 
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
|
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
70.24.152.185
I was fortunate to pick up a 7 1/2 ips capstan sleeve (with end cap) for my Akai GX-4000D from a kindly AA inmate. I still have one problem that I need to sort out. It might just need a new belt, but I think there is something else going on.
It plays (and records) perfectly at 3 3/4 ips (without the sleeve of course), but at 7 1/2 ips the tape plays for a bit then gradually slows to a stop, almost like something is slipping. I bought a new belt for it but I haven't installed it yet, and I am hoping that someone can give me some advice.
There is an "EQ" button on the front that switches between 3 3/4 and 7 1/2 ips, but I don't think it has anything to do with the actual transport speed. Can someone tell me what this "EQ" button is for? Is it possible that it could be the problem? Any other ideas that would help me to find the problem would also be appreciated.
Thanks!
Prehistoric 4-Channel Lizard
Follow Ups:
The EQ switch is there because the tape/head has less loss at the higher tape speed. The 3¾ IPS position boosts the HF response to bring the tape to NARTB specs during record and compensate for the tape/head losses during playback. The compensation becomes quite radical at 1 7/8 IPS, which is the speed cassettes use. So you have to respect Nakamichi for being able to record up to 20 KHz at that speed. The bias is also critical at that speed. If you flip the switch it probably changes the bias in record as well, but really, if you flip the switch on a good deck you hear very little difference in the sound.
As to your speed problem, it is a little bit backwards. Usually belts and idlers work better once warmed up. Therefore it is probably the motor. It might just need lube. If you don't want to tear it all down, use LPS 2, it will mix with the old lube and loosen it up.
The other possibility is extreme wear on the motor bushings. The shaft elongates the hole in the direction the belts and idlers but on it. The part where it is worn is very tight and seizes in extreme cases.
The hard way is to find a machine shop to make you some new bushings. There is almost no tooling up for the job so it should not cost an arm and a leg, and they will have to use their measuring instruments so you have to take the whole box of motor parts down there, plus they mmight have to press the new bushings in.
A quick and dirty alternative that works more than sometimes is to examine the motor mounts and determine which way the pressure is applied and see if you can't turn it 180 degrees. Doing this will put the force on the good side of the bushing. Depends on how it is mounted. Sometimes you can take the motor apart and turn the bushings around if their mounting method precludes rotating the whole motor.
In either case, there is no guarantee that the deck will meet its original wow and flutter specs.
One rubber part that doesn't really work better when warmed up is the pinch roller. In act if it is starting to get gummy it might well be the problem. I assume you probably had a good look at it during cleaning though.
Some decks have a completely different motor for the capstan, in which case everything about that motor applies. You know the force applied is from the pinch roller, so you know what to do.
If not mechanically inclined you could bring it to me, but likely is too far. Someone local should be able to handle this. I am in Cleveland, Ohio. If that is close enough and you want to, let me know. Shipping is a real drag. They screwed up a system I fixed at UPS, but what got me is it was $300 to do it.
Even with a discount because I put a small scuff mark on it, I had to charge around $300. I had to fix the power supply, and the cassette, and rebuild the amp because the IC was no longer available. I also put belts and a cartridge in it. To avoid further problems we decided to meet at the state line, as he is in Pennsylvania. Nice little hole in the wall bar on I-76.
Does your deck have crossfield heads ? Not sure completely but it seems that scheme eliminates some of the IM distortion during recording. I also noticed that Tandberg adopted the design. Not sure if they violated the patent, sidestepped it or possibly there was no patent, I don't know right now. Plus Tandberg is not a US company so our patent laws might not apply. Point is, they are a pretty much high end company and if they adopted the design it must have something going for it.
Good luck with it. I hate to see things go into the dumpster.
I appreciate your offer to help, but I am in Canada ... not that far though, about 5 hours around the lake from Cleveland. As it happens, I took the deck into a local stop a couple of weeks ago, and I got it back this afternoon.
They installed a new capstan belt that I supplied, cleaned and lubricated a few things, including a complete disassembly, cleaning and lubrication of the supply reel. Everything is working well now, and I hope it will be good for some time. Thanks again for your advice.
Prehistoric 4-Channel Lizard
| FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
||||||||||||||
This post is made possible by the generous support of people like you and our sponsors:
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2024, Audio Asylum, all rights reserved ]
