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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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5th Oct 2017, 4:19 pm | #21 |
Dekatron
Join Date: Nov 2003
Location: Heckmondwike, West Yorkshire, UK.
Posts: 9,637
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Re: Grundig Concert Boy 1100
Which component are you interested in?
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5th Oct 2017, 4:31 pm | #22 |
Triode
Join Date: Sep 2017
Location: Tavistock, Devon, UK.
Posts: 32
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Re: Grundig Concert Boy 1100
Thanks!
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7th Oct 2017, 5:14 pm | #23 |
Triode
Join Date: Sep 2017
Location: Tavistock, Devon, UK.
Posts: 32
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Re: Grundig Concert Boy 1100
Hi Bill, resevoir capacitors. I've just got hold of one for each set. Now I just need to find a day to do the work...
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9th Oct 2017, 3:42 pm | #24 |
Triode
Join Date: Sep 2017
Location: Tavistock, Devon, UK.
Posts: 32
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Re: Grundig Concert Boy 1100
Broke out the tools and my old Weller TCP, and set about replacing the resevoir capacitor on the black-case set. Leon's instructions worked perfectly, many thanks.
Result: no effect. Still faint signals and some hum. Fitted replacement antenna while I had a think. Realised I could put together some D cells if I raided the Maglites, so tried that. Then switched it to battery! Same faint signals without hum. Short rectifier pulling voltage down? All I can think of for the moment. EDIT: mains circuit does appear to be completely isolated when in Battery mode... I'm tempted to disconnect the back of the good set and tag it on, to see if a known good supply fires it up, but I'm also a little leery of ending up with two dead sets...further edit...fault probably on main board somewhere - if PSU id fully isolated on batteries, then substituting the known good PSU won't make any difference either. I'll get there! Last edited by DCBassman; 9th Oct 2017 at 4:04 pm. |
9th Oct 2017, 4:09 pm | #25 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,787
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Re: Grundig Concert Boy 1100
Just use the batteries.
You can eliminate anything pulling down the supply line by measuring the current. Quiescent current should be well under 20mA. Have you given the wavechange switch contacts a thorough clean? |
9th Oct 2017, 4:45 pm | #26 |
Triode
Join Date: Sep 2017
Location: Tavistock, Devon, UK.
Posts: 32
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Re: Grundig Concert Boy 1100
Actually, no. Meant to do that. Out with the Servisol...
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9th Oct 2017, 5:01 pm | #27 |
Triode
Join Date: Sep 2017
Location: Tavistock, Devon, UK.
Posts: 32
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Re: Grundig Concert Boy 1100
Instant result. Working well on mains and battery. Thank you Paul!
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9th Oct 2017, 5:16 pm | #28 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,787
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Re: Grundig Concert Boy 1100
Always the first thing to try.
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9th Oct 2017, 5:20 pm | #29 |
Octode
Join Date: Nov 2005
Location: Surrey, UK.
Posts: 1,869
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Re: Grundig Concert Boy 1100
Good result. The switches on these sets have lots of contacts, many wired in series. For example there could be 3 or 4 switches involved in connecting an AM section of the tuning gang to the coil it's trying to tune - so there are lots of possibilities for crackles and bad contacts.
These switches seem to respond well to being used after a dose of Servisol, so it's worth exercising the AM and particularly the SW switches a few times. The "gram" switch also benefits, although it has comparatively few contacts. If the set sounds good on FM when mains powered, the quiescent current is probably not too far off. If you have limited measuring equipment, I could measure the total supply current on my set (quiescent current recently adjusted) when battery powered on FM at minimum volume, to give you a guide as to whether your set is miles out or not. Leon. |
9th Oct 2017, 5:38 pm | #30 |
Triode
Join Date: Sep 2017
Location: Tavistock, Devon, UK.
Posts: 32
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Re: Grundig Concert Boy 1100
Will actually go over both sets in a more thorough fashion - I'd guess this might be why Woody is not so hot on AM. Certainly worth a go!
In fact, I think the resurrected one sounds the better of the two - really thumping bass, had to turn it down somewhat! |
9th Oct 2017, 8:12 pm | #31 |
Triode
Join Date: Sep 2017
Location: Tavistock, Devon, UK.
Posts: 32
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Re: Grundig Concert Boy 1100
Went into the Woody and gave it a spray. Not a great improvement, but some. There's nothing but motorboating on SW, and AM is definitely needing work. The ressurected one is much better across the board, although all the AM bands are badly affected by electrical noise here. Dwellings are such electrically dirty places these days! Fluorescents, switch-mode power supplies, etc etc. Will take it out onto Dartmoor next week (house and dog-sitting) and see how it does in the wild!
Will really need to invest in a good set of new D cells also. |
9th Oct 2017, 11:00 pm | #32 |
Pentode
Join Date: Oct 2005
Location: Harlow, Essex, UK.
