AKAI M-9 Tape recorder/player.

[AdrianH]

Some time ago I offered an AKAI M-9 Tape player, one that was passed to me by a friend. No one was interested at the time I think down to some cams having a bad reputation for disintegrating.

Today I started to have a look at it, the cams seem to be fine, I confirmed that the right channel had no output despite the VU meter moving, unfortunately on one switch on it decided it would no longer power up. I think one of the rectifiers has gone, no fuses have popped but I will have a look later on.

But I noticed that the IPS adaptor is missing, so at present, even if working it would only do 1 7/8 IPS.

So wondering if anyone would know what the diameter of the adaptor should be and I will see if I can make one out of some brass bar.

Cheers

Adrian

[Analogue man]

If the M9 is just a semiconductor version of the M8 then there should be a switch at the top centre of the deck to switch between low and high motor speeds this will give you 1 7/8 and 3 3/4. The capstan sleeve should be 8.05mm diameter. I believe that the M8 also had (or could be obtained) a sleeve for 71/2 and 15 IPS but I have never seen one.

[AdrianH]

I am not sure if the M-9 is a transistorised M-8 or not, this is my first time playing with these, it feels a bit too modern for me!



This is the chart in the owners guide

It uses the adaptor for everything baring 1 7/8. I was actually just measuring the spindle at 3mm dia and was calculating the size of it to get it to 3.75 IPS, and I get I would need a 6mm diameter spindle?

So thanks for the size i will go off and recheck my maths.

It mentions a 15 IPS adaptor as an optional extra

Adrian

[AdrianH]

Just an update on this, There is not a fault with the PSU, more an operator error, there is a two position switch which is either automatic 'Stop' or 'Shut-Off' It was in shut off which powers off the player.

The right hand speaker is open circuit, so I have a couple of speakers on order to replace this one, I need to test it first before to make sure there is no standing DC on it.

The biggest issue is that there is a cam that has failed, it appears to be one that raises and lowers an erase head, I believe it is described as M9-011i, 4T Cam, in the service manual.

I really doubt I could fabricate one of these with the gear I have, so this could be an end for getting the machine working again. A quick search via google and any AKAI spares I found did not include the M-9.

A shame as I was trying to get it working and then pass on for a donation to charity as before.

So I wonder if anyone can help suggest a way forward.

Adrian

I will ask the mods to change the title.

[DMcMahon]

That is extremely unfortunate about the damaged cam. I was going to suggest possible repair using some sort of metal filler but I see from the drawing that it looks like a securing screw screws into the cam which makes any repair much more difficult.

Is the securing screw missing ?

What you really need is a donor cam (in good condition) from a cheap/scrap M-9 or similar M machine that uses the same cam.

You most likely know that when switched to Automatic Shutdown that the mains power will be removed when the tape gets to the end or breaks, this removes tension from the Auto shutdown lever which breaks/opens the power microswitch.

David

[AdrianH]

I have the screw from the cam it was floating around in the machine mechanics. I can only think that it was forced over time and started to break up, it meant that there was lots of play in the control, and the erase head never moved up/down. I have checked the service manual for the older M-8 but it does not seem to have the same cam, not sure about later ones?

OK on the automatic shutdown, this is the first time I have looked at any Tape machines so is all new to me. This one originated in Lancaster, was passed to my friend some years ago and then on to me to see if I could do anything with it. There are some spares out in the US but costs seem to be very high for them and I doubt I could ever recover the costs and still get something to charity, it does not seem as popular here as over the water.

Adrian

[dave walsh]

That's a bit unfortunate Adrian. I think I've got one of these machines in Rammy. They look more sophisticated than the well known 4000 series but I'm surprised to note that the notorious "monkey metal" failure [see the 4000 cam failure threads] afflicts your recorder as well. It's a shame that AKAI economised just a step too far with either excellent model.

Dave W

[TIMTAPE]

If the broken cam only operates the erase head, it may not affect too many people. Probably most are interested in merely playing back/copying their old family recordings, rather than making new ones on an obsolete and often troublesome format such as open reel.

[DMcMahon]

Out of interest which control/control setting moves (should move) the erase head ?

David

[Radio Wrangler]

Originally Posted by AdrianH

So I wonder if anyone can help suggest a way forward.

A new cam with those shapes would be difficult to make even with a lathe and a mill, but there is a way round.

Thick brass sheets could be drilled and then hand-filed to shape, so that they would sit on a rod and stack up to make the finished shape. They could then be silver-soldered together before being drilled and tapped for the securing screw.

Before soldering, align carefully and cut an alignment slot somewhere safe, then use a steel strip to lold position during soldering.

I had one of those sptung briefcase locks break and I filed a new part out od solid brass. It took a few hours but it's nice stuff to work with.

What do you want the title to be?

David

[AdrianH]

Originally Posted by DMcMahon

Out of interest which control/control setting moves (should move) the erase head ?

David

It the one with the big X in the middle it it in this picture. If you notice the X has turned 90 degrees in this image it should not be more than a few degrees. The shaft from this goes through to beneath the heads moves the stepped cam and one gear.
.

