I have an AKAI Terecorder Deluxe (1/2 track mono) that has been restored.

Last night I used it and noticed a variance in the treble as a tape was played so knowing that tape tension in units without pressure pads is important I put some resistance on the supply reel and the treble sounded better.

What exactly would the problem be?

Sounds like the felt pads in the supply reel table are either going bad or are not under the proper tension.

If it is a tension issue how would I adjust?

If it is the felt going bad I have at least 2-3 AKAI tape transports which are similar I could pull some parts for the reel tables from.

Make sure the playback head doesn't have any oxide on the surface...or possibly the head is wearing. Try other tapes..Possible the tape is aging and losing its pliability, not conforming to the head as well as it used to.

Noticed it on two tapes that do not exhibit this issue on my AKAI GX-255.

To me when turning the reel table when no tape is installed and play is engaged the reel seemed to be a little easier to spin than most AKAIs using one motor are.

May open it up this afternoon and have a look.

It could be entirely possible that the brake is slipping as it is just a round piece of rubber on a stud which presses against the botom part of the reel table during playback so the one part is stationary providing the necessary tape tension via the felt discs slipping against each other.

I intend to use this to eventually copy all 1/2 track mono tapes I have to my computer as I figure it's better to use a 1/2 track mono machine for that versus a 1/4 track stereo machine.

Next on my list is a 1/2 track stereo machine to properly copy the three 1/2 track stereo tapes I have.

The first step is to measure the tension using a spring scale.

There is a way to adjust the tension on felt surfaced clutch disks.

But

I suspect you don't want to know about it.



Material on clutches on Akai, and other tape recorders can be found in my July 1965
PF Reporter article found here .



http://www.americanradiohistory.com/Arc ... 965-08.pdf

Thanks for the information.

based on your article it looks like I may first want to disassemble the supply reel table and clean the felt.

What would be a good modern sub for carbon tet and what is a good plastic cement?

Also will isopropyl alcohol sub for wood alcohol?

The use of solvents was in some cases, a surfactant which
was known to affect different materials. The removal, or
addition of lubricants adjusted drag.

The other thing was when the Akai, and other tape recorders,
were the current models, we could order entire clutch assemblies
so the issues of taking things apart was only used sometimes.

Single motor machines had a limited torque budget, and because
most of them were induction types, almost everything, including
the tape thickness and spool hub diameter impacted the speed.

Most of the time I used a tape strobe. It was a mounted on a handle
and held against the tape on the supply spool.

Later, when Akai needed to meet flutter specs, a 3000 Hz test tape,
playing with the frequency readout used.

Recorder makers also sold friction disks and kits of special washers of various
thicknesses.

These techniques and tricks had one thing in common. They were used to repair
low cost, mass produced machines.

Often the speed spec was the time in seconds a given length took to pass trough the capstan,
and what the +/- hours for a roll of their tape.

Perfect pitch was a joke.

The reference to carbon tetrachloride vanished from service manuals of a maker of decks,
using the same build as previous models.

What ever you do with clutch assemblies, you need to be able to measure the drag torque.

How would one check the torque of the supply side reel table?

Suppose one could use the same method with the string only setting the player in play and pulling the gauge until the reel starts to move

I never used string. Leader tape was used for tension measurements.

I think your tape recorder used a clutch similar in form to the Roberts 770X.

From Sams TR 11, Oct 64.

Yes most AKAI decks of that period used a similar tape transport so it would be the same.

I did notice that the reel table appears to be spring loaded and it seems like perhaps the portion of the supply reel table that the brake presses against is also spring loaded.

When I disassemble the supply reel table I'll look at the felt. If it is bad or otherwise in poor condition I may use a reel table from one of the other similar AKAI decks I have.

I don't have an actual strain gauge so I may have to improvise something.

I have a digital scale that reads up to 500 grams. Perhaps I can wind some leader tape on an empty reel and support the tape at the other end and have it press against the scale.

Try and find a 250 gram spring scale.like this on, or make one if you have
a box of springs.

About $4. from Banggood.

5N Lab Dynomometer Spring Scale Balance Newton Force Meter Student Mechanics Experiment

I'll find one when I get paid again.

Been sick with the flu so I decided to swap the reel table from an AKAI M7.

Was a fairly simple swap and the issue has been solved.

I can tell that I may need to do the take up reel table as well, but it still has enough tension to wind up the tape properly so I'll leave it alone for now.

Also I noticed playing one tape on 5" reel it seemed to slightly slow at the end of the first side.

Having not replaced the capstan belt I will start with that if the problem continues.

The torque angle with a 5 inch reel is poor on that kind of machine.

Perhaps it would be better to wind the tape onto standard 7 " reels. and play it that way.

Also a 'tape strobe' is a valuable tool.

Agreed about the 5" reel.

In fact the torque will vary as the tape unwinds from the supply reel.

I've become quire spoiled by my AKAI GX-255.

One of those tape strobes would be nice to have.

Better even than that is to use like the record labels use - a 7-inch reel with a NAB hub - holds up to 1000 ft of a normal 1.5 mil 1200 foot roll of normal 7-inch tape - i.e. plenty of room for the 600 ft of the same tape on a 5 inch reel. In short - if it fits on a 5 inch it will fit on here and play a lot better.

That indeed is a good idea.