Hi,

There's a lot of ReVox activity here so I thought I'd pose my question on this forum.

I just picked up a local PR99 with a rare (I think) ReVox monitor, original service manual, several NAB adapters, a few metal reels (2 of them the thick 5 screw precision type) and a roll around metal stand (not pictured). All of this for 600 Canadian so that's just under $500 USD, which I think is a good deal for what I got and also that the heads (correct me if I'm wrong) appear to have very little wear (excuse the reflections).

The machine appears to have been used for transferring tapes via REW / FF (the owner confirmed this) and I can see definite signs of that, especially under the tension arms as, for whatever reason, the original owner wanted to bypass going via the normal route and just rewound / forwarded the tapes almost directly, from the reel to reel, passing the tape just under the tension arms.

The tape lifters also appear to have a bit of wear but the heads, again, look to have minimal wear. Anyway, sorry for rambling but I do have a couple of questions:

(1) Rack mounting: I have all the screws but somehow I can't screw the brackets into the holes of the metal cage. The screw just passes easily through. There are no tracks there. Take a look at the photo. There appears to be something missing but what? [EDIT: I took another look and maybe the screw needs to go from the inside of the case, through that hole and then into the rack bracket, so that the thread is exposed on the outside of the recorder and not inside? Does this make sense?]

(2) Tension arms / tape lifters: Is it possible to rotate these to expose the unworn side? How would you deal with this? Are there any special "sleeves" that can be bought or is a replacement the only option? Right now it's fine but, for the future, how would I solve this?

(3) Service Manual: Again, take a look at the section in the service manual. Someone modified the line input section. What does this mean?

(4) Switches: I had some trouble getting the REC / SAFE switches to engage to record but after either the machine warming up more or persistent switching, it works well now. I assume it may be dirt or oxidation. How would I clean those switches?

(5) The Left Motor: All works fine but I'm getting a low level hum (like it goes and comes consistently), when it's in play or rec. I can especially hear it when I put my ear toward the front of the motor but it's much less when listening from the top of the cage. It's like it's coming from the very front of the motor shaft / reel table.

BTW, I'm mostly familiar with TEAC TASCAM decks but this one, the PR99 is so well built (and accessible) and sounds amazing, that I'm in awe. Man, and what's with those HUUUGE heads?!?! ;)

I know it's a lot of questions but I hope you can bear with me.

If applicable, please click on the photos to make them larger.

Thanks in advance. :)

That is a nice deck I say you made out with the extras. Is that the 7 1/2 15 ips version The heads look real good How does it sound when recording?
You may want to send it to JM technical arts for a go through Revox parts are still available

Thank you. Yes, that's the 7 1/2 + 15 ips version. I'm using Quantegy 406 and it sounds amazing when recording, be it that it's through the mic ins right now. I don't have the adapters for the Line In but I'll get to that later. It'll probably sound even better. Frankly, I usually do my own servicing, even if I have to learn a bit. I don't like anyone but me putting hands on my tape decks!:D

Great machine, congratulations. I have 2 of those (MK3) and can't stop tweaking.

There are more experienced people here, here are 2 cents:

1) I have no experience with rack-mounting;

2) Should be possible to rotate. Sleeving should work as well, I am considering this also. I have seen many mods along those lines, ranging from glass/ceramic sleeves/replacements to other stuff, including the addition of bearings.
Here the key is to use non-magnetic hard/low-friction/shiny materials. Someone proposed to me to use teflon sleeves and I sill wonder about it (he also proposed a teflon "hat" on the record head to redice its wear if not used often..). While teflon is soft, it has low friction and could easily be replaced more often. I also like the idea of bearings. If you make a material change, it would be good to readjust the tape tension accordingly.

3) It seems a reasonable mod that may improve noice rejection, if you don't need that mixing function. I also removed the mute function for the same reason (mutes the head output when you FF/REW but adds components to the audio circuit).

4) They need cleaning and possibly replacement. Be careful when you remove them as this seems tricky and they have up/down positions although they appear symetrical. The easiest cleaning is with deoxit type of chemicals, but I read that this may degrade the contacts and that it is best to remove the switches and clean them with ultrasound (this is how they clean eye glasses).

