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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 #65

From: Jay

Subject: Akai GX-747 dbx Counter Problem

Date: Fri, 21 May 2004 20:37:33 -0700 (PDT)

Jay wrote:

I have a mint Akai GX-747 dbx that draws raves from everyone that listens to it's sweet recordings!! The only problem I have ever experienced with it is that the electronic counter does not function. I have a copy of the owner's manual so I have verified that it is not something that is occurring due to user set-up. I can't understand how the tape can spool without the counter "reading" the tape travel. I'm thinking it is something minor but without a service manual I don't know where to start.

Any ideas?


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

I worked on a GX-747DBX a few weeks ago, and it didn't have this counter fault, but what I do recall - and wait till you get a load of this.... It has an optical interrupter wheels that turns, interrupting a lamp's output which is then counted digitally, which then drives the digital counting circuits and various programmed functions in a microprocessor and assorted IC's for led output circuits.

So it could be any number of things, from the belt on the interrupter wheel, to the light source, to the digital circuitry, to the readout, to the microprocessor and assorted IC's, to the power supply... Lots more complicated than the mechanical counter where the belt or stuck plastic wheel were the only fault modes...

Minor ? No.


Steven L. Bender, Designer of Vintage Audio Equipment

Comment #66

From: "Bill Williams"

Subject: Roberts 778X/Akai X-1800SD

Date: Mon, 14 Jun 2004 14:43:53 -0700 (PDT)

I need new heads for this machine. Can anyone supply me with the Akai (Roberts) part number? Nortronics does not have a listing for Akai (Roberts). Nortronics is out of business but a former employee does sell many heads for consumer-professional machines, he has no listing for Akai (Roberts)

Note- in the late 1960s Akai sold their reel to reel machines under the Roberts name. Roberts was a division of the Rheems co. which today sells water heaters!

Thank you very much for any help.

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

As much as you may like the Roberts 778x, it is a world behind in terms of wow and flutter, compared to Akai sets in the early 1980's. Worn heads can damage the edge of your tapes, and is quite undesirable.

The 778x also lacks the long life GX heads, and so replacement heads may not be available or satisfactory... and will be at a huge relative cost. I'd suggest getting a later set, like an Akai GX-266D, or something similar. Probably cost less than the heads and the labor to install and align them, if available, also the X style heads were only good for about 2000 hours, so you'll need them again...

I've got the 778x Service manual, if that helps you, might have those numbers. See:


Steven L. Bender, Designer of Vintage Audio Equipment

Comment #67

From: "Joe O'Brien"

Subject: Teac R-110

Date: Tue, 15 Jun 2004 12:03:29 -0700 (PDT)

I would like to get some info about the above unit. This unit was purchased new in Japan in 1963 and weighs 38LBS. Are parts available for it and can someone give me an idea as to value.


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

Hi Joe -

I'm not familiar with that model Teac, but in general, on sets that are 20, 30, or 40 years old, parts would be unavailable; or would have to be taken off another identical or "similar" set from the same manufacturer.

As to value, it would be based on more specifically its cosmetic condition, electrical condition, and mechanical condition, which includes its actual working / not working functionality; also basically whatever someone is willing to pull out of their wallet and give you, on any given day. So that could be actual zero to some unknown amount.

Forty year old sets like your Teac, have little appeal to most people, but to the proper collector, it might be worth something as either a source of parts to repair another identical unit in better condition, or as the unit to be restored for someone who has one in worse condition.

Based on the date and weight you provided, it seems likely this was a tube based unit; so its innerds must contain plenty of springs, rubber wheelies, friction rollers, and other rubber coated wheels and mechanical parts that are very subject to wear. Pinch Rollers and wheels can be re-tired if rubber coated, but probably doing each one will cost more than you will get for the unit.

Also the heads could be quite worn down by now, and only an inspection would determine if this is a low-hours unit, which would make it more valuable than one which has been used day in, and day out, with everything grinding and screeching ( if it still works at all )!

