Chronicle of repairs made to a 1973 Sony "ST-80W" AM/FM stereo tuner

Contents

• Ownership History
• Specification Overview
• Parts Needed
• Tuning Dial Pilot Lamps
• Repair History
• Wood Cabinet Restoration
• Table 1: Replacement Parts Needed
• References

Photo 1. Sony "ST-80W" AM/FM Stereo Tuner

Sony "ST-80W" AM/FM Stereo Tuner (Japan / circa 1973)

Tuning Range:
FM: 87 - 108 MHz
AM: 530 - 1605 kHz

Suitable Power Amps (circa 1973)

• Sony "TA-88" amplifier (matches the ST-80W tuner)

Most stereo computer speakers (with "wall wart" power supply, and volume control) will work, because they have built-in amplifiers.

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Ownership History

I purchased this AM/FM stereo tuner on Saturday, September 27, 2008, at the Elmira Hamfest for $2.00. Made by Sony (Japan / circa 1973) with an original price tag of $90.00. It was a bit yellowed from the "grunge of time," (probably from a smoker's home) and none of the tuning dial lamps or the stereo indicator lamp were working. You get what you pay for!

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Specification Overview

- Analog tuning
- Solid state design (16 transistors, 19 diodes)
- Intermediate Frequency (IF): 10.7 MHz (FM), 455 kHz (AM)
- Analog, backlit tuning dial
- Rear mounted Line Out sockets (RCA)
- Rear mounted variable output level controls (L and R)
- Mono / Stereo selector switch
- AFC On / Off selector switch
- Adjustable, ferrite, AM antenna
- Antenna connections: FM (300 Ω), AM, and ground
- Rear mounted "fixed level" DIN, record output
- Walnut veneer cabinet
- Weighs 2.6 kg (5 lbs., 12 oz.)

Parts Needed

• Tuning dial lamp (primary). Required a Type 50 miniature incandescent lamp
• Three miniature lamps - 6 volt, 25 mA

Tuning Dial Pilot Lamps

The main tuning dial pilot lamp (one required) is Type 50, 7.5 volt, 220 mA, miniature screw base, round bulb, clear glass. Tuning dial pilot lamps were available from Radio Daze for $0.34 each. They can also be found at local radio swap meets, sold as Type 50 pilot lamps, usually sold in packages of 10. See the Vintage Radio Links page for other vendors and sources.

There were also two other lamps for dial illumination, and one for the "stereo" signal strength meter. They were miniature style lamps (see photos). Available at Radio Shack. The 12 volt mini lamps were too dim, so I tried 6 volt, 25 mA mini lamps (Radio Shack catalog # 272-1140). The 6 volt lamps worked out well.

Repair History

29-sep-2008 (Monday): This tuner requires a separate power amplifier and external speakers. So, verified that both channels of the tuner were functional by borrowing a small amplifier.

Photo 2. Tuning dial lamp, and stereo indicator lamp

This photo shows the location of the primary tuning dial pilot lamp (one required). It is a standard Type 50 miniature screw base, round bulb, with clear glass.

The other lamp in the photo is part of the signal strength meter. It is a miniature style lamp with two insulated wires coming directly out of the base of the glass envelope.

Photo 3. AM and FM band dial lamps

There were also two other tuning dial miniature lamps. These indicate when either AM or FM is selected. Measured 9.25 volts dc on those wires, so I tried 6 volt, 25 mA mini lamps (Radio Shack catalog # 272-1140), which worked reasonably well.

09-oct-2008: Tried using a set of Philips (model: MMS140 CS) stereo computer speakers with internal amplifier. The amplifier power was supplied by a "wall wart" transformer. This configuration worked well. Cables needed for this configuration were: From the rear of the Sony tuner, a 6 foot Y-Adapter audio cable (Radio Shack # 42-2551). This consisted of two RCA phono plugs to one 1/8" (3.5 mm Ø) stereo phone plug. This then plugged into a 1/8" (3.5 mm Ø) "coupler" (Radio Shack catalog # 274-1555), which accepts 1/8" (3.5 mm Ø) plugs at both ends. finally, the computer speakers were plugged into the "coupler."

