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Slow Speed Tape Machine

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Re: Slow Speed Tape Machine

Postby ken long » Fri Sep 27, 2019 9:22 am

John Willett wrote:The only use for an open=reel running at cassette speeds was for ROT (Record Of Transmission) work...

But ROT work was the only real use of a machine with such an extremely low speed where cost and a long running tape was the only reason and audio quality was non-existant.

Also used to record conferences, political, corporate and some occasional domestic examples (although not usually 1/2 track).
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Re: Slow Speed Tape Machine

Postby ken long » Fri Sep 27, 2019 9:23 am

Tim Gillett wrote:Maybe replacing the 1/4 track head in a 1 7/8 machine with a half track head would be a good option.

Think there would be a lot of work with amplifiers and EQ to make this viable.
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Re: Slow Speed Tape Machine

Postby Tim Gillett » Fri Sep 27, 2019 10:34 am

ken long wrote:
Tim Gillett wrote:Maybe replacing the 1/4 track head in a 1 7/8 machine with a half track head would be a good option.

Think there would be a lot of work with amplifiers and EQ to make this viable.

That might be true for record. If it's only for playback it's much simpler. Swap the head and mechanically line it up. There might be 2 or 3 db's increase in output to the preamp but it's unlikely to overload it. Only on the PR99 is high EQ adjustable. A77/B77 high EQ is not adjustable.

I just noticed on a popular online auction site an A77 low speed capstan motor and shaft.
1 7/8 and 3 3/4. (Seller from Spain). With the smaller shaft, if would give 15/16 and 1 7/8. The motor could be fitted to a standard A77 machine which is much more readily available than the LS or SLS models. Some EQ resistors on the repro PCB would need changing. This is an easy mod as the relevent A77 repro board is easily unplugged from the machine. Resistor details are in the A77 Service Manual.
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Re: Slow Speed Tape Machine

Postby skysurfer » Fri Mar 06, 2020 12:10 pm

Hello,
I am not sure if the request still persists, but there is a super low version PR99 II. on sale on Reverb at speeds of 15/16 and 1 7/8.
Check it out.

For those who just watching this topic, any clue on how this mod was made? What would it take to reinstall it to the original speeds?
Cheers,
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Re: Slow Speed Tape Machine

Postby ef37a » Fri Mar 06, 2020 1:24 pm

A week ago I bought a Toshiba RD99DTKB HDD/DVD recorder from a charity shop for £30 complete with RC and A4 sized manual.

The HDD had been formatted and would record 50hrs at the highest video quality, 100 at SP and pro rata.

A feature of the model is if you have programmed it and power is lost it starts up again at power on.

You might not be so lucky as I but various machines are still available at £100-150.

The shop also had a Toshy DVD only recorder but I have 3 others of those anyway.

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Re: Slow Speed Tape Machine

Postby Hugh Robjohns » Fri Mar 06, 2020 2:09 pm

skysurfer wrote:For those who just watching this topic, any clue on how this mod was made? What would it take to reinstall it to the original speeds?

If memory serves -- and it's a long time since I've been in the innards of a PR99 -- the machine's speed pair is basically determined by the diameter of the capstan motor shaft. So to modify the machine to run at 7.5 and 3-3/4, for example, you'd need to acquire the appropriate replacement shaft, then remove the capstan motor from the chassis, disassemble it to swap out the capstan shaft, and then put it all back together...

...but a different shaft diameter would obviously affect the tape path to some extent. I can't remember whether the capstan motor position is adjustable or not... but I imagine it's likely you'd need to realign the head positions and other transport components after the refit.

And once all that is done, you'd then need to modify the record/replay EQ curves and levels for the higher speed standards and realign the electronics accordingly.

In other words... it's wouldn't be a trivial job.

