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Old 15th Mar 2018, 1:06 pm   #1
dazzlevision
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Default GEC 2541 transistor radio

A fellow forum member recently gave me this radio (thanks David!). It’s a bit scruffy cosmetically, but I already have another identical set with a better cabinet but with some serious issues internally! Hopefully, I can repair the chassis in this recently acquired radio and transplant it into the good cabinet.

The radio dates from around 1970 and was made in the UK by GEC Radio & Television Ltd (in effect, the company that used to be known as Radio & Allied Industries Ltd, which was originally established by Michael Sobell). In fact, an internally identical, but restyled version of the GEC 2541 was available, the Sobell 1541. The GEC August 1970 price list shows the 2541 at £48.50, which was a lot of money at that time.

It’s a six waveband set (LW, MW, SW1, SW2, SW3 and VHF-right up to 108MHz), with battery or mains operation. It also features treble and bass controls, switchable AFC on VHF, tuning meter, tuning scale illumination and a fine tuning control operative on the three SW bands.

There are three printed circuit boards: pushbutton switch bank with AM RF circuitry, IF amplifiers and audio output, VHF permeability tuned RF unit.

These all feature the infamous Radio & Allied double sided printed circuit with plated through holes. Before the advent of solder suckers and desoldering braid, this did not lend itself well to the removal of components such as valve holders! However, after years of desoldering on this type of PCB, I usually manage to extract such components without damaging the print.

I attach the relevant pages from the GEC and Sobell sales brochures of that time. Compare and contrast the sales pitches!


I removed the chassis from the cabinet (yes, a real metal chassis is used!) and gave the cabinet a dust out and clean up.

The first problem was a seized AM tuning gang, which was made by Preh, of Germany. I’ve come across this problem before on several Thorn group radios, radiograms and Unit Audio products using the same basic Preh tuning gang. After many years, the lubrication used in the ball races tends to dry out and act more like an adhesive (probably aggravated by complete lack of use of the set for many years after its “retirement”).

I used a dodge to free it that I first thought of when freeing seized turntable spindles in their bearings fitted on Thorn 1960 tape recorder decks – the deck with the five piano keys in a central position, near the front.

I applied heat from a soldering iron tip, which heats up the dried out grease and it becomes soft enough to allow spindle removal rotation. You have to be careful not to allow the heat to soften the plastic drive cord pulley that is fitted on the shaft! I used freezer aerosol to keep that end cold.

I didn’t want the serious hassle of dismantling the shaft and complicated drive cord system, so I applied a drop or two of Servisol to the shaft where it enters the ball race and that freed it up even more. I left that to dry out overnight and applied a drop of sewing machine oil to each end of the shaft. Tuning is now very easy. This radio uses permeability tuning on VHF and the cores are driven from the other end of the AM gang’s shaft by another drive cord (see photo).

The next problem was dirty and intermittent contacts in the pushbutton switch bank. I released all the push buttons and inverted the chassis, applying aerosol Servisol to the rear of the switches, where the white plastic moving part of each switch is visible. This forces the fluid well down into the entire set of sliding contacts. I then operated all the pushbuttons many times, to allow the fluid to really do its job. I use a clean tissue to absorb any fluid on the outside of the switches and PCB.

After this, I could receive signals on LW, MW, SW1 and VHF, although the audio on VHF was very distorted. I found that, by flexing the switch BCB, reception on the other two SW bands could be obtained. There are many wires to the solder tag terminals on the top of each slider switch and to various points on the copper tracks (both sides). To add to this, the metal chassis covers parts of the board and a lot of wires are run over the other side of the board.

So, I decided that I would have to completely remove the PCB. This was eventually achieved after a LOT of wires were desoldered. As I didn’t intend to ever remove this board again, I did an awful lot of work on it (the “scatter gun” approach!):

Reworked every soldered joint - from both sides of the board.

Replaced some of the larger plastic film capacitors with modern, much smaller equivalents, to improve accessibility. One of the originals, a Hunts/Erie axial green-sleeved type, had a bad connection at the capacitor end (I find this type is prone to such problems). There was also one of those notorious "Callins" black cylindrical cased axial electrolytics on this board, so I replaced that as well.

Removed and tested all the carbon composition resistors, which were all out of tolerance and replaced all of them with modern 0.5W carbon film types.

Checked the continuity of all coils.

Retreated the switches with Servisol.

Using a DMM on continuity checked all contacts of the slider switches, in both “up” and “down” positions.


After all that work, I spent several hours carefully refitting the PCB and there were a lot of wires to reconnect! Luckily, I have two of these radios, so I used the second as a reference for the connections, which is just as well as the ferrite rod windings are incorrectly component referenced in the GEC service manual!

When I switched the radio on, there was AF amplifier hiss from the speaker at maximum volume, but nothing else when pushbuttons were pressed. I used a small screwdriver to apply the “finger hum” test to the section of the VHF pushbutton switch that routes AM or FM sound to the audio stages. There was hum at the 0.22uF coupling cap (to the tone and volume circuitry) but nothing when I actually touched the slider contact terminal pin of the switch. Close inspection revealed that there was a problem with the plated through double sided print to this switch terminal pin. I fitted a short wire link between the top solder eyelet of the switch and the relevant PCB land and we were then in business!

The radio now worked on all six wavebands, with none of the previous intermittency when the PCB was flexed. There was no intermittency in the operation of the pushbutton switches.

However, there was severe audio distortion on VHF/FM and from experience, I expected this to be caused by a fault in the FM demodulator stage. My first suspect was the reservoir electrolytic, a small blue Mullard 2.5uF @ 64V, but it was OK. Even so, for future reliability, I replaced it with a very compact plastic film 2.2uF 63V radial type.

