grundig: 7063WF/3D; Musikschrank

ID: 160082
grundig: 7063WF/3D; Musikschrank 
06.Mar.08 07:05
0

Tom Ragan (USA)
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I'm restoring this model and could use your help.

I've replaced paper and electrolytic capacitors and tested all tubes but I'm still having two key problems.

1.  When tuning the AM broadcast band, signals whistle and oscillate.  Fine tuning sometimes clears it up, but adjusting the treble control which moves a ferrite rod into (an IF coil?) usually does the trick.  What might be wrong here?

2.  The FM band is distorted, even with an external antena connected, through most of the dial but is clear on one or two strong stations.  Is it just in need of a tuning? 

Thank you for any help you can provide.

 

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 2
IF oscillation? 
07.Mar.08 07:19

Thomas Albrecht (USA)
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Thomas Albrecht

Hi Tom,

Although I'm not as familiar with the details of these European radios as some of the other folks here, since no one has answered yet, I'll try to help you out.

The behavior you are describing on AM (whistles and oscillation) could be caused by oscillation in the IF stage.  I'm not familiar with the treble control configuration you are mentioning, nor can I see evidence of an adjustable core associated with the treble control on the schematic.  Nonetheless, such a configuration could be possible, since sharpening the IF bandwidth is actually a very intelligent way to trade off selectivity vs. treble response (bandwidth and fidelity).  If your radio really has such a device (to adjust a core in the IF with the treble control) it would make sense that moving the core would affect the tendency of the IF to oscillate.

There are a number of things which can cause the IF to oscillate, and this problem can be frustrating to track down.  Here are some things to look for:

1.  Poor ground connections in the RF or IF circuitry.  Look for connections to the chassis using rivets or screws.  Try cleaning, tightening, or hardwiring with soldered connections to connect the various ground points together.  Double check for any bad solder connections.

2.  Missing or bad bypass capacitors.  Check connections and values of capacitors which have one side grounded.

3.  Neutralization problems.  This radio has circuitry for neutralization of the IF stage.  See for example the two capacitors in series (10 nF and 8 nF) on the screen grid of the EF89.  Make sure those capacitors are both good and have proper value.

4.  Changes in component size, shape, or lead dress from the original.  If you've changed the wiring layout or location of components, try putting things back more in line with the way things were originally.

If all else fails, slightly detuning one of the cores in one of the AM IF transformers will lower the gain of the IF stage enough to stop the oscillation.  This will hurt the selectivity and sensitivity of the radio a little, but may be an acceptable compromise.

Your problem on FM could be one of the following:

1.  Bad ratio detector electrolytic capacitor.  This is the 10 uF capacitor shown just to the left of the EABC80 tube on the schematic.  Sometimes this capacitor is located inside the IF transformer housing, so you might have overlooked it when recapping.  If it's inside the can and difficult to get to, study the connections to see if you can add another 10 uF cap outside the can (ignoring the bad one inside).  Best case is if you can get to and replace the original cap.

2.  Alignment.  There are no alignment instructions for this radio here, so I would hesitate to monkey with this unless you're experienced with it.  After you've dealt with #1 above, if you still have distortion, one simple alignment step that sometimes helps, and won't get things too messed up is to adjust the secondary slug of the FM demodulator.  This should be one of the two cores on the second FM IF transformer (the transformer closest to the EABC80 tube).  I don't know whether this particular radio has the AM and FM IF transformers in a single can, or has separate cans.  If they're together, a little trial and error can identify which coils are for AM and which are for FM.  But there is risk of getting things misadjusted if you are unlucky.  If you think you can identify the secondary core of the FM demodulator, go ahead and adjust it to see if your distortion improves.  If adjusting it doesn't cure the problem, a more extensive alignment would be needed, and it would help to have alignment instructions from the manufacturer.

Best regards,

Tom 

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 3
 
07.Mar.08 09:33

Martin Renz (D)
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Martin Renz

Hi Tom,
You can find the alignment instructions for this radio here.
The 3035WF uses the same chassis.

Best regards,
Martin

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 4
No Answer? 
07.Mar.08 10:21

Hans M. Knoll (D)
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Hans M. Knoll

EDIT:   to Mr. Thomas Albrecht:

Zitat:   Although I'm not as familiar with the details of these European radios as some of the other folks here, since no one has answered yet, I'll try to help you out.

My answer:

first post from TOM RAGAN was at 06,03.08 7:05

second post (above) from Mr. Albrecht  was at 07.03.08 7:19 its one Day for us !

sometime whe have other (own) jobs to do.

regards, Knoll

Adresse praezisiert am 21.03.08  knoll

 

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 5
7063wf 
07.Mar.08 19:14

Tom Ragan (USA)
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Here's the moveable rod in question just below the banded resistor.  An interesting concept, this rod, which is connected by a cord attached to the treble control.  I've read other posts wherein the rod had a tendancy to stick if not used for awhile, easily resolved with scraping and some contact cleaner, in this radio it seemed to move with ease.

Thank you for all this great advice and I'll report back.

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 6
The 3-day rule and professional repair work 
21.Mar.08 20:06

Ernst Erb (CH)
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Ernst Erb

Back from a holiday I was confronted with this thread.

I would like to address two different topics:

1
Rule of 3 days waiting with an answer if a question can not be answered in a real professional manner.


I know that Thomas Albrecht is a very qualified person - and this as a human and as a professional in his job. Therefore this has nothing to do with him but with our principle which has probably not been addressed in English yet. Therefore I apologize that I come so late with this matter.

In the German speaking Forum we go so far that only about 75 editors can at all answer such questions posed to a model. The aim is to get real good answers because we also have the professionals who know how to deal with sophisticated radios which show some defects.

