AKAI M-9 Tape recorder/player.

[AdrianH]

After re-reading the operators book a bit, it looks as though one can either do stereo tracks per side, or one can do 4 tracks mono, (two per side). So I guess that the bias head is being shifted around so as not to overwrite, or cause issues with another track when in mono record mode?

See this page from the user guide.
Akai-M-9-4track.pdf

Adrian

[TIMTAPE]

Yes in mono the upper and lower portions of the heads (track 1 and track 3) actually swap roles. Eg in track 1 mono recording, track 1 bias and erase is actually lifted above the tape and out of the way, and track 3 is lifted into the track 1 position on the tape. For track 3 mono recording it's similar but the head descends and track 1 plays the role of track 3 bias and record.

Doing it mechanically like that saved Akai adding more complex head switching including adding dummy heads for correct loading of bias and erase oscillator in mono recording. I think Akai was the only company to use this mechanical method. It worked but the mechanicals could fail especially when the lubricant went sticky, and forcing the track change knob broke the cam as had happened with your deck. The portable Akai X4/X5 machines could fail more often as the cams were smaller and weaker as I recall.

Tandberg and Akai both eventually dropped cross field heads due I suspect to the inherent problem of increased tape dropouts in record mode.

[DMcMahon]

in my Akai X-201D the Track Select Control Knob is pretty difficult to turn to the 3 positions. The Forum seller said it was always like that from new, but to me it seems too stiff. Not sure if there is a cam but there is a nylon gearwheel in the assembly that rotates when the erase and bias heads are raised/lowered.

One day I will strip it apart to see if the stiffness can be improved, have not tried it before because it looks a difficult assembly to take apart and thought best to leave it alone while it is still functional.

David

[TIMTAPE]

Here's a picture of an Xfield head assy from an unknown Akai model (minus the bias head). From memory removing it wasnt too difficult although I think the head wires needed to be unsoldered.

[AdrianH]

Do you have a picture from the other side of the assembly?

Adrian

[DMcMahon]

Very stiff Track Select on this at Post 20.

https://www.google.com/url?client=in...8J5cIHi7XlRZbd

David

[AdrianH]

Every time some one mentions a machine I go off and try to download a SM to see if the machine has the same cam. The X355 I have just downloaded 3 SM's from different sites all are the same and to me look as though the exploded views are missing large chunks.

The 4T cam in the X355 is part number 03-017, I can not find it in the views unless I am missing something obvious.

I have started to measure the cam, basically it is 9.2mm thick with a 3.5mm step from low position to middle and 3.5mm step from mid to high, with something like a 30 degree angular rotation between each step rest position, although I need to check that later.

The hole for the shaft is smaller than 5mm so need to remove the head again to measure the shaft properly.

I have some brass lumps and could eventually machine something up although doing the slopes from one height to another has me stumped for a while.

Adrian

[TIMTAPE]

Originally Posted by AdrianH

Do you have a picture from the other side of the assembly?

Adrian

Here it is.

[AdrianH]

Yep same cam. It looks like chrome plated pot metal.

Adrian

Just to add that depending on where you set the cam and the brass gear via the X knob on the other side it means that they (Cam and gear) can then clear the actuation arms to allow it to be pulled clear of the mechanism. Mine was way out and took a while to figure it out.

[AdrianH]

Just to add that the gear on the end of yours is different to the one on mine, Mine being more like 180 degrees of gear wheel in brass. I get the impression that it has been changed in the past for a replacement and perhaps was not fitted or tightened correctly. It it allows the ise and lower peg to get passed the end of the cam it would lock it solid. I think that may have been the issue in the past.

Adrian

[DMcMahon]

Originally Posted by AdrianH

The 4T cam in the X355 is part number 03-017, I can not find it in the views unless I am missing something obvious.

Adrian

Yes I cannot see it either in the exploded view (s), how do you know that the 4T cam listed part is the cam in question ?

David

[DMcMahon]

Have now found my original 355 manual and can see the 4T cam in the heads assembly, shown on scanned attachments. Annoyingly could not get PDFs to stay saved in the correct orientation

On the 355 the heads area is busier due the auto reverse hardware.

David

[ms660]

Here's the said manual:

https://archives.doctsf.com/document...0927&ref=66185

Lawrence.

[AdrianH]

Yes they look very similar, although there is one area a bit different, I am not sure if they are compatible or not.



There seems to be an extra step here, not sure how that matters.

Adrian

[DMcMahon]

Probably academic, the chance of finding a 355 cam as a replacement would be very low.

David

[AdrianH]

I have found Wilkinson's in Nelson only do the Play cam that are compatable with a few machines, but searching on the likes of Ebay, most of the spares are in the States and not in the UK, the prices for machines seems to be a bit daft even for spares and repair?

Adrian

[DMcMahon]

I did ask Wilkinsons months ago if they could do other Akai cams apart from the Play cam but never received a response.

Yes you seldom see cheap Akai machines for spares/repair.

David

[AdrianH]

I spent more time cleaning lubing and having a serious look at the cams after a bit of brush work. and all I can say is AHHHHHHHHHHHHHHHH!

I can now appreciate what people have said about them. I have been looking at the running surfaces which seemed to be generally OK, no great groves, but with use of a camera and flash I can really see the state of them. So as well as the 4T cam we have these: -








I have had the unit playing a tape or two this afternoon, but how long the machine will work without breaking is guess work.

Adrian

[TIMTAPE]

In the past I've injected a low density glue like Super glue into the visible cracks and cleaned and lubed everything related to place the least stress on the cams. It seemed to help.

[DMcMahon]

Even though they look bad, sometimes the damage may be superficial/not deep and they may last for a long time more.

One with a screw screwed in potentially will be weaker and may fall apart when disturbed, example here at Post 10 (photo 2) and Post 18 (photo 3).

https://www.google.com/url?client=in...BB4trQLWC1oF12

David