My next suspects were the two Germanium AA119 FM demodulator diodes. These are screened by a small IFT “can”, so that was removed and the two diodes tested. One was open circuit. Replacing it has restored good quality FM audio.

The only other fault was a physically broken (but not burnt) 2.2Ohm 0.5W Erie carbon composition resistor in series with the output of the mains derived dc supply feed to the load. I replaced it with a 0.125W Philips carbon film type, which should also act as a fuse, if severely overloaded.

You’ll see from the photo that the mains input connector is the two bladed Pressac type much favoured by Philips in the first part of the 1960s (and, of course, inside every G8 CTV). From the point of view of electrical safety, I’m not sure the mains supply section would pass muster nowadays!

I had to adjust the position of the tuning cursor in order to get the usual stations appearing at the correct points on the tuning scale.

It seems to be quite sensitive on all bands and I roughly checked SW calibration against a modern(-ish) Grundig SW radio - it’s pretty good.
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Name:	GEC 2541 radio - brochure page - compressed.jpg
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Name:	Sobell 1541 radio - brochure page - compressed.jpg
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Last edited by dazzlevision; 15th Mar 2018 at 1:29 pm.
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Old 15th Mar 2018, 1:34 pm   #2
dazzlevision
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Default Re: GEC 2541 transistor radio

Here's a photo of the other side of the pushbutton and AM RF PCB.

You can see where a section of copper track has been damaged during the removal process and replaced with a wire link.

You'll also see that short section of missing print which caused loss of all signals when the PCB was refitted. It leads away from the second contact down of the VHF slider switch (right hand side).
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Last edited by dazzlevision; 15th Mar 2018 at 1:39 pm.
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Old 15th Mar 2018, 2:26 pm   #3
dazzlevision
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Default Re: GEC 2541 transistor radio

A few more photos of the chassis.

Note that, a black finished metal panel, which usually sits behind the tuning cursor, has been removed, to show the chassis in full.
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Last edited by dazzlevision; 15th Mar 2018 at 2:33 pm.
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Old 15th Mar 2018, 5:00 pm   #4
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Default Re: GEC 2541 transistor radio

What a fascinating radio: a sort-of GEC attempt at a Zenith Trans-Oceanic.

Looking at the construction-style, three PCBs and a rat's nest of unstructured interconnecting wires, it must have been horribly expensive to manufacture.
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Old 15th Mar 2018, 8:56 pm   #5
dazzlevision
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Default Re: GEC 2541 transistor radio

Yes, it is an interesting radio and probably the last one of it's like to be made by GEC in the UK, rather like its contemporary, the UK made Murphy "Overlander" (in a white cabinet) model B845, which didn't have a built-in mains operation facility, only two SW bands and fewer other features.

I have an example of the Japanese made Bush VTR178, which is similar to the GEC 2451 and was sold around the same time. It too is not designed and constructed to be "service engineer friendly".
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Old 16th Mar 2018, 1:25 am   #6
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Default Re: GEC 2541 transistor radio

That's a very nice, smart set. I must admit to being rather fond of radios from this period. I like the way the ad refers to 'a special zener diode' - wow, the technology!
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Old 16th Mar 2018, 10:41 am   #7
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Default Re: GEC 2541 transistor radio

That looks a really amazing radio, and must have been a top of the range model when it was new.
I own an earlier and more humble G817 which uses the same double sided pcb as found in all GEC televisions of this age.
Does your model use the later silicon transistors or were they still using the AF*** transistors
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Old 16th Mar 2018, 1:27 pm   #8
dazzlevision
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Default Re: GEC 2541 transistor radio

Hello Simon,

The GEC 2541/Sobell 1541 use Silicon transistors (most of which are Mullard "Lockfit" types), apart from four Germanium AC1xx devices in the audio driver and output stages.

Dave
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Old 16th Mar 2018, 1:34 pm   #9
dazzlevision
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Default Re: GEC 2541 transistor radio

I mentioned that I have two of these radios. Today, I fired up the one I've had for some time, but not a squeak could I get out of it!

The good old "hum finger" test on the top end of the volume pot produced no output from the speaker (which was OK).

I then measured the mid-point voltage of the complimentary output pair, which should be around mid-rail, but was only a few hundred millivolts.

Remembering that I had "tin whiskers" problems with an AC1xx type in a Philips N4308 tape recorder not long ago, I gently tapped (in turn) the three AC1xx types mounted on the small heatsink. When I tapped one, the set sprang back into life! So, another Germanium AC1xx audio device has been found to rival the AF11x tin whiskers phenomenon.
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Old 17th Mar 2018, 9:00 pm   #10
dazzlevision
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Default Re: GEC 2541 transistor radio

After replacing the “tin whiskered” AC187 in the audio output stage, I thought I’d check and replace (as a matter of course), the elderly electrolytic capacitors present on the IF/audio PCB, of which there are several. Some are the classic blue sleeved Philips/Mullard type, there are a couple of the notorious black “Callins”, one “Sprague” WT metal cased axial and four orange “SWT” plastic cased radial types (I presume SWT = Sprague WT).

I found that one of the Sprague SWT radial types (C92, 200uF/10V) would register a reading of 2.5 Ohms on my DMM whilst it was part way through charging up! It decouples the zener diode stabilised 5V rail that supplies the RF and IF stages. So, worth checking the electrolytics.

After fitting replacements, I thought I’d check VR62, the 220 Ohm horizontal skeleton preset pot that sets the working point of the output stage. It measured 1000 Ohms, so I replaced it and readjusted.
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Old 21st Jul 2018, 12:46 am   #11
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Default Re: GEC 2541 transistor radio

That is a solidly built chassis!
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Old 22nd Jul 2018, 11:36 pm   #12
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Default Re: GEC 2541 transistor radio

A nice set and a very thorough overhaul, well done for persevering!
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