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Bender Comments Page

These are Reel to Reel Questions, Answers, and comments, things I've posted on several discussion groups, some when people write and ask me questions.


Comment #10

Ray B wrote:

My Dokorder 1140 4-track is giving me fits: it records and plays on all 4 channels but suddenly it won't play back in all 4. I've triedshutting the recorder off, thinking that it might be a bad electrolytic capacitor, then turning it back on ,to no avail. I've switched amplifiers and checked all cables-no change.

The heads are all good and I've cleaned them thoroughly several times. When I record and then playback I get nothing and therefore I think that the machine didn't record but later I can play back what I thought hadn't recorded.

What is the likely cause of this problem? Any suggestions will be appreciated! Thanks!

Ray B.

********** And Bender Sez: **********

Hi Ray -

Almost all of the Dokorder Reel to Reel tape decks were known for having elusive problems, many were detailed in addendums to the Dokorder service manuals, and that is the most difficult type of service information to find. While I only have one complete Dokorder Service Manual, and the unfinished preliminary parts of another; I can state that among the more likely culprits in this instance, is a problem related to the plug in-board "edge connectors" and / or problems with the relays.

Unfortunately for the most part, these edge connectors are of a type that is no longer made, and probably for the most part unavailable. Such intermitant problems can be relays where years of arcing have caused the mechanical contacts to become non-contacts.

Also various soldering problems (cold solder joints) existed in many Dokorder machines, as detailed in service bulletins.

Other known Dokorder power supply problems, with failed transistors usually affect Dokorder solonoid functions, like the pinch roller unable to engage. By comparison that known problem is a simple and easy fix.

Intermittant problems have way too many maybe's, and because so many Dokorder problems existed back when they were new sets, today, 20 to 25 years later, probably ALL of the known problems affect each and every Dokorder set - 25 years later... So, sorry, I can't give you a definitive answer, but those are the three general areas where the problems will be found.

-Steven L. Bender

Comment #11

J. Helander wrote:

Looking to purchase a portable reel-to-reel recorder (built-in speaker/s) that accepts low-speed tapes @3 3/4 and 7 1/2 speeds.

Must be in good working order. Thanks

********** And Bender Sez: **********

Hi J -

Man, its amazing to me what some people consider "portable"... is a 55 lb. Sony that uses tubes the tape recorder ( without the weight of a box of tapes ) that this guy is asking about?

I have a Uher 4400 Series Report Monitor, that is 1/4 track stereo, and pretty amazing with four speeds, 5" reels, and runs on a bunch of D Cell batteries. Loaded up, it weighs in at about 15 or 16lbs. with batteries, and I call it luggable, yet not quite portable.

I guess one man's "portable" is another man's "boatanchor"... :-).

-Steven L. Bender

Comment #12

Re: Revox A77/B77 1/4 track alignment

Ken Cazakoff wrote:

When I record on one side of a blank tape using my 1/4 track A77 and then flip the tape over and play the opposite side, it will reproduce the opposite side recording backwards at a much lower level but still audible and annoying. It also isn't erased when the achine is put into record and the tape is monitored. There seems to be some alignment mismatch, or track width mismatch between record and play heads but I don't know how or why?

It doesn't seem to be the Azimuth. Might it be a too high record level problem of some sort? Has anyone heard of anything like this problem or a fix?

********** And Bender Sez: **********

Hi Ken -

While the crosstalk between sets of tracks on 1/4 track Reel to Reel tape is not infinite, it should be on the order of -40dB to -50dB down from peak level. Such crosstalk can often be heard on older pre-recorded tapes when the tape duplicators were not properly aligned, or had heads that mismatched the exact position of the recorded tracks due to excessive wear problems.

You didn't state just how "loud" this "much lower level" crosstalk was, is it enough to move the VU meters during playback, or is this crosstalk just faint and barely audible above the tape and electronics hiss level ( about -50 dB +/- ) ???

On tapes you make yourself, such problems have four possible causes:

1) At some point the heads were replaced, maybe with inferior 3rd party (non-original) heads, or a 2 track record head was installed and a 1/4 track play head, or with heads that were put in "out of alignment".

2) Worn head surfaces which cause the inner surface of the gap or gaps to become wider with age. The result is that the track or tracks become misaligned causing a wider than normal "track" or "tracks" hence more overlap with the "other" side's tracks, and more apparent crosstalk between the forward and reverse sides.

3) Some techie-wannabe has adjusted the head or heads or the tape path guides, at some time in the past, to be quite out of alignment; the result being that the recorded tracks are no longer evenly aligned along the width of the tape, making the pairs of tracks much closer to overlapping, increasing the apparent crosstalk.

4) Excessive recording levels will also exacerbate the problem; this will show up mostly as crosstalk in the bass, with thumping bass lines audible, but little else can be heard.

-Steven L. Bender

Comment #13

D'Antiques wrote:

Ray wrote:

Don wrote:

Hi.Just bought a 7030 GSL,without an operators manuel. Can some one tell me what the cue switch is, and what is its function. How is it used. Thanks, Don.

It helps locating blank and recorded portions! Turn the output control down (below 1/2), press and hold the CUE while in fast forward/rewind mode. BE CAREFUL OF YOUR EARS AND LOUDSPEAKERS!

