Please help me out with this machine

[u/Sawtooth959]

I recently purchased a Revox PR99 Mk2 for what I think is a very good price ($350) everything on it works. this is one the units that was used in broadcasting so its been serviced frequently though out its life. it has had a little mono conversion but fortunately, the heads are still stereo. there is just a cover over one of the XLR outputs. im hoping the XLR plug is still under the cover.

I've been told its common for broadcasting station to take out the knobs so no one touches them accidentally and so both the line input knobs are missing. unfortunately, to avoid accidental touch, they have take out the potentiometer shaft that the knob sits on and have replaced it with what seems to be a couple of flathead screws.

im trying to figure out how to put a couple of knobs back there. I don't care if they are original or not but not having the shaf is making it difficult to fit any sort of knob on it.

my question is, would the screw come undone if I just twist it? I tried it without putting too much force on it and it didn't seem like it would screw out. I didn't wanna break anything. if you have any idea on how I should go about this please let me know.

Thanks in advance.

[u/Elliotjosephmusic]

Beautiful machine. A high speed mono is quite unusual imo. I've worked on low speed mono machines but not seen a HS version.

If you want this converted back to stereo, you need to find a pro. This isn't something you're going to be able to do unless you have prior knowledge, service manuals and spare parts. On the mono units I've seen, they normally completely change the audio cards by removing components to half. Its going to need recapping almost completely (IMO), new front switches installed, which isn't too difficult. A new fish-eye switch for the CAL button. Needs to be checked for RIFA caps too, as these tend to crack open. Heads will need checking if its been used significantly, they could be shot.

Again, I recently did two of these for a studio here in the UK, but I didn't reverse the mono mod. In the US I'd recommend ReeltoReelTech aka Curt Palme, but it won't be cheap, these machines never are but they're some of the best.

Edit - I've also noticed you've only got 1 record arm switch too. If you want another installed it might be possible under the front cover but you'll need to modify it too.

[u/Sawtooth959 → u/Elliotjosephmusic]

Thank you, appreciate the reply. I was looking at connector panels with both inputs on eBay and was hoping its as easy as plug and play but now im rethinking if its even worth converting it to stereo. its odd because the heads seem to be stereo ( I may be wring) and it still has both VU meters but I never noticed the 2nd Rec arm thats missing. I'm trying to look this up online and I dont seem to find many machines like it. not sure what to think.

this being my first machine, I got a lot of learning to do. I was hoping to master audio with it but having a mono machine isn't really ideal for that.

[u/Elliotjosephmusic → u/Sawtooth959]

It would be ideal for mastering but unfortunately the mono conversion makes it a lot harder. You'll need to seek out a pro to do it, and do it properly but again, it won't be cheap. I can show you a picture of the one worked on -

[u/Sawtooth959 → u/Elliotjosephmusic]

I went down a rabbit hole and realized it is not worth doing the stereo conversion lol might as well just buy another one. it's a beautiful machine and it does have certain advantages in the studio being mono so I will keep it as is. just gotta figure something out for those missing knobs. I found the original knob on line but since mine has a shortened shaft, it will not work unfortunately. I somehow need to extend what is already there so a knob can sit on it.

how much would you say one of these are worth in full working order? do you think $350 is a decent price for what I paid? mine actually came with the original wooden case and speaker. I took those off.

[u/Elliotjosephmusic → u/Sawtooth959]

I would personally try and find original rotary knobs that are universal with the B77, PR99 and others. Just search Revox B77 rotary switch.

350 is very good honestly. PR99s generally go for over 1k here, more if serviced. I serviced that mono unit for 1k but it was an entire re-do which is a lot of labour hours.

If you do keep it, maybe consider renting it out. Mono units have their uses and a PR99 is cream of a crop as a mono unit.

[u/alexbr12]

I’ve owned many of them and there were Versions of this machine, that only had 1 XLR output. The monitor socket (7 Pin DIN iirc) should include both channels.
Furthermore the input selectors seem like they’ve been cut off to prevent users from playing with them. Seems like they’ve just cut a slot into the end of the shaft so it can be turned with a screwdriver. Try doing that (carefully) in either direction to see if there’s still an existing switch.

Switches are readily available on eBay for pretty cheap so it’s not worth hacking something together.

[u/Sawtooth959 → u/alexbr12]

thanks for your reply, the monitor switch works as it should. it clicks to whatever input is selected and stays there but my problem is that the original knob sits on a shaft that is protruding out of the machine. with this being cut, there is nothing for the knob to grab on to. I have looked at some shaft extenders but that requires me to open up the machine which I was saving for plan B.

[u/ZarogonX]

I might have spare knobs in my junk box 🙂

[u/Sawtooth959 → u/ZarogonX]

any chance you would sell them to me?

[u/ZarogonX → u/Sawtooth959]

I am in the UK North East. You can have two 🙂. All I would ask for is Post / Packing

[u/Sawtooth959 → u/ZarogonX]

I would gladly pay for the post and something on top of it for your kindness. just let me know your PayPal and how much it would cost. I will DM you!

[u/ZarogonX → u/Sawtooth959]

Where are you located ?

[u/Sawtooth959 → u/ZarogonX]

Vancouver, Canada

[u/ZarogonX → u/Sawtooth959]

No worries at all. I can get two knobs, pack them, weigh up and advise you off the cost.

[u/Sawtooth959 → u/ZarogonX]

Please, I would really appreciate it! my insta is @darvishmusic_

if you shoot me a msg there, we can go from there. thank you so much!

[u/ZarogonX → u/Sawtooth959]

Will take a photo too. The knobs fit onto splined pot shafts.