Knight Kit Star Roamer repair

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Knight Kit Star Roamer repair

Post by Ed in W. PA on Tue Feb 18, 2014 3:02 pm

This is a E-Bay find that wasn't quite as described in the posting. This radio was advertised as being in excellent condition, tested and checked over by a reputable electronics shop. Such was not the case. Upon receiving this set the first thing I noticed was loose parts rolling around inside and some kind of makeshift shield covering the power transformer, so much for reputable. After replacing the selenium rectifier and electrolytics it fired up and played ok, receiving something on each band except longwave. After burning it in for a few days I was going to do an alignment, however before this could be done I noticed the volume would fade in and out even on the local flamethrower-sometimes all the way out. This condition seems to happen mostly in the first 10 to 15 min. of operation, and when it does occur if I touch the terminal where the loopstick antenna is attached it will snap back to full volume and stay that way sometimes indefinitely. Also tapping on the second i.f. transformer will cause variations in signal strength and volume. I removed the i.f. transformer and disconnected one lead off of each of the two coils inside and noted the value in the event that this is SMD, but due to the construction of this transformer I did not attempt to dismantle any further. I put it back together thinking that if it becomes unusable I may have to attempt some kind of repair, since reassembly though it has not acted up. This may or may not be my problem (SMD) but can't be sure till it does it again. Comments and opinions are welcome. Thanks, Ed.






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Re: Knight Kit Star Roamer repair

Post by Wildcat445 on Tue Feb 18, 2014 3:25 pm

I will put my money on a bad connection somewhere. Perhaps at the antenna, perhaps somewhere down the signal stream from there. Got a chopstick and tap around in different areas until you get the set to misbehave. I had one with a corroded ground connection on the tuning cap that gave me fits. You might also darken the room totally, turn on the set, then tap and probe with the chopstick. If there is a bad connection somewhere, you may see a small spark. You did not say, but if this set has not been recapped, that is the first thing I would do. Capacitors can be intermittent. SMD is the last thing I suspect, since it is the most unlikely and is the hardest to fix. You might clean the bandswitch really well. Good luck.

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WC

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Knight Kit Star Roamer repair

Post by Ed in W. PA on Tue Feb 18, 2014 3:59 pm

This set has been re-capped and gone over very carefully for bad connections before exploring the i.f. transformer. The fact that it was a kit bad solder joints were the first thing I looked for. The ground connection on the variable capacitor has not been checked and will be next on my list.
Thanks, Ed

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Re: Knight Kit Star Roamer repair

Post by Wildcat445 on Tue Feb 18, 2014 4:24 pm

If I read correctly, I would respectfully suggest that your radio may have not been properly serviced. I would advise you to take nothing for granted. I would proceed in a manner just as if it had not been serviced at all. You say that it has been gone over carefully looking for bad connections, yet you may still have one. It is not going to cost you anything to look one more time. You have pretty much verified that there is a bad connection, since when you touch the antenna connection, the volume jumps back up. I would get a chopstick or a plastic alignment tool, and smack the dickens out of it several times. Smack the metal chassis and see if that makes it work or act up. You could have a bad connection in the IF can, and I know anything is possible, but I have never personally run into that. The wires in those transformers are so fine that they either work, or, if there is a short or intermittent, the wires burn in two and the radio is then dead. You might also be sure that there is not a poor connection at a tube socket. Take a needle nose plier and squeeze the terminals on the tube sockets. Wiggle the tubes back and forth gently to see if that affects the volume. I would also sub the tubes with a set known good, against the chance that there is a gremlin in one of those. I had a little Emerson one time that displayed symptoms something like what you are dealing with. The thing drove me nuts until I changed all the tubes and fixed the radio. I put the old tubes back in, one at a time, until I got to the 12BA6. The radio would come and go again. Apparently, there were shorting elements in that tube that would make connection when the tube warmed up. Good luck.

Regards

WC

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Re: Knight Kit Star Roamer repair

Post by Dr. Radio on Tue Feb 18, 2014 9:37 pm

Hi Ed,

Welcome to forums.

Here's a trick to determine if you have IF can issues....

Do as Wildcat suggests and get a chopstick or something strong and non-conductive. Instead of just beating on the radio, carefully turn the chassis upside down where the IF can's legs have their connections. NOW, carefully and methodically push DOWN directly on each leg of the suspect IF transformers. Then push on the side of each leg. What you are doing is forcing pressure onto the leg and ultimately on to the connection tab to the silver mica wafer. This will result in slight flex. If the set acts up, you do have IF transformer issues, but not the typical "SMD" due to migration of silver.  See my post in the electrical section about the GE rebuild. Pages 6 and 7 have lots of detail on the different failure points of IF transformers.
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Re: Knight Kit Star Roamer repair

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