Akai 4000DS Mk2 track/head select

[Liamo81]

Hi all.

I finally got hold of an Akai 4000DS last year after wanting one for a long time, first time I've had a reel to reel set up.

The only issue with it is when playing tapes with two tracks or sides, is that it's playing both at the same time, with one playing backwards over the side I'm listening to. The head selector switch makes no difference to this.

I've had a search through the forum, and have managed to confuse myself more than find answers. I'd initially wondered if the switch needed cleaning.

Does anyone have any suggestions before I start taking it apart?

Thanks in advance.

Liam

[Simon Gittins]

My guess would be that you are playing a 4-track mono tape on this 4-track stereo machine, however, the track selector switch should enable selection of the track you want.

You could confirm whether there is a problem with the machine by starting with a blank tape and seeing if it plays back its own recordings.

[Liamo81]

Sorry, yes I should have added, it's when playing mono recordings, but the track selector doesn't make any difference.

[Analogue man]

The track selector switch can be a problem on these machines due to dirt ingress and the symptoms suggest to me that the switch has been bypassed by someone in the past. If you have any knowledge of basic electrics removing the head cover (you need to remove the track selector switch first which has an awkward sized Allen headed screw holding it on) then look at the wiring in the right hand head does it go to the switch contacts or does it appear to miss them if the later then the switch has been bypassed.

You should try the machine on recordings made on it and played back on it to judge it fairly though.

[Trigon.]

Is the right hand level control pulled out ?

(Note the text appearing below it.)

Cheers

[Liamo81]

I've not taken it apart for a look yet. I suspected it was dirt or corrosion in this switch, as the first couple of times I tried to use the machine, turning the track selector gave some effect but more so a load of crackle as you'd normally get from a dirty pot, but after a few turns stopped doing anything at all.

Will pull it apart and have a look. Are these switches accessible for servisol or similar if that was the culprit?

Thanks for responses.

Liam

[Liamo81]

The text below the right hand level control has worn off, so hadn't even realised it pulled out. Just pulled it out for the first time and that got rid of the unwanted reversed track bleeding through. Time to get back into the manual, but what have I missed here?

Thanks guys.

[Liamo81]

Originally Posted by Trigon.

Is the right hand level control pulled out ?

(Note the text appearing below it.)

Cheers

Just dug the manual back out and see what the text should have said... thanks for spotting that!

[dave walsh]

It says "pull for mono use" Liam. You would be well advised to carefully check out the selector switch though. They are delicate as Analogue man advised. The one on my machine is a bit scratchy but it does work. I operate that with very great care as I don't want to end up trying to fix it: shrug: Servisol shouldn't hurt. I think I got my Allen key from a pound shop set?

The same goes for the famous "monkey metal" cam that can disintegrate very easily,. I've been lucky [see the threads] so it's worth applying caution on fast forward/reverse etc. These faults are a shame as this integrated [one motor] design that came out in the seventies provided an opportunity to purchase a professional looking [and sounding-not everyone agrees] r to r deck at an affordable price [circa £100-easy terms at Currys]. It's often said that they "spoiled the ship" by economising too much on the mechanical side but perhaps the weakness with this alternative material was yet to show up? I hope you've got the sleeve for the capstan to change the speed up to 7.5 ips? It has been known to go missing despite the post it lives on!

Dave W
Bexhill

[ms660]

Originally Posted by Liamo81

The only issue with it is when playing tapes with two tracks or sides, is that it's playing both at the same time, with one playing backwards over the side I'm listening to. The head selector switch makes no difference to this.

Are the mono recordings you are playing back 1/2 track or 1/4 track? The tape recorder in question is a 1/4 track machine.

The pull switch kills the right hand channel when monitoring tape or source when it's pulled out.

Lawrence.

[Radio Wrangler]

The switch doesn't just select which replay heads are in operation, it's needed to select erase and record heads too.

Pulling out the right-hand level control parallels up your replay amplifiers and runs both from the same head winding. The switch on the head cover then selects which winding. So if you move the head switch while playing a 2-track tape, one position will give you normal audio of one track out of both L and R outputs. Another position will give you backwards audio of the other track on the tape, again coming out both L and R outputs of the machine.

Four track machines have guard bands on the tape between each of the four tracks, so there are a couple of narrow strips on a tape which a two track machine has recorded on which a four track machine can't erase. If you have tape already recorded in 2-track, you can't use your Akai to completely erase it, you get a little background left. A bulk eraser is needed to get the best signal to noise ratio for subsequent 4-track recordings.

David

[ms660]

Originally Posted by Radio Wrangler

Pulling out the right-hand level control parallels up your replay amplifiers and runs both from the same head winding.

Not in the schematic I'm looking at.

From the user manual (screen shot)

Lawrence.

[Radio Wrangler]

Mine did.

