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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 #4

Date: Thu, 22 May 2003 04:32:26 -0700 (PDT)




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

The Sony Stereocorder TC-521 dates from around 1964 I believe, so it is a mid-1960's tape recorder using tubes. I also have one. The TC-521 was almost identical to the Sony Model 300, which was available with and without a case and speakers for custom installation. Both have an undistorted power output in the range of about 1.5 Watts - honest watts per channel ( rated 6 Watts in the inflated 1960's type ratings ).

The TC-300 apparently lacks the universal voltage switching selector switch that the TC-521 has on its rear panel. Both sets were single motors units which used lots of internal drive wheels, friction cams, wheelies, and drive pucks for driving various functions mechanically. I also have the Sony TC-521 Service Manual if you'd want a copy; its listed on my web site, the domain can be found at:

After 40 years, all of the capacitors in my TC-521 set have become bad or are failing, and so one channel barely works, the other just thumps with loud motorboating sounds. Also mechanically it grinds a bit. I recently got a Model 300 w/o case and speakers on ebay for all of $1. which turned out to be in even worse mechanical condition, and about the same in its electronics. It should be good for some parts, but after 40 years used parts aren't worth much.

I should state that it is quite a job to replace those capacitors, as no printed circuits were used in those early sets, just point to point soldering on lugs and wires. Replacement heads are unavailable, and head wear would be a major concern. Also, re-tiring of the rubber pinch rollers, drive pucks, or wheelies will set you back $35. each! So a full rebuild is usually economically out of the question on these old sets.

Any single motor set that old could fail at any time, even if it was rarely used, as caps fail mostly from disuse. Often, its heads and mechanical wheelies are probably a bit worse for wear. Also the cost of shipping such heavy sets ( today ) now can exceed $30. to $40. depending on your location, and proximity to the buyer. That is an amount which might be greatly in excess of its worth, depending on its "problems?".

Its unlikely that after 40 years, that it is "perfect" so giving people a good idea of its cosmetic, mechanical, and electrical functionality is perhaps a good idea if you are attempting to sell it.

-Steven L. Bender

Comment #5

Rick wrote:

I recently purchased my first RT-909. I purchased one of the best tapes that I knew of, a Maxell UDXLII (from my cassette days). Now that I have the tape I see that it is designated for use on machines that have EE capability. I have found nothing that indicates that the RT-909 is EE compatible. Is it safe to use this tape on this machine? What sort of recording and playback results will I get? In your experience what is the best tape to be used in this machine?

Thanks to anyone who may respond.


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

Rick -

The RT-909 does not have EE tape compatibility... Use of these tapes will result in the following... 1) On EE tape there will be a rising high end on recordings, and possibly a much lower playback level, by maybe 10 to 15 dB...

2) The machine will not be able to erase an existing recording made on EE tape to record over them.

3) Head wear will become excessive, as the Chromium EE tapes are much more like a file wearing down the head surface... also due to the extra high tension pioneer designed into the machine, compared to other RTR brand sets, the RT-909 head life is actually less than in other sets that also use permalloy heads. This will cause rapid deterioration if EE tape is used exclusively. Heads are basically no longer available for this machine. EE tape is just about the worst possible match possible.

Maxell UD and UD XLI, TDK Audua and LX, Scotch Classic and 207 are a good match for the RT-909 at its highest tape settings.

-Steven L. Bender

Comment #6

steve wrote:

Hi, Got this machine going with some replacement belts. Now when I play a tape, as the right hand reel gets to about two thirds full on a seven inch reel, the playback slows down and grinds to a halt. There is also some squeaking from the tape - not through the speakers (cheap tape?).

I believe the slowing down and halting is due to the left hand spool not being free enough to release the tape. i.e. the torque is strong enough when the left spool is full, but as the tensions change, then problems start. This event occurs even after a few minutes playing (when the right spool is almost full). But playing from the start of the tape (when the left hand spool is full) is fine - so I don't think it's a replacement Capacitor issue. It's mechanical.