5) I also have similar motor noice and still wonder if that is ok and what could be the reason. A number of reports about those machines mention that they are a bit noisy, so that if you use mic recording, to keep them appart accordingly...

Good luck

The rack mount screws DO go fron inssidethe cage to outside; the aluminium flanges are threaded.

The vertical poles are rivetted to the tension arms, They can be rotated to expose fresh metal.

Mine is totally quiet mechanically - so if this one is noisy, it might have a fault. Is the tape tension correct during play / rec? (there is NO tension adjustment internally)

Great machine, congratulations. I have 2 of those (MK3) and can't stop tweaking.

Thanks! I'm loving mine, despite a couple of issues. :)

2)Sleeving should work as well, I am considering this also. I have seen many mods along those lines, ranging from glass/ceramic sleeves/replacements to other stuff, including the addition of bearings.
Here the key is to use non-magnetic hard/low-friction/shiny materials. Someone proposed to me to use teflon sleeves and I sill wonder about it (he also proposed a teflon "hat" on the record head to redice its wear if not used often..). While teflon is soft, it has low friction and could easily be replaced more often.

Yeah, I was thinking about that also. Where would you suggest I should look for possible sleeves or who does this sort of work?

3) It seems a reasonable mod that may improve noice rejection, if you don't need that mixing function.

Sorry, maybe I should study the manual more but what exact mixing function are you suggesting?

4) They need cleaning and possibly replacement. Be careful when you remove them as this seems tricky and they have up/down positions although they appear symetrical. The easiest cleaning is with deoxit type of chemicals, but I read that this may degrade the contacts and that it is best to remove the switches and clean them with ultrasound (this is how they clean eye glasses).

I'm not too thrilled about ultrasound and probably would opt for something a bit easier. Yeah, I'd probably remove the switch first and wipe the contacts with deoxit.

5) I also have similar motor noice and still wonder if that is ok and what could be the reason. A number of reports about those machines mention that they are a bit noisy...

I might grab my little cassette recorder and a mic and record the noise so that you get a better idea what's going on.

Thanks again for the reply. I really appreciate it. :)

The rack mount screws DO go from inside the cage to outside; the aluminum flanges are threaded.

Yes, thank you. Makes sense now. :)

The vertical poles are riveted to the tension arms, They can be rotated to expose fresh metal.

Great to know. Thank you. I wonder if the tape lifters are also riveted and can be rotated?:saywhat:

Mine is totally quiet mechanically - so if this one is noisy, it might have a fault. Is the tape tension correct during play / rec? (there is NO tension adjustment internally)

Well, a bit noisy but only if I bring my ear to the front part of the left reel. I'll try to record that noise to give a better idea. I mean, it works fine and has power to spare. It's just that noise that I'm curious about.

Yeah, I was looking for the tape tension adjust, as all my TEAC / TASCAM recorders have it, but I see nothing in the PR99 manual about it. :saywhat:

Thanks for your help. :)

Great to know. Thank you. I wonder if the tape lifters are also riveted and can be rotated?

They are also rivetted; but I'd be wary of rotating these poles, since it may weaken the rivet. The tape tension arm poles only experience very light forces, whereas the lifters are subject to greater forces - i'd want mine as strong as possible.

The 'mixing' referred to - which wont happen on yours as the FETs are removed - works like this:
If you select the ready/safe switch 'on' for channel 1 only, then you will make a mono recording on track 1, but the recording will be made of signals applied to BOTH audio inputs, mixed to mono by the two level controls. With your FETs missing, this mono recording would only be made up from audio applied to line input 1, and line or mic input 2's signal would be lost entirely.
For stereo recordings, this function does not do anything - its is disabled.

The Ready/Safe and Input/Tape switches are easy to clean - BUT a bitch to get at. You have to remove ALL the audio plug in boards, Remove the front knobs, remove the front trim panel from the audio section, and then remove the big audio-interconnection board. Then you can remove the three switches which are screwed onto that board, as are the 3 rotary switches. Its not difficult, just tedious.

