Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives :: Books
Support This Site: The Souvenir Shop :: Contributors :: Advertise


It is currently May Sun 19, 2013 8:51 pm


All times are UTC [ DST ]



Post New Topic Post Reply  [ 7 posts ] 
Author Message
 Post subject: RCA-10K Troubleshooting steps recommendations
PostPosted: Apr Sat 14, 2012 2:13 pm 
New Member
User avatar

Joined: Apr Wed 04, 2012 5:54 pm
Posts: 15
A little background - I have extensive electronics training but not much practical experience. I've recapped a few 5 tube radios but no other tube radio repairs. I'm trying to bring an RCA-10K back to life. 10 tubes, tuning eye, and a Magic Brain. I know this is not a good radio to train on, but I love this thing and would really like to get it going. The power tube was shorted and the electrolytics were shot when I bought it. Didn't know better at the time and plugged it in. The power tube started doing the frankenstein thing (pretty impressive) so I unplugged it. Fast forward 7 or 8 years. I replaced the electrolytics and have recapped everything except the magic brain (hope to finish this weekend). Replaced power tube and tested all of the others. Used a dim bulb tester for power up and it went well. Now all tubes light but of course no sound on any of the 5 bands. It has a slight bit of static (maybe) at full volume. It will sometimes at least make a loud scratch noise through the speaker when switching bands. So to my questions:
First, for future reference, what are your recommendations for general troubleshooting steps - Recap, do resistance checks, do voltage checks, signal trace etc.? What order to do these things? I'm going to set up a spare radio to make it a signal checker per the youtube video. I don't have a sig gen or O scope.
Second - any specific recommendations on what to check on this radio? It appears unmolested other than my recapping. Component layout seems to conform to the schematics and diagrams.
I apologize if this has been extensively covered before - I didn't find recommendations in my search.


Top
 Profile  
 
 Post subject: Re: RCA-10K Troubleshooting steps recommendations
PostPosted: Apr Sat 14, 2012 4:23 pm 
Member

Joined: Jun Wed 14, 2006 11:49 pm
Posts: 3992
Location: Leo, IN
I would start with voltage checks. It may well show something obvious missing or way off voltage. Are you
sure that the tubes are all good?

The RCA 9K and 10K are two of the best radios RCA ever built.

John k9uwa


Top
 Profile  
 
 Post subject: Re: RCA-10K Troubleshooting steps recommendations
PostPosted: Apr Sat 14, 2012 6:26 pm 
New Member
User avatar

Joined: Apr Wed 04, 2012 5:54 pm
Posts: 15
Yes tubes all test good on my tester. I turned in on again this morning and definitely have quiet static at the speaker will full volume. I'll take a look at voltages - thanks!


Top
 Profile  
 
 Post subject: Re: RCA-10K Troubleshooting steps recommendations
PostPosted: Apr Sun 15, 2012 9:55 pm 
New Member
User avatar

Joined: Apr Wed 04, 2012 5:54 pm
Posts: 15
Voltage checks showed no voltage at the oscillator. Found R10 open. It is a 10k wire wound resistor. How can I determine what wattage the replacement needs to be? The parts list shows 10K but doesn't list wattage.


Attachments:
RCA 10K Extract 1a.jpg
RCA 10K Extract 1a.jpg [ 220.65 KiB | Viewed 217 times ]
Top
 Profile  
 
 Post subject: Re: RCA-10K Troubleshooting steps recommendations
PostPosted: Apr Mon 16, 2012 1:30 am 
Member

Joined: Jun Wed 14, 2006 11:49 pm
Posts: 3992
Location: Leo, IN
tomgrigsby wrote:
Voltage checks showed no voltage at the oscillator. Found R10 open. It is a 10k wire wound resistor. How can I determine what wattage the replacement needs to be? The parts list shows 10K but doesn't list wattage.


Most likely a 1 watt will be OK but a 2 watt for sure will be excellent. R-10 is only feeding the plate and screen grid of the 6J7
Osc tube. Since resistor is open do an ohm meter test from the plate to chassis and Screen Grid to chassis. If done before replacing that R-10 resistor it should read infinity or close to it. If Low Ohms then look for some short. Most likely it is OK and some leaky bypass cap is what caused R-10 to open up.
John k9uwa

PS. Check R5 and R6 while your in there to be sure they are OK.


Top
 Profile  
 
 Post subject: Re: RCA-10K Troubleshooting steps recommendations
PostPosted: Apr Sat 21, 2012 9:48 pm 
New Member
User avatar

Joined: Apr Wed 04, 2012 5:54 pm
Posts: 15
Replaced R10 and R5, and it works! Checked resistance as recommended and all was ok. It isn't as sensitive as I'd like yet (lousy antenna), and there are a few old caps in the majic brain that I need to change out yet, but it lives! Thanks for the help. The recommendation to do voltage checks was spot on.


Top
 Profile  
 
 Post subject: Re: RCA-10K Troubleshooting steps recommendations
PostPosted: Apr Sun 22, 2012 6:20 pm 
New Member
User avatar

Joined: Apr Wed 04, 2012 5:54 pm
Posts: 15
I have weak receive but when touch C41/C42 the volume of the tuned in station gets very loud. When I touch the top of the RF tube it gets better but not nearly as loud as when I touch that cap section or when I touch the top of the 1st Detector. Any ideas where to look? I read out the RF coil and didn't find any open windings.


Top
 Profile  
 
Post New Topic Post Reply  [ 7 posts ]  Moderators: Marcc, Norm Leal

All times are UTC [ DST ]


Who is online

Users browsing this forum: Dave Mc, easyrider8, G.S.D., Google [Bot], Jerrad, Norm Leal, Philco Fan, Usually Lurking and 4 guests



Search for:
Jump to:  










Privacy Policy :: Powered by phpBB