Align AKAI GX-365 reel tape deck

[TLS Guy]

I had to take my PC to have a faulty RAM replaced. I am in the middle of editing a wedding video and creating a DVD so the RAM couldn't wait. I will also have to rebuild my PC because the faulty RAM has created a few problems in my OS. This means I will be off line for a few days. I managed to remove the replay head and rotate the head around the y axis slightly. Unfortunately, there is no fine adjustment for this. The screws holding the head housing at the bottom can be moved slightly in the baseplate holes that are slighly bigger than the screws. I am now slighly rotated too much in the opposite direction. I would have expected a change in the signal level in the reverse direction but it is still up to 10 dB lower in signal level than forward. I will mark the head with the grease pencil I bought yesterday. Perhaps the top of the head is slanting forward so that the reverse motion over the bottom part of the head does not have the same contact. Another curious problem is that I cannot find a gap. Can it be that the sensing area is over the whole front part of the head?

Sorry to hear of your computer problems!

There has to be a gap. Playback heads have a narrower gap, and record heads a wider one. Record/replay heads split the difference.

Have you tried looking at the head with a magnifying glass? If there is no gap any longer, then the head needs re-lapping or replacing. Heads can wear and the burr on the pole pieces seal the gap. A head with no gap will not work properly, as the pole pieces are then magnetically shunted. Heads that are misaligned easily wear in this fashion.

You can usually see the gap naked eye, but certainly with a magnifying glass.

From what you tell me, I fear that head my be no good.

I'm 62 and can easily still see the head gaps naked eye on all my heads.

 

[JohnCPR]

I agree, there has to be a gap otherwise the head could not pick up the narrow vertical magnetized strips on the tape correctly. The AKAI heads of the GX-365 are surfaced with a crystal like material that prolongs the wear life of the heads. Since the glassy surface appears to be intact, the gap must still be there somewhere in the center of the V angle. What makes this puzzling, is that all components used by forward and reverse are the same, including the head. One would imagine that either forward or reverse should be reacting the same with either direction of tape movement. The head, being critical for alignment, must be the problem. When I rotate the playback head around the y axis a few degrees to correct for the approximate 2 degrees off alignment I mentioned earlier, the forward and reverse appear to be acting the same as before rotation. Using the protractor again, I appear to have slightly over rotated the head housing. I can rotate a little back to where it was set originaly to find a more central position. While the head housing is removed, I can also check for the gap more closely with a magnifying glass and mark it with the grease pencil before remounting.

What would happen if the ground and signal connection at the back of the head was reversed? Judging by the sloppy job of the previous repair, it is possible that the head could either have been replaced upside down or the signal and ground wires reversed. Of course, the soldering of the wires could have damaged the head by overheating.

If all else fails, I will just have to use the tape deck in the forward direction only. At least I gave it a good shot and it has been good exercise for a brain in retirement.

Welcome to the sixties. I am 67.

 

[TLS Guy]

I agree, there has to be a gap otherwise the head could not pick up the narrow vertical magnetized strips on the tape correctly. The AKAI heads of the GX-365 are surfaced with a crystal like material that prolongs the wear life of the heads. Since the glassy surface appears to be intact, the gap must still be there somewhere in the center of the V angle. What makes this puzzling, is that all components used by forward and reverse are the same, including the head. One would imagine that either forward or reverse should be reacting the same with either direction of tape movement. The head, being critical for alignment, must be the problem. When I rotate the playback head around the y axis a few degrees to correct for the approximate 2 degrees off alignment I mentioned earlier, the forward and reverse appear to be acting the same as before rotation. Using the protractor again, I appear to have slightly over rotated the head housing. I can rotate a little back to where it was set originaly to find a more central position. While the head housing is removed, I can also check for the gap more closely with a magnifying glass and mark it with the grease pencil before remounting.

What would happen if the ground and signal connection at the back of the head was reversed? Judging by the sloppy job of the previous repair, it is possible that the head could either have been replaced upside down or the signal and ground wires reversed. Of course, the soldering of the wires could have damaged the head by overheating.

If all else fails, I will just have to use the tape deck in the forward direction only. At least I gave it a good shot and it has been good exercise for a brain in retirement.

Welcome to the sixties. I am 67.

If the heads are wired out of phase you can pick that up on the scope. It is the same stacked heads used for forward and reverse. Reversing decks were renowned for just what you are experiencing. That is why the Nakamichi dragon turned the tape over!

If you can get a good frequency response forward, I recommend you call it a day.

Willi Studer never made a reversing deck. He was the grand master, and if the idea had any merit, he would have made a reversing deck, but he didn't.

I think there is agreement that he made the best tape decks ever produced.

 

[JohnCPR]

Thanks TSL for all your help. I will arrange the head so I can rotate it slightly for the best signal then set it in place. If the reverse is still off, I will settle for forward only. I will use my scope to check for the correct phasing.

 

[JohnCPR]

One last message. I found a way to twist the head slightly without having to remove the head mount from the base. I placed a small tensioned spring between the screw and a flat washer holding the head mount to the vertically moveable base. The vertical movement is to shift the head for reverse. The spring is tensioned to allow the head mount to be twisted slightly around the base with my hand while at the same time providing sufficient force to prevent twisting by the tape movement over the head. Once set for maximum signal level and alignment, I will use a little goop on the sides of the head mount and base to set it in place.

I empathise with your concern for the lower quality of cheaper reel-to-reel recorders. This separated the average consumer from the serious audiofile due to the cost. Unfortunately, some manufacturers suffered as a result. However, it did allow more average consumers to enter the market because of cost. It also created challenges for repair adicts such as myself. I am concerned for the junk and buy new mentality that has created more waste for the land fills so I try to repair as much as possible. Being an electrical/electronics engineer has helped. I valued your experience and it has been a pleasure working with you.