NB NB NB: HELPFUL HINT: If you decide to do all this: BEFORE you start, wrap the silvery toggle of the switches in one turn of masking tape, otherwise they WILL get scratched, and nick the hole bezel, when yo remove the front trim panel.

They are also rivetted; but I'd be wary of rotating these poles, since it may weaken the rivet. The tape tension arm poles only experience very light forces, whereas the lifters are subject to greater forces - i'd want mine as strong as possible.

OK, so I'll look into sleeves first, as this may make more sense. The only problem is finding a source. ;)

The 'mixing' referred to - which wont happen on yours as the FETs are removed - works like this:
If you select the ready/safe switch 'on' for channel 1 only, then you will make a mono recording on track 1, but the recording will be made of signals applied to BOTH audio inputs, mixed to mono by the two level controls. With your FETs missing, this mono recording would only be made up from audio applied to line input 1, and line or mic input 2's signal would be lost entirely.
For stereo recordings, this function does not do anything - its is disabled.

OK, I think I understand. Thanks for explaining. :)

The Ready/Safe and Input/Tape switches are easy to clean - BUT a bitch to get at. You have to remove ALL the audio plug in boards, Remove the front knobs, remove the front trim panel from the audio section, and then remove the big audio-interconnection board. Then you can remove the three switches which are screwed onto that board, as are the 3 rotary switches. Its not difficult, just tedious.

Yeah, I'm getting more and more familiar with the service manual and the machine itself. It looks so much easier than the other recorders I have. I love my TASCAM decks but they're an absolute pain to service, very much unlike the ReVox, at least from what I can tell right now.

NB NB NB: HELPFUL HINT: If you decide to do all this: BEFORE you start, wrap the silvery toggle of the switches in one turn of masking tape, otherwise they WILL get scratched, and nick the hole bezel, when yo remove the front trim panel.

Excellent hint, thanks! :)

Thanks again for the fantastic help. :)

I am happy to see a new revox fan and help a brother in arms


Yeah, I was thinking about that also. Where would you suggest I should look for possible sleeves or who does this sort of work?
If you go for teflon, there are heat-shrink teflon sleeves (mostly in US I think), if you fail to find, pm me and I may dig the source of mine. Those heatshrinks require a lot of heat to shrink. If go for glass - any glass workshop should do. I have seen also glass guides offered for Ampex (ATR magnetics site perhaps) but don't know if they would fit (if the glass tube is a bit lose, it may be glued with epoxy.


Sorry, maybe I should study the manual more but what exact mixing function are you suggesting?
This was well answered already.


I'm not too thrilled about ultrasound and probably would opt for something a bit easier. Yeah, I'd probably remove the switch first and wipe the contacts with deoxit.
Also covered.


I might grab my little cassette recorder and a mic and record the noise so that you get a better idea what's going on.
I hear mine at about 1m, rather high pitch tone.

Good luck and be careful with the various single wire plugs with the cards, perhaps take a pic before you remove those.

I just tried one of the mods I proposed (as doctors used to test drugs on thenselves). I placed a teflon sleeve on the tape lifters of my Technics and the first test was good - the tape runs smoothly and the sleeves do not wear as they are very slippery.

However, when I looked closely at the tape over the lifters during a fast rewind I was shocked - the tape was glowing with a purple light! It was not the tape but the teflon sleeve beneeth on which the tape was riding. The friction caused this electro-effect.

As I suspected, the tape was also (moderately) charged with static electricity (the cause for the purple light).

So this option must be dropped. I don't expect any issues with glass, as I know Ampex are selling glass parts for the tape path.

Thanks for your reply traf and also for the eye opening experiment with the teflon sleeves!:yikes:

Was just reading about your new treasure, Congratulations Daniel :thmbsp:

Was just reading about your new treasure, Congratulations Daniel :thmbsp:

Thanks Rolf!:thmbsp::D:o

(Who would have thought I'd find something this nice locally? ;))

You were very lucky finding a gem like this locally.
Little different compare to the Tascam's I bet :)

You were very lucky finding a gem like this locally.
Little different compare to the Tascam's I bet :)

Yes, quite lucky as you very well know. ;)

Yeah, different in that I know TASCAM well but not so much the ReVox but from what I see, it's really worth keeping and servicing this PR99 (not that it needs it now). Have you ever worked on one of those?

