This page chronicles restoration work on a Grundig 2440U table-top radio. It performs reasonably well, and I have made several repairs to it since purchasing it in September, 2004. The most recent changes are at the bottom of the page.
Photo 1. Grundig (West Germany) "2440U" (2440 U)
Years manufactured: 1964-1965
Broadcast (AM): 510 - 1620 kHz
Short Wave: 5.9 - 16 MHz
Frequency Modulated (FM): 88 - 108 MHz
Serial number: 1322604668
Valve (tube) line up: ECC85, ECH81, EF89, EABC80, EL84, EM87
3 loudspeakers: One large, two small. All behind front grille.
Two (2) Type 40 dial lamps.
IF (Intermediate Frequency): FM: 10.7 MHz, AM: 460 kHz
Sister model: Type "2420U" (2420 U)
Photo 2. Side View / September 2004
The Grundig 2440U is the second radio I found at the Kutztown, Pennsylvania antique radio swap meet on September 18, 2004. The swap meet was hosted by the DVHRC (Delaware Valley Historic Radio Club). Having been built for the 1964-1965 season, it is surprising that the tuning dial still bears the CD (Civil Defense) symbols for the AM band, which were required by law only until 1963. CONELRAD, in case you have forgotten, was the emergency radio broadcast system that was supposed to provide civil defense instructions in case of a nuclear attack by tuning to 640 kHz or 1240 kHz on your AM radio dial. CONELRAD stood for CONtrol of ELectromagnetic RADiation. This admirable little beauty set me back $25.
Photo 3. Rear View / September 2004
The schematic and "PhotoFact Folder" (Howard W. Sams Company / June 1965) for the Type 2440U was available from "Just Radios." The Sam's PhotoFact Folder includes the English schematic, annotated layout photos with part numbers indicated, and a complete parts list. The package also covers the Grundig model 2420U radio. The cost of the package was $5.00.
American tube equivalents (2004 Radio Daze prices, unless noted):
ECC85 = 6AQ8 / $10.00
ECH81 = 6AJ8 / $5.75
EF89 = 6DA6 / $10.90 (AES / www.tubesandmore.com)
EABC80 = 6AK8 / $7.10 (AES / www.tubesandmore.com)
EL84 = 6BQ5 / $18.00
EM87 = 6HU6 / $5.00
November 26, 2004:
Replaced all the tubes in the 2440U with NOS. Also cleaned up the inside of the chassis.March 22, 2009:Received an email from a reader of this page who requested the dial cord stringing diagram. Here is the scan of the diagram from the Sams Photofact folder.
Valve ( tube ) line-up ( 6 total )
|Original Tube||Cross Reference||Tube Type|
|ECC85||6AQ8||Double Triode VHF-tube (FM tuner section)
|ECH81||6AJ8||Triode-Heptode Frequency converter controlling "mu"
(Greek letter µ = symbol for amplification factor) (AM converter, and FM first IF
|EF89||6DA6||Pentode RF/IF-tube controlling "mu" (Greek
letter µ = symbol for amplification factor) IF stage (Intermediate Frequency) for both FM and AM reception.
(affects audio level)
|EABC80||6AK8||Triple Diode-Triode Detector tube. Used in AM and FM
detection, and the first audio amplification stage.
|EL84||6BQ5||Pentode Power tube (audio amplification)
|EM87||6HU6||Tuning indicator tube ("magic eye")
Photo 4. EM87 "Magic Eye" Tuning Tube
Left: quiescent state. Right: appearance when tuned to a strong signal. Note the slight overlap.
Photo 5. Unique Power Connector
Here is the end of the Grundig 2440U "cheater plug" style power cord which is riveted to a small metal anchor plate. The anchor plate is part of the original "safety interlock" on the back of the Type 2440U. The plate gets screwed into the back of the radio. This exact style power cord is available from AES (Antique Electronic Supply / www.tubesandmore.com) for $1.50 plus a $2.50 surcharge "for being under a $10 order." So the total came to $12.25 to send it from Arizona to New York via the US Postal Service "Priority Mail." Item description: cord, power, non polarized, 5/16" (cord width) cheater plug, brown, 6'.
