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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 13th Jul 2018, 10:50 pm   #1
RevoxNewbieUK
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Default Philips N4520 Blowing fuses.

Hi all. I'm onto my next project, the Philips N4520. I've stripped it, cleaned it and have it all back together and now it's time to make it work.

Everything works but for the counter (not too worried for now).

And the fact that when you thread a tape and hit play, it just blows the fuse (lower 2A one).

I'm assuming the motors are drawing too much current, because it's fine when you have no tape threaded. I've had one of the reel motors apart and this has a heap of 4.7uF caps in it. I'm sure they will be knackered by now but should I risk changing them or just leave them be?

Also is there anything else I should be looking at? (it's not the capstan motor, still does it with it disconnected.)

Thanks all.
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Old 14th Jul 2018, 9:33 am   #2
RevoxNewbieUK
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Default Re: Philips N4520 Blowing fuses.

Just so you know what I'm talking about.

I'm assuming they are there to prevent sparking between the zones.

How critical are the values? I'm thinking I should find one that fits the seat rather than worry about the values in this instance.

Thanks for any help.
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Old 15th Jul 2018, 12:12 pm   #3
jim221
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Default Re: Philips N4520 Blowing fuses.

I personally would not have dismantled the motors until I had functionally checked it out beforehand, but I have had two of these and never had motor trouble. I assume you have checked the basics like checking the motor can be rotated by hand. I think the lower fuse is 801 which is in the 35v line. You don't say if you have a circuit diagram or have any great knowledge of electronics and if you have any test equipment. Please let us know.
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Old 18th Jul 2018, 2:43 pm   #4
Welsh Anorak
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Default Re: Philips N4520 Blowing fuses.

Those capacitors look like the reliable Japanese ones to me. Before going to the trouble of replacing them I would remove one wire from one capacitor, then check it for value and ESR. If it's OK then it's a safe bet the others will be too, and it would save you a lot of work. I can't see how increased load on the motor causing fuse failure would be due to a capacitor, though I may be wrong. Perhaps you could find out if it is the motor that's drawing too much current - possibly by swapping the supply and take-up motors over if they are the same type.
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Old 18th Jul 2018, 6:24 pm   #5
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Default Re: Philips N4520 Blowing fuses.

Have you tried disconnecting the motor/s and then pressing play? If the fuse still blows it rules out the motor as cause.
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Old 18th Jul 2018, 9:49 pm   #6
buggies
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Default Re: Philips N4520 Blowing fuses.

Came across this when looking for info on the fuse type (slo-blo or ?)

http://www.tapeheads.net/showthread.php?t=29103
"One other problem they sometimes have is that when the reel motors become older they start drawing more current which causes a fuse to blow. "
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Old 19th Jul 2018, 6:05 pm   #7
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Default Re: Philips N4520 Blowing fuses.

If there is an age related mechanism that causes these motors to draw excessive current, it may be that there are dendrites of metal being drawn across the commutator gaps by the brushes, especially if they are all-metal ones.

This used to be a common cause of failure with Japanese cassette recorder motors which caused overheating and subsequent failure of their internal regulator.
The dendrites could be cleaned away if caught before the regulator died, and the motor would be then ok for some further service.

I suspect it was also seen in some CD spindle motors where application of 9V from an external supply would clear these shorts and temporarily clear the symptoms.
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Old 19th Jul 2018, 7:39 pm   #8
Ted Kendall
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Default Re: Philips N4520 Blowing fuses.

The other age related thing on these motors is bearing collapse. Much prefer Revoxes, where you can replace the ballraces, which of course seldom wear out anyway.
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Old Yesterday, 10:35 pm   #9
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Default Re: Philips N4520 Blowing fuses.

Sorry guys been really busy . I`ll try an answer you all .

I didnt replace the caps in the end I decided they would be ok . I put the motors on my bench supply and one of them was over drawing so I pulled it apart and it was full of the black stuff , cleaned it out , no more blown fuses . It now works as it should and I have now recapped it , completely rewired it , changed the tape counter IC which had died , painted the chassis , completely rebuilt it and I`m now waiting one a couple parts before I can finish the restore of it . I am blown away by the sound quality of it . Its just amazing and the speed of the FF and REW should be made illegal , its insane ...lol .

All in all its a fantastic piece of kit and I`ve really enjoyed rebuilding it .
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