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RCA Victor 29k

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Post by Ben Delk on Thu Dec 13, 2012 12:32 pm

scratch Yes sir it does. The sites you posted do shed a little light but darn if I can determine where to start. If it is a resistor then the yellow body should come into play as the 1st color then orange then violet then silver for tolerance. If it is a cap, does yellow come into play or just the colr before adding the stripes. There are some 470k ohm resistors in that area but this part does not match up with that color code, or least I don't see how.
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Post by Ben Delk on Thu Dec 13, 2012 1:02 pm

Stop the presses, I may have found a clue. I found this info on AngelFire. The Tubular Capcitor color codes, about 3/4 way down the page.
http://www.angelfire.com/electronic/funwithtubes/How_To-Reading_Codes.html#Capacitor_C_C-back

This would make it 430000pf 700V 100+degree.

Whatcha' think?
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Post by jerryhawthorne on Thu Dec 13, 2012 3:42 pm

Ben, you have not responded to Bill's comment as to hooking up the loop antenna. You will get all kinds of funny things happening, none of which will be radio reception without it. A long wire alone will not work. Did the hook up help any?

Jerry


Last edited by jerryhawthorne on Thu Dec 13, 2012 3:45 pm; edited 1 time in total (Reason for editing : added a bit)

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Post by Ben Delk on Thu Dec 13, 2012 3:46 pm

Somewhere in the blog I did repond but here it is again.
I connected the magic loop and connected my external to the "A" connection on the rear of the chassis. Did not help.

Thank,
Ben
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Post by Guest on Thu Dec 13, 2012 4:19 pm

+1 on connecting the loop antenna. I have had units completely inoperative due to just the variable cap for the antenna being maligned. Also the component on pin a. Have you checked it for resistance with 1 lead lifted? If I were sure (as possible) that the xfmr were the original and the rest of that circuit portion was unaltered and the component appeared to read as a cap, I would try the unit with a lead lifted. I would double check the area for continuity and resistance to make certain it matches the schematic.

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Post by Ben Delk on Thu Dec 13, 2012 4:31 pm

+1 on connecting the loop antenna. huh?
I haven't tried lifting one lead but I did the the resistance in place. Both IF's reading about 7ohms. As soon as I complete a bit more wire replacement I'm going to remove the IF's and check the inside for a bad cap, loose connects, cock roach, etc.... Also going to chip off the outside of this mystery cap or resistor and see if it has anything written ot stamped on it.
Thanks again
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Post by Guest on Thu Dec 13, 2012 5:00 pm

7 ohms is what the schematic specs for the windings, so at least you don't have shorted caps across them. That may reduce the necessity of removing the I.F. coils. You don't want to risk any handling damage on one.

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Post by Ben Delk on Thu Dec 13, 2012 5:17 pm

Good point....if it can happen and it shouldn't it will happen.
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Post by Dr. Radio on Thu Dec 13, 2012 8:35 pm

I'm probably wrong, but I still think it's a resistor....

To me they are using the old dog-bone style system on a more modern resistor.

Body End Dot configuration.

Body is yellow.

End is purple.

Dot (is actually the stripe "floating" in the middle of the body) is orange.

4 7 3

47,000 (47k)


Here's some pictures (scroll down):

http://www.vintage-radio.com/repair-restore-information/valve_resistors.html

http://www.antiqueradios.com/forums/viewtopic.php?f=12&t=170801



BUT since we can't say for sure that "thing" should even be in there, get rid of it.There is a 47k resistor close by on the schematic, but not "across" the first IF.


Make a note of where it is, remove it and move on Very Happy
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Post by Ben Delk on Fri Dec 14, 2012 8:33 am

The resistor on the right under the Old Resistor Coding is a good match for shape and color coding with the exception mine also has a tolerance band. But still this makes good sence. Since the radio is not producing any audible sound (not even static) but fluttering from the speaker at 3/4 volume, which I take as an over driven speaker. I'm not sure what removing the "resistor" will do but what the heck, until it picks up a station it is just a paper weight anyway.
I completed replacing all the funky old crumbling wire last night so that should eliminate possible wire shorting out of the equation. The new multicap electrolytic should be in today so I'll swap that out soon. The original top mount had 3 taps which one tap was bad and had already been replaced underneath. The other two are still reading good but we all know that means nothing.

