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Post by Ben Delk on Wed Nov 21, 2012 7:51 pm

I have an RCA Victor 29k with a nice cabinet but the chassis....well not so nice. Rubber wire insulation cracked and falling apart. All tubes test good but had nothing but a low hiss from the speaker. I have replace the filter caps (10/450, 10/440, 20/25) and plenty of volume now but not picking up any station and the speaker has sound like helicopter blades spinning. I have replaced a few of the wires and was cautious to keep them against the chassis and in the same route.
I have checked the 1st and 2nd IF trnsfm and they are all between 7 and 8.4 ohms.

Cathode voltage should be around 19v, I have 23.5.

Heater voltage is 6.3

Both output 6k6gt tube plates voltages are about 250v and the grid 2 are 270v.

Any ideas on where to go from here is greatly appreciated.
http://www.nostalgiaair.org/PagesByModel/878/M0014878.pdf

Ben


Last edited by Ben Delk on Thu Nov 22, 2012 9:16 am; edited 2 times in total
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Post by Dr. Radio on Wed Nov 21, 2012 8:55 pm

Ben Delk wrote:I have an RCA Victor 29k with a nice cabinet but the chassis....well not so nice. Rubber wire insulation cracked and falling apart. All tubes test good but had nothing but a low hiss from the speaker. I have replace the filter caps (10/450, 10/440, 20/25) and plenty of volume now but not picking up any station and the speaker has sound like helicopter blades spinning. I have replaced a few of the wires and was cautious to keep them against the chassis and in the same route.
I have checked the 1st and 2nd IF trnsfm and they are all between 7 and 8.4 ohms.

Filament voltage should be around 19v, I have 23.5.

Both output 6k6gt tube plates voltages are about 250v and the grid 2 are 270v.

Any ideas on where to go from here is greatly appreciated.
http://www.nostalgiaair.org/PagesByModel/878/M0014878.pdf

Ben

Hi Ben,

Looks like you've got a fun project there Very Happy You gotta love the pre-war RCA's with the wonderful rubber wiring.

You wrote: Filament voltage should be around 19v, I have 23.5.

Huh???? Filament voltage is 6 volts, not 23.5....do you mean cathode voltage on the output tubes???


Couple things, are you sure the "range selector" (band switch) is in the correct position?

I would recommend you replace C35 and C37 right away. Well all wax caps should be replaced, but you don't want to trash your audio output transformer and related circuitry thanks to a shorted or leaky plate cap. C33 as well.

Couple of helpful hints on this radio....

You can check your AF (audio) circuits by turning your range selector to the "phono/television" position. Use a battery operated personal radio or walkman and feed audio into the jack. Use a .1 capacitor in series with the input to prevent walkman damage is there is stray DC leaking. If you hear music, you know your AF side is alive and kicking.

RCA cheated on transformers. The ones I've dealt with were supplied by GI (General Instruments), they are cheap and lack laminations. Running these sets on today's line voltages is not good, the power transformer with quickly get too hot. In my RCA 17k I installed a dropping resistor so even though my wall outlets provide around 120 volts, the radio only "sees" about 110 volts to keep the transformer cooler.

RCA loved to use those black "logenze" capacitors. Some people affectionately refer to them as "deer turd capacitors" Embarassed For the best results, I would replace them....all...after getting the basic operation of the radio in good order. These are like the micamold capacitors in other radios, not sealed well and tend to leak (electrically). Since they are used in tuned circuits, use dipped silver mica caps.

I also disassembled my IF cans on my 17k--guess what I found hiding inside? Capacitors! They weren't even sealed, just crudely made with the assemblies exposed to oxygen. I replaced those as well with dipped silver mica capacitors.

