The Ampex ATR 102 (or 100 series, as they are called) has long been considered to be a top of the line reel to reel deck for mastering studio recordings. It was introduced in 1976, and quickly became popular with studios, with many hit records being mastered on these decks.
The Ampex ATR 100 series is unique in that it doesn’t use a pinch roller to move the tape. Instead, it uses a capstan motor only, that is servo locked with the reel motors in order to drive the tape. This results in an unusually low wow and flutter, but can also snap master tapes quickly if you have the misfortune to have the machine fail while in operation.
Features of the deck:
- 2 or 4 speed operation, depending on the audio cards installed in the deck
- servo controlled operation, that must be locked prior to pressing ‘play’
- ability to remove the head block with a single screw, allowing quick changes between ¼ and ½” tape by changing the head block and tape guides only. This makes the deck very versatile in a studio situation, where engineers may want to switch tape width within a matter of minutes.
- fully modular construction, making on site service relatively easy once you know the inner workings of the deck
- well written service manual, that goes into great detail as to the operation of the deck
The ATR series is also a highly complex machine, and we’ve had a few of these sitting around for a number of years, as a ‘rainy day’ project. During the Christmas 2023 season, we decided to stop taking in repairs for the month of December, so that we could learn the intimate workings of the servo transports, which was plaguing all of the decks we had in stock, and to literally start on page 1 of the well written service manual, and do each calibration procedure several times with each machine to get each deck running.
Slot 7 is the transport control card. Slot 8 is the capstan servo card, and slot 9 is the reel motor control card.
This article isn’t designed to be an in-depth look into how the transport and the rest of the deck works, the service manual, readily available online does a very thorough job of doing that. This article will merely summarize some of the faults we’ve seen with the first few decks we’ve worked on, and things to be aware of.
IMPORTANT NOTE: THE ATR 100 SERIES DECKS ARE NOT DESIGNED FOR A CASUAL OR AMATEUR TECH TO DIVE INTO, RANDOMLY ADJUSTING TRIMPOTS, ETC. IF YOU TAKE THIS APPROACH, GUARANTEED YOU WILL MAKE THE DECK WORSE!
There are select few techs in North America that know these decks well, and those include Andrey (Andrew) who purchased ATR Service, and moved it from Pennsylvania to Seattle Wa in the summer of 2023. Dan Labrie of Myriad Magnetic in Pennsylvania is a former ATR Service tech, who now has his own business. Both are listed in the service referral list on the website:
https://reeltoreeltech.com/service-referrals/
There are a number of sensors that feed information to the transport PC boards to control the transport itself, and to lock the servo, allowing proper transport operation. These include:
-photo-resistors that are tied to the tape tension rollers
-microswitches that sense the end of tape to shut down the transport
-combination LEDs and photocells on the capstan itself, that control capstan speed, the capstan speed lock (servo), which then tie to the reel motors, completing the servo loop.
The service manual does an excellent job of outlining how these sensors should work, and how to adjust/calibrate them.
Capstan shaft/Opto Sensors
A critical area to maintain the capstan speed and servo lock are the two LEDs and two opto sensors located at the spinning disc that is part of the capstan assembly. There are a series of lines cut into the capstan disc, and there’s a thin piece of glass that covers the opto sensors, with additional lines cut into it. The placement of this piece of glass is absolutely crucial to the operation of the capstan shaft, and we’ve now seen several cases where the glass piece has fallen off the opto PC board due to glue failure, causing capstan runaway condition. That glass piece can usually be found sitting in the capstan well if it has fallen off.
As per the service manual, the adjustment and positioning of the optosensors vs the LEDs on the underside of the capstan are critical to the correct capstan operation. The adjustment is detailed exactly in the service manual, and again, if you do not have the proper test equipment, you will make things worse if you try to randomly adjust settings in this area of the deck.
The capstan assembly has a bunch of tiny ridges on it, designed to grab the tape. Over time, these ridges wear down, and the capstan loses grip on the tape. The solution is to purchase a new capstan assembly from Athan Corporation in California, that machines down the capstan, and puts a new rubber coating onto the capstan assembly. All of the machines that get serviced at our shop get a new capstan assembly installed: https://www.athan.com/store/p18/ATR-100_Ampex_Capstan%2F_Tach_Assembly_1%2F2%22.html
End of Tape Microswitches
Another point of wear/failure are the microswitches for the ‘end of tape’ function. While the switches can fail, what’s more likely to happen is that the foam that prevents premature triggering of the microswitch can fall off or crumble. Replacements are available from ATR Service in Seattle and Myriad Magnetics in Pennsylvania. Again, positioning of these foam pieces is critical.
Variable Opto-Potentiometer
Tied to the tension arms are two tiny LEDs that move over an opto-potentiometer, as the tension arm moves from side to side. This is another critical adjustment as covered in the service manual. Not only do the LEDs need to be the correct part number, the opto-potentiometer is currently discontinued, so care must be taken not to damage the existing unit, and to correctly determine whether they are defective or not. See the above picture for the part.
Electronics Problems
Bad Capacitors
The Ampex ATR decks are full of tantalum capacitors. These were chosen for their stability, however 40+ years later, tantalum capacitors are known to short out at random. This shuts the deck down, and worse, since one of the sub-power supplies is located on the capstan servo board, a short in a capacitor that is fed from this capstan board power supply will also blow that power supply.
Based on our experience, we strongly recommend a full recap of every tantalum capacitor on every board, audio and transport control board. This is a lengthy (and expensive) procedure, however for long term reliability, these caps should be changed.
Power Supply
Similar to recapping the audio and transport boards, the power supply should also be recapped. Fortunately, the large can capacitors are available from several online suppliers, and we are recapping every power supply in every Ampex ATR 102 that comes in here. This consists of replacing 7 main filter capacitors, as well as the small capacitors on the PC board as well.
Cosmetics
Finally, since the vast majority of these decks came from radio stations or recording studios, the front panels are often pretty hacked up, full of razor blade marks, making even a 100% functional deck look ugly. In our quest to rebuild these ATR decks as much as possible, we are getting the front panels and head covers sandblasted and powder coated.
