08/01/2025
Hi everyone! The long-awaited Tascam 52 is finally on the table. Set of unsoldered heads arrived also. This machine is built well. Some rust and scratches. Not a big deal. All metal parts are subject to stripping and cleaning anyway , then some have to be reanodized, some powdercoated. Without question, all bolts and bearings have to be replaced. All boards have to be cleaned and recapped. For audio circuits planning to use the highest grade AudioNote capacitors and non-magnetic resistors. My dear friends who prefer "just fix and restore" or "must be original", please do not read below.
This may p**s you off, and I don't want to ruin your relationship. 🧐
I have explored Tascam 52 for a serious amount of time and have become familiar with a lot of features.
This machine is subject to something bigger than just fixing and restoring.
Foremost, every part of this machine has to be 3D scanned, measured and digitally mated to full 3D assembly. I have enough skills and all the equipment to do this.
Now step by step.
1. Battery-powered audio circuit. Impressed with the roomy interior of the 52 (as expected), I decided to do it. A lot of research and experiments have already been done, and now I'm just ready to implement them. Two batteries and a battery management unit connected to the main control unit were to be installed. Two modes are considered: auto and manual. In auto mode, one battery feeds the circuit while the second charges if necessary. When near proper discharge level, the battery-managing processor will switch batteries during STOP mode. Battery capacity will be enough to feed audio circuits for a serious amount of time. Manual mode for manual control. We will use widely available parts.
2. This machine uses 5V logic level for control circuits. Makes me happy. The installed MB8841 controller is prehistoric and works with a max 4MHz clock speed, which makes me smile. Probably all control PCBs to be redesigned to adopt a 600MHz controller with a lot more GPIO and wireless connectivity. Wireless connectivity is needed for full-featured remote control with color screen and maximum control.
3. Reel motors make me happy as well. The shaft extended from the back and had enough room to install an encoder on each motor. Reading motor speed during rotation makes all operation with counter and tension much easier. Without question, the original bulky counter encoder will fly to the garbage can soon. Modern high-resolution encoder to be installed. Each reel motor will be driven by an individual 600MHz controller which will also monitor tension.
4. Most likely, a total revision of the capstan motor driver, also implementing a 600MHz controller and color screen.
All controllers will be Teensy 4.0 or 4.1(as main CPU). Widely available, superfast and reliable. Open source. Will make it very well-documented and easy to replace. Even planning to place a spare preprogrammed controllers for each unit inside for quick replacement.
5. Funny prehistoric tension sensors to be replaced with modern high-resolution encoders. Connected to Teensy, this will make mechanical deviations' measurement easy.
6. Most likely solenoids to be replaced with steppers. Purpose:
1. Minimize magnetic influence. They produce a significant magnetic field. It is not moving, but the reels rotate.
2. Using fast stepper motors allows full tension control of the brakes and pinch roller.
7. The room near headblock makes me happy as well. The head block will contain two parts. The playback head is still installed. Erase and record heads to be installed on a movable platform which will move heads into tape pattern only during record mode. 316L non-magnetic stainless steel, C64200 aluminum bronze and titanium are materials to be used in headblock.
8. 250nW-320nW switch and NAB-IEC switch to be installed on the front panel.
9. As seen in the images, my screens fit perfectly! Yes, I'll install them as background or as main VU meters without a mechanical needle. Also driven by Teensy 4,1. This controller allowed a lot. First and very important to me is a lot of fast memory. Depending on tape speed and distance between recording and playheads, I can store the input audio signal in the buffer array with calibrated delay. During recording, I'll align the frequency spectrum from playback head and delayed input signal spectrum. This operation will make me see what frequency deviates.
10. Digital Potentiometers will replace mechanical when possible.
The SPI interface allowed to control large number of DP from one microcontroller. This option opens the gate for dynamic control and parameter storing of almost everything.
Just saying fast and precise EQ calibration for any tape with the possibility to store parameters become reality.
11. Last for today but not last for this machine.
OPAMPs in audio circuits are also subject to replacement. We will look for a modern high slew rate, ultra-low noise substitute.
It is too early to design the appearance, but I think symmetrical placement of VU meters is needed.
Velvet black paint, bronze , exotic wood and glass are considered.
Large brown plastic piece from the front already in the garbage can.
My WEB site is under construction now for total rebuilt.
Will post updates.
