Grundig Elite-Boy 500 maintenance manual in German - can anyone help?
 

I am looking to check the alignment of a Grundig Elite-Boy 500, and trying to do it "by the book". Unfortunately, the book (Grundig manual) is in technical German. I've come up against "uber 50kΩ Kabel" with reference to the "Sichtgeräteanschluß". I think the second refers generically to a display device - so, say oscilloscope. What would a "50kΩ Kabel" be (I've worked out that "Kabel" means "cable, but "50kΩ Kabel"...?

Copy of instructions attached - in case anyone can bear to look at them!.

Thanks to anyone who can help.

Mike

Re: Grundig maintenance manual in German - can anyone help?
 

I'm no expert on using wobbulators (nor understanding German!) but isn't this about making connections using attenuation (50k) when carrying out FM-AM alignment checks? I've got some French versions of Grundig radio manuals from this era which I find easier to follow but I can't remember where they came from.

Alan

Re: Grundig maintenance manual in German - can anyone help?
 

Basically connect the wobbulator to MP5, monitor MP4 with a scope with greater than 50kohm impedance and adjust for symmetry. Sichtgerateanscluss is just 'test point'.

Re: Grundig maintenance manual in German - can anyone help?
 

FM-ZF (FM intermediate frequency)
The column "Abgleichreihenfolge" tells you which order to do things. Start at the top and work down."Ankopplung des Wobbelausganges" tells you where to connect the wobbulator for each step. "Sichtgerät" is a visualising device (like an oscilloscope) and "Anschluss" a connection. so Sichtgerätanschluss tells you how to connect the oscilloscope. "Abgleich" tells you how to adjust what.
Most adjustments are done with a fixed probe containing the circuit illustrated connected to MP6. For the discriminator adjustment it is connected to low-frequency (NF) input M11 via a 50kOhm cable.
Following the last column, do the following in sequence:
Detune a
Adjust b - h in the various steps for maximum and symmetry.
Adjust a for symmetry keeping the signal small so that there is no limiting in the IF section.

Re: Grundig maintenance manual in German - can anyone help?
 

Thanks for the responses - all very helpful. I was really puzzled by the "uber 50kΩ Kabel" bit. After posting, I realised that it possibly just referred to the input impedance of the measuring equipment, rather than the characteristic of the connecting lead ("50kΩ lead" seems a funny way to say "50kΩ input impedance). So, good to have that confirmed. If I'm not successful with the "Grundig method", I'll try the two-resistors-across-C526 method. I have an FM generator arriving soon, so I'll be able to get on with it.

Mike

Re: Grundig maintenance manual in German - can anyone help?
 

Stuart.

You have got it. Yes it is obvious that the technical terms of German of these days sound a bit strange to today's ears. Even to me, given the fact German is my mother language.

The term "Sichtgeraet" originates from early days of RADAR equipment describing the unit where signals became visible.

Regards, Joe

Re: Grundig maintenance manual in German - can anyone help?
 

Years ago I got confused by the term Sperrkreis which occurred in the alignment instructions of a Mende radio. A "blocking circuit"? Nowadays I suppose it would be called "ein Filter".

Re: Grundig maintenance manual in German - can anyone help?
 

A little lateral thinking is required here. In essence all Grundig Radios of this era use a similar front end and IF strip. This can be seen when looking at the schematics for Melody Boy, Elite Boy and so on. The Service Manuals are though also in German. Should you also include Yacht Boy 208, hey presto the manual is in English. Simples

Chris
PS Just why do you need to re align the set, I have never come across a Grundig radio which need the IF realigning, and that includes the likes of 2038's even the front end is close to spot on.

Re: Grundig maintenance manual in German - can anyone help?
 

Chris

It's just the ratio detector I'm really focused on at the moment. The set has intrusive sibillance and a bit of distortion on the audio output. This seems to be characteristic of a ratio detector problem. I have already replaced the stabilising capacitor, and checked the germanium diodes. Tried a couple of shottkys in their place, which hardly worked at all. In the process of doing that, I had to tweak the ratio-detector transformer, so I want to get it back spot on. It's difficult as I've had to remove the overall screening box for the IF section, so I'm getting very bad am breakthrough on FM, but getting the box off was such an appalling business, that I don't want to replace it until the problem is fixed. And, those old PCBs will only take so much removal/replacement.

Mike

Re: Grundig maintenance manual in German - can anyone help?
 

In the second paragraph (Einstellung der NF-Gegentaktendstufe), you are instructed to replace the link to the collector of AC188k by a milliammeter, (remove at point -x-) and (with the supply voltage set at 9V), adjust the quiescent current using R410 (500Ω) to 6.5mA. . After adjustment, re-solder the link.

The third paragraph (Einstellung des ZF-Verstärkers) instructs you to adjust the collector current of T/V using R515 so that a voltage of 1.35V appears across the emitter resistor R518.

"Sperr(en)" has caused problems for translators who do not understand the technology in the interval before newly-coined technical terms reach the technical dictionaries. In the 1980's we used to get copies of newly-published german-language patents at work, accompanied by english-language abstracts produced by a commercial abstracting service that used freelance translators who I knew were expected to cope with pretty well any electrical or mechanical subject matter (I used to be a part-time one myself to profitably pass the 2 hours spent commuting every day). We were puzzled as to why circuits that were clearly producing DC were described as "Blocking Oscillators". The original german word "Sperrwandler" did not appear in any of the technical dictionaries, and the translators, doing their best, evidently knew that one meaning of "Sperren" was "to block", while a meaning of "Wandler" was "Oscillator", and while they must have heard of "Blocking oscillators", possibly didn't appreciate that the circuits in question were definitely not those. A colleague phoned a contact at Philips who explained that they were "flyback convertors", "Sperr" signifying that the conversion took place in response to the turning-off of a switching element, and another meaning of "Wandler" was "transformer" or "convertor ".

