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Success Stories If you have successfully repaired or restored a piece of equipment, why not write up what you did and post details here. Particularly if it was interesting, unusual or challenging. PLEASE DO NOT POST REQUESTS FOR HELP HERE! |
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28th Mar 2012, 10:00 pm | #1 |
Nonode
Join Date: May 2005
Location: Godalming, Surrey, UK.
Posts: 2,593
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1956 Grundig 3028/GB Marlborough AM/FM table radio
Hello again,
This Grundig 3028/GB is the GB version of my Grundig 3028 Hi-Fi Zauberklang German radio which appeared as a Success Story some time ago. It is more or less identical to the Grundig 3028/W/3D GB model as well which is covered by a R&TVS service sheet available here .... http://www.service-data.com/section.php/3423/1 I have a scrap 3028/W/3D set here and the only obvious differences that I spotted between the two GB models were different badges and knob colours. Both have a 240 volt AC mains option, the 3028/W/3D has a German transformer with a 220 volt tapping with an 82 ohm 10w wirewound resistor added to drop the voltage from 240 volts, the transformer in the 3028/GB has a 240 volt tapping. The 3028/GB arrived for restoration in good cosmetic condition and working but was lacking gain on all wavebands. It had been worked on previously as it had a complement of five replacement Colomor valves probably of Eastern European or Russian origin, only an original Mullard EM34 remained and that was quite dim. It was surprisingly straightforward to restore this chassis, after the usual cleaning of valve pins/sockets, pots and waveband switches with DeoxiT switch cleaner, fitting a new 3 core mains lead and the replacement of all its tubular capacitors the radio worked well, its magic eye was replaced with a NOS Cossor EM34 and that opened and closed correctly. The cord driving the revolving ferrite aerial was slack and had been rejoined in two places so that was replaced. There was one problem remaining though, as the set warmed up there was a periodic drop in gain which then corrected itself, but when fully warmed up the drop in gain remained. As the valves weren't that old I had assumed that they were all good but that wasn't the case, I swapped the Colomor EL84 with a well used Mullard EL84 which I knew worked OK and the problem ceased. It would seem that the Colomor EL84 had developed an internal leakage causing HT to drop. HT then checked out fine and critical resistors were tested and they too were good. A couple of electrolytics were tested and were fine but a 10uf tubular crossover capacitor mounted on the output transformer was leaky so that was replaced. The cosmetic restoration took longer to do. The cabinet was completely dismantled including the removal of all three loudspeakers and baffles. The wooden case which had a few minor dinks, scratches and fading was cleaned with a 50/50 mix of linseed oil and pure turpentine and that worked wonders. The trims around the front and side loudspeaker grilles were just polished with Brasso but the varnish on the tarnished badges and knobs was cleaned off with fine wire wool, polished with Brasso, cleaned in cellulose thinners and then revarnished with Rustins metal lacquer. The strips of sponge behind the centre front brass bar and under the main loudspeaker had turned to dust so that was all replaced with brown draught excluder, and the rubber band which links the tone control indicators was reinstated using a single strand of white knicker elastic. The set was then reassembled and the cabinet given several coats of polish. Finally, AM RF realignment was performed, LW and SW were a touch out but not by much. Sensitivity is very good on MW and SW but LW is not quite as good, a feature also noticed with the 3028 Zauberklang. FM is spot on and needed no realignment. These are rather nice big mid 1950s German AM/FM radios and this one looks and sounds superb. Amongst all the AM/FM radios that I have restored over the years only the SABA Schwarzwald AM/FM radio clearly outshone the Grundig 3028s, but then SABAs are even more expensive. Howard Last edited by howard; 28th Mar 2012 at 10:11 pm. |
28th Mar 2012, 10:09 pm | #2 |
Dekatron
Join Date: Jan 2005
Location: Oxford, UK.
Posts: 17,820
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Re: 1956 Grundig 3028/GB Marlborough AM/FM table radio
Nice work as always, Howard.
You've inspired me to bring one of my huge German sets forward in the "to do" pile. Nick. |
28th Mar 2012, 10:23 pm | #3 |
Octode
Join Date: Jul 2011
Location: Stockport, Greater Manchester
Posts: 1,208
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Re: 1956 Grundig 3028/GB Marlborough AM/FM table radio
Good job as usual Howard, you make it sound so easy!!
I have one of these and although I French polished the cabinet I didn't change all the caps I should have done (!!!) so it doesn't yet work as well as it could... Robert |
28th Mar 2012, 11:19 pm | #4 |
Nonode
Join Date: May 2005
Location: Godalming, Surrey, UK.
Posts: 2,593
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Re: 1956 Grundig 3028/GB Marlborough AM/FM table radio
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28th Mar 2012, 11:49 pm | #5 | |
Nonode
Join Date: May 2005
Location: Godalming, Surrey, UK.
