Chronicle of Repairs Made to a 1962-1963 Telefunken "Concertino 5384 W" Stereo Hi-Fi Table-top Radio
Photo 1. Typical mid-century, European styling
Broadcast (AM): 510 - 1620 kHz
Short Wave: 2.3 MHz - 6.9 MHz (SW2), 7.0 MHz - 22 MHz (SW1)
Frequency Modulated (FM): 88 - 108 MHz
Serial Number: 585238
Valve (tube) line up: ECC85, ECH81, EBF89, ECC83, EBC91, 2*ECL86, EM84
4 loudspeakers: Two large (behind front grille), two small (on each end behind grille).
Two (2) Type 40 dial lamps.
IF (Intermediate Frequency): FM: 10.7 MHz, AM: 460 kHz
Photo 2. Inside view
The stereo decoder plug-in module was an extra cost option, but was not included with this set. The inside back panel had an envelope for a schematic, but unfortunately, it was missing.
Photo 3. Bass and treble thumbwheel dial lubrication
Valve ( tube ) line-up ( 8 total ):
Tube Cross Reference Schematic Ref. Nr. Type Reference ECC85 6AQ8 Double Triode VHF-tube (FM tuner section) www.r-type.org/exb/exb03323.htm ECH81 6AJ8 Triode-Heptode Frequency converter controlling "mu" (Greek letter µ = symbol for amplification factor) (AM converter, and FM first IF stage) www.r-type.org/exb/exb03328.htm EBF89 www.r-type.org/exhib/aai0094.htm ECC83 www.r-type.org/exhib/aaa0046.htm EBC91 ECL86 Final output (4 w) ECL86 Final output (4 w) EM84 6FG6 Tuning indicator tube ("magic eye")
Tuning Dial Pilot Lamps
The original OSRAM bulbs with frosted glass were in the radio, so I just cleaned them up a bit. Replacement lamps are generic Type 40, 6.3v, 150mA (0.15A) miniature screw base, cylindrical bulb, clear glass. Tuning dial pilot lamps are available from Radio Daze for $0.35 each. The standard "Type 40" lamp (sold in packs of 10 at radio swap meets) work well with these radios.
This radio was purchased by Scott Van Dusen for $100 on April 22, 2008. Scott is an old friend, so when he said it had audio problems at high volume settings, I told him I would take a look at it. On Sunday May 4, 2008, he brought it to my house, and we removed the tubes. We were pleasantly surprised to find that they were all Original Equipment Manufacturer (OEM) Telefunken. Usually at this point in an antique radio's life, at least some of the tubes have been replaced with "domestic" (USA) brand tubes. This radio was all original. No obvious updates or modifications to the circuitry had been made.
We took the tubes to the Antique Wireless Association Museum in Bloomfield, NY for testing. They all tested good. Upon arriving back home, I used De-Oxit on the pins of the tubes and also in the pin sockets. Then, I brought the radio up slowly on a variable power transformer. First 50 volts, then 75, then 90, and finally 115 Vac. This was over the course of maybe five minutes. The radio had been used recently, otherwise, I would have taken more time to increase the power. After we tuned a station in, and increased the volume, Scott said that the earlier audio problem was now gone.
He left the radio at my house and I detailed the cabinet for him and also lubricated the thumbwheel knobs for the bass and treble settings. They were frozen stiff. See photo. I also removed the tuning dials and cleaned them with Murphy's Oil Soap and finished them off with Novus Plastic Polish #2. The dials cleaned up very nice.
The woodwork was cleaned using rottenstone and paraffin oil. Rottenstone is a powdered form of weathered and decomposed siliceous limestone used for polishing. 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. I mixed this into a slurry, and used a cotton cloth to hand rub it into the areas needing the most attention first.
- Electronic Amplifiers: en.wikipedia.org/wiki/Electronic_amplifier