In the sections for other languages we have not introduced that only qualified editors may answer at all but I think we should introduce the rule that somebody answers only if he/she knows good answers - except there is no answer for 3 days. I hope that Thomas can enlarge and put into good English which is already linked to the forum main page as "Some examples of well done texts and help plus our forum rules." Perhaps some members write to him first what they would change or add?

I know that good cracks will not answer once guesswork has been started. Why should they?

2
Repairing/Restoring - "quick and dirty" or in a professional way?
This depends on the given set and/or on you and your goals. Everybody sees this question different therefore I can only split the readership by dealing with this question. It still has to be outspoken: The way depends first on your goals and your ability / sources.


a)
Quick and dirty: I know that often people just throw out the condensers and put in tubes which are reading "good" - and that's it. You can do so with simple sets if you only want to get them playing again and therefore this "quick and dirty" method is widespread. You even find it done here in Europe with more complicated radios from the 50ies - and therefore also many of those just working without their real quality reception ... That is the best case. the worst case is that you build in errors ...

Result: No learning process, a receiver which operates - often poor - sometimes not even that. Correcting this can be awful.

b)
The better way is to use one of the common techniques for error tracing which I have put together in the book "Radios von gestern" (in German). There are many good books on that in English and they are often found at auctions etc.

One of the techniques is to focus on the different stages like Power Supply, Power Amplifier, driver, second detection etc. The other is to use a Signal Tracer, doing more or less the same - especially if the set is not working at all. A third method is to listen to the problems and to work through the possibilities of causes until one has a good result. If possible then followed by an alignment.

If a set has been worked through without a solid method it can be hard to get it well again. A professional would rather help on an untouched set where the original development is still there. Many problems can arise by placing things differently or even changing grounding points.

c)
You can have professional help if you tell what you have done and what you can measure  (instruments and your ability). Such a helper has first to study the schematic (if possible) and do some other preparements if he wants to give a professional help for a sophisticated radio. Therefore don't expect an answer within 24 hours. In any case: Do use the link *** Please remind me *** or better "To activate e-mail notification for this board (or thread only)" to assure that you give an answer. Do tell if you will not be able to give an answer within short time.

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 7
3-day rule 
23.Mar.08 00:13

Thomas Albrecht (USA)
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Thomas Albrecht

Ernst,

Thanks for mentioning the 3-day rule, and also making a number of good points both for those seeking help and those wanting to provide help.  These guidelines are probably well known to the German-speaking community here, but perhaps not all of us English speakers had a clear understanding of this yet.

By mentioning that "I am not as familiar with the details of these European radios..." I hoped to leave the door open for one of the experts to followup with better information where appropriate.

Herr Knoll,

Sorry about not giving you enough time!  You are certainly one of the people I had in mind when I mentioned not being as familiar "as some of the other folks here" with the details of European radios (especially a Grundig!).

If you still are willing to provide some more expert advice than I was able to give, both Tom Ragan and I will very likely learn something useful for the future.  I often learn new things about German radios from your answers to technical questions.

Best regards to both of you,

Tom

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 8
Help on a GRUNDIG Radio 
27.Mar.08 15:10

Hans M. Knoll (D)
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Hans M. Knoll

Hello Grundig Friends.

Here is may Statement but only in German Language.

regards Hans M. Knoll

 

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 9
The quick and dirty method ... 
02.Apr.08 19:49

Rolf Nickel (D)
Articles: 240
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Rolf Nickel

... means cross-the-board replacement.

Dear friends of the Radiomuseum,

reference is made to the document of Herrn Knoll regarding Grundig radios, but his and my statements should be generally taken into account. So I thought it could be useful to publish my answer also in English language:
At first thank you very much, Herr Knoll. It was necessary to point this out. I still would like to complete your statements. The trend of cross-the-board replacement of components during restoration to reach a quick success, especially capacitors, which was watched by you is still actually observable.
This wrong because unsystematic approach must be changed into another one, namely the systematic way. That is to say concretely:
  • First of all the safety-relevant components must be inspected and replaced if necessary.
Of safety relevance are all those parts whose failure will cause immediately danger to the user or to the equipment itself.
Regarding a typical old radio this area is usually limited to the power supply and the AF-output stage/s which always should be observed at first "with the magnifying glass": that means by carefully checking of all values during operation.
In most cases one has already "won" then and may restrict to replacing only few parts, namely the "usually suspicious ones". These are in my opinion e. g. selenium rectifiers, canned electrolytic capacitors, high power resistors within the wiring path to the screen grid/s and the input stages and the cathode resistor/s of the output tube/s.
For all other (following) steps keep calm and be patient !
  • Regarding RF- and IF-stages one should replace or change nothing at all during the first maintenance period, as Herr Knoll advised.
Only if a component has really been identified as faulty, one may start work.
  • But at first it is necessary to record the original state by taking a photo or drawing a figure.
And: Never replace e. g. all kinds of capacitors from which you had heard that "they are always faulty". Do not change anything only because it seems "strange" to you ! Do not shorten e. g. connection wires because this would look "more elegant" in your eyes afterwards, or bend coils. Do not try to get progress by turning any alignment elements. Such a behaviour leaves the worst consequences regarding RF stages. Globally replacing of tubes should also be avoided. Check one by one with its comparison and this only in case of concrete suspicion. In most cases the tube is not the defective part!
  • Always replace only one single component at the moment and check after doing so whether it was really faulty or has contributed to the fault.
If yes, you may let it in place. If not, it is necessary to reinstall the original part exactly as found before. And after that you should continue searching step by step. Remember that also "cold" (bad) soldered connections, broken wires and oxidized contacts of switches or socket outlets can occur.
This method requires care, patience and personal discipline. But a damage without any possibility to come back on the right track can only be prevented by closely observation of these recommendations.

Best regards
Rolf

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