GRUNOW LIVES!

8/26/2009 8:11:05 PMScott Tracey

Dancing a jig...fist pumps...smiling at the tunes!
After serious work on this Grunow 752 and help from this forum, my hope for life in the chassis has been realized.
The coil rewinding of secondary oscillation and tickler and then the SW coil on the detector coil has been worthwhile....as well as capping etc.
Need some advice on this issue: SW bands are performing well but BC band is fading out from about 1120 and up. What would be your thoughts on likely cause? I have not done anything with alignment yet.

8/27/2009 12:36:01 AMWarren

Good going Scott, glad you had the stick-to-it-ness bringing the Grunow back to life. If the dial is tracking right, it's just a matter of a little tweaking on the overall alignment. That sounds like all it needs.

8/28/2009 8:41:03 AMScott Tracey

:Good going Scott, glad you had the stick-to-it-ness bringing the Grunow back to life. If the dial is tracking right, it's just a matter of a little tweaking on the overall alignment. That sounds like all it needs.
:
Thanks Warren....Well sometimes things aren't as easy as they might seem. After thinking about this issue I decided that I would try reversing the terminal connections on the tickler coil. Did so and then the full BC band came in loud and clear however the shortwave reception suffered badly. So I pulled coil and rewound tickler going a bit higher on the secondary coil with the same number of windings (10). Now the SW reception is improved but lost the highend of BC from about 1150 and up. Any thoughts on this would be appreciated. I am not sure what is happening so am unsure what next step should be.

8/28/2009 8:56:20 AMWarren

I guess it's just a matter of playing around with the coils until you get the best performance out of it. That seems to be a well tuned circuit. A lot of thought went into making that kind of design.

8/28/2009 4:14:24 PMEdd

Sir Scott. . . .

Most honnable apologies, for the delay. . . .seems that I had enhanced + marked up the last photo and then “forgotted” where I had stored it.

Initially, I had to consult the schematic to see where the heck that “Bi-selector” buzz word fit in, and then seeing it being associated with the plate
circuitry of the RF amp tube.

It also seems to be an almost carbon copy of your previous oscillator coil with the additional fact that they are dealing with frequencies that are within
175 Khz of each other. With a difference in the respect of the inter phasing aspect of the tertiary, wanting a NON oscillative condition in the RF stage, while
wanting an oscillative state in the local oscillator position.

Also, this coil seems to be almost dripping with a wax over coating, unless that is very thick varnish ?

I also am not seeing a great voltage difference between the different coils, with the SWB and BCB windings isolated at every end circuit path with a
capacitor, which would block DC voltage flow. Also with the miniscule RF power involved, there is certainly no possibility of a “blue” RF arc over.

The last thought would be a possible skewed outer rotor leaf on the RF section of the tuning condenser, thus shorting out for a portion of the tuning coverage, and getting closer to a grounded winding to arc over to.
BUT your mentioning of the ABOVE 1120 cleared that up.

Will you review my mark ups added to your coil photo, it’s up to the degree of enhancement that I think that I can make out the tertiary winding having
in the order of 12 +/-2 turns. But I am unable to confirm its winding direction.

As per the other SWB and BCB resonating windings, with the use of a directional reference, of one then facing the open end of the coil form.

Don’t I see the SWB winding having its start winding being routed up from coil terminal #2 inside the coil form and coming out of the wire lashing porthole at
[BLACK numeral reference 2] and starting on a CCW wind at [BLACK numeral reference 1] of some ~ 20 turns and then ending at 1 of 2 hollow star rivets placed in the existent space between SWB and BCB windings. That winding ends at a hollow star rivet and its companion, which are wire jumpered, and they connect down to coil terminal 5. The companion rivet is connected to the Start / finish of the BCB coil . . . .and the over-covering precludes me from making out its winding direction . . . . but I suspicion that BCB winding to be in a CW direction with it then ending at the very open end of the coil form and being routed down to terminal #4.

I do note that you are now getting into the general order of the common procedure of assigning coil terminals in the like manner of tube pin connections.

That is being in the respect of viewing from the bottom, referencing to an index, and then assigning designators clockwise.