Can any fellow owner of one of these machines tell me if, in the playback mode, if the left hand wheel should be completley free, have a slight bit of tension or be quite stiff to move by hand.

Thank you

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

Steve -

Often on the single motor sets such as the Akai 4000, the Sony 521 and Model 300, and many other sets, there are problems caused by weakening of the motor run capacitor; this can cause a set's motor to stop, or run poorly.

In addition, there can also be problems related to the belts and lubrication that has drived up, and also friction cams, wheelies and springs which "drive" the reel tables. Sometimes the friction in a reel table drive cam system is excessive when some "techie wanna be" has altered the system at some time in the past. This can lead to stretched and ruined tape, and I've seen this in several Akai 4000 sets.

Also the opposite can happen, which is insufficient friction, and then the reel doesn't take-up adequately, the shut-off arm will lower down, and the set will shut off. Another problem can be excessive friction within the tape path, from tape residue clumped onto the tape guides, from tape that is shedding its oxide, or has developed sticky binder / backcoating problems.

I recently found a reel of the later TDK LX backcoated tape, which was both depositing white "stuff" in the tape path and was also at various points sticky, sticky enough to bring a 3 motor Tandberg to an irregular and slow speed.

The Akai 4000 sets prior to intriduction of the GX heads are not worth much in terms of resale on the used market. Such sets heads are prone to head wear, and thus misalignment problems of reproduction, along with non head problems of gunked lubrication, worn friction cams, worn drive pucks, bad wheelies and springs.

So frankly such sets shouldn't be bothered with much. If you just love your "Money Pit", if you must, keep it clean and be careful how you mess with the takeup torque, unless you know what you are doing, or stretched and permanently damaged tapes might be the end result.

If one is going to put lots of time, effort, and money into a set, best if it is a better unit to begin with, like an: Akai GX-260D, GX-265D, GX-266D, GX-267, GX-266II, GX-255, GX-400D, GX-600D, GX-620, GX-625, GX-630D, GX-635D, GX-636, GX-646 or other later three motor, GX Head set. Additional Akai Reel to Reel pictures and info can be found on my web site the new domain is:

Also I have the Akai 4000 series Service Manuals and most other Akai Reel Service Manuals at:

The Akai dates & details page: Also info on my vintage Dynaco and Harman-Kardon Amplifier Rebuild Kits can be found at: Or through the Audiophile Webring.

-Steven L. Bender

Comment #7

Vance Daberko wrote:

Is there a way to adjust or, in this case, slow down the playback speed on my Dokorder model 8100 reel to reel? I can detect this on commercial recordings and recordings made from my Pioneer RT-707. Of course when I record and playback on the Dokorder, the play speed sounds fine.

Thanks, Vance

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

Well Vance -

There are primarily two ways speed to obtained in the tape drive systems of tape recorders...

The first type uses an AC motor which has a fixed speed at 1800 rpm, or some other speed dpending on the number of poles present in the motor. Often these sets have two or three speeds which can be switched by a switch which connects / disconnects motor poles, so a 4 pole motor can be set to work on only 2 poles, often at the expense of consistency of speed, in other words when set to 2 poles its action will be more jerky and hence more WOW and FLUTTER will the end result at the slower speed.

Such motors are AC driven, almost always directly from the AC line, and it will use a motor run cap, which kick-starts the inductive motor on its way about 100 or 120 times per second. So its speed will be a fixed multiple of 50 or 60, and typically a speed of 1800 rpm. This motor has a rotor shaft, on which there is attached a pully, and that pully drives a flywheel via a rubber belt. At the other end of the system, in the center of that flywheel is the rotating capstan.

Altering the diameter of the pully can change the speed, as is usually done for 50 / 60 cycle changes worldwide.

As far as I know, the Dokorder sets use a fixed speed capstan motor and its speed cannot be appreciably altered, even using a variac.

