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 Post subject: Fisher DD-280 cutting out on play randomly
PostPosted: May Sun 17, 2020 4:38 pm 
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Joined: Dec Tue 08, 2015 12:53 am
Posts: 443
Location: shirley NY...Long Island
Hello to all...does anyone know why this deck cuts out whenever it wants to during play only....I thought it was the very touchy switches for play, rewind, etc, but its not..
I took the switch apart, removed the membrane that makes contact with the buttons when you press it on..and it's not that....I can lightly touch the main motor's flywheel, and it will cut off the same way it does randomly...

thanks for you help..

Kenny


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 Post subject: Re: Fisher DD-280 cutting out on play randomly
PostPosted: May Mon 18, 2020 11:52 am 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 7257
Location: Sunbury, Ohio 43074
Just a guess from this remote viewpoint, but it sounds like a tape tracking/head contact problem. Usually dirt, could be very worn tape path parts, or one of the reel clutches not providing proper tape tension.

Usually the other cause of dropouts is dirty switches or potentiometers. Even cleaned, sometimes they need to be cleaned again. And again.

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https://www.bbtvtestequipment.com


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 Post subject: Re: Fisher DD-280 cutting out on play randomly
PostPosted: May Mon 18, 2020 11:03 pm 
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Joined: Aug Fri 12, 2016 1:49 am
Posts: 1260
Location: Houston area, TX
Is the speed consistent and accurate when it isn't cutting out? Have you verified this (e.g., via test tape and counter or scope)?

Is there a delay after you touch the capstan or flywheel before audio comes back, or is it instantaneous?

I'm wondering whether a muting circuit (if this unit has one, some do) is activating due to speed fluctuations.

IF you're having out-of-spec speed fluctuations (will probably be noticeable to the ears), that needs to be fixed anyway, so do that first and see if it fixes the audio drops.

If you are not having out-of-spec speed fluctuations, then try tapping things with something light enough to not cause damage but heavy enough to reveal an electrical intermittent via mechanical shock. My "tapper" is an improvised rubber mallet of sorts — I pressed an old audio pinch roller onto the end of a flimsy plastic alignment driver. It works great for finding bad ground connections, PCB cracks, cold solder joints, etc.
Tap various places around the relevant PCB's and grounds. If that doesn't cause audio to cut out, then lastly tap gently on the front of the tape head during playback. Certainly be careful not to cause any misalignment of the head or any tech adjustment pots.
A fingernail will do in a pinch, but my tapper has caught things my fingernails didn't. :)


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 Post subject: Re: Fisher DD-280 cutting out on play randomly
PostPosted: May Tue 19, 2020 7:45 pm 
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Joined: Dec Tue 08, 2015 12:53 am
Posts: 443
Location: shirley NY...Long Island
Its not fluctuation at all...speed is perfect...it is mechanically cutting off...as in if the tape ended...noting to do with sound
Its like you hit the stop button...the head pulls down and it cuts off...that is all that is wrong with it...


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 Post subject: Re: Fisher DD-280 cutting out on play randomly
PostPosted: May Tue 19, 2020 7:52 pm 
Member

Joined: Nov Wed 30, 2016 7:35 pm
Posts: 7257
Location: Sunbury, Ohio 43074
Ok, you described it a little vaguely. Usually "cutting out" means audio dropout, not the tape stopping.

So, tape stopping can be a few different things. See if there is an EOT sensor (end of tape) ... sometimes its a photocell, could be dirty, or going bad. Check the switches in the tension arms with an ohmmeter (deck powered off please) ... see if you are getting zero ohms. You may have to monitor this with a voltmeter while it's playing.

It really could be about anything, including the power supply. You'll have to find a way to narrow it down a bit. If you have a DMM, even a cheap one, monitor each of the power supply voltages while its playing.

Could also be a dirty switch contact, or a dirty relay contact. Try gently tapping on things while it's in play and see if you can make it stop.

_________________
Preserving the hist. of electronics, one boat anchor at a time! :)
https://www.bbtvtestequipment.com


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 Post subject: Re: Fisher DD-280 cutting out on play randomly
PostPosted: May Tue 19, 2020 9:00 pm 
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Joined: Aug Fri 12, 2016 1:49 am
Posts: 1260
Location: Houston area, TX
An entirely different issue than I read into the OP, which calls for an entirely different troubleshooting approach.

Based on this further description, I suggest the takeup reel is sticking or the idler tire is slipping. This is not a gear-driven direct drive unit, it uses a rubber tire that flips between the two reels.
You make no mention of the takeup reel stalling or stopping, so at this point I don't know whether you simply haven't watched for it or just haven't mentioned it yet.
I'll proceed on the assumption that you just haven't noticed it doing this.

Most decent decks have a sensor that monitors movement of the takeup reel and will shut off the mechanism if the takeup reel stops rotating, in order to prevent (or at least minimize) tape spillage. Without this protection, the capstan/pinch roller keeps pulling tape out of the cassette, but it just pours into the deck instead of going where it's supposed to on the takeup spool.

You say you can force shut off of playback by manually stopping the capstan/flywheel from moving. Doing so also stops the takeup reel from rotating, since it's being prevented from taking up tape that is no longer moving — IOW, it's pulling against the overwhelming tension of the length of tape between the capstan/roller and itself. So, though you can force the same symptom manually, the end result is happening for a completely different reason.

Anything that stalls or stops the takeup reel can cause the deck to shutoff playback.

I suggest carefully watching the takeup reel, if you haven't already, and when it "sticks", tap it and see if it starts moving again. You may have to be a bit more aggressive and force it to move with a small screwdriver or some such, but tapping on it and/or the carriage will probably do the trick.
If you get it moving again and there's no shutoff, bingo.
If you're lucky, a light lube job will fix it. If not so lucky, you may be looking at new rubber (tire/anything slipping).

I have also had tape deck motors become "sticky", the shaft stops rotating until manually encouraged. If you're really unlucky, the reel drive motor may be getting weak and hitting a "dead spot" occasionally during playback. Removing and testing the motor is a last resort, so try the other things first.


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 Post subject: Re: Fisher DD-280 cutting out on play randomly
PostPosted: May Thu 21, 2020 1:20 am 
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Joined: Dec Tue 08, 2015 12:53 am
Posts: 443
Location: shirley NY...Long Island
Ok will do all I can to test it..very sorry for not explaining the way it was in the beggining.
This deck have VERY sensitive control buttons...and VERY LIGHTLY touching them will change play, ff or rev, so I thought it might be that...I cleaned what I could of the buttons...and it still does it...The buttons work but I want to replace them if anyone knows where I can get the board that has the contacts...thanks...They just dont look right to me...and I have already remove the board that the switch's are on...or should I say disconnected the wires that go to the main board from the switch's with not change..it still cuts off out of the blue....

Thanks for all your help...

Kenny


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