Revox PR99 mechanical and electronic service & potential rebuild - my 1st Revox adventure

[GPS16]

Hi Smurfer,

whilst all is in bits, removed the crank and bearing for the pinch roller. The ones I have removed have been pretty much dry. One of these was one of the C270 machines which was a comparative youngster. It is an easy adjustment following the removal!!

That would leave the mechanicals dealt with!!!

Well done!!!

GPS16

 

[soundmig]

Smurf ... I know what you mean about the Master Tape copies and prices ... but as Chad (at Acoustic Sounds) says, the tape and reels alone (2 Per Album) cost $100. By the time you add engineering time and someone to run the real time copies and to do QA - they pretty much have to be that much - and the margin isn't that big even at $400-450 a pop.
I was a bit put-off by their refusal to even consider making 4 Track 7" 7.5 ips copies. I talked to the guy that does the Mastering for their analog tape copies and he simply stated 7.5ips 4 track on 1/4" tape isn't Hi-Fi. Didn't care to discuss it any further. Chris Mara (of Mara Machines and Welcome to 1979) is the guy, and I like him really well, but he (and Chad) just see no value or market for 7.5ips 1/4 track copies. Since even those would likely cost well North of $100 they are probably right. There are just so many more 1/4track machines that will run at 7.5ips than there are 2 track 15 ips machines out there. So, I thought there might be a lot more customers? But .... hey, this is just my hobby not my business, so I'm not in a position "know" what they know. I guess if you think about it, most of the MANY consumer R2R's our there that run 1/4 track 7.5 ips are not really in working condition anymore - so maybe there aren't so many after all?

 

[smurfer77]

Smurf ... I know what you mean about the Master Tape copies and prices ... but as Chad (at Acoustic Sounds) says, the tape and reels alone (2 Per Album) cost $100. By the time you add engineering time and someone to run the real time copies and to do QA - they pretty much have to be that much - and the margin isn't that big even at $400-450 a pop.
I was a bit put-off by their refusal to even consider making 4 Track 7" 7.5 ips copies. I talked to the guy that does the Mastering for their analog tape copies and he simply stated 7.5ips 4 track on 1/4" tape isn't Hi-Fi. Didn't care to discuss it any further. Chris Mara (of Mara Machines and Welcome to 1979) is the guy, and I like him really well, but he (and Chad) just see no value or market for 7.5ips 1/4 track copies. Since even those would likely cost well North of $100 they are probably right. There are just so many more 1/4track machines that will run at 7.5ips than there are 2 track 15 ips machines out there. So, I thought there might be a lot more customers? But .... hey, this is just my hobby not my business, so I'm not in a position "know" what they know. I guess if you think about it, most of the MANY consumer R2R's our there that run 1/4 track 7.5 ips are not really in working condition anymore - so maybe there aren't so many after all?

Yeah, I've never really doubted that making those tapes is expensive and I'm definitely aware of tape stock costs; I just didn't like the short uncaring response I got to my detailed email. I have several vinyl records in that price range - it's not out of the question for me - although I do find those purchases harder and harder to justify. We shall see... if they release something I truly want, not just for the sound quality, I might go for it.

 

[smurfer77]

whilst all is in bits, removed the crank and bearing for the pinch roller. The ones I have removed have been pretty much dry. One of these was one of the C270 machines which was a comparative youngster. It is an easy adjustment following the removal!!
GPS16

GPS, I replaced the pinch roller bearing, not just the rubber (is that the bearing you mean or I missed something?). While I had the head block off the other day I did pull the pinch roller assembly out and clean/lube.

The slight annoyance is that while I have gotten the clean/lube/new-bearings done, I will have to go around and do various mechanical checks/adjustments again, once I have the machine powered up again. On that note, the cap arrived! I was waiting on those before I put the power supply back in.

Bye Bye Frako. Glued down. Funny how much easier removing glued caps is after doing a few.

A bit of blue to clean up.

And here is the board now:

Now, before I put the PS back in, do you remember I have a problem of the board that plug in not mating properly with both power supply and case mount? Well here is why.

It was reasonably malleable and I was able to bend it back with hand tools. So I'm now ready to pop the power supply back in and (a) trouble shoot my blowing F2 and (b) recap the other boards as I go along. But that will have to wait, probably a few days . But things are moving along nevertheless.

 

[GPS16]

Hi Smurfer,

the first photo of the last entry show the bearing I was concerned about. The shiny shaft near to Ch2 Safe Switch and the bearing holder which is screwed to the chassis. After this was done, the C270 was way less clunky in operation.

Sorry to see the damage on the Mains Transformer mounting rails. The Cine retainers on the reel tables were probably bent at the same time as this happened!! Now that is sorted the Logic/Servo PCBs should now sit flat to the PSU PCB and allow the Heat Sinks to sit flat against the chassis too. Another niggle solved which will add to the reliability/longevity of the machine.