I truly think that this coils windings were in such good condition that you were able to replicate any windings perfectly, turn wise as well direction of winding (phase).
With just consideration in now going back to the oscillator coil where you initially was suggestive of the tertiary winding consisting of as few as 5 turns but your having placed on more turns, (~10 ?) and now, the possibility of even more turns being involved.

I think that you were able to positively ascertain the BCB and SWB windings turns count on that oscillator coil as well as their direction. The probable cause of the
the current situation is relevant to the number of turns placed on that tertiary winding, with it possibly still being on the short side.

The other aspect is the tertiary winding, with it sitting atop the edge of the BCB coil, it is going to be getting maximum capacitive as well as inductive coupling to the BCB coil.

As far as the SWB coil coupling, it being spaced apart, as it is, is going to skimp on the capacitive coupling aspect. Now I did mention the unknown factor of your not being able to positively ascertain the initial winding direction of that tertiary winding. With the then option of making correction of a miss winding direction by the switching of the tertiary coils start and finish wire ends, thus initiating a phase reversal.

Now here is one possible quirk in that aspect, say that the working connective procedure ended up with the circuit oscillating with the winding end of the tertiary portion ending up with the plate connected end being over nearer the center of the BCB, rather than it ending up being connected so that the plate connection end is closer to the SWB coil.

Now looking into the overall scheme of those possibilities you would want a tertiary winding with a closer count to the one on the RF coil, and then you try the winding to see if it oscillates and then evaluate performance on SWB and BCB. You then pull that winding and rewind in an opposite direction and make the same evaluation.

I suspicion that the optimal result will be with the tertiary windings end, associative to the osc plate connection, ending up being being the closest to the adjunct SWB winding.

Thassit. . . .feed back ?

73's de Edd

BLOW-UP OF R.F.COIL FORM Info:

8/29/2009 10:42:23 AMScott Tracey(78307:78294)

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:Sir Scott. . . .
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:Most honnable apologies, for the delay. . . .seems that I had enhanced + marked up the last photo and then “forgotted” where I had stored it.
:THANKS FOR GETTING BACK TO ME. EXCELLENT SUMMARY AND GOOD HELP ON UNDERSTANDING THIS ISSUE.
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:Initially, I had to consult the schematic to see where the heck that “Bi-selector” buzz word fit in, and then seeing it being associated with the plate
:circuitry of the RF amp tube.
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:
:It also seems to be an almost carbon copy of your previous oscillator coil with the additional fact that they are dealing with frequencies that are within
:175 Khz of each other. With a difference in the respect of the inter phasing aspect of the tertiary, wanting a NON oscillative condition in the RF stage, while
:wanting an oscillative state in the local oscillator position.
:
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:Also, this coil seems to be almost dripping with a wax over coating, unless that is very thick varnish ?
:THIS COIL LIKE THE OSC COIL HAD A MICA SLEEVE UNDER TERTIARY WINDING AND WAX OVER.NOT TOO THICK THOUGH.
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: I also am not seeing a great voltage difference between the different coils, with the SWB and BCB windings isolated at every end circuit path with a
:capacitor, which would block DC voltage flow. Also with the miniscule RF power involved, there is certainly no possibility of a “blue” RF arc over.
:
:
:The last thought would be a possible skewed outer rotor leaf on the RF section of the tuning condenser, thus shorting out for a portion of the tuning coverage, and getting closer to a grounded winding to arc over to.
:BUT your mentioning of the ABOVE 1120 cleared that up.
:TUNING CONDENSER IN GREAT SHAPE.
:
:Will you review my mark ups added to your coil photo, it’s up to the degree of enhancement that I think that I can make out the tertiary winding having
:in the order of 12 +/-2 turns. But I am unable to confirm its winding direction.

