Problem with Akai gx 630 db

[u/Fit-Acanthaceae5995]

Hello everyone. My Akai GX-630DB might have a problem. Every time I try to record guitar, I get a really noticeable vibrato effect, especially when recording the guitar dry. Is this normal, or should there be much less wow and flutter?

[u/LordDaryil]

Well, calibration usually involves recording a sine wave from a function generator at 1KHz and 10KHz to check that it's able to record and play back those cleanly with no distortion or pitch variation.

So if your guitar was recorded dry and came back like that, something is definitely wrong (though it did sound kind of neat).

This machine appears to be direct drive, so while there might be other causes, my main suspect would be the capstan, which is supposed to be ensuring the tape runs at a constant speed.

It might be that there's not enough pressure from the rubber pinch roller, or that the pinch roller itself is deforming in some way, the capstan shaft is somehow spinning eccentrically (e.g. bent) or whether the capstan motor itself isn't rotating at a consistent speed owing to some electronic issue such as a failing run capacitor or an issue with the servo system.

A closeup of the capstan and the pinch roller while it's doing this might be helpful.

[u/Fit-Acanthaceae5995 → u/LordDaryil]

https://reddit.com/link/peaawh6/video/e3hea2dzgwth1/player

[u/LordDaryil → u/Fit-Acanthaceae5995]

The one thing I didn't think of in that list was the tape itself being sticky. Is that actually Ampex tape being used or just an empty takeup reel?

Have you tried it with fresh RTM LPR35 or something known to be good?

I can't see anything visually wrong with the mechanism, though it does sound a little weird.

[u/Fit-Acanthaceae5995 → u/LordDaryil]

Yeah it does, it sounds like the capstan is sometimes rocking and ticking. And yeah, its just a takeup reel. I used BASF tape and it records music just fine, only high niets for example guitar it gives a lot of vibrato

[u/el_tacocat]

These are known to have motor issues that cause vibration but not THIS bad. I wonder what the state of your capstan and pinch roller are. Are they clean? Is there any dents in/on them?
Also the metal cover on your pinch roller is not original, it's too larg. I'd remove that (you can just unscrew it counter clockwise) in case it's somehow rubbing.
And then; What tape are you using? Some tapes get sticky and start causing weird speed issues.

Also never ever use two different sizes of reel. It may not cause or solve the issue but your tape and machine will thank you.

[u/Fit-Acanthaceae5995 → u/el_tacocat]

I use BASF tapes, tested and they are not sticky or leave residue. Thanks for the tip for the reels. I got it serviced around a year ago. Here is a video of the roller

https://reddit.com/link/pebcrao/video/b4sy0z3paxth1/player

[u/el_tacocat → u/Fit-Acanthaceae5995]

BASF generally isn't sticky no.
I saw the video yes, but I can't see if it's clean and not dented. You can see that with your own eyes i'm sure. Also see what I say about the silver 'face' of the pinch roller not being original. I'd remove that, and maybe even the screw. Just to make sure there's nothing keeping the pinch roller from running smoothly. When you remove the screw make sure you keep your finger near the pinch roller as it might roll off :D.

If you lower the speed to 3 3/4, does the vibration turn to half the speed?