RCA Victor 9-X-572

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RCA Victor 9-X-572

Post by tuberadiogeek on Sun Mar 08, 2015 8:41 am

I was able to snag one of these nice AA5's for 25.00 about a week ago. It's all original and it surprisingly played really well. I plugged in my DBT to be certain the filter caps were not totally shot. The only issues with it physically is one of the grille rings is slightly cracked, which I could of done transporting it. Also the lady was apparently a heavy smoker. I got caps for it the same time I got caps for my Zenith. I'm in the middle of doing the 3 filter caps and i'm having a bit of difficulty locating the last cap wire and where to ground them to. The schematic is located in Rider's Perpetual, Volume 20. I changed the two 120 mfd caps, they got replaced with 100's. The 40 is the one I didn't touch yet, that will get replaced with a 47. I'd get photo's up, but I had to get a new SD card reader and i'm waiting for it to arrive. Any help would be greatly appreciated. Thanks. A link to a photo for reference: http://www.smsnoveltiques.com/images/tn-rca-gold.jpg
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Re: RCA Victor 9-X-572

Post by Bill Cahill on Sun Mar 08, 2015 8:46 am

You will get some power supply hum out of it. You need to be as close to the original value as you can.. Twenty mics down each is pretty low....

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Re: RCA Victor 9-X-572

Post by tuberadiogeek on Sun Mar 08, 2015 8:53 am

Well, that was the closest value I could get. I ordered caps from Sal and that is what he had. I didn't want to go too high in value. If I get too much hum, I can always change them to closer values later, as they will be easy to change.
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Re: RCA Victor 9-X-572

Post by Wildcat445 on Sun Mar 08, 2015 11:44 am

Sal has a 120uf @ 450 volts, radial, available. Like Bill said, 20 mics down on that set may cause some hum to remain. Or you could parallel two 68's. Good luck.

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Re: RCA Victor 9-X-572

Post by Bill Cahill on Sun Mar 08, 2015 3:54 pm

Even 120 at 450v is fine.

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Re: RCA Victor 9-X-572

Post by 75X11 on Sun Mar 08, 2015 4:22 pm

As long as the grille is complete, you could remove it and repair the cracking with super glue, smooth the area and give it a fresh coat of gold paint. The only difficulty is matching the original color.
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Re: RCA Victor 9-X-572

Post by Wildcat445 on Mon Mar 09, 2015 3:20 am

Windex takes off smoke scum and is cheap.

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Re: RCA Victor 9-X-572

Post by tuberadiogeek on Mon Mar 09, 2015 4:03 am

I'll keep that in mind when I go to clean the cabinet. I want to recap it first. It's just been a bit too cool in my basement the past week to do much down there. Once I finish the filter caps, it should be an easy project. That sucker has over bright red wax caps. Since I bought small radial caps i'm probably going to have to use the leads from the old caps so they reach. Next time i'm going to get axial caps.
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Re: RCA Victor 9-X-572

Post by tuberadiogeek on Tue Mar 17, 2015 4:33 pm

I finally got the filters changed, but now it won't pull in any stations. I plugged into my DBT at first and it stayed dim, which is good. I'll snap a photo for you guys to look at to make sure I didn't screw anything up. It will be a few before I go back down there.
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Re: RCA Victor 9-X-572

Post by Wildcat445 on Tue Mar 17, 2015 5:08 pm

I think I would start by taking some voltage measurements. B+ at the rectifier cathode, B+ after the first filter cap and second filter cap. The output tube plate and screen. Touch your finger to the center terminal of the volume control and see if it hums. I'll bet one of those would tell you something. Recheck wiring per the schematic and go from there.

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Re: RCA Victor 9-X-572

Post by tuberadiogeek on Tue Mar 17, 2015 7:09 pm

As far as voltages, I'm getting 118 at the rectifier, First cap 5, second cap 100. I forgot to measure at the 50L6. I touched a meter lead to the volume control and it hummed quite loudly. I checked all my connections to the schematic and they all look good. I even re-secured my filter caps ground lead. I looked on the Riders manual to see if it gave voltages, but it does not. So, I do not know the correct voltages since they are not listed.