:THE WINDING COUNT WAS 22 AND CCW.
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:As per the other SWB and BCB resonating windings, with the use of a directional reference, of one then facing the open end of the coil form.
:
:
:Don’t I see the SWB winding having its start winding being routed up from coil terminal #2 inside the coil form and coming out of the wire lashing porthole at
:[BLACK numeral reference 2] and starting on a CCW wind at [BLACK numeral reference 1] of some ~ 20 turns and then ending at 1 of 2 hollow star rivets placed in the existent space between SWB and BCB windings. That winding ends at a hollow star rivet and its companion, which are wire jumpered, and they connect down to coil terminal 5. The companion rivet is connected to the Start / finish of the BCB coil . . . .and the over-covering precludes me from making out its winding direction . . . . but I suspicion that BCB winding to be in a CW direction with it then ending at the very open end of the coil form and being routed down to terminal #4.
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:
:
:I do note that you are now getting into the general order of the common procedure of assigning coil terminals in the like manner of tube pin connections.
:
:
:That is being in the respect of viewing from the bottom, referencing to an index, and then assigning designators clockwise.
:
:
:
:I truly think that this coils windings were in such good condition that you were able to replicate any windings perfectly, turn wise as well direction of winding (phase).
YES THIS IS CORRECT.
:With just consideration in now going back to the oscillator coil where you initially was suggestive of the tertiary winding consisting of as few as 5 turns but your having placed on more turns, (~10 ?) and now, the possibility of even more turns being involved.
:WOUND 10 TURNS BUT LAST NIGHT WENT BACK TO FRAGMENTS OF ORIGINAL WINDINGS AND MEASURED EACH PIECE. TOTAL WAS APPROX. 23". THAT SHOULD EQUATE TO ABOUT 6 TURNS. I INITIALLY REPLACED THE MICA SLEEVE WITH AN OLD PHOTO NEGATIVE CUT TO SIZE AND ADDED A SCOTCH TAPE OVERLAY, HOPING TO APPROXIMATE THE MICA DIAMETER.
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:I think that you were able to positively ascertain the BCB and SWB windings turns count on that oscillator coil as well as their direction. The probable cause of the
:the current situation is relevant to the number of turns placed on that tertiary winding, with it possibly still being on the short side.

:QUESTION: THE ORIGINAL TERTIARY WINDING WAS COVERED WITH WAX. I DID NOT DO THIS ON THE REWIND. WILL THIS AFFECT THE CAPACITANCE/INDUCTANCE? ALSO IF THERE ARE TOO MANY WINDINGS WILL THIS EXTRA INDUCTANCE CAUSE THE LOSS OF HIGH END BC SIGNAL?
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:The other aspect is the tertiary winding, with it sitting atop the edge of the BCB coil, it is going to be getting maximum capacitive as well as inductive coupling to the BCB coil.
:
:
:As far as the SWB coil coupling, it being spaced apart, as it is, is going to skimp on the capacitive coupling aspect. Now I did mention the unknown factor of your not being able to positively ascertain the initial winding direction of that tertiary winding. With the then option of making correction of a miss winding direction by the switching of the tertiary coils start and finish wire ends, thus initiating a phase reversal.
:UNDER CONSIDERATION AND TESTING.
:
:Now here is one possible quirk in that aspect, say that the working connective procedure ended up with the circuit oscillating with the winding end of the tertiary portion ending up with the plate connected end being over nearer the center of the BCB, rather than it ending up being connected so that the plate connection end is closer to the SWB coil.
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:
:
:Now looking into the overall scheme of those possibilities you would want a tertiary winding with a closer count to the one on the RF coil, and then you try the winding to see if it oscillates and then evaluate performance on SWB and BCB. You then pull that winding and rewind in an opposite direction and make the same evaluation.
:GOOD INFO...WILL INCORPORATE INTO TESTING AS NECESSARY.
:
:I suspicion that the optimal result will be with the tertiary windings end, associative to the osc plate connection, ending up being being the closest to the adjunct SWB winding.
:THAT WOULD BE TERMINAL 1...OK GOT THAT POSSIBILITY UNDERSTOOD.
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:Thassit. . . .feed back ?
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:THANKS AGAIN EDD. I LISTED FEEDBACK (IN CAPS) UNDER YOUR PARAGRAPHED NOTES AS NEEDED.
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:73's de Edd
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BLOW-UP OF R.F.COIL FORM Info:
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