RCAs of this era are a LOT of work. You may also find several resistors have drifted high....but once they are rebuilt properly, and aligned, the sensitivity and sound is amazing. They are truly under-appreciated as everyone is fixated on the eye candy designs of round dial sets like Zeniths.
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Post by Ben Delk on Wed Nov 21, 2012 11:04 pm

My bad...been a long day. I have corrected the original blog. it is the Cathrode at 23.5. I'll look over the rest of your resonse and reply tomoorw. Thanks for your reply and correction.
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Post by Ben Delk on Thu Nov 22, 2012 12:23 pm

Man this thing is a mess. Each time a work around the wires to check something I have go back over and make sure no nake wires are touching anywhere. I hate scrapping a pretty cabinet but this chassis is a wreck and someone has matched parts out of who knows what into it. I like a challenge but this may be more time than it is worth. I have $25 in it and the speaker and magic loop antenna are worth more than that. Anyway, I'll press on a bit more.
The attached picture are what I'm taking you to mean by black losgenze or deer turd mica. Any idea what their values are. Each one is marked with a different # and I can find to RCA mica mold reference fore them. The schematic I downloaded from Nostalgia does not show a component placement or value for the caps or resistors list accept on the accural drawing. Another odd thing is R15, 16, 17 show 470M on the schematic but they are color coded 470k. Type-O?

. I have not tried the walkman to the phono jack yet since I don't have one. I need to round one up

I have replaced C35 and C37. I removed C33 and tested it , it was ok.

https://servimg.com/view/17421296/86
https://servimg.com/view/17421296/87


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Post by Dr. Radio on Fri Nov 23, 2012 10:04 pm

Ben Delk wrote:Man this thing is a mess. Each time a work around the wires to check something I have go back over and make sure no nake wires are touching anywhere. I hate scrapping a pretty cabinet but this chassis is a wreck and someone has matched parts out of who knows what into it. I like a challenge but this may be more time than it is worth. I have $25 in it and the speaker and magic loop antenna are worth more than that. Anyway, I'll press on a bit more.
The attached picture are what I'm taking you to mean by black losgenze or deer turd mica. Any idea what their values are. Each one is marked with a different # and I can find to RCA mica mold reference fore them. The schematic I downloaded from Nostalgia does not show a component placement or value for the caps or resistors list accept on the accural drawing. Another odd thing is R15, 16, 17 show 470M on the schematic but they are color coded 470k. Type-O?

. I have not tried the walkman to the phono jack yet since I don't have one. I need to round one up

I have replaced C35 and C37. I removed C33 and tested it , it was ok.

https://servimg.com/view/17421296/86
https://servimg.com/view/17421296/87



Ben-

Yup, those little black critters are RCA's version of micamold caps. The number printed on them is the literal value. So if it says "68" it is a 68 pF capacitor (that's picofarad--very small value).

The "M" question comes up every once and a while. Back in the OOOOOLD days, M was used instead of k (M=1000 in Roman numerals). So 470M is actually 470k (470,000 ohms). Had it been million, the diagram would have shown MEG. Later they went to K to avoid confusion.

If it gets to be too much, maybe keep your eye out for a junker chassis if the cabinet is good. They are a good playing radio, just a pain in the butt to reconstruct.

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Post by Ben Delk on Sat Nov 24, 2012 10:04 am

Ok that clears up a few questions. I'll get back on this a few days. My wife asked me to build her a sewing work station for her new sewing machine so that should keep be busy for 3 or 4 days while I order some new caps and such. Thanks for help.
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Post by Ben Delk on Wed Dec 05, 2012 3:27 pm

Well back to work on the 29k. Got the new caps in and started the replacing the losgenz caps with the new replacements last night. Still more to replace tonight. The replacement did slow down the flutter sound from the speaker but still can't bring in a station. I'll get back on it a little today before heading to church. I'm not sure if there are too many hours in a day or not enough. I have discovered we do have a battery operated radio I can use to test the AF curcuit I just need to conveince my wife I won't blow up her weather alert radio. Ha!
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Post by Ben Delk on Wed Dec 05, 2012 9:01 pm

Question gentlemen. I have not attempted repairs on a radio with push button and an automatic tuning selector on it. If I set the selector to manual tuning can I disconnect the wires from the push button assembly and set it aside. That thing just flops all over the place, a real pain.
http://www.nostalgiaair.org/PagesByModel/878/M0014878.pdf
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Post by Dr. Radio on Thu Dec 06, 2012 7:06 pm