Posts: 162
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Re: Grundig Concert Boy 1100
Hi, there is a pcb at right angles to the main board with several solder connections joining them. These joints can fail so it's worth while re-flowing them with a small amount of fresh solder. Also the bridge rectifier can give problems so replace this with four suitable diodes. I have two of these and even though the radios worked the sound improved greatly when the rectifier was changed. Mike
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9th Oct 2017, 11:57 pm | #33 |
Octode
Join Date: Sep 2017
Location: Bristol, UK.
Posts: 1,642
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Re: Grundig Concert Boy 1100
"..there is a pcb at right angles to the main board with several solder connections joining them."
I've come across problems with this type of connection with adjacent circuit boards - just close physical proximity, and use solder to bridge the gap! Always worth checking the tracks for good continuity. I always used to bridge the gap with scraps of wire soldered to each adjacent track. Whatever happened to that "old-time" advice - "never rely on solder alone for a connection, make sure there is a sound physical electrical connection first, then "seal" it with solder"? |
10th Oct 2017, 8:48 am | #34 |
Triode
Join Date: Sep 2017
Location: Tavistock, Devon, UK.
Posts: 32
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Re: Grundig Concert Boy 1100
Yes, I've been giving the right-angled connections some thought already, particularly for Woody. That may be the source of the 'no AM' fault as the spray didn't miraculously fix it!
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10th Oct 2017, 9:53 am | #35 |
Octode
Join Date: Nov 2005
Location: Surrey, UK.
Posts: 1,869
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Re: Grundig Concert Boy 1100
For general information, I've measured the current drawn from the battery terminals of this set when fed from an accurate 9V external power supply. FM was selected and the volume set to minimum.
Using an AVO Model 8, the current draw settles at about 27 mA, there being some change as the output transistors warm up. This set has previously had the quiescent current set accurately according to Grundig's published service sheet (in German). Leon. One characteristic of these sets when set to an AM band is high oscillator radiation. A look at the circuit shows that the oscillator output is fed to a coil on the ferrite rod to achieve mixing with the incoming signal. You could exploit this by using your second set (or any other suitable AM set) to detect the oscillator radiation from the set under investigation. The oscillator runs high and the AM IF is 460 kHz, meaning that if you tune your suspect set to a quiet spot at the low frequency end of the MW band, the oscillator will be receivable on a second set towards the high frequency end of the same band. (Tuned frequency + 460 kHz). I tried this test and it works well. |
11th Oct 2017, 10:36 am | #36 | |
Triode
Join Date: Sep 2017
Location: Tavistock, Devon, UK.
Posts: 32
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Re: Grundig Concert Boy 1100
Quote:
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12th Oct 2017, 9:10 pm | #37 |
Triode
Join Date: Sep 2017
Location: Tavistock, Devon, UK.
Posts: 32
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Re: Grundig Concert Boy 1100
Now out on western Dartmoor. It's relatively free of electrical noise, and has enabled me to confirm all AM bands as working. Once evening came, there were a few stations on the K1band and quite a few more on K2. Both benefitted from augmentation with a Sony AN-71 long wire. Medium and Long waves were much clearer than in the centre of Tavistock.
I have myself a good set, when all I expected was a scrapper for parts! Just needs a handle to be complete... |
12th Oct 2017, 11:14 pm | #38 |
Octode
Join Date: Nov 2005
Location: Surrey, UK.
Posts: 1,869
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Re: Grundig Concert Boy 1100
If you can trim the RF front end, the AM performance will almost certainly improve. I wonder if the ferrite rod permeability changes with age.
Don't risk getting the set hopelessly out of alignment, but if you feel confident setting it up, preferably with a generator, you will find the AM to be good - better than a contemporary Hacker. Anyway, glad they both now work. Leon. |
12th Oct 2017, 11:52 pm | #39 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,787
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Re: Grundig Concert Boy 1100
Grundigs of that era perform pretty well. They weren't cheap when they were new.
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13th Oct 2017, 11:41 am | #40 |
Triode
Join Date: Sep 2017
Location: Tavistock, Devon, UK.
Posts: 32
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Re: Grundig Concert Boy 1100
Oh, indeed! You just looked at them and thought, "Ooh, I bet that sounds good!"
I'm going to leave well alone, I think. It will be mostly used on FM anyway, and its performance there is nothing short of that oft-misused word, awesome! If I can get near some test equipment in the future, I might be tempted to align them both, but it's likely to be years, if ever, that i have the space to do that. Next month, I'll be out here on Dartmoor again, and I'll bring out the other one to see if the AM has improved, as I intend to really have a good go at the switching before then, as well as check out the connections between the PCBs. If I'm really lucky, it will also work well. |