Revox PR99 - dead transport buttons

[SaSi]

I recently purchased a PR99 MkII from an ebay seller in a fair price (as the unit was advertised "fully serviced and tested"). I paid ~$250 for it. Unfortunatelly, servicing was limited in replacing the pinch roller.

The unit seems to function in terms of capstan motor, however pressing any of the transport control buttons results in ... nothing.

There was of course communication and a dispute on the matter which was resolved with a replacement unit being sent FOC. I should return the original unit but the replacement unit was functional but shot.

The whole thing is settled now, and I ended up keeping both units in order to make one good out of them.

I have already checked the obvious, like disconnected plugs and cut wires and everything appears to be in order by comparing the problem unit with a fully working PR99 MkII I already have (now I have 3 of them and no place to store them...)

Can anyone offer a hint on where to start looking?

[steerpike2]

Have you checked the power supply? It puts out 21.0v regulated for the audio, and 24v unreg for the mechanics. Separate fuses & rectifiers for each; the 24V rectifier runs very hot & may suffer dry joints. And the 2 big electrolytics tend to go short circuit these days, blowing the associated fuse.

There is an issue with these machines that if you plug in an unmodded B202 IR receiver module (as designed for the B77) it will damage the transport logic of the PR99. A "remote" possibility.

[SaSi]

Thanks, both these hints make sense. I've checked the fuses visually and they seem ok. Haven't checked voltages though. I think I could start by comparing voltage readings between a working and the non-working machine.

This is something I plan to do over the weekend, after perhaps some pointers are collected, and will report during the investigation.

[Tinman]

If the power supply checks good, check the transport logic card. Also, of course, make sure the button assembly is plugged in.

Shipping always seems to unsettle something in these machines. BTW, if it has ANY gold FRAKO caps in it, measure them for dead short. I suggest replacing as a rule on those anyway.

Aaaand you looked at the tape sensor, right?

That reminds me..... I do not know if the PR99 had a remote jumper plug..... you know where I'm going with that.

I only have Studers, an A700 and a B77. Alas... no pr99. Looking for a MKIII

[SaSi]

Thanks Tinman.

YES, I did check the tape sensor, but only superficially, putting a blocker between the LED and the sensor. If the sensor is dead, that's another story. I do have (somewhere) a working B77 headblock, if only I could find it. My wife had me tidy up things.

No, there's no remote plug but I did try the B77 cable remote just in case someone modded the deck. Nothing appears unplugged.

The sensor, however, is one of the things to check out thoroughly. If it doesn't sense any tape then the unit appears dead. Acts like the tension arms on other decks.

And gold Frako caps.... It's full of it... But it's a MkIII and I've had no problems with much older Revox kit with such caps. That said, my B790 power supply doesn't provide a stable DC on the scope. And it has 2200uF gold Frako caps.

Hmmm... It's going to be a busy (and interesting) weekend.

[steerpike2]

Even if the end-of-tape sensor is faulty, the transport operates normally, it just that the functions don't 'lock'. i.e., it plays while you hold the play button in, it rewinds while you hold the rewind button in.

If the PAUSE button is stuck in, it will behave as dead, since pause functions in all modes even FF and REW. If you put the ready/safe switches to READY, and press REC+PLAY, do you get red lights?

It doesn't need a remote plug.

But is this a MKii or a Mkiii ? The MKiii has an autolocator, and a serial comms port for tape transport and remote autolocator. That adds a whole xtra microprocessor circuit to what might be faulty, that isn't possible in the Mkii.

[SaSi]

Even if the end-of-tape sensor is faulty, the transport operates normally, it just that the functions don't 'lock'. i.e., it plays while you hold the play button in, it rewinds while you hold the rewind button in.

If the PAUSE button is stuck in, it will behave as dead, since pause functions in all modes even FF and REW. If you put the ready/safe switches to READY, and press REC+PLAY, do you get red lights?

It doesn't need a remote plug.

But is this a MKii or a Mkiii ? The MKiii has an autolocator, and a serial comms port for tape transport and remote autolocator. That adds a whole xtra microprocessor circuit to what might be faulty, that isn't possible in the Mkii.

I stand corrected on the tape sensor function. It has been a while that my working unit is in storage.

Thanks for the hint on the pause button. Will check that of course.

The unit is a Mk III. It doesn't have REC/SAFE swiches nor REC level pots. It does record but level control is expected from a console. The MkII and MkIII versions both have the auto locator. I also suspected a fault from there could cause transport lockup but studied the schematics and it appears the locator board only accepts pulses and speed selection to calculate tape time.

BTW, the locator board has a set of 3-4 jumpers (that could be replaced by removable jumpers or a dip switch bank) that allow the board to be "customized" for different speeds. It certainly allows lower speeds (like 1 7/8 and 3 3/4 and such) but IIRC, has an option for 15/30 ips.

[SaSi]

BTW, would you be interested in an illustrated walkthrough of the dismantling, investigation and stripping of the unit before it takes it's long needed bath?

[Tinman]

BTW, would you be interested in an illustrated walkthrough of the dismantling, investigation and stripping of the unit before it takes it's long needed bath?

ABSOLUTELY!!! :thmbsp: You should have seen my A810 apart. I thought I'd never get it back together. The B77/PR99 is sooo simple in comparison.

I'll have to D/L the schematic and have a looksee. Maybe I can pick up on some spots to check. Too bad you don't have a spare transport board.
That's so rare and off the wall, though. It has to be something stupid and simple.
You'll probably find it while cleaning the unit.


Marc

[SaSi]

I did strip my first PR99 down to bits and pieces once. I had to strip everything, remove the main audio board, remove the pots and switches and wash everything as it was filthy and pots were scratching and switches missed contact at times.

I was overwhelmed by the number of small cables going around, but that feeling went away when I opened up a Technics RS-1500.

[Tinman]

I was overwhelmed by the number of small cables going around, but that feeling went away when I opened up a Technics RS-1500.

Been there. But seen WAYYY worse. Try an AKAI GX-747DBX. :yikes:
I like my 2 1500's. Wish I could find a 1506 head block, though.

[SaSi]

I am "lucky" in that. I bought my second RS-1500 less headblock for what was a good price for a parts machine. I later was able to find a 2422 headblock for a good price and a 2224 headblock with soft box and accessories for as much as I've paid for the parts machine.

Now, both my 1500 and 1506 have dual headblocks.

And for parts, I was able to obtain "guts" from a 1500 machine including amplifier boards, motor control boards, a capstan motor block and a spooling motor.

I think that will get me going for a while, but was a lot of money...