted off. You may be able to test the radio by connecting a wall wart with a DC voltage at or a bit below that the battery pack is supposed to make ( for AA,AAA,D andC cells that is 1.5xnumber of batteries).
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Old 11-17-2018, 01:30 PM
dieseljeep dieseljeep is offline
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Quote:
Originally Posted by Electronic M View Post
What probably happened is you got a bad batch from the store.. lots of counterfeit Chinese batteries have came in to the country... sometimes the do that in the package in the store.... I've had remotes pee acid into my hand while I was using them and they were still working.

If half were backwards there should not be any voltage across the output terminals of the pack and no current should flow so that should not have caused your issue...

Get them out clean the acid off and assess the condition of the terminals... you may have to replace the springs if they rotted off. You may be able to test the radio by connecting a wall wart with a DC voltage at or a bit below that the battery pack is supposed to make ( for AA,AAA,D andC cells that is 1.5xnumber of batteries).
If the batteries were installed reverse polarity, all of them that is, didn't do the radio any good. The electrolytics, plus the transistors don't like reverse polarity much. I don't remember if that radio has silicon or germanium transistors.
When Alkaline cells run hot, it means some serious current in being drawn from them.
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Old 11-17-2018, 02:37 PM
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Are radios of this vintage ever protected by a shunt diode?

jr
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Old 11-18-2018, 10:25 AM
dieseljeep dieseljeep is offline
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Originally Posted by jr_tech View Post
Are radios of this vintage ever protected by a shunt diode?

jr
Back then, It was probably a cost issue, plus the diodes made then were still low current, 500ma max.
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Old 12-13-2018, 12:14 AM
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I just had a thought, the transistors of a zenith 755 are mounted in sockets like vacuum tubes. Pull out all of the transistors and carefully label them to where they go and what number they are. Then apply correct voltage at the right polarity, with a current meter in series with the radio and see what the current draw is. It should be next to nill. if it isn't then you know you have a shorted cap, transformer etc. If no current draw then start replacing the transistors one at a time and see if anyone of these cause excessive current. i found the schematic for a 755m and it says the current should be 17.5 milliamps with the volume turned down but still on. also there are 2 electrolytics connected just after the power switch. they would likely be the best candidates for drawing enough excessive current to drain those batteries in only one day. here is a link to the schematic i found.
https://radiojayallen.files.wordpres...ce-manual1.pdf
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