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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 2nd Feb 2019, 4:56 pm   #1
NorfolkDaveUK
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Default Akai GX-270D No FFW / RW

Hey all ,
Another one to puzzle over , this one is REALLY nice , its very clean indeed , not a scratch on it in fact . Its working as far as play / rec goes , but no FFw or Rw , the brakes disengage but no reel movement , so I`m suspecting something on the sys con board , but if anyone has encountered this and can give me a hint where to start that would be great . As always many thanks .

David
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Old 2nd Feb 2019, 5:12 pm   #2
NorfolkDaveUK
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Default Re: Akai GX-270D No FFW / RW

Nevermind ....blown fuse ...hahah ... Nice !
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Old 5th Feb 2019, 8:43 pm   #3
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Default Akai 270D Rewind issues .

OK so having now got round to this in a more substantial manor . I have found that this has a fault on rewind which is probably why it came in with a blown fuse . There is however weirdness involved .

If I lift the tape in arm and press rewind , it rewinds correctly , with good torque and the take up spool goes loose but holds tension .

However , if i put a tape in , it will FFW like a demon , but will not rewind , and i dont mean its sluggish , I mean if you press the rew button , no rewind at all . If i manually spin the take up spool (backwards of course) the the rewind keeps up no matter how fast I spin it . So to me this indicates dirty tape path , but , no , I have cleaned it up very very well and its certainly not that because - the same thing happens if I take the tape out of the tape path , sometimes it will crawl rew , but most of the time its just sits with a buzzing rew motor and no movement until I manually operate the take up spool.

It plays in Rev just fine at the correct speed . I have changed the 5uf (3+2) and 330uf 160v caps . I have not changed the 4 + 4 uf cap .

This thing is an absolute pain in the backside to get in to , its been put together with no thought of a service in mind at all , getting the power supply board to show me its goodies is a mare of a performance .

So , anyone have any Ideas . I`m thinking the relay / diode on the PSU board maybe , but you guys might know better , this is the fist one of these I`ve had .

BTW , the brakes are releasing fine !
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Old 5th Feb 2019, 9:09 pm   #4
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Default Re: Akai 270D Rewind issues .

CR5 and 7 snubbers are reading dead short in circuit (no power) , whilst 4 and 6 are reading 100ohms . I dont know if this is at all relevent but thought I would add it . I`m kind of at a loss as to why it has great REW with lots of torque with no tape and yet with a tape even when its not in the tape path it doesn`t move at all . It seems more electronic than mechanical to me . Something to do with tension maybe ?
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Old 5th Feb 2019, 11:01 pm   #5
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Default Re: Akai GX-270D No FFW / RW

got it , im not too sure what was going on but its now doing what it should after re-capping the power supply . Weak cap maybe i dunno, anyway , all fixed , thanks.
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Old 6th Feb 2019, 12:19 pm   #6
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Default Re: Akai GX-270D No FFW / RW

It could have been too much torque in the take up motor or not enough in the supply motor, basically in that circuit the supply and take up motors are connected in series across the supply from the transformer (90 volts in play, 120 volts in FF/REW) In FF the supply motor is shunted by a 43 Ohm resistor, in REW the take up motor is shunted by the same resistor, in play the value of the resistor is changed to 220 Ohms, in forward play the supply motor is shunted by that resistor and in reverse play the take up motor is shunted by that resistor, in the schematic the rev/rew and the fast relay contact positions are shown with the relays not energised, eg: they are shown in the forward play position, so far as I can make out if that's any help for future reference for that model.

Lawrence.
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Old 6th Feb 2019, 5:13 pm   #7
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Default Re: Akai GX-270D No FFW / RW

Simplified schematics to go with the above, 'scuse scrawl, guilty as charged for any errors.
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Old 23rd Apr 2019, 10:19 pm   #8
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Default Re: Akai GX-270D No FFW / RW

Quote:
Originally Posted by NorfolkDaveUK View Post
got it , im not too sure what was going on but its now doing what it should after re-capping the power supply . Weak cap maybe i dunno, anyway , all fixed , thanks.
Hi Dave

Thanks for your contribution.

I have here a GX-270D with a similar problem:

Spools good in Fast REVERSE but rather slow in Fast FORWARD.

1) Could you please indicate which capacitors you replaced on the power supply board?
(did you also replace all of the snubbers and capacitors C5 and C6 (0.47uF 250v MP)?

2) Did you also replace the 4 uF and 4UF reel motor capacitors?

