A Chronicle of Repairs Made to a 1973 Sony "ST-80W" AM/FM Stereo Tuner
Photo 1. Sony "ST-80W" AM/FM Stereo Tuner
Sony "ST-80W" AM/FM Stereo Tuner (Japan / circa 1973)
FM: 87 - 108 MHz
AM: 530 - 1605 kHz
Suitable Power Amps (circa 1973)
Most stereo computer speakers (with "wall wart" power supply, and volume control) will work, because they have built-in amplifiers.
- Sony "TA-88" amplifier (matches the ST-80W tuner)
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 came 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!
- 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.)
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 are 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 ten per package. 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.
This tuner requires a separate power amplifier and external speakers. So, on Monday (29-sep-2008) I 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 illustrates the primary tuning dial pilot lamp (one required). It is a standard Type 50 miniature screw base, round bulb, 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. I measured 9.25 volts dc on those wires, so I tried 6 volt, 25 mA mini lamps (Radio Shack Catalog # 272-1140). The 6 volt lamps 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 #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 (3 total). They were 6 volt, 25 mA lamps. Purchased lamps at Radio Shack. Part number 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. I guess that is how Sony did it back 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."
06-nov-2008: Ordered a set of Klipsch "Groove PM20 2.0" speakers (black) for $60 from amazon.com. They arrived Friday 07-nov-2008, and sounded good with the Sony ST-80W tuner. No discreet amplifier is 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 ($1.69). This was a 6 volt, 25 mA "grain of wheat" lamp. At first it seemed the new lamp was not working, but I noticed the stereo/mono switch (front panel) was in the "mono" position. I began to think the switch was in the same position all along, and that the lamp never needed to be replaced. Would I do something like that? Possibly.
Wood Cabinet Restoration
13-oct-2008: The cabinet of the Sony ST-80W was made of wood, and the exterior had a thin walnut veneer. I used "rottenstone" (a powdered form of weathered and decomposed siliceous limestone used for polishing) and paraffin oil, as the veneer had some fine scuffs, swirls and light scratches from what appeared to be 35 years of normal usage. I first sprinkled some rottenstone powder on the top of the cabinet and then poured out a little bit of paraffin oil to go along with it. Using a soft cotton cloth, I mixed this into a slurry and hand rubbed it into the areas needing the most attention first. This removed the small scratches and stains as well as gave the walnut veneer a much improved overall appearance. Unfortunately, part of the veneer had worn off near the bottom of the cabinet. There was nothing that could be done to repair that damage.
Replacement Parts for Sony "ST-80W"
Compiled: 15-oct-2008 through 15-oct-2008.
Vendor 1: RS (Radio Shack) - www.radioshack.com
Vendor 2: RD (Radio Daze) - www.radiosupply.com
|Schematic part number||Original component and composition||Value (original)|| Value (replacement)
||Composition of new part||Vendor (Part number)||Price ($)||Quantity (actual)||Purchased / Ordered||Date||Total ($)|
|unknown||mini lamp with 1¾" insulated leads||unknown||6 volts, 25 mA||mini lamp with 1¾" insulated hookup leads||RS (272-1140)||1.49||3||3||10-oct-2008||4.47|
|unknown||miniature screw base, cylindrical bulb, clear glass||unmarked||Type 40, 6.3 volt, 150 mA (0.25A). Burned out after three weeks of minimal usage||miniature screw base, cylindrical bulb, clear glass||N/A||had in stock||1||N/A||09-oct-2008||N/A|
|unknown||miniature screw base, cylindrical bulb, clear glass||unmarked|| Type 46, 6.3 volt, 250 mA (0.25A)
Used for one night. Replaced with Type 50 lamp
|miniature screw base, cylindrical bulb, clear glass||N/A||had in stock||1||N/A||09-oct-2008||N/A|
|unknown||miniature screw base, cylindrical bulb, clear glass||unmarked||Type 50, 7.5 volt, 220 mA (0.22A) (1.65 watt)||miniature screw base, round bulb, clear glass||RD (DL-50)||$0.34||1||box of 10||10-oct-2008||$3.40|
- Photo of original Sony system with speakers and "TA-88" amplifier