Another observation on the teflon sleeve over the tape lifters: after passing a dozen of reels at fast ff, the glowing does not occur anymore (the teflon was polished? or only some tapes glow?).

The static charge on the tapes also seems lower now, but it is there. Not sure how it compares to the charge after a normal (no teflon) rewind, may check that after I remove the teflons at some point. I assess the charge by the distance at which the end of the tape starts to be attracted to a metal part on the deck. A tape that was not used is not attracted, while the freshly rewind tape sticks to the metal upon reaching about 2cm distance from it.

Perhaps the other idea of a teflon hat over rec head may not be too bad, due to the lower speed at playback.

Could it be that tape residue on the teflon sleeve makes the surface conductive - or almost - causing the charge to be dispersed? A rather long shot but only thing that comes to mind.

Don't think so. It could be that the first tapes (glowing) I tested were of bad quality (sheding) and therefore causing more friction between the tape and its sheding particles that attached to the teflon. Strange thing. However the teflon accumulates less particles compared to the metal pins and is more easy to clean.

Guys, just a quick follow-up question: I'm looking to buy a DIN to PHONO (RCA JACKS) adapter so that I can go via "MONITOR", bypassing the XLR circuitry. It's a 7 pin DIN but I understand that I can get a 5 pin which has 3 + 5 wired (that's Left & Right). Is this correct?
EDIT XXX XXX

Also, can I RECORD using the MONITOR DIN or is this strictly for playback? I know the B77 has both but the PR99 doesn't appear to.

Thanks again! :)

Consider installing 2 good RCAs, replacing the DIN output (as I did, on the back of the deck). Many report a better quality from that (-10dB) output, which makes snce (I did not tested it yet) as you don't need the studio-type +4db level, and the assosiated electronics/tranformers, which are useful for long cable runs (studio).

For input, only the xlrs, the DIN/monitor is playback only.

I am not very familiar with the forum rules but wonder if/how such a theme (working on PR99) could be made sticky and perhaps broadened(if the author/s agree, ofcourse), as the interest seems high.

Same would probably be useful for another popular beast - the Technics 1500.

Yeah, that's something worth considering, definitely.

I just tried one of the mods I proposed (as doctors used to test drugs on thenselves). I placed a teflon sleeve on the tape lifters of my Technics and the first test was good - the tape runs smoothly and the sleeves do not wear as they are very slippery.

However, when I looked closely at the tape over the lifters during a fast rewind I was shocked - the tape was glowing with a purple light! It was not the tape but the teflon sleeve beneeth on which the tape was riding. The friction caused this electro-effect.

As I suspected, the tape was also (moderately) charged with static electricity (the cause for the purple light).

So this option must be dropped. I don't expect any issues with glass, as I know Ampex are selling glass parts for the tape path.
You simply created a static electricity generator. This happens when you vigorously rub two dielectrics together.

BTW: Great machine! I'm a big Revox fan as well.

Consider installing 2 good RCAs, replacing the DIN output (as I did, on the back of the deck). Many report a better quality from that (-10dB) output, which makes snce (I did not tested it yet) as you don't need the studio-type +4db level, and the assosiated electronics/tranformers, which are useful for long cable runs (studio).

For input, only the xlrs, the DIN/monitor is playback only.

Are you open to putting up your instructions (maybe with a pictorial) on how to source and actually replace all the XLR's (IN / OUT) with RCA's? Perhaps someone else will? Maybe we can make this sticky, as we're getting good hits and indeed interest.

Sure. However, I think that it is better to leave all xlrs as they are, as they provide better contact than rcas. You would just need a xlr-rca cable set, which is easy to find or even make.

It is the DIN/monitor socket that is not so good (and finding a DIN-rca cable a bit more difficult) and therefore a candidate for rca replacement.

Yeah, I think I'll leave the DIN alone as I have the MONITOR speaker attached and even then, I think I'll just find some DIN to RCA cables and they're pretty easy to find.