This 2440U is a very nice radio and it plays strong and loud (if desired). The grille cloth has a bit of a moisture stain in the bottom left corner as seen in the photo. The cabinet is in very good condition but with two small chips on the top right side (see photo). The gold outer surround ring has a very small dent near the top left corner. The "magic eye" tuning tube (EM87) works correctly. Note that the Model 2440U has a plastic face plate instead of the glass used on earlier models. Tuning dial pilot lamp (two required) is 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. Note that the schematic says the bulbs are 7v, 100mA. Is this a standard size bulb? The standard "Type 40" lamp (sold in packs of 10 at radio swap meets) work well with these radios.
Photo 6. Inside the Grundig "2440U"
R43 (black), C69 (orange cap on left) and C68 (orange cap on right)
The only trouble with this radio was that it was working intermittently. I investigated this problem in my newly created electronic workshop. I opened it up, and by visual inspection, and probing around inside with a pencil, I discovered a bad power resistor (R43). It was cracked and arcing. See photos. I also replaced the two paper capacitors (C68 - 470pF and C69 - 0.0015µF)
original paper capacitor (C69): 0.1500pF (0.0015 µF) 400Vac 1000Vdc
original paper capacitor (C68): 470pF (0.00047 µF) 400Vac 1000Vdc
original power resistor (R43): 1.3k 4W 2%
The voltage ratings printed on the body of the capacitors "400 ~" (Vac) and "1000 -" (Vdc) are both significant when seeking replacement. The DC voltage rating is called the Working Voltage. The capacitance ratings are 1500 pF and 470 pF.
Does the double stripe at one end indicate the positive end as in a polarized electrolytic capacitor? No, the second stripe signifies the outer foil. The outside foil would go to the lower impedance side of the circuit, which might not be the 'ground-ward' side. For instance, in a plate-to-grid coupling application, the lower impedance side would be the plate, so the capacitor's outside foil would preferentially go there. Also, an electrolytic capacitor would never be produced for such a small value capacitor.
Photo 8. Inside the Grundig "2440U"
Here are the new ceramic capacitors and power resistor installed.
The capacitors and power resistor were available at Glenwood Sales on Hague Street in Rochester, NY. The ceramic capacitors were $0.16 each and were an exact capacitance and working voltage (Vdc) match but they are a disc style and are yellow (470pF) and beige (1500pF) in color. The resistor was $0.25 and was rated a little differently than the original. The replacement was 1.3k 5W 5% but using a higher power resistor will be okay. So to fix this intermittent problem, it cost $0.57 excluding my time and fuel (diesel) to drive to Glenwood Sales which is about a 10 minute drive from where I work. So my total investment on this radio so far is $25.57. Well, not including the 10 hour round trip to Kutztown, Pennsylvania and the approximately $37 in diesel fuel (566 miles, 30mpg, $1.97 average fuel price) a room at the Super 8 Motel ($69.00), dinner for two ($22) at the local pizza joint and breakfast ($15). So the actual total investment is closer to $168!
Photo 9. Working Well Again / October 2004
October 5, 2004: The Grundig 2440U "in action" with Mozart coming in loud and clear. Also note the "magic eye" tuning tube (EM87) at the left. The way this tube works is when a signal is weak, there is a wider gap between the top and bottom. As signal strength increases, the gap closes. The gap should close completely on strong signals.August 25, 2007:
Having just finished working on a 1958-1959 Grundig "2066 PX", I swapped the 2440U in to the workshop space for another look. The radio performs well enough, but the EM87 magic eye tube has never closed up completely on strong signals (see photo, above). I plan to fix that problem.August 21, 2008:
Found an original Sam's Photofact for the Grundig "2440 U" at the Antique Wireless Association (AWA) annual conference. Price was $2.00. I had previously purchased a photo-copy of the same Photofact set on-line.
Photo 10. August 17, 2010
August 17, 2010 (Tuesday):
Got a quote via email from Brian Sargeant (Radio Daze) to re-cap and refurbish the radio, so I dropped it off at their shop in Mendon. Estimate was $144. I saw Brian again later that day at the AWA Conference (to preview Larry Babcock's estate auction). Turn-around time was estimated to be about two or three weeks. I picked up the radio after our summer vacation (Long Lake, NY and Canada [a couter-clockwise trip around Lake Ontario]), and honestly, there was no difference in the performance. The magic eye tube behaved the same as before, which is to say, it did not completely close on my favorite FM station. I hoped to resolve that problem some day!