Revox PR99 restoration

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SaSi

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Hello all, I am new here - found this forum googling for relevant information. Nice forum for recording enthousiasts.

I recently acquired a Revox PR99MkII. It is in generaly good condition. The heads and pinch roller appear to have been recently replaced as they show no signs of wear.

I have two mechanical issues to correct.

Firstly, I need to find replacement tape tension arms, as the existing ones appear to have been worn and have a tape width flatout. I am looking at ebay for that. Are there any other - better sources?

The second thing that troubles me is the NAB adapters. The unit came with Revox NAB adapters with aluminum handles.

NAB reels appear to turn irregularly - decentered.

I have confirmed that the reel plates and shafts are centered as using plastic Revox 10.5 reels without NAB holes gives the machine a perfect run for the tapes.

I can visually identify that the NAB reels rotate decentered. Like the one of the three plastic discs in the NAB adapter is protrudes more and forces the reel to decenter.

I have changed disks and rubber rings to the NAB adapters and saw no improvement.

Checking the adapters closely, I can feel they are somewhat worn and I can force the upper part of the ring (the one that fixes the reel) to decenter relatively to the bottom part (the one that is in contact with the reel plates).

I tried to take one adapter apart and check for wear inside, but could not separate the two parts of it. Removing the Revox decorative ring didn't reveal any screws or latches. I feel I cannot take this apart unless I break it. And the service manual makes no reference to servicing the NAB adapters.

I tried different makes, a pair of TEAC plastic adapters, but they are thinner and are not fixed on the plates as well. FF/REW generates severe vibration with them, so I need to go back to the revox design.

I have seen several NAB adapters on ebay but all appear to be used and I fear they have every reason to show the same symptoms.

Apart from buying empty Revox NAB-less reels and transfer all tape on such reels, is there any other idea on how to fix the NAB adapters or a source for good quality new ones?

Any pointers would be valuable,

Thanks in advance
 
If the heads are new you are in luck. They are not cheap to buy.

Are you sure the O rings and plastic discs are OK? Another thing is there is some "wiggle room" to centre a reel manually on the adaptor once you've loaded it. That's the case with other type hubs also.

I think many people prefer the Teac/Tascam hubs as more reliable.

Re the tension arms, you should be able to turn them around to reveal an ungrooved surface. I dont recall if they are attached by a screw or a rivet but whatever, they can still be rotated.

Cheers Tim.
 
thanks - you are right about the tension arms, there is a fastening screw behind. Perhaps I can find a source for replacement rods...

Re the NABs, it is possible to perfectly center the adapter so that it runs smoothly without a reel. But the alignment isn't able to hold - one a reel get's on there it is lost.

I have not been able to fine tune the centering of the reel-adapter combo. But in any case I expected them be "self centering", by design.

Anyone has any idea how to dismantle the two plastic parts of the hub adapter? (without breaking them - that is)...
 
Revox Parts and Information

Ahh

I have a complete service and maintainance manual for these machines.

I have also managed to get hold of a Revox Parts dealer in Germany so i can get replacement parts for my machines.

I Have 2 Revox Machines

Revox PR99 MKIII (cost Uk £695.00)

Revox A77 MKII (Cost Uk £375.00)

As you can see hehe i spent a LOT on these 2 machines and for the sound quality they produce it was really worth it. These machines produce better sound quality than ANY cd player i have ever owned.

Gimme a shout if you need any help with your revox machines.

Keith
 
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Revox PR99 MKII

Hi Keith,

I was wondering if you can help me. I am having problems with the reel to reel on a Revox PR99 MKII. The buttons 'play', 'rewind' and 'fast forward' do not hold when pressed. Would you know of a solution for this?

Your help is much appreciated.

Jose Jose
 
ahh

The reason for this is that there is a photoelectric sensor along the tape travel path for the auto-stop system.

The only time the functions will remain active is if you load a reel of tape.

Just after the first guide roller is the location of the photoelectric sensor.

If your having trouble finding it i can upload an image to help you.

Keith
 
Revox PR99MKII

Thanks for your reply, I have received a new sensor from (technical workshop-victoria Australia)-part number EOT sensor which was ordered from Germany. I have installed it but still the same problem. With my multimeter I read 27v DC when I press Play the voltage changes to 25v. I would appreciate any help. Thank you
 
ok so you can confirm the sensor is recieving current.

Bearing in mind that the auto stop systems is comprised of 2 units the sender unit and the reciever unit.

First you will need to confirm that both are working.

Also i will enclose a link here so you can download the service manual for this machine.

For the relevant information see section "Tape Transport System"

Hope this info helps

Keith

P.S here is the link

ftp://ftp.studer.ch/Public/Products/Revox/Revox_PR99

This link will take you to the Revox PR99 section.
All you have to do is select and download the file that matches your machine model.
 
Thanks for your help, I just have one more quesiton. In regards to the service manual it says the tape end sensore without tape should read 24V (I have 27V) and tape present 0v but in this case it does not go down to 0V. The motion sensor and end tape sensor are ok. I checked the transistor, resistor in the tape transport system. It seems to be the IC PROM, do you have any suggestion?
 
hmm... thats strange.

Ok so the tape end sensors are good.

The control board for the tape end sensor is the most likely the area you next want to look at, i have never yet had to change one of these boards as they rarely develop any faults. If the board is seperate from the main board, then there shouldn't be too much trouble in changing it out.

If you need further info just gimme a shout.

Keith
 
Keith my last message was incorrect. I do have 27 V in the photoelectric sensor (DL anade and QP collector) but no voltage in the test point resistor R-6 (next to the trimmer R-51). any ionformation you may have, thanks
 
that could be that there may be a sensor fault. The current has to pass through to engage the solenoid circuit.

I have the full service manual which i could upload for you if that will help you fix this fault.

Keith
 
Hello everybody,

I am new to this forum and decided to seek here relevant experiences and tips on a similar PR99MK3 restoration/upgrade project (hope Sasi does not mind, I've already got many useful tips from him).

My goal is not just to restore the deck to its normal specs but improve it as much as possible, by relevant mods. So far I have replaced various caps and resistors (Black Gate and Caddock) on the signal path of the input/output boards, along with all trim pots and a few caps of the power supply board.

I wish to go further and wonder if anyone has experience/references/ideas to share, e.g. what (critical) components are worth replacing at the record and other boards?

Best regards
 
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