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  #1  
Old 04-16-2011, 02:30 PM
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radiotvnut radiotvnut is offline
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'56 Magnavox

I just bought this '56 Magnavox record player at the flea market. One unusual thing that I see is that it uses a VM changer. I've only seen one other VM changer in a Magnavox and it was in a lower end portable from the late '50's. I thought the medium and higher end stuff used Collaro and Webster-Chicago changers.

The amp uses a power transformer and uses the following tubes: 12AX7, 5Y3, and 6AQ5 x 2. There are controls for bass, volume, and treble. Upon power up, I find that the changer is gummed up (no surprise) and the amp is totally dead (no tube filaments). Overall, the case is in decent shape and should only need cleaning and polishing.





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Old 04-17-2011, 08:59 AM
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Well, I have bad news. The reason it's dead is because the power transformer is burnt to a crisp. Hopefully, I can find something in my junk that will work. I certainly don't want to shell out for a new transformer, if I can help it.
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Old 04-17-2011, 12:11 PM
bob91343 bob91343 is offline
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How about repairing the transformer?
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Old 04-17-2011, 12:56 PM
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I think it's past repairing. When I opened it up, it looks like it actually caught on fire. And, the chassis is black in the area surrounding the transformer. I think someone let this one smoke and burn until the primary winding opened up.
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Old 04-17-2011, 04:00 PM
bob91343 bob91343 is offline
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It's perhaps possible to gut the transformer and use the core to rewind a new one. Less work, of course, to find a substitute. Especially in this case, where there is really nothing special about the unit and nearly anything close will work.

It points out the cheapness with which these things were made. Cost was the important factor. Times haven't changed at all.
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Old 05-14-2011, 11:41 PM
neali neali is offline
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Quote:
Originally Posted by bob91343 View Post
It points out the cheapness with which these things were made. Cost was the important factor. Times haven't changed at all.
These things cost $129.50 in 1956 and were not cheaply made at all. I just finished recapping an amp from one and the amp and the dual 6x9 oval bass drivers and five inch mid range sound fantastic. 1956 tubes work as good as new.

Filter caps dry out and short and if you plug the amp in the transformer will catch on fire. Now, as to why they didn't put in a fuse, you got me.
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Old 05-16-2011, 09:19 PM
mbates14 mbates14 is offline
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sounds like someone let it run with a shorted lytic and bye bye transformer.
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Old 05-17-2011, 01:38 PM
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I'm amazed Magnavox didn't put a fuse in the power supply, to protect the transformer against shorted electrolytics or even a short in the rectifier tube. However, I have to wonder why the house fuse or circuit breaker didn't trip open as soon as the filter cap shorted; after all, these caps are in a position to short the AC line directly to ground when they fail. Another thing: Didn't the set's owner notice that the sound had a 60-Hz hum when the filter cap started to go bad, long before it shorted?

As much as these Magnavox phonographs cost when they were new, I don't think it would have added that much to the price to include a line fuse. Magnavox was a top-of-the-line manufacturer in the 1950s, not one to cut corners, which makes it difficult for me to understand why they would leave the transformer unprotected. The only other thing I can come up with is that there may well have been a line fuse in the set, but the owner foolishly bypassed it. Again, I wonder why the owner didn't get the hint when the sound became distorted from 60-Hz AC hum when the filter cap was just starting to fail. Why the person would just leave the thing on when the cap eventually shorted, leading of course to the transformer burning up, is far beyond me.
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Last edited by Jeffhs; 05-17-2011 at 01:43 PM.
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Old 05-17-2011, 05:14 PM
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I really wished more manufacturers would have put a fuse in the power supply but almost none did (but I always do when repairing). The only Magnavox tube type radio or phono I have ever seen with a factory fuse is a 1946 large radio/phono console I have.


I bet you can replace that transformer pretty easily, you might have to go to a silicon bridge rectifier or silicon diodes or a 6X5 tube if you can't find one with a rectifier filament winding. Just as long as you don't go over the voltage of the original supply I would think a somewhat lower voltage output unit would do too. You could use a bridge rectifier off the center tap and outer lead of a higher-voltage output unit.
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Old 05-22-2011, 02:50 PM
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i can tell you that the VM turntable that is on your unit is NOT the original, the original was a brittish made Collaro. the reason i know this is because i have the exact same identical model here. mine, however is fully functional & in working condition. it even has a really good quality sound to it.
if you can find the original turntable for it at a low cost or free, then it would make it worth restoring. otherwise, being that the transformer was burnt to a crisp, & the original turntable missing, as well as the modifications that was done to the deck that holds the turntable in order to make that VM fit, it just leads up to being a piece of junk.
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Old 05-22-2011, 03:01 PM
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Quote:
Originally Posted by mbates14 View Post
sounds like someone let it run with a shorted lytic and bye bye transformer.
not necessaraly, i personally witnessed one of these failing on their own accord due to a winding that has a shorted turn. that usually happens with no warning & ends up burning up pretty quickly.
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Old 05-22-2011, 06:24 PM
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Quote:
Originally Posted by robert1 View Post
i can tell you that the VM turntable that is on your unit is NOT the original, the original was a brittish made Collaro. the reason i know this is because i have the exact same identical model here. mine, however is fully functional & in working condition. it even has a really good quality sound to it.
if you can find the original turntable for it at a low cost or free, then it would make it worth restoring. otherwise, being that the transformer was burnt to a crisp, & the original turntable missing, as well as the modifications that was done to the deck that holds the turntable in order to make that VM fit, it just leads up to being a piece of junk.
I thought the same thing, until someone on ARF chimed in, with the same machine, that uses the exact same VM changer. And, I did find out that Magnavox used some VM changers during the '50's. If this changer is indeed non-original, someone did a good job as most of the conversions I've seen were very sloppy. Of course, I'd rather have the Collaro version; but, at least someone didn't stick some plastic '70's BSR changer in there (I've seen that done more than a few times).
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Old 05-22-2011, 09:56 PM
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Magnavox used V-M changers in some models at least through the early 1970's.

Here's the specs on that power transformer:
Primary: 117vac @ .37a
Sec. 1: 475vct @ .064a
Sec. 2: 6.3vac @ 1.8a
Magnavox 300068-1, Halldorson P9205, Merit P-3048, Stancor PM-8419, Triad R-8B

I have the Sams if you need me to scan it.
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Old 05-22-2011, 10:17 PM
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radiotvnut radiotvnut is offline
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Actually, I did find a transformer. I just have not had time to finish installing it. Thanks for the diagram offer; but, I have the schematic on this amp.
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Old 06-04-2011, 11:58 AM
neali neali is offline
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Quote:
Originally Posted by robert1 View Post
i can tell you that the VM turntable that is on your unit is NOT the original, the original was a brittish made Collaro. the reason i know this is because i have the exact same identical model here. mine, however is fully functional & in working condition. it even has a really good quality sound to it.
if you can find the original turntable for it at a low cost or free, then it would make it worth restoring. otherwise, being that the transformer was burnt to a crisp, & the original turntable missing, as well as the modifications that was done to the deck that holds the turntable in order to make that VM fit, it just leads up to being a piece of junk.
I have the exact unit that radiotvnut has and the vm changer is original. There are no modifications to the deck and it fits perfectly.
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