Adrian

[AdrianH]

Originally Posted by Radio Wrangler

A new cam with those shapes would be difficult to make even with a lathe and a mill, but there is a way round.

Thick brass sheets could be drilled and then hand-filed to shape, so that they would sit on a rod and stack up to make the finished shape. They could then be silver-soldered together before being drilled and tapped for the securing screw.

Before soldering, align carefully and cut an alignment slot somewhere safe, then use a steel strip to lold position during soldering.

I had one of those sptung briefcase locks break and I filed a new part out od solid brass. It took a few hours but it's nice stuff to work with.

What do you want the title to be?

David

Thanks for the idea, lots of hand work I know, but a possibility.

I wanted the title to be AKAI M-9 Tape recorder/player. but it seems to vary through the thread.

Can one solder this monkey metal? One thing I thought of was to mill out the broken section on a milling machine and to make up a circular brass section to replace it, I can easily turn a piece of brass in the lathe, drill and tap it for a screw, basically just replacing the broken section, but not aware if it would solder?

Adrian

[Boulevardier]

Originally Posted by AdrianH

It the one with the big X in the middle it it in this picture. If you notice the X has turned 90 degrees in this image it should not be more than a few degrees. The shaft from this goes through to beneath the heads moves the stepped cam and one gear.
Attachment 275266.

Adrian

Isn't that knob something to do with the cross-field bias head, rather than the erase head?
Mike

[AdrianH]

It could be, it would move a base plate that would shift the bias head up and down. I am not sure what the bias head does to be honest and there are some images in the manual that describe it as E.H



That is unless I am reading it completely wrong.

Adrian

[Boulevardier]

Originally Posted by AdrianH

It could be, it would move a base plate that would shift the bias head up and down. I am not sure what the bias head does to be honest and there are some images in the manual that describe it as E.H

Attachment 275268

That is unless I am reading it completely wrong.

Adrian

I don't understand the "EH" legend - an erase head wouldn't be mounted in that position. Hope I'm not teaching grandmother to suck eggs, but all tape recorders put a magnetic bias on the tape. This high-frequency (inaudible) ac bias voltage sits "beneath" the recorded signal to lift it above the non-linear part of the record head's hysteresis curve. This ac bias signal is normally added to the audio signal from the recording amplifier in the record head, but this has the disadvantage that the bias tends to interact with the recording signal and attenuate higher audio frequencies in the head. To try and avoid this problem, Akai experimented with a method of applying the bias signal through a separate bias head, and through the tape from the other side (the non-ferrous-coated side ("cross-field bias"). They made quite a feature of this technique, but I'm not aware that any other manufacturers tried it, and I don't think it caught on.

That's as far as I understand it anyway.

Mike

[Radio Wrangler]

Originally Posted by AdrianH

I wanted the title to be AKAI M-9 Tape recorder/player. but it seems to vary through the thread.

Can one solder this monkey metal? One thing I thought of was to mill out the broken section on a milling machine and to make up a circular brass section to replace it, I can easily turn a piece of brass in the lathe, drill and tap it for a screw, basically just replacing the broken section, but not aware if it would solder?

Someone's already changed the title in your first post, so that has changed the title on the higher level of the forum. Changing the replies would mean having to hand edit every single reply individually (ouch!)

Monkey metal has constituents which dissolve in solder. It just makes the stuff worse.

The good looking monkey metal will degrade so you really have to be rid of the stuff.

The head which moves is the bias head. This machine has 'Cross-Field bias' with a head on the opposite side of the tape to where the tape meets the record head gap. A Tandberg invention licensed by Akai. So the X on the track select knob is symbolic!

David

[AdrianH]

I know nothing about the tape record/playback/erase or bias practicalities, so what it is doing is pure guesswork at my end, all I know is that it mechanically does not work. the markings on the head surround are either ST which I assume to be stereo and 3-2 or 1-4 so I guess it would effect these track numbers.

Adrian

ps Thanks David for your explanation.

[DMcMahon]

I think the Track Selector knob operation most likely is similar to my Akai X-201D (also with cross field bias) in that it electrically switches the tracks for the Record/Playback heads and mechanically adjusts the height of the erase & bias heads.

I agree with Mike that the E.H. legend does not make sense, The E.H. legend appears to be on the Bias Head, so I would suggest it should say B.H.

David

[DMcMahon]

Related closed Thread referencing the potentially problematic cam material:-

https://www.vintage-radio.net/forum/...d.php?t=194727

I see Mazak was a tradename for Zamak / Zamac

David

[Boulevardier]

Originally Posted by DMcMahon

I think the Track Selector knob operation most likely is similar to my Akai X-201D (also with cross field bias) in that it electrically switches the tracks for the Record/Playback heads and mechanically adjusts the height of the erase & bias heads.

I agree with Mike that the E.H. legend does not make sense, The E.H. legend appears to be on the Bias Head, so I would suggest it should say B.H.

David

Thinking about it, why does the height of the bias and/or erase heads need to be adjusted at all? Surely they will always be at the same height as the R/P head. Tracks will be changed by turning the spools over, as with any other recorder (unless it has auto-reverse play). As far as I can see, there will only be a need to move the bias head back and away from the erase and R/P heads to allow easy tape threading. I must be missing something...