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Swapping the Deck

A project log for Tape Artchive

Images with audio on cassette tape

Blaine MurphyBlaine Murphy 10/06/2017 at 02:092 Comments

The end of the previous log stated I would be working on format comparisons this log, but that isn't true. This log will be focused on the Sony TC-FX160 stereo cassette deck that I picked up at a thrift shop today.

This deck appears newer than the Panasonic deck from my previous logs. The Sony deck is a single-purpose device where the Panasonic was a radio, phono pre-amp, and amplifier. I plan to use the better deck for recording and put the runner-up aside for a future project.

As I expected from a thrift shop find, the Sony deck didn't work. I tried playing a tape, but nothing in the player moved. I did hear a motor start when I pressed play, so I took the unit apart to look at the belts.

At first it looked like the belts were broken, but when I tried to remove them I got a surprise; they had gone so soft the texture was like uncured silicone. The belts disintegrated as I tried to remove it from the pulleys. I had to scrape for a little while to get most of the goop cleaned out.

I googled around a bit and found that rubber bands or string can be used as replacement belts. I didn't know how to install the bands as belts on this particular model because the old belts were completely gone. I couldn't find a service manual for this model, so I had to use the remnants of the old belts as a guide to place the rubber bands.

This seemed to work. The Sony deck will now play and rewind, but will not fast forward. I think this is because the rubber band attaching the top pulley to the motor pulls the pulley so that it does not fully engage when the fast-forward button is pressed.

I decided to run the same test as I did on the Panasonic to approximate the frequency response of the Sony deck. The following is a screenshot of audacity showing the spectrograms of a 20kHz to 20Hz sweeps on the decks.

The Sony responds to higher frequencies than the Panasonic. The Sony also sounds better and has much less noise. I'll be using the Sony deck to record the tape tests and the final tape (unless I see something really good out in the wild).

Discussions

Mr C Clarke wrote 01/20/2022 at 09:32 point

As an aside to my previous comment, the power supply for this deck is barely adequate. The power transformer is very small and there is a crude voltage regulator circuit for the +-6.5v dc supply to the deck. built into the circuit is the ON/OFF switch which simply shuts down the 6v supplies and leaves the transformer on as long as the deck is connected to a supply. Applying only slight pressure to the flywheel when rotating caused the motor to slow down due to the supply sagging under increase current load. I found some variable + and - voltage regulators with an enable pin and replace the transistor regulators. Fortunately the minus and plus regs could be controlled by a common +ve supply, I used the raw smoothed DC before the regulators around 12v dc through a resistor to the ON/OFF switch, shutting down when the voltage was reduced to zero by the ON/OFF switch. I then replaced the mains transformer with a 9-0-9V toroidal transformer with a 1A capability, God knows there's plenty of room, the first time i opened the case I thought half of it was missing. This proved to be a good move as the motor now regulated without eliminating the dc supply. All this will impact on the steadiness of the tape speed.

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Mr C Clarke wrote 01/20/2022 at 08:45 point

I have one of these decks and pretty well fixed it. The flutter was caused by wear in 2 places. The fly wheel bearing and the pulley which drives the rest of the mechanism. I ended up grafting a Technics flywheel and pulley with a flat belt and sleeving the drive pulley bearing with some fine tubing plus correcting the twisted plastic pulley bearing molding which had caused the pulley to lean due to the belt tension. much of the wobbly sound is caused by the worn bearing and miss alignment of the drive pulley. The motor I also replaced with the Technics motor which is speed programmed with a resistor. By adding some tiny limit switches to the fast forward and rewind keys I switched in an extra small variable resistor and set the FF and REW to a higher speed to reduce the time. This deck does not seem to auto detect end of tape when FF or REW is used this must be monitored and stopped manually. belts are easily obtained by buying a selection from ebay for a few quid and selecting appropriate ones. I bought a flat belt from GB Audio to match the new position of the motor and flywheel, top place if you need specialist belts.

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