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Old 23rd Nov 2019, 9:50 am   #1
ValvoStef
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Default Grundig Model Number?

Morning peeps, a question for the Grundig experts on this forum. I have here a Grundig 3D Sound, missing rear panel, it has their serial number 1004573008. What is the model number? Surely, I can purchase the schematics from the data base. No indication on the chassis apart from the serial number. Audio is not working, probably a contact problem as the set was in an attic for many years. Anyone recognises this model?

Thanks for your help.

Stef.
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Old 23rd Nov 2019, 9:52 am   #2
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Default Re: Grinding Model Number?

I forgot to add the valve line-up: ECC85 ECH81 EF89 EABC80 EL84 EM34.
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Old 23rd Nov 2019, 9:57 am   #3
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Default Re: Grinding Model Number?

Looks like a 3028. Check the dial station names to see if it's a GB (British) model or a continental version. The GB model can be used on 240 volts - the others will be over run as the voltage selector only goes up to 220. The GB model should have stickers to indicate the voltage settings applied to the fuse block over the stamped in voltages on the fuse plate. The 3028 usually has the model number on the front like the 3D sound logo.
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Old 23rd Nov 2019, 10:01 am   #4
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Default Re: Grinding Model Number?

Hi vidjoman,

It is a British model, but no model number on the front.
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Old 23rd Nov 2019, 10:03 am   #5
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Default Re: Grinding Model Number?

I just looked up the model number vidjoman gave me, on RM it is described as Marlborough W3D
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Old 23rd Nov 2019, 10:13 am   #6
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Default Re: Grinding Model Number?

All sorted, now. I have the schematics downloaded from the database, thanks, vidjioman.
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Old 23rd Nov 2019, 10:15 am   #7
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Default Re: Grinding Model Number?

There were several versions of the circuit diagram when I was looking for them. Only slight differences.
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Old 23rd Nov 2019, 11:17 am   #8
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Default Re: Grundig Model Number?

It's a 3028 with the badge missing, I got one that I use with a pantry transmitter on FM. Excellent sound!
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Old 24th Nov 2019, 8:20 am   #9
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Default Re: Grundig Model Number?

Quote:
Originally Posted by plaka78 View Post
It's a 3028 with the badge missing, I got one that I use with a pantry transmitter on FM. Excellent sound!
Yes, quite surprised about that as well. In comparison with other sets, the output transformer is quite large in dimensions.
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Old 24th Nov 2019, 8:21 am   #10
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Default Re: Grundig Model Number?

Plaka78, you are right, the brass badge is missing.
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Old 24th Nov 2019, 8:23 am   #11
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Default Re: Grinding Model Number?

Quote:
Originally Posted by vidjoman View Post
There were several versions of the circuit diagram when I was looking for them. Only slight differences.
The one I downloaded has not the equaliser circuit. Apart from that it is ok.
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Old 24th Nov 2019, 10:44 am   #12
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Default Re: Grundig Model Number?

Are you sure the download doesn't show the wunschklang register. If this information is missing, so is the audio output stage, EABC AM/FM detector and pre amp plus the PU input switching.

https://www.service-data.com/section...3d-marlborough

Chris

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Old 24th Nov 2019, 10:52 am   #13
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Default Re: Grundig Model Number?

Thanks, Chris. The schematics I downloaded are different indeed. Thanks for the updated version, much appreciated.
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Old 24th Nov 2019, 11:38 am   #14
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Default Re: Grundig Model Number?

No worries Stef.

These are well designed expensive radios with a sound quality way above almost all domestically produced radios mostly because the speakers are well engineered and the tone controls do not adversely affect the negative feedback path.

A BBC report on a UK produced set was particularly critical of the way engineers had arranged the tone control circuit. Nothing changed because of it. What's new!!

Watch out for the EABC80 anode coupling capacitor C58 which I would change. When leaking, it will cause the output valve EL84 to draw excessive current never mind the distortion. Be generous in choosing capacitor operating voltages as the HT rail will be quite high until the valves warm up. 350vdc would be my choice.

When changing it or other components, be careful as component wires are wrapped on the soldered post of the tag strip. If in doubt, snip the wires of the old component and make good the new connnections.

Note that FM de-emphasis is not correct for the UK. Depepending on the issue date, C47 cpuld be 200pf or 1000pf. It should be 4700pf or 4.7nF. Then the tone controls when set at mid point will give you as near as dammit a flat FM response.

Also note the mains dropper resistor mounted above the mains selector panel. It gets very hot and easy to touch.

There are many threads and repair details on the web including the tuning clutch adjustment, if needed, which is simple but can be difficult to master.

Good luck

Chris
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