If there is a speed problem, perhaps the motor run cap is failing or there is now excessive friction somewhere in the mechanical path of the drive system. Its somewhat difficult to diagnose.

The second possible system is a servo driven motor, this motor can also have multiple poles, 6 poles, 4 poles, 2 poles, for different speeds; or a continuous motor driven by the AC frequency of the servo-circuit, where the servo varies it frequency and pulses to vary the motor speed.

These servo systems can exist as a motor with belt drive or a direct drive system where the capstan is the rotor of the motor shaft; either way they are wholly adjusted by the applied servo-circuit's frequency and so likely can be adjusted by small pots within the servo-circuit, and all such sets have internal adjustments.

In the case of the former, the AC motor speed is fixed, unless one shaves metal off of the motor pully, which would be both a time consuming method, and a permanent change of speed. In the case of the latter servo system, the speed can likely be adjusted within a range of +/- 30% within the servo system it depends on how much variation was allowed when the circuit was designed.

Some servo systems are discrete, some use IC circuits, some are a combination of both. In any case sets like the Pioneer RT-707, RT-909, Akai GX-266II, and others use a small pot on the front panel directly wired to the servo-circuits allowing for speed changes, typically these are limited to +/-6% to +/-10% while the internal adjustment pots allow for much more range of adjustment. Often these pitch controls only work on playback, with the recording speed fixed.

It should be noted, that while most of the sophisticated sets using servo systems have close tolerances for speed, when the sets were designed in the 1970's and 1980's the US A.C. power grid had 110 to 115 Volts as nominal and rural towns tended to be as low as 95 Volts or so. Sets that have voltage selection features usually have a 110 Volt and a 120 or 125 Volt selection.

Now, 30 years later the power grid is typically 125 Volts, sometimes approaching 130 Volts and this is more consistent across the nation. While Servo sets have multiple power supply regulators inside, the voltages applied to these regulators now is about 10% to 15% higher than when the set was built.

Since the parts do age, and since the extra applied voltage is now stressing these parts more - its is not uncommon to find these Servo controlled sets running a good 1% or 2% faster ( or slower ) today than they were back when the set was new.

This can be enough to be objectionable to some people. A known accuracy speed test tape and digital frequency meter can be used to return such sets to precise speed, or a mechanical tape strobeoscope can be used.

-Steven L. Bender

Comment #8

Travis Wrote:

Pardon the delay in responding to your message and thank you for responding to my request. I recently purchased an Akai X-1800SD on Ebay.

1.) It seems to be fairly functional but there is no output on the amplified right side speaker or thru the right side speaker of the headphones. There is output thru both line out jacks and the right side volume control will regulate volume when the head selector has been set to stereo but not when set to heads 3-2 or heads 1-4.

2.) In the rear of the unit are two fuses marked for the right and left. The fuse on the right is blown and blows each time it is replaced.

3.) The VU meter does not function on the right side. I replaced the blown fuse and watched the meter as I turned the unit on, there was a slight movement of that meters hand as it blew, so it may still be functional

4.) When it arrived there was a round ball bearing rolling around inside the front cover. I thought it may have come from the play and rwd/fwd selector switches but it appears slightly larger than those used there. I believe it was dislodged in shipping but have no idea from where.

I also want to let you know that I used the collection of data on your website to build a database from which to shop for this unit. I sent an email thanking you for sharing your research. I purchased this unit in order to convert the few tapes that remain of my highschool rock band and its successor to cd's. Those tapes were made 1n 1964/65 on my brothers Roberts1057. I have every confidence in your ability to repair this unit but I am restrained by the shipping expense.

Thanks for any advice or suggestions you may want to pass along.

Travis Bearden

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

Hi Travis -

The problems you experienced here are common to older machines like the Akai X-1800SD, but due to the many parts that can fail, its near impossible to just know what the problem is long distance.

Yes, the shipping costs are quite prohibitive on such sets, often they can exceed ther value of the set.