I bought it new in 1974 so I know it had not been modified. It was a mark I DS, and not a mark II. I used it for seven years before I bought a Revox, and used it with some older tapes from a 2-track machine.

Never had occasion to go into the track selection switching on it. It did what I needed. The only thing was the bush-type bearings for the spool shafts needed replacing twice. It got a lot of use.

Maybe a mis-wire somewhere? or some production change? but I know exactly what mine did.

David

[ms660]

Originally Posted by Radio Wrangler

Mine did.

I bought it new in 1974 so I know it had not been modified. It was a mark I DS, and not a mark II. I used it for seven years before I bought a Revox, and used it with some older tapes from a 2-track machine.

Never had occasion to go into the track selection switching on it. It did what I needed. The only thing was the bush-type bearings for the spool shafts needed replacing twice. It got a lot of use.

Maybe a mis-wire somewhere? or some production change? but I know exactly what mine did.

David

Yes but I was referring to the OP's machine which is given as a Akai 4000DS MKII.

For anyone that wants, here's a link to a service manual for the Akai 4000DS MKII which also includes a schematic for the Akai 4000DS:

https://archives.doctsf.com/document...0900&ref=37027

And here's a link to a operators manual for the Akai 4000DS MKII:

https://archives.doctsf.com/document...1546&ref=37027

I haven't got a link at the moment for the Akai 4000DS operators manual, the screenshot shown below regarding playing back pre-recorded tapes was taken from my own copy of that manual which I have on file, the manual file is to large to upload to the forum.

In the schematic for the Akai 4000DS MKII the pull for mono switch is shown connected between ground and one of the poles of the monitor switch (S4) that connects to the R channel line output stage via a section of the SOS switch.

Lawrence.

[Liamo81]

Thanks all, playing fine now with that switch pulled out, and enjoying some of the mono tapes I'd put to one side. Can't believe I missed something so simple. Track select switch is a bit scratchy, so still needs a clean, but will leave that for now while I enjoy listening to it again.

It does still have its capstan sleeve thankfully, it's a nice condition machine.

Thanks for the service guide Lawrence, only had the user manual previously.

[DMcMahon]

Interesting the wiring/connection difference between the 4000DS and the 4000DS Mk. II

I have yet to see/find the "Pull for mono use switch" on the 4000DS schematic, can see it on the Mk. II schematic.

David

[DMcMahon]

Initially thought it was SW1b but discounted it because it is ganged with what looks like SW1e (maybe its an "a) which has EQ SW alongside it , but now realise that the Equalisation switch must be SW2.

David

[Trigon.]

Originally Posted by DMcMahon

Interesting the wiring/connection difference between the 4000DS and the 4000DS Mk. II

I can't speculate as to why RW's particular machine might have been different, but I believe normal everyday 4000DS and 4000DS MkII both work as below. (My unmodified 4000DS certainly does.)

On the replay side of things the track select switch merely swaps the replay head windings in the '3-2' position.

(Position)...(Head -> Preamp)
'Stereo'....... L -> L, R -> R
'1-4'........... L -> L, R -> R
'3-2'........... L -> R, R -> L

So:-

If playing a 1/4 track mono tape, 1st side: track 1 is on the 'left' head and track 3 on the 'right' head
The left channel plays either 1 or 3 as selected by the track switch, with the unwanted 3 or 1 on the muted right channel.

If playing a 1/4 track mono tape, 2nd side: track 4 is on the 'left' head and track 2 on the 'right' head
The left channel plays either 4 or 2 as selected by the track switch, with the unwanted 2 or 4 on the muted right channel.

If playing a 1/2 track mono tape, 1st side: side 1 track is on the 'left' head and side 2 track reversed on the right head.
The left channel plays side 1, and the unwanted reversed right channel is muted.

If playing a 1/2 track mono tape, 2nd side: side 2 track is on the 'left' head and side 1 track reversed on the right head.
The left channel plays side 2, and the unwanted reversed right channel is muted.

Cheers

[Restoration73]

The very first 4000DS (I had one Aug 1972 - Lasky's 66gns) did not have the pull for
mono switch on VR02. The neat way of implementing replay of a single track on a MkII
is to repurpose the pull for mono switch to control a small relay that will disconnect the
right channel preamp out and connect the line amp to the left channel preamp out. The
signal will be heard in mono both channels.

If your tape has a single track recorded (4 or 2 track recording) jam the track switch between
"stereo" and "3-2" for mono replay with audio on both channels without the above modification.

[DMcMahon]

Found a clearer 4000DS schematic that confirms SW1a.

Now also see that the dotted line that shows the ganging of SW1a with SW1b identifies it as the S.O.S switch (Sound On Sound).

So still struggling to see the "Pull for mono use switch", it must be there somewhere.

David