The mechanical setups following this are not too involved. The one for the Pinch Solenoid is probably the worse and even that is not too taxing. With the new pinch roller fitted, the 1mm gap between the crank pusher and the solenoid armature shaft is easy to achieve. Unless the spring on the pusher has relaxed, the Pinch Pressure should remain unchanged. A Check first, before a set up is or isn't necessary.

Get Those Frako Caps out and in the nearest bin!!! We are all "dissing" them but they have lasted nigh on 30 Years!!!

Why have you not got R4 on the PSU board??!!

Keep us posted!!!

GPS16

 

[soundmig]

Yeah, I've never really doubted that making those tapes is expensive and I'm definitely aware of tape stock costs; I just didn't like the short uncaring response I got to my detailed email. I have several vinyl records in that price range - it's not out of the question for me - although I do find those purchases harder and harder to justify. We shall see... if they release something I truly want, not just for the sound quality, I might go for it.

Well ... I won't be buying any of them - my RT-707 won't play them. I'm not up for either rebuilding a 2 Track deck or forking over the cash for one that is already refurbished, so .... I guess I'll stick with hi-rez digital - for now anyway.

 

[smurfer77]

Well ... I won't be buying any of them - my RT-707 won't play them. I'm not up for either rebuilding a 2 Track deck or forking over the cash for one that is already refurbished, so .... I guess I'll stick with hi-rez digital - for now anyway.

I'm very happy with the results of recording 24-bit 96kHz FLAC to my 'lowly' RT-707.

 

[soundmig]

I'm very happy with the results of recording 24-bit 96kHz FLAC to my 'lowly' RT-707.

The RT-707 is quite amazing. I'd like to say that it really doesn't have any tape hiss, but then again I'm not sure I can hear high enough to hear tape hiss anymore ... LOL!!! I'll probably keep listening to my 24/96 files and 24/192 files direct off the computer through JRiver and my Schitt DAC ... but they sound fine coming off the 707 too!

 

[smurfer77]

Why have you not got R4 on the PSU board??!!

It's missing! Good spot. I did notice something else missing previously (a cap near D3) but then comparing B77 and PR99 manuals it seems it was dropped. okay, so I will have to pay much closer attention to the boards (with schematic in hand as I go along as the components are silkscreened onto the PCBs and there are legitimate through holes left empty so it makes things hard). Resister is coming in a few days (with caps for my Luxman SQ38FD).

 

[GPS16]

Morning Smurfer,

It is no real detriment as it gives a little more back tension during fast winds when large reels are present. The resistor is put in parallel with R1 (820 Ohm) on the Logic PCB by the relay when large reels are selected. At the start of a large reel fast wind there will not be much back tension and it could affect how the tape wraps. I wonder if the machine had been modded, in it's previous life, to do Library Winds!!! The Dog C270 had a free cable tacked onto the Erase Amp and dangling out of the side of the Audio Rack!!!

When checking drawings look for notes. There are quite a few modifications listed by date. When I re populated the equalisation cards in the C270 from IEC to NAB, I had to keep track of mods up to 4.

This missing cap has been pointed out in B77 threads.

Your keeping busy I see!!! Not so much a bench as a production line!!!!!!!

Cheers.

GPS16

 

[smurfer77]

On the logic board (Tape Drive Control PCB) there is one electrolytic, C2 (47uF, 50V), next to the optocoupler (DLQ1/4N28). This cap is housed in a metal can. Should I be worried about not using a metal can on a replacement cap?

 

[GPS16]

Hi Smurfer,

the Cap in question is the reservoir cap for a small dedicated supply for the gate of Triac Q4. It is elevated to the full motor drive voltage so if there is any exposed metal on the replacement will be live when the machine is powered.

Was the cap removed totally enclosed with no part of the can uncovered?

Cheers.

GPS16

 

[smurfer77]

Hi Smurfer,

the Cap in question is the reservoir cap for a small dedicated supply for the gate of Triac Q4. It is elevated to the full motor drive voltage so if there is any exposed metal on the replacement will be live when the machine is powered.

Was the cap removed totally enclosed with no part of the can uncovered?

Cheers.

GPS16

It is a metal can but is completely sealed in a thin, slightly blue, translucent insulating coating. Underneath is black plastic and no metal part is exposed. Will take care with that replacement. Thank you

 

[smurfer77]

I am still waiting for a couple of caps to arrive, mainly the smaller axials, but today got my butt into gear and made my way around the PCBs with what caps I have. I guess I will save the pics for when I have the other caps and the boards are completely down, but anyway 95% of the leg work has been done. Really got stuck into it this morning!