Thanks for a reply!

Regards,

Martin
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Old 24th Apr 2019, 4:03 pm   #9
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Default Re: Akai GX-270D No FFW / RW

Dave is no longer a member, but his technique was to change all electrolytics, so this is presumably what he did to the PSU. He said he didn't change the 4+4 capacitor.
If this does not help, please start a new thread about your GX-270D.
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Old 29th Apr 2019, 10:15 pm   #10
REDGUUZ
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Default Re: Akai GX-270D No FFW / RW

Sorry Moderator, to disagree.

You assume that only electorlytic capacitors have been replaced on the Power supply board but it is not at all a confirmed fact that other cpacitors (MP: C5 and C6 (0.47uF /250V) and spark quenchers: CR2 and CR3 (each : 0.1 uF +120 Ohm) have not been replaced, as well.

Also, it is, in my opinion, quite relevant to continue this thread as member MS660 was so kind to unravel the schematic, see preceding posts.

Member MS660 showed that spark quenchers CR 2 and CR3 and the MP capacitors C5 and C6 (0.47 uF , 250 V (NB these are not the regular motorcapacitors) have a profound influence on the reeling operation.

The Hitachi metal tubular MP capacitors (e.g. C5 and C6, 0.47uF, 250V ) have generally a poor track record in AKAI equipment (electric leakage, even emitting their waxy content);
The black spark quenchers (Brand Okaya) used in AKAI's and TEAC's are on the other hand, normally very reliable.
(Note that the European RIFA Miniprint spark quenchers (also used in some AKAI equipemnt for the CEE/UK market) on the contrary have a failure rate of 100 %, not only in AKAI equipment, but also REVOX and many household items (washing machines, hoovers etc.).

However in this deck, AKAI elected to use another (unknown) brand of Spark Quenchers (Blue type), of which the reliability is unknown.

Note: The Electrolytic capacitors on the Power supply board are governing the 24 Power supply and totally not related to the reel motor problem; hence irrelevant.

This triggered my question, whether indeed the MP capacitors C5 and C6 and/or the spark quenchers CR2 and CR3 had been replaced by Dave, because he claimed that the sluggish reeling was cured.

Maybe MS660 (or another member) could comment whether a failed CR2 or CR3, and/or a partially failing C5 or C6 could result in a poor FF reeling problem, whilst FR reeling is OK, as well as Forward and Reverse Play.

Any comment on the above is highly appreciated!

I will perform a full recap of the power supply board, in any case (not only the electrolytic capacitors, but also the MP's (C5 and C6) and the spark quenchers).
Time will tell whether this is the solution!

Kind Regards, Martin
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Old 30th Apr 2019, 11:00 pm   #11
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Default Re: Akai GX-270D No FFW / RW

By all means.
You asked Dave to comment on his actions, but as he's no longer here he won't be able to but Lawrence may be able to help.
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Old 1st May 2019, 11:21 am   #12
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Default Re: Akai GX-270D No FFW / RW

I did that diagram/schematic as an aid to help Norfolk Dave (or anyone else) should he or anyone else wish to understand the circuit for the spool motors etc, the schematic I did wasn't requested.

Regarding snubbers CR2 & CR3 that are connected across the OP-SW2 switch and the Fast-2 relay contacts and the capacitors C5 & C6 that are connected across the motors and their effects in FF mode.....so far as I can make out CR2 & CR3 are not in circuit in FF (or REW) C5 electrically leaking could affect FF depending on how bad the leakage is.

Lawrence.
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Old 8th May 2019, 6:30 pm   #13
REDGUUZ
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Default Re: Akai GX-270D No FFW / RW

Hi Lawrence,

Thank you for your suggestion.
I had the same idea (i.e. a suspect C5), but I have not had any time (yet) to overhaul the various boards.
I will definitly replace C5 and C6 as a first step!

In the AKAI GX-630D (larger brother of the GX-270D) on the same place Hitachi MP Tubular capacitors (0.47 uF, 250V) have been employed (1960's design), of which many seem to fail in AKAI recorders. (they emit a waxy substance).
Pre-emptive replacement is in order there, so I will surely replace those C5 and C6..
(similar story apparently for the grey coloured, Oil Filled Suzuki capacitors ("Suzuki bombs, , used in much older AKAI equipmen, which have a failure rate of 100% by now.
(They spectucarly expel their contents).

Again,

My Thanks!

Cheers, Martin
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