Regards, Ray

The Cue position places the tape against the heads, as in the Play position. Its purpose is to precisely locate the point at which one wants to cut the tape for a splice or add/subtract recorded material. One could use it in fast speeds, I guess but it works better to turn the reels by hand. Decks with electronic Pause control do the same thing when activated in Play mode.



********** And Bender Sez: **********

While many sets have a Cue button, Teac's X-10R, A-7030GSL, etc., not all sets have the ability to "cue" during play when they are in pause; in this case the Akai GX-255 comes to mind, it is definately fully muted during play/pause, one of its few annoyances; while many other sets, like the Akai GX-230D, GX-266D, GX-266II are not muted during play/pause.

A few rare sets seem to have a cue position which seems to depend on the sequence of operational buttons pressed, with no separate cue function. This simply involves whether the tape lifters are engaged or not. In the "not" sequence, the tape is against the heaqd for what is a cue function. I'm not quite sure if this was a mistake in their "logic" states, or an actual "function" that was provided and maybe poorly documented or not documented at all.

Lastly, other sets that have the "cue" don't have a pause position; an example here would be the Tandberg 9200xd; so the cue is definately a fast-wind function there.

-Steven L. Bender

Comment #14

Pete wrote:

I have an Akai GX-635D machine and the Owners Manual says for Remote Control to use an Akai RC-18 or RC-70 (What in the world is an RC-70!!). My question is I have an RC-16 for my Akai GX-285D and the plug fits into the back of the GX-635D (I did this with the power off!!). Can I use the RC-16 with my GX-635D? I wanted to ask other opinions before I turn it on and blow an IC or something trying to use this remote. If it doesn't work what about the RC-17? or other choices

********** And Bender Sez: **********

Hi Pete,

First, the RC-70 is a wireless 2 piece remote ( transmitter and Receiver, which plugs into the rear of the GX-635D; it is rarely if ever seen. There was also the RC-90 which is for the GX-636, GX-77, and later sets which used the smaller 8 Pin DIN plug for the remote connection. It also is a an IR wireless remote system consisting of two pieces.

As far as I know, each and every Akai Remote Control Box has a different wiring setup. Some sets might be able to take an RC-17, or an RC-18, it depends how Akai wired its socket up. If the set says RC-18 or RC-70, I'd take that as truth.

In only a few instances will a given Remote Box work in more than one Akai model. Yes, the RC-16 does work in at least four of the really old Akai's, made from 1972 to 1974: the GX-280D, GX-280D-ss ( and the GX-285D and GX-286DB they are in the same Series ) also the GX-365D, and GX-370D. But the one thing that all of those sets had in common, they all used a lot of internal power relays, I think twelve were in the GX-365D.

Note that despite having the same numbers, but in a different sequence, the Akai GX-365D is quite unlike the Akai GX-635D.

As you can see, on your GX-635D, there are 11 pins on that remote plug. All of these can be either open with no connection, or they can be made to connect to ground level, a voltage level, or to normally open or normally closed switch contacts.

Simply stated, putting in the wrong wired remote will kill your GX-635D's logic chip ( an almost impossible to find proprietary part ) which along with its associated IC's and transistors replaced many of the power relays found in earlier sets.

I believe someone else once wrote about something similar, his later Akai ( maybe it was a GX-635D ) wasn't working and he decided to make up a shorting plug ( dummy plug ) designed for the earlier Akai's, based on something that he read on a web site. Well, he and plugged it into his later Akai, and burned-out his machine big-time.

Will the damage be permanent if you try the RC-16 in your GX-635D ?

Probably not. I often wondered how the power transformer was blown out on my own GX-266II. That is a very permanent kind of damage, and I conclude that plugging in the wrong Remote Controller would not likely do that. Since my set worked after I replaced the power transformer ( which took 3 years to find ) it could not be related to some mishap at the remote plug. The first thing to get damaged from error conditions on those 11 pin jacks would be the Primary Logic IC.

So, Pete you will need some serious repairs, likely the Proprietary Logic IC will need to be replaced and also some work in the power supply, there's about half a dozen discrete voltage regulators that you could blow, plus a bunch of smaller IC's and transistors that will likely catastrophically blow-up in sequence. My estimate is about $450. worth of damage, plus bothways shipping.

I use a three check method, first check is the estimated amount, the second check is $100. for contingency or damage incurred during shipping, or other problems unrelated to damage you caused, while the third check is $40. for return shipping ( since at this point I don't know where you are located, I can't know what the return shipping costs will be ).

If you truly love your machine, well connect her up, apply power, and jam that RC-16 remote plug in there... After the smoke clears, pack it up well, write me the three checks for the estimated damage as per above, mail it out to me via Fed Ex Ground, or USPS ( do not use UPS! ). If the damage runs more, I'll send it back COD... repairs could take up to 6 months or so.

Yes, I can get very facetious ( so look it up! ) when dummies wanna plug stuff in where it doesn't belong.

On the cheeeap side, if you should decide to blow your Akai's Logic IC, I do have them, they are available for $65. each, shipped conus. Any other needed repairs are basically up to you.

-Steven L. Bender

This page is under construction ( Like software, the job is never done!....)
Last Update - February 5th, 2004 9:00 PAM.

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