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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 28th Jul 2016, 3:46 pm   #1
Michael Maurice
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Join Date: Feb 2006
Location: Wembley, Middlesex
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Default Akai GX365

The problem with the above deck is that I cant set the bias on the RH channel (tracks 2-3)

The high frequencies are far too high and no adjustment of the bias can reduce it.

I've scoped the output of the bias pots. On CH1 there is a good range of bias control, on CH2, not so.

I swapped the record amplifiers but that made no difference.

The pot and the associated resistor are within spec.

Which leaves one thing, the record head or possibly the erase head. Can anyone concur or if you think of another cause then let me know
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Old 29th Jul 2016, 12:04 am   #2
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Default Re: Akai GX365

Between the bias oscillator output board and the record head is relay R401 on the track selector board. On a few occasions have had to clean the contacts, or replace relay in severe cases. Also the bias appears to be routed through track selector switch which may have an open circuit. In both instances no head load gives high output with little or no adjustment level.

Try swapping over the bias output connections on pins 8 and 9 of the bias oscillator board to help confirm location of fault.

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Old 3rd Aug 2016, 9:24 am   #3
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Default Re: Akai GX365

The output of right channel rec amp board (pin 2) goes to a 5.6 mH coil L401

which is in parallel with a 470 pFd capacitor. These are on the track selector

board. This circuit passes the audio from the rec amp to the head, but blocks

the bias from flowing back to the rec amp. If the 470 pFd was shorted, or L401

was open, bias would be shunted to ground with the trap inoperative.

Insets from pages 117, 120 and 123 Akai Schematic Register Sect 0.
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