One thing is I'm feeling a bit lazy not replacing the VRs so I will probably order some of those and replace those when the machine is up and running, and before calibration. I kind of like the multiturn devices anyway. What are peoples thoughts on the ceramics on these units? I don't want to get into a sound quality debate, I'm asking thinking more about reliability. Also, I notice relays for sync and oscillation boards are available, but so far I have no reason to replace mine and old boards are still readily available right?

 

[GPS16]

Hi Smurfer,

I would leave the pots for the moment and replace them on their merits. Also bear in mind that there are holes in the cover which holds the PCBs in place to allow the PCBs to be adjusted with the cover in situ (B77). This may not be possible if the pots are replaced with multiturn versions!!!

I have not had any trouble with relays apart from the Initial Delay Relay on one of my A700s. I replaced that relay with 2 TO3 Encapsulated relays which I had "on stock".

Thanks for the link to the source of relay replacements.

Cheers.

GPS16

 

[smurfer77]

I reinstalled the PS and powered on. All good.

Added the capstan speed control board. All good.

Hooked up the 3 capstan motor wires and the 2 tacho wires (since I didn't check the circuit to see what would happen if I don't hook that up but I'm assuming the speed control board will try to speed up the motor if there is no feedback) to the PS board. And, we have the gentle whirring of a capstan motor. Am monitoring current draw and at the line, and it's sitting nicely at 0.11 A draw.

If I put my ear close to it (within 5cm or so), or run my finger on the housing bell, it is possible to detect a slight wobble, with a period similar to the spinning of the motor. No vibration can be seen or felt on the business end of the capstan shaft. Should i wait and see until I hook up the test gear for calibration if it is an issue, or should I run it a bit since I have the new bearings (its not a bad crunchy noise (more of a balance induced noise), or crack open the motor again?

 

[smurfer77]

I installed all of the audio boards except the output board, which is missing a couple of caps still, and F2 fuse is still holding.

So I then hooked up the tape logic board into the power supply too. Now that I fixed the bent transformer housing the logic board mates perfectly with both chassis and power supply socket. Fired her up and now unusual current draw... so I started pressing buttons. All logic and speed controls are working fine. Although my supply reel is going the wrong way, so I guess I wired something up back to front (but boy, i thought I was careful!). Also the take-up reel had a 'ticking' noise, but it is not coming from the motor itself but from the break band (when i release the break manual it is noise free). Anyway, taking a break now! pics to come too. So after fixing up my supply wiring, and the couple of caps on the output board I believe we can declare this 'a runner'!

Onto the mechanical adjustments when time permits.

 

[smurfer77]

Although my supply reel is going the wrong way, so I guess I wired something up back to front (but boy, i thought I was careful!).

*PALM IN FACE* The supply reel direction is fine.... you see I'm still quite new to tapes and forget basic things from time to time. The supply reel goes backwards with no tape, which it should as designed to provide appropriate tape tension. So... all is good. Onto the mechanical adjustments (assuming my output amp board is okay when i get the caps).

 

[smurfer77]

Also, just have to add that the schematics are phenomenal. I took pics of which leads go were but when i put it back together I checked against schematics and it was much clearer and simpler than any other schematic I've used before. That said, I'm use to working only on japanese gear...

The same goes for the service manual on disassembly. But the amazing this is I only used that once as the machine is so intuitive. And, physically, everything comes apart and back together really easily once you have thought about it a bit. It is really not a big deal to strip this thing down or get the motors out again for fun.

ok, growing love for revox rant over.

 

[GPS16]

Hi Smurfer,

glad to see the progress you are making.

2 points.

1. As the brakes have been disturbed, the release lever lifting point needs to be checked. Carefully and slowly move the brake release armature to the released position and check the point at which the lifter pin moves the brake band lever. It should happen at the same time for BOTH levers. If this is not the case then the whole brake plate needs to be shifted until they do. Slacken the 3 mounting screws and adjust the position of the plate to ensure the lifters lift at the same time. Fiddly but not difficult.

2. Set the speed to 7.5 and the reel size to small. Block the light gate, near to the erase head, and run the machine with no tape or reels for about an hour. This will run in the oils and bearings before you run the beast "in anger". This will run the motors in at the lowest possible power levels.

I did wonder about the supply reel direction!!!! But if it was wrong it would be easily solved.

As you now have changed bearings/hardware on the head plate, make sure that it is demagnetised before any tape is brought near it!!!

How are the 2 tape tensioners. Do they still feel gloopy? They should have silicon lube in them to act as a damper.

Also check the operation of the high tension pulse of the take up reel which you get on the initiation of play. As you have the 15 IPS version the pulse should be quite pronounced. My B77 is a NS version, so the pulse widths would be lower that on your machine. There should be 4 distinct pulse widths. 2 for 7.5/15 IPS and 2 for large/small reels. That gives 4 to check. If you get any errors then the resistors on the Fader Start Logic PCB need to be checked along with the Reel Size Switch.

Keep us posted.

Cheers.

GPS16