While the PR99's MONITOR out is 7 pin, you can also use 5 pin (with 3+5 wired).

What I may end up doing is using my console's balanced XLR's OUT, to go balanced LINE IN of the PR-99, to use for mixdowns, dubbing, tracking or whatever and then using the MONITOR DIN to RCA cables to go back to my mixer or amp for listening. That way I should get the cleanest signal going IN and OUT.:thmbsp:

Rather than start another thread, I'd thought I'd tack in a follow-up question with regard to the rack / metal cage screws:

Guys, take a look at the photos. Are those the original screws? As it stands now, I can't get the cage back on the recorder because the screws seem to be sticking out inside too much and making "re-entry" impossible. :dammit: :confused:

Again, click to enlarge the photos.

Any help would be much appreciated. :)

Did you check the service manual Daniel ? :scratch2:

Did you check the service manual Daniel ? :scratch2:

Hi Rolf,

I did go through the service manual but did not see any reference to this, unfortunately. I did have a feeling, though, that the screws are not original, 'cause it would fit otherwise. I found this on eBay (oops, sorry, forgot that I can't post links :( ):

(see attached photo of rack ears, with different (maybe original) screws).

Yeah, I'm just gonna go to my local hardware store and buy some new screws so that I can rack the PR99 properly. Thanks for your reply Rolf. :) ;)

They look good, shame they are too long, I would try find something similar :)

Will do. Thanks Rolf! :)

Those hex-head screws are not original.
I took the ears off my PR99 to make it look neater - they were held on by ordinary (although short) Posidrive (Phillips) 5mm or 6mm screws - I can't recall where I put them now so I can't measure.

I also spray painted the cage black; I've had the machine since new - 1983.

Guys
I had the luck of getting a PR99 from a bud, this recorder looks like it was never used.
No wear what so ever, the cord wasn´t even unwound, even came with the rack mount wings.
Great sounding deck, I get a tiny bit of noise in the right record channel, I suspect a aging cap, bit it´s hardly noticeable.
I would like to have a cabinet made for it, itś now my every day reel.

bob

I am planning to make a cabinet myself. The back of the deck appears too "industrial" with the perforated steel.

I am planning to use 1cm thick plywood and veneer it.

Measurements are not that difficult - it's a fairly orthogonal unit. The power window in the back is fairly easy to route. I am planning to have the top part closed - don't like the cables coming out on the top - and place a slot in the top back with a hinged cover on the top for accesing the connectors.

What really baffles me is the arrays of trimmer pot holes in the bottom. I will probably leave that part uncovered but I'm a bit worried about the sturdiness. But it will probably be fine once the wooden shell is firmly attached around the deck.

BTW, great find to get one in mint condition. One way to confirm condition is to closely check the tape guards close to the heads and the tension rod to the left. If they have no wear groove then very little tape or no tape was ever threaded through.

Sorry for the delay but finally got this thing racked. (Photo attached). BTW, thanks steerpike2. :) Thanks again to everyone and it'd be cool to have this thread going for anyone who owns a PR99 so if anyone has any questions / comments, by all means tack it on. It'd be nice to have a PR99 resource all under one thread.:thmbsp:

I LURVE that trolley cjacek!
I'd like to make a few similar trolleys for my assorted recorders - if they were 'self standing' they might get more use, rather than just be stacked out of the way!

There's a photo here of the PR99 of a guy who put it in a B77 skin. Looks GOOD!
http://www.revox.name/curiosity/schell.htm

Sasi, maybe you could retain a solid bottom on your wood cabinet, and drill holes to line up with the trimpot openings? Then a large, smart clip-on verneer cover for *all* the holes.

...they were held on by ordinary (although short) Posidrive (Phillips) 5mm or 6mm screws - I can't recall where I put them now so I can't measure.

Careful now, Pozidriv and Phillips are not the same. I've gone round and round with Triumph car guys about this, who wonder why all the 'Phillips' fastners on their cars are rounded out. A Phillips driver will work on a Pozidriv fastener, but not the other way round. Repeated use of a Phillips will round out and *eventually* strip out the head. Pozidriv were (and still are) used on european electronics. I've got Pozidriv drivers because of my Triumphs, but they're mighty useful on things like Revox and B & O equipment.

