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Pulled out my 37-650 tonight - Printable Version

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RE: Pulled out my 37-650 tonight - hsusmann - 12-29-2013

Well, I got looking again on the finish on this radio
and I believe it's been painted!

I can chip off small flakes on the edges of where
the bare spots are.

At least the chassis seems to be in pretty good shape.

The only thing that will give me some headaches
is one of the broadcast band coils is all messed up
by someone in the past poking around in there
and tearing through the windings.

Will have to be re-wound. I hope someone
here knows about how many turns should
go on.

When I get the coil out I can give more details
on which coil it is etc...

Shouldn't be a big deal if I can find out the
number of turns to put back on.

Worked more on it tonight and got the
IF strip and audio section working.

I can inject a 470 kHz AM modulated signal
into the front of the IF strip and it comes out
clean at the speaker!

Herb S.
Ithaca NY

RE: Pulled out my 37-650 tonight - Ron Ramirez - 12-30-2013

Regarding photos: The Phorum 101 section is your friend. Too many people never see this important Phorum section because you have to scroll down all the way to the bottom of the Phorum homepage to find it. (Hmmm, maybe I should put it at the top and move the regular discussion forums to the bottom...naah, then people would think the Phorum has gone out of business.) Icon_rolleyes

Anyway...please follow these links:
http://www.philcoradio.com/phorum/showthread.php?tid=29
http://www.philcoradio.com/phorum/showthread.php?tid=4371

Adding photos to a post is not difficult at all!

Finally, to answer one of your questions: No, the grille cloth you have is not original. Get some of Kenny Richmond's chevron cloth put in that cabinet...once you refinish it, that is...

RE: Pulled out my 37-650 tonight - Joe Rossi - 12-30-2013

Herb, I'm hoping this comes through. This is what a restored 37-650 cabinet looks like. I am not sure of the photo attribution...Joe

RE: Pulled out my 37-650 tonight - hsusmann - 12-31-2013

Joe,

Wow! It is sure nice looking! I did find some similar
pictures online.

Mine needs alot of work then...

UPDATE:

Just hooked up the RF chassis tonight
(separate on the bench with long wires) and
the radio works on all bands!

I'm pretty sure the messed up coil is the
Broadcast Antenna Coil which is probably
the best one to be messed up if one has to be...

Can anyone give me a 2 cent description of how
the shadow meter is supposed to work? I get
no deflection of the internal vane. I assume I
am supposed to get this??

Now to find the right rubber bushings to re-mount
the RF chassis into the main chassis...

Herb S.

RE: Pulled out my 37-650 tonight - BrendaAnnD - 12-31-2013

You can find your bushings at renovatedradios.com

Yes, you should get deflection on the vane. Depending upon the particular radio, there may be a resistor across the shadow meter, and the meter could be open. Alternatively, the vane could be frozen (more like sticking), I've had good luck using a small spritz of Liquid Wrench on the vane itself to free it up. A third possibility is that the magnet may have lost gauss, and need to be remagnetized.

RE: Pulled out my 37-650 tonight - hsusmann - 12-31-2013

BrendaAnnD:

OK, thanks for the info. I have not even ohmed out the shadow meter coil yet so I guess that's the first step.

I am a little unsure if I got the coil wires put back in the right way.
I don't know if polarity matters or not but am suspecting that it
does matter so that may also be my problem.

Now to tackle the Broadcast Band antenna coil. One of the
windings is destroyed, any idea where I could find out how
many turns it should have?

Thanks!

Herb S.

RE: Pulled out my 37-650 tonight - hsusmann - 01-05-2014

Update on the 37-650 Restoration:

I finally took out the Broadcast Band antenna coil and
it turns out that the messed up coil was the primary winding
which only had about 30 turns of wire on it. The secondary
was all good (had hundreds of turns).

I used some #32 magnet wire and got it all re-wound, and put back.
I now get MUCH better reception on the broadcast band!

Also, I read up on the shadow meter and discovered that one can slide the coil forwards or backwards to set the shadow offset. (I have the "New style" shadow meter).

So, I tweeked that and now the shadow meter is working much much better also.

Final step is to order a set of rubber bushings for the RF chassis and I think that will about do it for the electronic restoration.

Now to tackle that horrible cabinet!

Herb S.
Ithaca NY

RE: Pulled out my 37-650 tonight - hsusmann - 01-05-2014

One final question regarding my 37-650:

I noticed that the two 6F6 output tubes are wired in what I consider a strange way. They don't have a separate phase splitter, they seem to be using one of the 6F6's screen grid to generate the 180 degree out of phase drive to the other 6F6's grid.

They use a 3500 ohm dropping resistor to the first 6F6's screen and then
AC couple that screen to the grid of the second 6F6. The second 6F6's screen is tied directly to the screen voltage line.

Kind of a clever trick I guess, I just never have seen this in any book
before, even the books from the 30's and 40's.

Does anyone have any info on this technique?

Certainly saves either an extra tube or another audio transformer...

Thanks,

Herb S.
Ithaca NY

RE: Pulled out my 37-650 tonight - codefox1 - 01-05-2014

Phase splitter works OK this way PROVIDED the tubes are OK and pretty closely matched, and did save a stage. So long as all the caps and carbons are replaced, leave it be.

RE: Pulled out my 37-650 tonight - hsusmann - 01-06-2014

OK on the advice. I have already re-capped the whole radio and changed most of the old resistors as well (most were quite high).

I will check the transconductance of both 6F6's to make sure they are close.

The radio sounds good but it would be nice to know that my push-pull stage is really functioning as a push-pull stage!

Herb S.

RE: Pulled out my 37-650 tonight - Eric T - 01-10-2014

My $0.02 on the cabinet:

I'm like you. Decent on the 'tron wrangling, but not so much on the wood-working. Since the cabinet seems to be in poor shape, I'd take it on as a learning project without a second thought. You can't mess it up much worse than it is unless you set it on fire or drop it out the second story window. I'd be willing to bet you have a whole new feeling about it once you carefully get rid of that horrid paint job and see the bare wood.

RE: Pulled out my 37-650 tonight - Jamie - 01-11-2014

That cabinet might not be in as bad as shape as you think. You won't know for sure until you get it stripped. Mine looked a lot worse than it turned out to be and now I am proud to display it. One thing for sure, when you get it up and running, they are good sounding and playing radios. It will be well worth the effort.

Here are some photos of mine..

   

Before..

   

After.. It will be a big job, but you will end up with a beautiful radio.

RE: Pulled out my 37-650 tonight - hsusmann - 01-11-2014

Thanks for the words of encouragement!

The radio is all working electronically, sounds very good.
The speaker is shot but I'm working on a couple options for that.

I'd like to learn how to recone them myself, from what
I've seen on youtube it doesn't look that difficult.

I am going to wait until spring to try to work on the cabinet.

Too confined a space to work in here, much better if I can
do it outside once the weather warms up.

Herb S.
Ithaca NY