Thanks Dr. Radio
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Post by Bill Cahill on Fri Dec 14, 2012 8:42 am

You can't go by capacitance readings for judging electrolytics as being good.
You must use peoper equipment to do that.
A DMM meter won't be proper, either....
I don't care how perfectly they appear to be working. There are no good antique electrolytics.
They are a ticking time bomb.
Ben, on something like this you need to do a complete proper job first. Then, you service the set. It's much easier than trying to find the problems around a bunch of troubles.
Bill Cahill

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Post by Ben Delk on Fri Dec 14, 2012 8:58 am

Correct you are sir. I had already replaced the electrolytics with new one and it made no change so I said I'll put it all back where I started and start from scratch. I know, putting the old electrolytic back in was a bonehead move. Hopefully the new cap will be in today. Hope you are feeling better today.
Thanks, Bill
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Post by Bill Cahill on Fri Dec 14, 2012 9:35 am

I'm fine agin, thank you.....
I'm not trying to be nasty. Iit is just wrong to go backwards.
And, I still can't stress enough that you restore first, then, service.
Alot of issues can be solved by doing it correctly.....
Bill Cahill

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Post by Ben Delk on Fri Dec 14, 2012 9:59 am

Thanks Bill and point well taken. It may be misguided thinking but as a novice my thinking was to get something more like sound out of it before attempting to rewire and replace everything. That way swapping out on component at a time and testing for a result would lessen the risk of a mistake. Perhaps this is flawed thinking but it made sence at the time. Sorry gentlemen if I have created undue or unwarranted research.

Blessings to all and have a happy hoilday season,
Ben
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Post by Guest on Fri Dec 14, 2012 10:31 am

It's just part of the learning process. You are finding out as we have, what works well in the process and what doesn't work so well and the only way to get that is to engage in the process and ask when needed.

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Post by Ben Delk on Fri Dec 14, 2012 10:44 am

At best I will get it working at some point or at worst make another paper weight for ebay. Sloooowly but surely I'm learning. Sometimes with excitement, often with disappointment but always trying. Heck who knows, when I've been doing this for 30 years I may remember which knob turns it on.
Thanks again to all.
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Post by Wildcat445 on Fri Dec 14, 2012 12:16 pm

Like Doc said, replace ALL electrolytic caps. Don't risk them being good, cause they ain't! Also recheck C31, the output filter cap. The "helicopter propeller" sound you are hearing is commonly called "motorboating". Often caused by an open, leaky, miswired output filter cap. The suggestion has been made to connect a i-pod or some such contraption to the phono input to test the audio section. You can also just use your finger or the end of your plugged-in soldering iron. Just touch one of the above to the center terminal of the volume control. A loud buzz confirms that all is well with the audio section. No buzz, you have found where to start looking.

Regards

WC

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Post by Ben Delk on Fri Dec 14, 2012 1:02 pm

Yeah I did connect another radio to the 29k phono input and I have sound for sure. At this point I'm waiting on parts to arrive and hope all of this will go away. Thanks for the info WC.

Ben
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Post by Ben Delk on Mon Dec 17, 2012 3:17 pm

Put the new electrolytics in this weekend and that stopped the motorboating sound. Connected the signal tracer starting at the antenna loop and I have reception thru the selector to the RF (6sg7) but stops there so back to the schematic to see what I can find. I got bored with no success on this radio so I put it back on the shelf until I'm in a better mood. Started rebuilding a Silvertone 7251. It is coming allong nicely.
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Post by Bill Cahill on Mon Dec 17, 2012 5:42 pm

NOthing wrong in taking time off. But, now that you know you have signal to the 6SQ7, it should be easy.
First, have you checked that tube?
If diodes are dead, radio can't detect the signal.
Second, what's your voltage on plate of that tube?
Didn't you say you had 0 volts on one of the diodes?
That's your det. section.
The diodes go to second I F transformer.
ARe you getting correct positive voltage on primary??

Seconday shouldn't have any positive voltage at all.
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Post by Ben Delk on Mon Dec 17, 2012 8:17 pm

Thanks Bill, I'll check those item when I put it back on the workbench. I have the new project (Silvertone 7251) in the refurb process. Bought it with the dial string already off so I'm trying to figure out how that goes on. Not as easy as it looks without a diagram.
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