I am planning to make a cabinet myself. The back of the deck appears too "industrial" with the perforated steel.

I am planning to use 1cm thick plywood and veneer it.

Measurements are not that difficult - it's a fairly orthogonal unit. The power window in the back is fairly easy to route. I am planning to have the top part closed - don't like the cables coming out on the top - and place a slot in the top back with a hinged cover on the top for accesing the connectors.

What really baffles me is the arrays of trimmer pot holes in the bottom. I will probably leave that part uncovered but I'm a bit worried about the sturdiness. But it will probably be fine once the wooden shell is firmly attached around the deck.

BTW, great find to get one in mint condition. One way to confirm condition is to closely check the tape guards close to the heads and the tension rod to the left. If they have no wear groove then very little tape or no tape was ever threaded through.

Hello
Whan I got the PR99 I was floored at the condition, checking the heads and guides there was no wear whatsoever, I honestly think this guy was never used, the rack sides were never mounted, no damage where the screws would have fastened it to a rack.
No polish marks,flats nothing. I actually saw polish after running a couple full reels thru.
bob

I LURVE that trolley cjacek!
I'd like to make a few similar trolleys for my assorted recorders - if they were 'self standing' they might get more use, rather than just be stacked out of the way!

There's a photo here of the PR99 of a guy who put it in a B77 skin. Looks GOOD!
http://www.revox.name/curiosity/schell.htm

Sasi, maybe you could retain a solid bottom on your wood cabinet, and drill holes to line up with the trimpot openings? Then a large, smart clip-on verneer cover for *all* the holes.

Cool
I was wondering of the B77 cabinet would fit the PR99, they are basically the same machine. I could live with the B77 cabinet, the only hassle is the XLR connectors coming out the top of the PR99.

Anyhow, I was thinking about building a cabinet out of 18mm ply with all the ventilation cutouts, and an oak veneer to match the rest of my equipment cabinets. maybe slanted legs like in older MAC cabinets.

I wonder if there are 90 degree XLR's out there.

bob

I modded the cabinet by 2 wood panes on the sides and a slot with a plate for all connectors at the back.

The only issue I still wonder is where is the best place to take the ground wire for the new monitor outputs as I use 2 RCAs at the back. The monitor output at the top has a different ground from the the one on the XLRs (XLR ground is dirrectly attached to cabinet while the DIN ground goes to the cabinet via a small cap.

I wonder about this as it does not seem good to take the ground from the DIN on the top to the new RCAs at the back. Perhaps I may use the Ground that is on the interconnect pcb, just below the grey and white wires for the DIN monitor out signal?

The XLRs are true galvanically isolated transformer outputs. There is NO current path at all from either pin 2 or pin 3 of the XLRs to ground.

I'd suggest the ground pins on the Audio Interconnect board - they are the closest accesible ground point to the unbalanced circuitry on the Output card.

Re: Phillips & Posidrive: I know technically they are different, but noone at component supplier I have to deal with seems to distinguish between them. You're lucky if they use either of those terms - they'll normaly refer to it as 'a cross head screw'. Awk!

Thanks, will use the ground pin on the interconnect pcb, the pin below the other 2 where the monitor signal comes from. This G pin is however connected to the cabinet but I hope this would not cause any issue (I became hummofobic after a long hum hunting with my 3 amp system...)

Will post some info about the final mod results (have not heard of any PR so heavily modded) on my old thread - mod/upgrade of PR99 - finally its all done and working, all great, except a few leveling/adjustment puzzles I may need to solve (I have to record with the 2 rec pots near their max, signal coming from cd)

As to the side wood panels I mentioned, if someone likes to do the same, attach them with some spacers, prividing clearance from the metal cabinet, so that the vent holes under the wood would not be closed.

I was also contemplating to make a new back cover, like Sasi, but abandoned the idea as the original cover is well galvanised with cadmium, providing effective conductivity/shielding - you may also wish to consider that aspect.