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Re: RCA Victor 9-X-572

Post by jerryhawthorne on Tue Mar 17, 2015 7:56 pm

Well, the voltages look reasonable and with the loud hum the audio section is working well. I'm guessing you e-cap replacement was just fine. Seeings how it worked before, what else might you have changed? Perhaps some of the "waxies"? Double check that. Do you have a signal generator?
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Re: RCA Victor 9-X-572

Post by tuberadiogeek on Tue Mar 17, 2015 8:02 pm

I haven't touched anything else. I may of damaged some of the wax caps with my iron while poking around to solder in the filters. No signal generator, but I did make an audio injector I seen in another thread on here. Using a 3.5 mm plug, a capacitor and some leads. I haven't used it yet. I'm guessing I would inject a signal into one of the pins of the 50L6?
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Re: RCA Victor 9-X-572

Post by tuberadiogeek on Tue Mar 17, 2015 9:45 pm

I made a mistake and connected the grounds to the chassis instead of the insulated ground. All my voltages are correct except C16B. It should be 89 volts, but less than 1 volt. Apparently there are voltages listed, I just overlooked them due to small writing.
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Re: RCA Victor 9-X-572

Post by jerryhawthorne on Wed Mar 18, 2015 12:14 am

Is it working now? It would be nice if at the start of the post you would put a link to the schematic if you wish help. I did not see one.
Jerry
http://www.nostalgiaair.org/PagesByModel/389/M0015389.pdf

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Re: RCA Victor 9-X-572

Post by tuberadiogeek on Wed Mar 18, 2015 1:47 am

Still not working correctly. I have not messed with it any more. I'm still only getting less than 1 volt where I should have 89. I totally forgot to post a link to the Riders manual.
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Re: RCA Victor 9-X-572

Post by jerryhawthorne on Wed Mar 18, 2015 2:30 am

OK, if your not getting any significant voltage off of C14 look closely at the schematic. Either the resistor that feeds the voltage from the output transformer is open or the tap that feeds it has problems. Perhaps wiring?
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Re: RCA Victor 9-X-572

Post by tuberadiogeek on Wed Mar 18, 2015 2:34 am

Its not C14, its C16B. The center cap in the photo.
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Re: RCA Victor 9-X-572

Post by Wildcat445 on Wed Mar 18, 2015 3:50 am

Delete. Sorry for the intrusion.

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Re: RCA Victor 9-X-572

Post by Bill Cahill on Wed Mar 18, 2015 2:18 pm

llooks like you may have a filter wired wrong.
Positive should go to positive. Negative should go to B-. Looks like you connected it to the plate of the output tube.
Second picture.
Where have you got it connected??

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Re: RCA Victor 9-X-572

Post by jerryhawthorne on Wed Mar 18, 2015 10:13 pm

Sorry but with my comment I should have said C16B. No voltage there? Not rocket science, follow the schematic. These are the easiest of problems to solve. Check the wiring and follow the flow of B+. One resistor to get voltage to the cap and a winding of the output transformer. Go for it. Laughing

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Re: RCA Victor 9-X-572

Post by Bill Cahill on Wed Mar 18, 2015 10:44 pm

The negative doesn't go to the transformer. It goes to B-.

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Re: RCA Victor 9-X-572

Post by Bill Cahill on Wed Mar 18, 2015 10:45 pm

Hold it. Let me see the schematic.
Got a link??

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Re: RCA Victor 9-X-572

Post by 75X11 on Thu Mar 19, 2015 12:24 am

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Re: RCA Victor 9-X-572

Post by Bill Cahill on Thu Mar 19, 2015 11:29 am

Hey. I have that radio! Restored it many years ago............
You have a replacement transformer. RCA used cloth wiring, and, it was a three wire primary because it was tapped for resistance for filters. I believe you put the negative end of one main filter on the plate of the output tube, instead of B-. Both negative ends go to B-, which is not the chassis.
I wonder what convergence work was done to finnish power supply at the transformer.

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Re: RCA Victor 9-X-572

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