H
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Re: Slow Speed Tape Machine

Postby Tim Gillett » Fri Mar 06, 2020 7:15 pm

Hugh has it basically correct. It's a combination of the shaft diameter and changes to two capacitors on the speed control board. To compensate for the changed tape position due to the different shaft size, motors came with different chassis mounting hole positions for the three different shaft diameters. You needed the specially small 3mm dia. shaft for the very slow 15/16ips speed. Then as Hugh said, the EQ changes on the appropriate record and play cards.

So yes changing over is not trivial. Fortunately for the EQ changes the appropriate PCB cards are plug in types and it might have made sense to make up spare cards for an easy swap but unfortunately, the speed control PCB is not plug in and is more difficult to remove and replace for mods. From new Revox designated these different speed pairs as different models, the High Speed, Standard, Low Speed and Super Low Speed.
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Re: Slow Speed Tape Machine

Postby Davetep » Fri Apr 16, 2021 1:47 am

I found your post while researching the A77 slow speed version, it is the top Google entry. I just purchased an A77 mkIV in a Revox suitcase. I am waiting for it to arrive in a few days and today, while researching the value of just the suitcase, I found out about other versions of the A77, which include a slow speed version, something I obviously had no idea about. I rushed over to the pics provided by the person I bought the machine from and looked closely at the controls. It appears it is indeed a slow speed version. I'm not sure I really want it now, as I was planning on recording live music with it. Is this something you would be interested in?
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Re: Slow Speed Tape Machine

Postby Arpangel » Fri Apr 16, 2021 7:07 am

twotoedsloth wrote:In the unlikely event that you are in Toronto (Canada) I have a Revox G36.

Best of luck!

I wish I lived in Canada, I’ve been wanting one of those for a long time.
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Re: Slow Speed Tape Machine

Postby Tim Gillett » Fri Apr 16, 2021 7:55 am

Davetep wrote:I found your post while researching the A77 slow speed version, it is the top Google entry. I just purchased an A77 mkIV in a Revox suitcase. I am waiting for it to arrive in a few days and today, while researching the value of just the suitcase, I found out about other versions of the A77, which include a slow speed version, something I obviously had no idea about. I rushed over to the pics provided by the person I bought the machine from and looked closely at the controls. It appears it is indeed a slow speed version. I'm not sure I really want it now, as I was planning on recording live music with it. Is this something you would be interested in?

It may be the slow or super slow version but it also may have been converted to higher speed without them having bothered to change the written markings on the front panel. A good photo of the capstan shaft (under the plastic head cover ) should reveal what diameter the shaft is.

I've been servicing open reel tape machines for 40 or so years and have a number here in excellent working condition, but I stopped lugging the big, heavy recorders to live gigs over 20 years ago.
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Re: Slow Speed Tape Machine

Postby ken long » Fri Apr 16, 2021 10:11 am

Davetep wrote:I found your post while researching the A77 slow speed version, it is the top Google entry. I just purchased an A77 mkIV in a Revox suitcase. I am waiting for it to arrive in a few days and today, while researching the value of just the suitcase, I found out about other versions of the A77, which include a slow speed version, something I obviously had no idea about. I rushed over to the pics provided by the person I bought the machine from and looked closely at the controls. It appears it is indeed a slow speed version. I'm not sure I really want it now, as I was planning on recording live music with it. Is this something you would be interested in?

Please DM me. Thanks.
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Re: Slow Speed Tape Machine

Postby Wonks » Fri Apr 16, 2021 10:13 am

ken long wrote:
Davetep wrote:I found your post while researching the A77 slow speed version, it is the top Google entry. I just purchased an A77 mkIV in a Revox suitcase. I am waiting for it to arrive in a few days and today, while researching the value of just the suitcase, I found out about other versions of the A77, which include a slow speed version, something I obviously had no idea about. I rushed over to the pics provided by the person I bought the machine from and looked closely at the controls. It appears it is indeed a slow speed version. I'm not sure I really want it now, as I was planning on recording live music with it. Is this something you would be interested in?

Please DM me. Thanks.

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