2 tracks vs. 4 tracks decks

[ZioGuido]

Ok, this may be a dumb question, but... Well, I own 2 Revox A77, a Mark I dated 1969 and a Mark III dated 1972, they're both 2 tracks at 3-3/4 & 7-1/2 IPS and they're both in great shape, so they're basically the same machine. I can record a tape on one and play it back on the other one, swap tapes all the time without ever noticing any difference, either by ear and by instrumentation (scope and fft).

Recently I acquired an AKAI GX-210D, I got it cheap because it needed some attention. It's a 4-track deck with auto reverse, but unfortunately the reverse function can't be used because the solenoid that moves the floating head seems too weak for doing its job (the deck is dated 1975).

If I play back on the Akai a tape recorded on the A77 it sounds dull with prevalence of amplitude on the left channel; and if I play back on the A77 a tape recorded on the Akai it sounds way more duller. Now it's evident that their heads don't have the same alignment.

Since the auto-reverse is unusable, I thought to block the floating head and re-align the heads on the Akai so to make it compatible with the Revox. Mission accomplished as far the playback is concerned. But there's something wrong with the recording. When I try to overwrite a tape with the Akai and play it back on the Revox, I can still hear what was recorded behind.

And now my question: is there a relevant difference in the 'pitch' (or width) of the recordable tracks on the two decks? I came up with the conclusion that the tracks recorded by the Revox are wider than those recorded by the Akai. Because of this, when the Akai deletes the two tracks, it only 'digs' in the middle of the tracks, while the Revox is still able to read their edges.

Is this correct? And if the answer is yes, this means that there is no way to make the two decks compatible? And does this apply to all other 4-track decks?

Guido.

 

[jjones1700]

I would assume that either the tracks on the heads vary slightly (either in width or location in relation to the tape), or that there is something awry with either the erase head or accompanying circuitry. If it's the track configuration, there is going to be some residual "bleed' since the Akai won't be able to erase outside it's set path. If it's the erase head/circuitry, somebody else might be of better help on that subject.

 

[The Ghost of FM]

Consumer 1/4 track stereo decks should have the same or extremely similar track width and guard band spacing. The alignment of the heads on the Akai may be off and have a host of other problems that you alluded to when you said you got a good deal on it.

Keep in mind that back in the era of those machines being new, there was a good variety of commercially available pre-recorded music, so all of those machines had to be compatible with all that.

Cheers!

 

[ZioGuido]

Keep in mind that back in the era of those machines being new, there was a good variety of commercially available pre-recorded music, so all of those machines had to be compatible with all that.

Right, this is the info I missed.

I don't think the Akai has some issues other than the solenoid thing. If I take a blank tape, record it on the Akai, overwrite and play it back, it plays fine, everything is OK. The bad deletion problem is when I try to delete a tape previously recorded on the Revox and play it back on the Revox again.

I was just having a closer look at the heads on the two units, and I could clearly notice that the erase head on the Revox has wider bands than those on the Akai, this could explain why the Akai can't erase a tape recorded by the Revox.

 

[jpmorris]

The akai will be able to play Revox tapes, but the Revox will not be able to play akai tapes. It just won't work.

 

[ZioGuido]

At the end, I've realigned the heads on the Akai so that the two decks are compatible one each other but a tape recorded on the Revox can't be properly erased by the Akai.