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Old 18th Jan 2020, 11:52 pm   #21
Leon Crampin
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Default Re: Grundig Concertboy 1100

The 'speaker coupling capacitor is indeed 1000uF 10V.

If you let the smoothing capacitor fail dead short on our 250V (sometimes) mains, the selenium bridge rectifier may be damaged before the 400 mA fuse blows.

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Old 19th Jan 2020, 9:13 am   #22
rojosuiza
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Default Re: Grundig Concertboy 1100

Good to hear, that the radio runs again.

Something called 'Desolv-it' seems to be doing just thatů Some cleaners might even desolve the plastic itself...
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Old 19th Jan 2020, 10:48 am   #23
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Default Re: Grundig Concertboy 1100

Quote:
Originally Posted by Leon Crampin View Post
The 'speaker coupling capacitor is indeed 1000uF 10V.

If you let the smoothing capacitor fail dead short on our 250V (sometimes) mains, the selenium bridge rectifier may be damaged before the 400 mA fuse blows.

Leon.
Perhaps the one with the wooden front had the slenium rectifier? This one has a silicon rectifier.

Though this year at the rallies I'll be looking out for a woody grille 1100.
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Old 19th Jan 2020, 10:56 am   #24
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Default Re: Grundig Concertboy 1100

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Originally Posted by rojosuiza View Post
Good to hear, that the radio runs again.

Something called 'Desolv-it' seems to be doing just thatů Some cleaners might even desolve the plastic itself...
It jogs my memory that it's happened before. It seems a quick wipe is alright, but leaving it to soak around any thing which was printed or painted (however that badge was done) will dissolve the emblem.

As this is a concerning factor to consider when restoring vintage gear, I was doing some searching for a data sheet for this spray. It appears that this is a natural solvent.

Photo attached of the can.
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Old 19th Jan 2020, 12:09 pm   #25
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Default Re: Grundig Concertboy 1100

Foaming cleaner can remove some lettering on aluminium or plastic. I once damaged some text on a Technics cassette deck front panel that way. It's easy to get caught out, as most surfaces survive perfectly well.

You may be able to reconstruct the logo by printing it on a waterslide transfer.
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Old 19th Jan 2020, 1:21 pm   #26
Leon Crampin
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Default Re: Grundig Concertboy 1100

My black sets all have Se rectifiers, although different types are fitted and the board is drilled for at least 2 pin outs. One black ITT rectifier looks like a Si bridge, but is definitely Se.

If run within limits, Se rectifiers are usually OK, with the notable exception of devices made by AEG. These are definitely change on sight and have caused damage in many cases by their failure.

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Old 19th Jan 2020, 1:44 pm   #27
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Default Re: Grundig Concertboy 1100

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Originally Posted by paulsherwin View Post
Foaming cleaner can remove some lettering on aluminium or plastic. I once damaged some text on a Technics cassette deck front panel that way. It's easy to get caught out, as most surfaces survive perfectly well.

You may be able to reconstruct the logo by printing it on a waterslide transfer.
Where I haven't had any issues are on the aluminium strips (where the volume and tone controls are) where the lettering appears to be printed, perhaps it's an ink which can't be dissolved very well or not at all.

Hmmm, I'm going to have to restrict the use of this stuff to just 'casing' where there is no lettering at all. In the meanwhile it might be worth trying to find an alternative cleaner.
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Old 19th Jan 2020, 2:17 pm   #28
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Default Re: Grundig Concertboy 1100

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Originally Posted by Leon Crampin View Post
My black sets all have Se rectifiers, although different types are fitted and the board is drilled for at least 2 pin outs. One black ITT rectifier looks like a Si bridge, but is definitely Se.

If run within limits, Se rectifiers are usually OK, with the notable exception of devices made by AEG. These are definitely change on sight and have caused damage in many cases by their failure.

Leon.
There's a BU8-04 in mine, perhaps it was replaced in the past?
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Old 19th Jan 2020, 2:22 pm   #29
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Default Re: Grundig Concertboy 1100

That does look like a replacement, though it may be a factory mod introduced late in the production run.
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Old 19th Jan 2020, 3:41 pm   #30
Leon Crampin
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Default Re: Grundig Concertboy 1100

Definitely a replacement. The overrun capacitor on UK mains probably destroyed its predecessor. Check that the fuse is correctly rated at 400 mAT (delay).

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Old 19th Jan 2020, 4:55 pm   #31
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Default Re: Grundig Concertboy 1100

I'd better check that out.

I ought to get some contact adhesive tomorrow to put the aluminium strips back on.
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