My first guess would either be a failed output amplfier section or if it has plug-in boards, the edge connector may have become broken during shipping. I have a GX-630D-ss here now with all of its plug-in boards edge connector parts broken, and impossible task to repair so many.

The fuse blowing does indicate a short in and power supply or an output amplifier, many Akai's used a hybrid "blob" IC amp section, some of these are impossible to find.

The ball bearing found rolling around has most likely has come from the axis of the flywheel that the capstan is center to. This part often has some play, and excessive impact, the type that breaks edge connectors and other parts is often enough to dislodge parts of this type. Other ball bearings exist in the mechanical lever systems of the Operational Controls.

The X-1800SD was perhaps a bad choice for the following reasons...

First its older circuitry, and while nice to look at and heavy beyond belief, it does not have superior signal to noise ratio, or wow and flutter charactoristics or due to the mechanical single motor tape handling system, with cams, rubber pucks, rubber wheelies, friction cams, and springs internally to control the tension on tape takeup and winding functions of the tape, so tape handling is inferior to later three motor decks that came ten or so years later.

Quality tape handing would be one thing one would look for would look for in a set being used to transfer one of a kind music from ancient archive to a modern CD Medium.

I suggest you abandon the X-1800SD, and perhaps stay away from ebay, most of the stuff at lower prices tends to be broken, defective, or badly packed, or ends up being broken during shipping, since most ebay sellers have only a remote clue about proper packing for large sets with a huge mass or center of gravity, about to undergo a 12 foot drop off a conveyer belt to a cement floor, or several such drops during the shipping process.

The better "later" Akai RTR sets which are three motor units, and Post-1973, to watch out for are, will be found to be the highest in price... especially if they end up on ebay.... GX-230D, GX-255, GX-265D, GX-266D, GX-267D, GX-266II, GX-270D, GX-270D-ss, GX-370D, GX-400D, GX-400D-ss, GX-600D, GX-620, GX-625, GX-630D, GX-635D, GX-636, GX-646.

Also its best to deal with someone who know a few things about the sets, instead of someone who doesn't even know how to make it work, except that the light turns on when its plugged in...

-Steven L. Bender

Comment #9

Noctaire wrote:

I am looking for a reel to reel recorder/player deck. I have a variety of reels I would like to encode digitally. If you have one for sale, please e-mail with specifications and pricing.

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

Well Noctaire -

Most people want to do that, in order to do so, you need to know the following things about your vintage tapes:

1) Are the source tapes on 5" reels, 7" reels, or 10.5" reels.

2) Are in 1/2 track mono, 2 track stereo, 1/4 track stereo, or Quad 4 channel, or 8 track format ( most sets won't properly play more than one of those various formats ).

3) The speed while 3.75" per second and 7.5" per second are the most common speeds; some vintage machines also had slower 1 7/8" per second; or faster 15" per second speeds, so you need to know a lot about the original tapes, or you might buy the wrong machine, that won't do the proper job. So it does all depend on what equipment the tapes were recorded on.

4) Whether you want a simple basic set like a single motor Sony, or a 3 motor Tandberg; or a more feature packed unit like a later 3 motor, 6 head Akai, with auto-reverse, reverse recording, and remote control capabilities.

Now, thirty or so years after most Reel to Reel machines were made, some sets will playback just fine, but others will no longer record well. Head wear becomes an issue now, 20 to 30 years later, as replacement tape heads, as well as other mechanical parts such as pinch rollers, and internal drive parts such as rubber pucks, friction cams, etc. can be worn, and these parts are generally no longer available.

So the price of the set will be dependent overall on: its cosmetic condition; electrical condition; and mechanical condition, and what repairs or restorations have been applied.

I have several units available, price depends on what features you want, and what you plan to use it for, playback only; play and recording, etc.

When you know what you want... LMK, and I'll see if I have anything that matches up.

-Steven L. Bender

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Last Update - February 5th, 2004 9:00 PAM.

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