Recap 48-482 - Printable Version
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Recap 48-482 - Guest - 03-03-2010
Greetings all-
A couple of weeks ago I purchased a 48-482 in pretty fair shape. Initially, it would pull in the local AM station, but that was all. I started by cleaning the tuner, switches and pots. I tested it after I put it all back together, and to my surprise, everything was worse. There was so much noise in everything, I couldn't hear any stations. Then, over the next few days, it slowly got better. I could pick up the local FM station, with no external antenna. I was able to pick up several Shortwave stations. And the AM, wow. It was great. I spent some time and dialed in the presets. Then, as suddenly as it started working, it went back to all noise again. Last night, I pulled the chassis out and re-cleaned everything, including the tube sockets this time. While I had it out, I checked voltages at the test points shown on the service literature. Everything was way out of spec. So, I guess my question is would recapping take care of my problems? The reason I ask is I didn't think that bad capacitors would give an intermittent problem. Also, what all is involved in recapping? Could someone explain it, or point me in the right direction of where to find info about it? I can solder a little bit, but that is about the extent of my electronic knowledge. Any help will be greatly appreciated.
Thanks!!!
Tim
Re: Recap 48-482 - Sean - 03-03-2010
Hi Tim,
I just finished restoring one of these sets within the past couple of months. It is sitting on my desk at work and I am listening to it as I type. It is best to replace the capacitors in the radio for long term reliability. They may or may not be causing your issues. This model uses mostly loktal base tubes (7F8, 7B7, 7H7, FM1000, etc) which I have found to have problems with making good contact in the sockets unless you clean the pins properly. What I have done that has been very successful is to use a piece of 220 grit sandpaper on the tube pins to clean off any oxidation. Put contact cleaner in the tube socket on the chassis and work the tube in and out of the socket a few times. After cleaning all of the loktal tubes this way I then will extensively wiggle each tube in the socket while the set is playing just to make sure that the pins and socket contacts are cleaned sufficiently. If you get any scratchiness while wiggling a tube you know that it will need more attention.
For the capacitors you can get them from a few vendors on the internet. Radio Daze, Just Radios, Antique Electronic Supply just to name a few carry the higher voltage capacitors needed to replace the original capacitors in vacuum tube type equipment. There are about 30 paper capacitors in the 48-482 and another half-dozen or so electrolytics. This radio really is not for a beginner but I have worked on worse radios that definitely are not for the beginner.
Re: Recap 48-482 - Guest - 03-04-2010
Sean-
Thanks for the reply. The recapping looks like a pretty daunting task, especially with those multi-section capacitors. Even figuring out what caps I need... Anyway, I am planning on trying your trick with the tubes and sockets first. It is really frustrating, though, that the thing worked quite nicely for several days.
Anyway, thanks again!
Tim
P.S. It looks like we are practically neighbors. I live just down the road in Rolla. :-)
Re: Recap 48-482 - Sean - 03-04-2010
Is this the radio that was advertised on Rollanet a few days ago? I was tempted to buy it but I figured I didn't need another 482. I went to school at UMR and worked in Rolla for a couple of years after college.
Re: Recap 48-482 - Guest - 03-04-2010
That's the one. It was advertised for $40, but when I went to check it out, the guy had dropped it to $30. There was a big ring on the top, like someone had put a plant on it, but a little Liquid Gold pretty well took care of it. Not a bad looking radio, if I can just get it to work.
When were you at UMR? I was there for 2 years, fall semester 1992-winter semester 1994. I decided engineering wasn't for me, so I quit and went to drafting school.
Tim
Re: Recap 48-482 - Sean - 03-05-2010
I was there from fall '99 to spring '02 when I graduated with BSEE (I went to community college for pre-engineering). I work with a couple of ME's who were there in the early '90s.
Re: Recap 48-482 - Guest - 03-05-2010
I've found something interesting as I was cleaning the tube contacts...the 5Y3GT rectifier tube has been replaced with a 5U4GA/5U4GB. Is that a compatable replacement? Maybe I'm grasping at straws, but I really don't want to have to recap the radio.
Update: while cleaning the tube contacts, I also cleaned the pots and selector switches again. As I was test driving it, I noticed that the treble pot seemed to be the offending component. All of the voltages are still out of spec, but the radio is playing quite nicely, and has now for several hours.
Re: Recap 48-482 - gary rabbitt - 03-06-2010
Hi,
I would strongly suggest that you think about replacing the filter caps at the very least. If one of those shorts out, it can take out your transformer in a hurry. The filters are the 'main' capacitors that filter out the current in the power supply. Generally we will leave the old capacitor can on the chassis for looks, disconnect it, and add the new (smaller) caps under the chassis.
As you already know the set works, that is a good sign. So by replacing the filter caps first, then testing, you should at least have a more reliable set. But from that point, you should consider replacing the other caps too.
I am not sure, but your set might have bakelite block capacitors under the chassis. YOu can find info on this site and Chuck's site on how to rebuild them. They are pretty easy really once you have done one, your next ones go fast. You don't have to unwire the block either. I rebuild them left wired in place, shove out the old caps, insert and solder new ones in. Takes less than 5 minutes each to do.
Usually it is suggested that a new restorer replace one or two at a time, then test. If you replace all at once, and you make a mistake, it is harder for you to find your mistake. Replace one at a time, then you know where the mistake was. YOur static cold be cause by dirty controls. Contact cleaner made for potentiometers will clear up any static caused by the controls. If your set has pushbuttons, that is another place that poor contact happens, causing static. The bandswitch (FM/AM/SW/Phono, etc) is another place that poor contact happens.
Good luck with your set,
Gary
Re: Recap 48-482 - Joe Rossi - 03-06-2010
Take Gary's advice: RECAP THE RADIO. Otherwise, it will return to it's last use, a nice place to put a potted plant. I can't remember if that model has the rectifier on the transformer ot if it is chassis mounted but it would seem that someone either made a little socket adapter or rewired the chassis socket to replace the 5Y3 with the 5U4GB. That should be no problem. Good Luck!
Re: Recap 48-482 - Ron Ramirez - 03-06-2010
The 5Y3GT and 5U4GB have the same basing, so if you plug a 5U4 into a 5Y3 socket, the radio will still work -
HOWEVER -
The 5U4 draws 3 amps of filament current at 5 volts, while the 5Y3 draws 2 amps. So the 5U4 is not really a good substitute for the 5Y3. Continuous use of a 5U4 in a 5Y3 will place a heavy strain on the radio's power transformer, which could lead to its failure.
So...replace that 5U4 with a 5Y3 right away. 5Y3 tubes are not difficult to find, and they are inexpensive.
Also I must echo what Gary and Joe have already warned you: please do replace all of the paper and electrolytic capacitors if you intend to use the radio. Also check all of the resistors, and replace any found to be more than 20% off published specifications.
Re: Recap 48-482 - Guest - 03-06-2010
Thank you all for your help. I certainly appreciate the guidance. I guess I will be honing my soldering skills soon. It really seems like a daunting task to undertake, but I don't want to ruin the radio, so...
Thanks again, all!!!
Re: Recap 48-482 - Joe Rossi - 03-07-2010
I apologize for the error! I keep confusing the 5Y3 with the 5Y4. The 5Y4 has the same electronic characteristics as the 5Y3 EXCEPT the pin base. Enjoy your radio once you've recapped it.
