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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 24th Mar 2017, 12:32 am   #1
Michael Maurice
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Default Akai GX-R77 cassette deck.

This machine is very complex for what it is and dismantling it to fit 3 belts then re-assembling it, took around 3 hours.

However, I now have a very odd fault.

When I switch on, If I press eject, the door comes out, Rew and FF all work, but if I press play, the heads move up, the cam motor starts up, there's no sound, but if I leave it for around 1½ minutes, the cam motor stops and plays normally.

During the time the cam motor id running, no other function works, you have to physically switch it off and back on.

Any ideas?
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Old 24th Mar 2017, 5:52 am   #2
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Default Re: Akai GX-R77 cassette deck.

I haven't got your schematic, but in the GXC 75, there is a reed switch
activated by a rotating part that sends pulses into the system control
board.

Might this be related to belts if used in the 77 ?
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Old 24th Mar 2017, 5:01 pm   #3
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Default Re: Akai GX-R77 cassette deck.

No, this is far more sophisticated. The counter is totally. Electronic, and in real time..
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Old 24th Mar 2017, 9:18 pm   #4
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Default Re: Akai GX-R77 cassette deck.

Have you checked the timing of the main cam and the rotary switch (mode switch), this is for the GX-R70 Deck but IIRC the 77 is very similar.
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Old 28th Mar 2017, 12:34 am   #5
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Default Re: Akai GX-R77 cassette deck.

The timing of the main cam wasn't disturbed and its a pig to get to. However there is no mode switch, instead there is a 'volume control' and you have to set the high voltage and low voltage using two pots.

Below are a couple of pages from the manual
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Old 29th Mar 2017, 3:55 pm   #6
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Default Re: Akai GX-R77 cassette deck.

Hi MM,
I have only ever came across 2 of those Akai machines with the "volume control" for mode sensing and possibly 2 or 3 with the rotary switch, this was way back in the very early 90's and I don't recall mode problems as such, other than the usual belt trouble on any of them.

I agree with you though on the level of sophistication, they were more akin to a contemporary VCR of the day.

I don't have a manual of the 99 that you posted a snippet of either, however the mode sensing is either done by comparators or possibly voltage control (resistor ladders) as some VCR machines did for key scan back in the day.

So if the output from the rotary "volume control" is correct then how about the reference (fixed voltage) it is compared with at the other end so to speak ?

Alternatively it could be a missing syscon input that the machine is expecting to be present and isn't that is upsetting things (odd behaviour).
Just like you would with older vcrs I would be checking inputs (and expected outputs) to be present, or not, as the case may be.

I am going to see if I can find a copy of the manual on line to have a look, I am intrigued now.
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Old 29th Mar 2017, 5:13 pm   #7
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Default Re: Akai GX-R77 cassette deck.

I have managed to get it to work, but tested it from cold this morning and it didn't work properly. You cant set the 'high voltage' because the 10.5V rail was low at around 9.5V but its actually designed that way!

Its an absolute swine to set up, but I'm hoping (fingers crossed) that I've got there.

I got the manual from hifi engine.
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