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Old 27th June 2006, 07:02 PM   #1
Nam402 is offline Nam402  United Kingdom
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Default Slow running Akai GX4000D

Hi folks,

My vintage hi fi system is gradually coming together, but not without it's problems.

The Akai GX4000D has a tendency to run slow, although not all the time. Sometimes it needs a push to get it going.

I've had a look inside and found that there is a drive belt which looks difficult to replace. The slow running doesn't feel like drive belt trouble, more like a sluggish motor. It's slow rather than slippy.

Any ideas?

The deck came from the continent, would voltages be an issue?

Cheers, Nam
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Old 27th June 2006, 07:19 PM   #2
anatech is offline anatech  Canada
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Hi Nam,
Often, the old lubricants become very thick. The solution is to remove, clean and relubricate the mechanical parts. Often the grease will appear to be a greenish colour.

So, take it all apart. Clean each piece with solvents (work outside). Relubricate with the recommended oils or greases. These will be additive free. Oils will be single weight. Take pictures as you go.

-Chris
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Old 4th July 2006, 04:12 PM   #3
Nam402 is offline Nam402  United Kingdom
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Hi folks,

This was a tough one.

After getting hold of the service manual, I had to strip the machine right down. Turns out that it wasn't the belt, or lubrication, that was the problem.

The belt was good, but the motor pulley and the flywheel were out of line and had to be realigned with shims. The belt had been creeping off the flywheel after a couple of tapes.

Maybe this happened in transit, who knows. It looks more like a pre existing problem to me.

For anyone faced with this kind of trouble, I think it's worth having a look. If we take it slow we can get things right in the end!

Cheers, Nam
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Old 4th July 2006, 04:26 PM   #4
anatech is offline anatech  Canada
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Hi Nam,
Check the play on the capstan bearing then. It is most likely worn. You must remove the thrust bearing and belt to check to see how much lateral play there is. It will be in the direction of the pinch roller pressure.

-Chris
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Old 6th July 2006, 02:18 PM   #5
Nam402 is offline Nam402  United Kingdom
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Hi Chris,

Yes, it would seem logical that bearing wear could cause some unwanted movement. I checked lateral wear when the machine was stripped down, but there was nothing detectable.

There was some end float on the flywheel and this was easily remedied by adjusting the captive nut at the end of the spindle, as noted in the service manual.

Applying shims to the motor mounting was the recommended procedure for adjusting the belt on the motor pulley, and that's what I did. It had been running very considerably offcentre on the flywheel pulley, hence the slipping off, although it looked central on the motor pulley.

I did notice a heavy indentation in the receiving plate at the end of the flywheel spindle, where the steel ball makes contact, and I was able to reposition the plate to make a clean 0.3mm gap possible between the ball and the plate.

I have fitted a new belt as a matter of course, although the old one didn't seem too bad. All is working fine now.

This is still a puzzle. I do know that the machine had taken a very hard knock at some time, and this would be before recent transit. One (mdf) side of the machine showed evidence of a hard impact and the mounting screws were buckled, but also corroded, indicating an old impact.

Maybe an impact could have moved the flywheel position somehow, who knows? I do know that this machine had been in a collection of machines and probably not used for many years.

It's always difficult talking about this stuff when we don't have the machine in front of us, but your suggestions have been most helpful.

Thanks for taking an interest.

Cheers, Nam

PS - This recorder sound great now, especially on the faster recording speed. Lovely analog sound.
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Old 6th July 2006, 02:33 PM   #6
anatech is offline anatech  Canada
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Hi Nam,
It is possible that the chassis front plate is buckled slightly. It doesn't take much the throw out the alignment. Something must have happened, because the machine was unacceptable the way it was. Setting up a tape path can be a pain. I've had to shim a few up over the years.

You are correct of course. Shimming the motor by the mounting screws is the correct procedure. So you have it runninng smoothly - good job!

-Chris
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Old 6th July 2006, 11:52 PM   #7
Nam402 is offline Nam402  United Kingdom
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Hi Chris,

You're right, the chassis is slightly out. I had the machine delivered from Germany (purchased on ebay) and I guess this is one of the pitfalls of long distance deliveries.

Great machine though.

Cheers, Nam
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