Posts: 2,593
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Re: 1956 Grundig 3028/GB Marlborough AM/FM table radio
Quote:
It did in fact take 5 days to restore this set but these days I do work at a leisurely pace. Much of the work can be done with the chassis in the cabinet as there is plenty of room inside and most of the tubular capacitors are accessible via the hole underneath, Once the chassis is out of its cabinet then it gets tricky as its very heavy and unwieldy. The original tubular capacitors were leaky in both 3028s so do replace any remaining in yours. This 3028/GB has only had one owner from new and has been well looked after so the cabinet arrived in good undamaged condition and didn't need stripping and revarnishing. One thing to watch out for on the Grundig 3028s is chunks of print missing from the dial above the two large knobs, because 3 inch strips of sellotape were stuck on the back of the dial there which eventually lift off and can take the print off with them. Both restored 3028s here luckily are OK, the scrap one however has a poor dial. Howard |
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29th Mar 2012, 10:05 am | #6 |
Octode
Join Date: Jul 2011
Location: Stockport, Greater Manchester
Posts: 1,208
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Re: 1956 Grundig 3028/GB Marlborough AM/FM table radio
Thanks for the advice Howard!
Robert |
29th Mar 2012, 5:27 pm | #7 |
Tetrode
Join Date: May 2008
Location: Bristol, UK.
Posts: 86
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Re: 1956 Grundig 3028/GB Marlborough AM/FM table radio
Hi Howard
I have one of these radios & the sound is very good. It feels the whole room up. I bought it by chance. I was in a local second hand shop & was buying a Marconiphone T62DA when the assistant was surprised at my interest in old radios. He was standing in for the usual owner. After buying the Marconiphone he said he had an old valve radio & would I be interested. It was in his loft. When I got to his house that evening he already had it ready & powered up. Alas it was silent. We agreed a price & it was mine. All that was wrong was a wire off the speaker. This was about 10 years ago. I use to use it at least once a week, but it is now upstairs. As the radio is untouched I should change the capacitors as when I switch it off it gives off a load click ( a bit like HT crack) Regards Keith
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9th Apr 2012, 11:51 am | #8 |
Triode
Join Date: Jan 2009
Location: Newcastle upon Tyne, Tyne and Wear, UK.
Posts: 41
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Re: 1956 Grundig 3028/GB Marlborough AM/FM table radio
Hi Howard, good work as always, this is making me want one of these - I've resisted so far due to the sheer size of the set, but perhaps we can make an exception!
Out of interest, what are the dimensions of this set, I'd just like to know so I can see if it will fit in the space I have in mind for it. Cheers Angus. |
9th Apr 2012, 3:14 pm | #9 |
Rest in Peace
Join Date: Oct 2006
Location: North Wiltshire, UK.
Posts: 638
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Re: 1956 Grundig 3028/GB Marlborough AM/FM table radio
Another superb job as usual Howard. Sean had one of those in the "to be done" pile in my workshop but decided to sell it instead! Nice radio.
Ian |
10th Apr 2012, 11:18 pm | #10 | |
Nonode
Join Date: May 2005
Location: Godalming, Surrey, UK.
Posts: 2,593
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Re: 1956 Grundig 3028/GB Marlborough AM/FM table radio
Quote:
It is a big radio, 24 inches wide, 14 inches high and just over 9 inches deep. If you can get one in the house then look out for one, they turn up on Ebay occasionally for usually well under £100. Past Times Radio sold a very nice example recently in the same sort of cosmetic condition as this one and fully overhauled for £240 ! Regards ..... Howard |
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10th Apr 2012, 11:28 pm | #11 | |
Nonode
Join Date: May 2005
Location: Godalming, Surrey, UK.
Posts: 2,593
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Re: 1956 Grundig 3028/GB Marlborough AM/FM table radio
Quote:
Regards ......... Howard |
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11th Apr 2012, 7:46 am | #12 |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,548
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Re: 1956 Grundig 3028/GB Marlborough AM/FM table radio
The Wima capacitors of that type are a 'change on sight' component. Even in the 60's they were failing s/c and were an engineers nightmare! We used to get lots of Grundig tape recorders come in which were full of these things and coupling capacitors were nearly always going short. It didn't do the poor old ECC83's any good at all!
Note that modern day Wima capacitors are every bit as good as any other polyester. Rich.
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11th Apr 2012, 7:47 pm | #13 | ||
Tetrode
Join Date: May 2008
Location: Bristol, UK.
Posts: 86
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Re: 1956 Grundig 3028/GB Marlborough AM/FM table radio
Quote:
Will do soon Regards Keith
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