I happen to own one of the earliest self-contained Stereo Reel to Reel tape recorders dating from 1961, the Sony model TC-521. It's vinyl covered wood case is almost like new, but inside the set, the transport has some mechanical and electrical problems. So it will play tapes, but only one channel works fairly well and the other just makes a motorboat sound if it is turned up more than a bit.

Basically it needs all the coupling and bypass caps replaced, to repair these audio problems, but the 1960's point-to-point tube circuitry lacks circuit boards, which makes it one heck of a labor-intensive mess to work on.

Purusing ebay, I bought a Sony Model 300, which happens to be the same exact transport and tube based amplifiers in a self-contained unit, suitable for custom installation, same as in the TC-521, but without the outer case, and the built-in speakers. I was gambling that mechanically and electrically it would be better, and I could just "drop-it-in" to the outer case to repair the functional problems.

In this case, the Model 300 Sony was even worse mechanically, with loud grinding noises, and uneven speed, and less than was hoped for in the audio section with hum and neither channel quite working.

So it is good for a couple of missing nuts, screws, and cosmetic parts, and maybe a spare pinch roller, but in overall poor working condition, it just takes up space.

Anything that old is likely to be a significant gamble; but it only cost me $1.00 on ebay (plus about another $12. shipping). Note: for heavy sets, look for units that are local or at best only one or two States away. Shipping can give you wallet-shock these days!


Steven L. Bender, Designer of Vintage Audio Equipment

Comment #68

From: "Greg Ror"

Subject: Technics RS-1506 channel loss

Date: Sat, 26 June 2004 23:54:54 -0400 (PDT)

Greg Ror wrote:

I've lost the left channel in playback. It's still there in record. Any ideas?

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

Of course, it could be one or more than one of a half-a-dozen types of failures ... from an open head winding; to a failed transistor; or soldeing fault; or circuit board copper trace failure; but the most likely of all - I'd get out the old soldering iron and start replacing all of the electrolytic capacitors in the audio path and audio section, in both channels. There are likely to be thirty or forty of those caps in each channel.

Once one cap has gone open, losing the audio, all of them are now suspect, and more can fail.

And the same advice goes for that Pioneer RT-1020H also...


Steven L. Bender, Designer of Vintage Audio Equipment

Comment #69

From: "Jose"

Subject: Fair Price of an Akai GX-255

Date: Sun, 11 Jul 2004 08:30:25 -0700 (PDT)

Jose wrote:

What is a fair price for a used akai 255 reel to reel?

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

Just as in real estate, where a fair price is based on its: Location, Location, Location... With Reel to Reel its: Mechanical Condition, Electrical Condition; Cosmetic Condition... which summed up is the overall: Functional Condition, something which lay people are totally unable to evaluate.

Just as unfortunately, the GX-255, and several other late Akai RTR sets, are subject to having defective transistors making its Recordings and Playback hissy in the extreme! Such sets can be easily heard to have these "hiss-fit" noise problems in both "Source" (the Microphone and Line Inputs) and "Tape" (Playback electronics) conditions. Often one channel will be heard to be quiet, while the other is totally hissy.

As these parts become defective over time, its impossible to know beforehand when the problem will strike any set that still contains original the parts. In such cases both channels will need to be purged of all the "hissy-fit" transistors, and checked for proper operation with a whole bunch of "Lab" equipment.

Sets so affected do require significant repairs and also in the case of the GX-255, upgrades to cure slow fast-forward and rewinding problems, and other service problems that showed up after 10, 15, or 20 years. It requires a battery of electrical and mechanical Certification Tests including: weighted and unweighted wow and flutter levels; frequency response, distortion, signal-to-noise ratio, and speed accuracy tests to define just what Functional Condition a set is in.

Perhaps with a set of Certification Tests indicating that it meets all original factory specifications ( likely after repairs and upgrades ) the GX-255 might be worth $300. (if also minty and like new with no scratches). The typical used, and abused, untested, GX-255 is likely worth in the range of about $50. max. as on average, they tend to need considerable work, to bring it back to the original functional condition.


Steven L. Bender, Designer of Vintage Audio Equipment

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