Re: Grundig maintenance manual in German - can anyone help?
 

Having worked for a Blaupunkt dealer for 23 years, I know a little Technical German, at least as it was between 1971 and 1995, and, IIRC, the phrase 'Einstellung des ZF Verstarkers' should refer to the I.F. stages (ZF = zwischenkreis = Intermediate frequency), but I stand to be corrected!

Re: Grundig maintenance manual in German - can anyone help?
 

ZF = ZwischenFrequenz ;)

Re: Grundig maintenance manual in German - can anyone help?
 

Hi Mike

There are quite a few posts on this site the subject of sibilance which I guess you are familiar with.

They included replacing the capacitor across the diodes.

Also noted is multipath distortion and so using a better aerial before delving in too deeply which I too have forgotten to do before now.

You mentioned slight audio distortion and I just wonder if this could be exacerbating the problem given the high frequency lift the loudness circuit gives to the amp.

Unless already done, feed the DIN in/out with a known good source.

Lastly, I forgot to mention that the Yach Boy Service Manual is available via Electrotanya.

Chris

Re: Grundig maintenance manual in German - can anyone help?
 

If you have problems with AF breakthrough, one method of adjustment involves getting a little DC brush type motor and connecting it to a battery. Move as far away as to keep noise fairly low, then adjust the final core to minimise the impulsive interference.
I don't know off hand where or not there is a resistive "twiddle pot" in the diode part, but if so, you can then play with that for optimum, bringing the motor closer if required to improve on the minimum noise, even having a repeat twiddle of both the core and the resistive pot.
I think that method is outlined in one of the NordMende manuals, possibly a Globetrotter.
Les.

Re: Grundig maintenance manual in German - can anyone help?
 

Thanks all for very useful comments. I don't think it's an RF signal problem - I have other radios that work OK in exactly the same places without any distortion. But I probably should think about Simpsons' point on the audio amp - I have been assuming that it isn't the problem (it doesn't really "sound" like that), but maybe I should check this.

MotorBikeLes - thanks - though I'm probably not going to be able to minimise the af breakthrough until I can get the screening can back on the IF board, and to do that I need to be sure that I'm not going to have to rip it off again to check something else inside.

I haven't got too much time for this repair for a short time - too much other work coming in to give it more than occasional thought. But I'll update when I can get more hands-on again.

Mike

Re: Grundig maintenance manual in German - can anyone help?
 

One of those "occasional thoughts". Just looked at the Yacht Boy 208 Trader service sheet (thanks for the suggestion Simpsons), and it's no better. It gives the following instruction -

"Connect ...oscilloscope to point 8 IF4 via a 50k ohm lead..."

So obviously Grundig themselves (or Trader, if they did it) weren't any good at translating their German into technically meaningful English! That is, unless they're talking about something other than the scope's/VTVM's input impedance...

Mike

Re: Grundig maintenance manual in German - can anyone help?
 

Mike, the reason why a 50k ohm lead is specified is so that the discriminator response is not impacted by the capacitance of the cable.

I've looked through a number of Grundig Service Manuals and it common practice to specify this. I can only assume that a German service engineer would recognise this instruction from his formal training and apprenticeship.

UK radio and TV Service Manual instructions often include placing a resistor and small capacitor in series with the sweep generator and scope lead when aligning IF transformers.

With SAW's to define the TV IF response and adjustment free IC demodulation circuits now the norm for both radio's and TV's, "old school" basics can easily be forgotten.

Re: Grundig maintenance manual in German - can anyone help?
 

Thanks. So is the 50k ohm lead just a coaxial with a 50kΩ resistor somewhere in series (or parallel?), or is it the 2x100kΩ grounded resistors plus OA70 set-up shown in the service sheet under "Alignment"?

Please excuse my ignorance on this - I do very little radio-frequency work.

Mike

Re: Grundig maintenance manual in German - can anyone help?
 

Mike, no worries

We're all here helping eachother get our heads around what is needed to be done.

The Service Manual says that for IF adjustment the "loose capacity" circuit is required at points 5,3 & 2 adjusting for symetry. If you havent altered these transformers leave alone, just make sure by fine tuning the wobbulator that the display is symetrical.

For the discriminator adjustment, solder a 50k ohm resistor in series with the scope coaxial inner cable to point MP11, which is the audio output, for best AM rejection on the discriminator transformer (a).

Personally, if using a scope and wobulator is unfamiliar to you, tuning in the radio to a programme and then with interference from a motor, for example, adjusting the core for minimum interference should be more than accurate.

Alternatively retract the aerial or find a weak station and adjust for minimum noise.

I would solder an earth wire onto the screening can and place it over the transformer BEFORE making any adjustments as its removal will affect the coil's tuning.


Chris

Re: Grundig maintenance manual in German - can anyone help?
 

Thanks Chris, that is really helpful advice, and you've captured all of my questions in one fell swoop!. I have only done any minor tweaking on the ratio detector transformer (the rest are still as factory aligned) when I tried different diodes. So can I assume that I could re-align this for symmetry and minimum AM with a 10.7 Mc/s amplitude modulated sine into the RD transformer? I will be getting hold of an FM generator soon, so if frequency modulation is needed for the adjustment I could leave it until then. Thanks for the tip about refitting the screening before doing this. Thanks again!

Mike