diyAudio (
-   Analogue Source (
-   -   Revox PR99 remote control (

Netlist 16th March 2006 01:05 PM

Revox PR99 remote control
A revox PR99 has lost his remote control plug. It's needed when no remocon is used and plugged in the socket, making one or more bridges to make the recorder behave. Without plug, everything works fine except the play button has to be kept pressed. Could someone with knowledge of logic electronics find out what pins I have to bridge to fix this problem.
Schematic here.


Ghianni 17th March 2006 11:22 PM


I believe that is like Revox A77 dummy connector. Go there perhaps it will help you.


moamps 18th March 2006 08:27 AM


the standard wired PR99 doesn't need any connector with setting bridges instead of the real remote controller. Your PR is maybe tweaked. Just check Fader Start Logic Pcb for changes. Check also what's source of +24V signal on the pcb for the start signal.


Netlist 18th March 2006 08:56 AM

I found out, as Milan said that no plug is needed in the PR99.
Next thing I looked for was the ‘tape end sensor’ and I believe its working properly. Q10 stops conducting when the sensor light is interrupted. The 24V is 28V however. 5V is present.
There is no indication of tweaks inside.

Looking at the ‘fader start logic’ schematic, I assume K1 is activated when the ‘tape dump' button is pressed. In that condition, the play button stays active. FFW and REW don't work which is a perfectly normal condition.
I forgot to tell in my first post that FFW and REW don't stay put as well.
My lack of knowledge with ports and logic as used in the 'tape drive control' schematic prevents me from fixing that beauty.


moamps 18th March 2006 10:26 AM

does it going into play mode without the tape present?
Is +24V present all the time at play signal line on the control board?
Can you stop machine from the play mode?


Originally posted by Netlist
My lack of knowledge with ports and logic as used in the 'tape drive control' schematic prevents me from fixing that beauty.
/Hugo [/B]
I have few old PRs for spares and can send you the critical boards for free. PM me if you are interested.


Netlist 18th March 2006 10:26 AM

Persistence is sometimes a good thing.
A tantalum (again) was short-circuit. For those interested, C2, a 3.3µF cap on the Fader start logic PCB.
Thanks for helping.
Edit: Milan, thanks for the great offer. I'll remember that.

/Hugo :)

anatech 18th March 2006 11:45 PM

Hi Hugo,
Yes, the tantalums. I change them out for electrolytics. The dummy plug comment really threw me Hugo! I always forgot to put the A/B-77 plug back in while working on them. I couldn't recall the PR-99 with those memories rolling around. (ever stick the case back on with the dummy plug still in?)

Also, the bridge rectifiers tend to overheat. I have installed heatsinks on them in the past with thermal epoxy from Wakefield.

The PR-99 was one of my fav machines. Pretty too!


Netlist 29th March 2006 06:18 PM

Didn't notice your post till now.
That PR99 was in real bad condition. Had been standing for years in a moist area. The cost to repair that would be enormous.
The owner is a very caring pro but has no money to store his equipment in a decent garage and even less to pay repairs.
So I fixed what had to be fixed and let the rest alone.
Nice machine indeed.


anatech 30th March 2006 12:12 AM

Hi Hugo,
What other choice do you have then? I do the same in those situations, or condem the machine. I must admit I'm not nearly as interested in proving I can make junk work anymore! ;)


chanwoo 24th May 2009 02:50 PM

I have similar trouble

A year ago, I bought used PR99 and I found something strange as below. I believe someone can explain what happens.

1. When I turn on power SW, it plays automatically regardress tape present. Is this normal?

2. 'PAUSE' butten only working when I holding it down while playing music. And playing again when I release it. Is this normal?

3. I could hear hum from monitoring speaker and it actually amplifying by turning volume when playing PR99 without tape set and I pretty sure it still humming when playing music but can't recongnize because of music. Strangely it's not appear from main speaker. Is someone have an experience about this?

Please give me any of your idea or cure.

Thank you in advance.

:bawling: :bawling: :bawling:

All times are GMT. The time now is 02:30 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2