13-oct-2008 (Monday night): Replaced the remaining mini lamps (three total). They were 6 volt, 25 mA lamps. Purchased lamps at Radio Shack (catalog # 272-1140).

The two mini lamps (for indicating which band is selected) were originally wrapped in black, cloth-based electrical tape (see photo) and glued in place. This must be how Sony did it in 1973. When replacing the lamps, I also used cloth electrical tape (to wrap the bulbs) and glued them back into the small receptacles on the inside of the tuner faceplate with "rubber cement" (a.k.a. contact cement).

05-nov-2008: Ordered a set of Klipsch "Groove PM20 2.0" speakers (black) for $59.99 (plus tax, shipping and handling, minus discount) from Amazon (total: $64.26). They arrived Friday 07-nov-2008, and sounded good with the Sony ST-80W tuner. A discreet amplifier is not needed as long as the computer speakers have an internal amplifier powered by a "wall wart" transformer.

09-nov-2008: Replaced the four-week-old Type 40 pilot lamp (6.3 volt, 0.125 amp) with a Type 46 lamp (6.3 volt, 0.250 amp). The lamp that was in the radio when I got it was not marked.

10-nov-2008: (Monday) Replaced the Type 46 lamp with a Type 50 (7.5 volt, 0.22 amp).

26-jun-2011: (Sunday) Replaced the stereo signal lamp with Radio Shack part number 272-1140 ($1.69). This was a 6 volt, 25 mA "grain of wheat" lamp. At first it seemed the new lamp was not working, but I noticed the stereo/mono switch (front panel) was in the "mono" position. I began to think the switch was in the same position all along, and that the lamp never needed to be replaced. Would I do something like that? Possibly.

 28-apr-2022: (Thursday) While scanning the AM band in the early hours of the morning, the dial went dark. Replaced the primary tuning dial pilot lamp (one required). It was a standard, Type 50 (7.5 volt, 220 mA, miniature, screw base, round bulb, with clear glass). Note that when the radio was placed on the work bench and opened up, the lamp began working again. It probably had a broken filament, and when it was on its side, the connection was made again, and it came back to life. The old bulb appeared to have been arcing internally, as it had darkened significantly (see photos). Had a box of Type 50 lamps in stock, so swapped it for a new one.

Note: the Type 50 main dial lamp was last replaced 10-nov-2008 (14 years ago).

Photo 4. Main tuning dial lamp (Type 50) / Replaced April 28, 2022
Photo 5. Intermittent dial lamp (darkened bulb) and replacement lamps

Photos 4, and 5 uploaded April 28, 2022 / iPhone 13

Photo 4 shows the new Type 50 lamp installed. The old one can be seen to the left of the radio. Photo 5 compares the old Type 50 lamp (dark bulb) with the new ones.

Wood Cabinet Restoration

13-oct-2008: The cabinet of the Sony ST-80W is made of wood, and the exterior has a thin walnut veneer. I used "rottenstone" (a powdered form of weathered and decomposed siliceous limestone used for polishing) and paraffin oil, as the veneer had some fine scuffs, swirls and light scratches from what appeared to be 35 years of normal use. I first sprinkled some rottenstone powder on the top of the cabinet and then poured out a little bit of paraffin oil to use with it. Using a soft cotton cloth, I mixed this into a slurry, and hand rubbed it into the areas needing the most attention first. This removed the small scratches and stains as well as gave the walnut veneer a much improved overall appearance. Unfortunately, part of the veneer had worn off near the bottom of the cabinet. Nothing could be done to repair that damage.

References

1. Photo of original Sony system with speakers and "TA-88" amplifier

c o n t a c t / r a d i o  w o r l d

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Sony "ST-80W" AM/FM Stereo Tuner
Established: October 10, 2008
Last Update: November 07, 2022
© Black Sparrow Photography / Jeffrey P. Miller (N2AWA)

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