Ben Delk wrote:Question gentlemen. I have not attempted repairs on a radio with push button and an automatic tuning selector on it. If I set the selector to manual tuning can I disconnect the wires from the push button assembly and set it aside. That thing just flops all over the place, a real pain.
http://www.nostalgiaair.org/PagesByModel/878/M0014878.pdf

Ben,

By all means, carefully remove the leads and remove the assembly. This system uses independent L/C tuners to home in on a particular station. Another word of warning Very Happy These RCA tuners are a pain in the but. The pushbutton assemblies need to really be worked and cleaned to get the contacts good enough to conduct, otherwise the system won't oscillate. Even my 17k doesn't always tune correctly until I "work" the buttons a number of times--it sits a lot and the internal switch contacts oxidize.
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Post by Ben Delk on Fri Dec 07, 2012 8:45 am

Good info, thanks. Picked up and old radio to connect to the phono input to test the AF. Hope to finish replacing the "logenze" caps tonight. Then try and straighten up lots of bogus looking solder joints that simply look tacked in and none of them with insulators on the legs.
Going one step (cap) at a time but no change. Still not bringing in stations but still have a flutter sound coming out of the speaker at about 3/4 volume.
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Post by Ben Delk on Sat Dec 08, 2012 5:51 pm

Removed the automatic tuning push button assembly and set the radio on manual tuning. Finished replacing caps last night, no change, still nothing but a flutter from the speaker at 3/4 volume. Checked the oldelectrolytic caps. Thye 2 10mfd are reading a little about 12mfd, the 20mfd around 18. I had replaced them all but put the old one back in just in case I wire it wrong. Replaced the one 10mfd that had been perviously replaced just to update it. When I get sound out of this "turd" I'll swap them back out. Connected a cable from portable radio to phono input. With the 29k radio selector on radio there was very faint sound on the speaker. With the selector on phono I good volume. Suggestion?

http://s1356.beta.photobucket.com/user/bd2776/library/#/user/bd2776/library/Photobucket%20Desktop%20-%20QH3BD?&_suid=135500232246706797035333781923
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Post by Guest on Sat Dec 08, 2012 8:28 pm

Have you given the selector switch a good cleaning? I had an RCA 8R71 that behaved pretty much like that and I had to take my typing eraser to the wafer switches and then brush them out with 91% isopropyl alcohol to get them working reliably.

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Post by Guest on Sat Dec 08, 2012 8:36 pm

http://www.misterart.com/drawing-illustration/pencils/erasers/faber-castell-perfection-eraser-pencil-for-ink-with-brush.html?utm_source=ShoppingCom&utm_medium=datafeed&utm_term=10010&utm_campaign=ShoppingComProducts

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Post by Dr. Radio on Sat Dec 08, 2012 9:39 pm

Ben, checked your pictures, I see an awful lot of original resistors, have you checked resistances? Like a said, there are a lot that like to go high in value, especially the little ones in close proximity to tube sockets where the heat travels up their leads and makes the drift. Wiring errors could be an issue to if someone did a hack job before you...

Also, never put an old electrolytic capacitor back in circuit. Old caps are BAD period, ticking time bombs. If you suspect a bad new component or install it wrong (wire an electrolytic backwards for example), simply install a different new unit.

So if I understand correctly, with your test radio connected into the audio jack, and the selector in a phono position, you get good, clean audio???
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Post by Dr. Radio on Sun Dec 09, 2012 12:58 am

Just had a thought.... You are testing the radio with the RCA Magic Loop antenna connected, right?
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Post by Ben Delk on Sun Dec 09, 2012 10:44 am

Thanks for the suggestion guys.

Have you given the selector switch a good cleaning?
I have sprayed the selector with contact cleaner and worked the switch back and forth several times but I have not used a burnisher of any type.
have you checked resistances?
Checked the resistors, in circuit, and found 1 out with a crack on the underside. Replaced

So if I understand correctly, with your test radio connected into the audio jack, and the selector in a phono position, you get good, clean audio???
With the test radio connected into the audio jack, and the selector in a phono position I have good clean audio.
I'm not testing it with the magic loop connect. I have 50 foot antenna wire running around the ceiling in the garage connected to the wafer on the back marked A.


