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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 11th Jul 2021, 2:52 pm   #1
Wolfman998
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Cool JVC KDA-55 cassette deck problem

I have a JVC Kda-55 cassette deck which upon moving house recently due to user error(namely I inserted the din plug incorrectly in the remote control socket - pre wireless RC days here!!!), anyone have any experience on these decks. No spooling or playing now. R554 popped, which I replaced. Need HELP PLEASE.

Last edited by Cobaltblue; 11th Jul 2021 at 2:55 pm. Reason: tidy title
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Old 11th Jul 2021, 11:30 pm   #2
DMcMahon
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Default Re: JVC KDA-55 cassette deck problem

Hello Wolfman and welcome to the Forum, unfortunately I have no experience of this deck.

Looking at the schematic in the service manual, I had trouble initially locating R554 but now see that it is on the base of the the brake solenoid driver transistor X504. The transistor base is driven (via R553) by the active high brake signal at pin 10 of Tape Controller IC M54886P (IC 501).

It is difficult to theorize what actually occurred when the DIN connector was plugged in incorrectly, the fact that R554 popped presumably means it took too much current, maybe it also took out the transistor.

In table 2 of the data sheet for the M54886P it lists the various outputs for the various operating modes, you may have to check these out as well as also checking the relevant driver transistors. Also make sure that the various DC supply voltages are good from the power supply circuitry.

David
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Old 12th Jul 2021, 8:50 am   #3
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Default Re: JVC KDA-55 cassette deck problem

First functionally check that the brake solenoid is energising and releasing the brake (s) when Play, Fast Forward and Rewind are selected.

David
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Old 13th Jul 2021, 3:29 pm   #4
Wolfman998
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Default Re: JVC KDA-55 cassette deck problem

Hi David, many thanks for getting back to me. I've investigated a bit further, changed r544 and checked all the drive transistors, one suspect x510 changed along with its partner x508. On switch on checked the 20, 15 and 5 volt supplies from the regulator chip getting 19.8, 13.6 and 2.2 respectively. Changed the chip and am getting the same. It seems like something is dragging it down. Unfortunately due to the way the unit is constructed (both boards hardwired together) it makes it very difficult to do split half fault finding. Any thoughts? And the reel and capstain motors, can I test these and if so can a dc voltage just be applied, regards Neil
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Old 14th Jul 2021, 12:13 am   #5
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Default Re: JVC KDA-55 cassette deck problem

Neil, I would guess you could test the motors with DC power supply but I have no idea of the motor (s) voltage/current specs.

Certainly sounds like the +5V is being dragged down by something, sounds like difficult to isolate loads without cutting tracks or lifting components, not easy. Can you first isolate the +5V at the power supply end just to make sure the +5V is OK off load.

David
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Old 24th Jul 2021, 2:38 pm   #6
Wolfman998
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Question Re: JVC KDA-55 cassette deck problem

Many thanks again for the reply. I think I have solved it! It appears that the cassette lamp and VU lamp bulbs act as a load for the power regulator. If blown or removed the 5v regulated voltage drops from 5.05 volts to around 2.4 volts. Put them back in circuit and all is resolved. I now need somewhere in Europe that supplies a 12volt, 0.15A, 8 ohm glass cartridge bulb 30mm x7mm! Any ideas on that please.
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