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 Post subject: JVC 1250 8 track player issue
PostPosted: Jan Tue 30, 2018 4:42 am 
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Location: Warner Robins, GA
I have a JVC 1280 8 track player/recorder that is restored which I hadn't used in a few months.

Tonight I went to play a tape and I noticed when the CONTINUOUS PLAY - REPEAT - AUTO EJECT switch is in CONTINUOUS PLAY or AUTO EJECT sometimes I get a noise in the audio which is more like a combination of a hiss and higher frequency buzz, but I can wiggle the tape cartridge and the noise goes away for awhile.

Tried two good tapes so I know it isn't a tape.

Any idea what the issue could be or is it just due to non-use




Also I think the contacts that operate the track change directly control the solenoid. Is there a way to possibly have the contacts control a transistor or other thing that then controls the solenoid in order to reduce the current the foil strip on the tape has to pass? Figure that would prolong the life of the strip.


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 Post subject: Re: JVC 1250 8 track player issue
PostPosted: Jan Tue 30, 2018 5:53 pm 
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Joined: Feb Mon 06, 2012 7:24 pm
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Location: Gold Country, (Stanislaus National Forest) California 95235
Is your head demagnetized and is the cable shielding good?

Sometimes those old 8-track decks can get broken shielding where the head would pick up noises from the switch or the solenoid it's controlling.

Also check the solenoid and switch itself and maybe spray the Blue Shower tuner cleaner in there or whatever they call it anymore.

And then take a wand-demagnetizer and go in and demagnetize the heads and see if that helps any.

_________________
2 kinds of men/tape. Low Noise/Wide Range.
LN=kind. WR=abrasive. Engineers=same thing.


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 Post subject: Re: JVC 1250 8 track player issue
PostPosted: Jan Tue 30, 2018 6:29 pm 
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Location: Warner Robins, GA
I'll try that, but doesn't explain why the noise is only present in two positions of the switch unless the contacts that control the track change are loose and are moving around with the tape.

I always like the Japanese audio stuff like this as most of the better quality stuff was a step above most everything else consumer grade.

The motor itself is quite beefy with a heavier rotor and a heavier capstan pulley than what a lot of 8 track players with an AC motor have.


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 Post subject: Re: JVC 1250 8 track player issue
PostPosted: Jan Tue 30, 2018 11:04 pm 
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Joined: Feb Sat 12, 2011 2:29 pm
Posts: 445
Location: Fayette County, Pa
I had something similar on an 8 track a while back. It turned out the issue was the sensing contacts. Two factors contributed to it Dirt on the contacts and the polarity of the DC voltage. What was happening was the contact nearest the head was the one with the supply voltage present instead of ground which was the first contact. When the tape went past it, the graphite lubricant on the tape would pick up this DC and although a high resistance would carry this voltage through the coating coming to ground on the next metal item, which was the head itself. This resulted in a hiss / buzzing / frying sound at times. A good cleaning helped for a while, but when dirt built up again the problem returned. I resolved it by simply reversing the leads to the sensing contacts which put the grounded side nearest the head and resulted in that one bleeding off any leakage through the graphite before it got to the head..

And yes, you can switch using a transistor instead of passing this current directly through the sense foil. Some 8 tracks actually use this method on their better quality models.


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 Post subject: Re: JVC 1250 8 track player issue
PostPosted: Jan Wed 31, 2018 2:20 am 
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Location: Warner Robins, GA
Sounds exactly like my problem.

Will have to refer to the schematic to see how the switching is done to the track change solenoid. If not through a transistor I will add a transistor and put a reverse biased diode across the solenoid if one isn't already present.


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