Ok, today’s project will be burnishing the selector contacts.
Remove the old resistors and replace.
Replace some of the crappy looking wires which I was putting off until I got some music to come out.

Here's what I know electrically.
Heater circuit 5.6-6.3
(2)Outputs 6k6-gt Grid> 265v, plates 245v
(2)6sq7 (AF and Phono Inv) Tplate > 90v, Dplate > 225v, TGrid > -2
I did not make notes on the other tubes. I recall they were all in limit so I need to go back over them and make notes.
The 1st and 2nd IF trnsf windings measure roughly 7 ohms input voltage about 235v
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Post by Ben Delk on Sun Dec 09, 2012 8:40 pm

Replaced all the resistors today but one which is connected across the 1st IF trnfm. The colors are yellow-orange-violet 430Meg according to my chart. I don't have one and cannot find one on the interenet.
What am I missing here?
http://s1356.beta.photobucket.com/user/bd2776/media/Radios/IMG_0148.jpg.html#/user/bd2776/media/Radios/IMG_0148.jpg.html?&_suid=1355099963754048619918797828654
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Post by Bill Cahill on Sun Dec 09, 2012 10:57 pm

That's not a resistor. It's a capacitor. You must have the loop antenna connected properly for the radio to play. It won't work on just a wire.
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Post by Ben Delk on Sun Dec 09, 2012 11:06 pm

Oh...mannnnn......dah.....that's a new one on me. Looks like a resistor but now it make perfect sence. Ok I'll go with that tomorrow as well as connecting the magic loop. The schematic shows the "A" connection as the antenna that wraps around the inside of the cabinet so I thought that was in leiu of the magic loop. Sorry, I not the bright bulb in the box. Thanks guys.
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Post by Ben Delk on Thu Dec 13, 2012 8:24 am

I'm trying to move forward with this RCA 29k and it is like molasses in the winter. Most of the original rubber covering on the wiring was brittle and falling off so I have started replacing it all. I have replaced most of the resistors, caps and micas but have more on order to replace. One little bugger has me stumped and I have not been able to determine whether it is a resistor or an early type cap.
In the close up you can see it is connected to the 1st IF on post A & B. and you can also see I still have a bit of wiring to replace. The component’s base color is yellow, then orange (maybe red), then violet for sure, then silver. If I go with these colors as a resistor it a 430meg/10% but I don’t see that on the schematic. If I go with an early cap color code dismiss the yellow, 1st color orange, 2nd violet, 3rd silver I have 0.37. I don’t see that on the schematic either. Trying to read it with a dmm or cap reader the reading are all over the place so I can’t trust any of them. I do know this….I scratched off one end on it and there is a metal top where the wire comes out.
The question here is what do you think it is? Cap or resistor?
http://www.nostalgiaair.org/Resources/876/M0014876.htm

[url=RCA Victor 29k IMG_0156][IMG]


[url=RCA Victor 29k IMG_0153][IMG]
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Post by Guest on Thu Dec 13, 2012 9:25 am

By the base color, that component shouldn't be a resistor. I have been checking the schematic and can find only A C F and D in use on that transformer. Might it have been replaced? My reference is Rider's Vol. 13 Pg. 35.

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Post by Ben Delk on Thu Dec 13, 2012 9:37 am

I am using the same Rider's. Thank you, since I didn't see B on the 1st IF schematic I had the question so I rechecked it last night. The part appears to be original an untouch prior to my removing it. If it is a cap what value would you put on it? Does yours have a parts replacement sheet?
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Post by Guest on Thu Dec 13, 2012 10:28 am

It has no parts list, and I can't see a externally mounted cap pictured. I would imagine one of these should decode the value.

http://www.bing.com/images/search?q=capacitor+color+codes&qpvt=capacitor+color+codes&FORM=IGRE

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Post by Bill Cahill on Thu Dec 13, 2012 11:14 am

O.K. Ben. I see it now. Looks like a resistor. Maybe 470K?
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Post by Guest on Thu Dec 13, 2012 12:15 pm

He said the component had metal end walls where the leads came out. I've never seen a resistor constructed like that. Question

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