Late May, 2026, a friend from the village mentioned that he had a Revox tape recorder “somewhere” and asked if I’d be interested. He thought it was an A700. Now, I’m not a big fan of the model but it probably wouldn’t hurt to have a look.
About a week later a PR99mkII arrived: a welcome stroke of luck. The machine seemed whole, albeit covered in dust and cobwebs inside out. A deal was soon struck. Once on the workbench and with its innards exposed, it became instantly clear that a full teardown was in order. It took a day or two to pry the PR99 apart. Remarkably, a well-preserved PR99 appeared from underneath all that barn dust.
After cleaning odd bits of hardware, and subjected the cast aluminum chassis parts to a water jet at the local carwash, reassembly could begin. Motor bearings and capacitors, tape guides, led lights, etc. have been ordered.
Early next week the record and playback heads are off to AM Belgium (Antwerp) for grinding. This sounds like a destructive process but is actually preferable over polishing (relaxing) because grinding recovers the heads’ original curvature, resulting in an as-new performance. The reel tables are off to Switzerland for a Nextel treatment.
Work Performed
- Complete strip down
- Ultrasound cleaning of all mechanical parts
- 3 Motor capacitors replaced
- SKF bearings (4) in reel motors replaced
- Installed metal levers (3) in toggle switches
- Cleaned and lubricated rotary switches
- Cleaned potentiometers
- Reseated and cleaned all receptacles
- Upper face plate cleaned
- All new screws on face plate
- All electrolytic capacitors replaced
- 3 heads (erase, recording & play back) reworked
- Tape path realigned and new bearings
- Original Revox Mic pre-amp installed for low-impedance transformer-balanced mic inputs
A tour of the stripped down Revox PR99mkII
Reassembly
The reassembly of the PR99 started on Saturday June 6 with the chassis. Tape lifters and pinch roller solenoid have been reattached.
Work progressed slowly albeit without much trouble. The switchboard was duly taken apart with switches and rotary knobs pried apart, cleaned, and put back together again.
The three motors received new ball bearings whilst the wiring harnesses went back into place. Next up, the recapping.
The switchboard, now cleaned, is going back into place together with the lower face plate. This enables most wiring harnesses to be put back and sets the scene for the various modules to be plugged in after recapping.
The recapping has now begun (June 19) with the power supply and input printed circuit boards first in line. The double-sided PCBs of the output and recording amplifiers are a bit more finicky to work on but even so their countless tantalum capacitors need to go. These ‘caps’ are particularly susceptible changes in value over time. Of course, all the infamous ‘Frako’ caps have been hunted down and replaced.
Adjustments & Alignment
After a ten-day-delay due to a few missing parts, on July 9 the restored and reassembled PR99mkII was ready to be fired up. Plugging the machine into the shop’s regulated and protected AC power, the Revox sprang to life without sparks, fumes, or other mishaps. All transport functions worked as advertised while the 21V regulated and 24V unregulated DC power lines were spot-on. The tacho head, once properly seated at 0.35mm from the capstan rotor, produced a signal of about 40mV – perfect.
With those preliminary test done and passed, the time has come for a few mechanical adjustments. First up the brake tensions on the supply and take-up motors and after that the correct setting of the pinch roller pressure. Once this is done, the front cover and reel tables may be mounted and the PR99mkII confined to its newly-painted cage.