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Post by 238 on Jul 21, 2021 22:00:30 GMT -5
This receiver goes with the transmitter i am having trouble with. Has not been ran in 2 years. Sometimes when you turn it on everything is ok & then the receive drops down low. You can bump it & sometimes it come back up. Have checked all the tubes an cleaned all the pots. When i cleaned the S meter pot it started working for a couple of days, then dropped off again. Jim/238
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Post by 2600 on Jul 21, 2021 23:38:23 GMT -5
Sure sounds like dirty tube sockets. The pins on the tubes and the spring contacts in the tube sockets are subject to having a layer of oxide. And if the radio was used by a tobacco smoker the process to clean all that out can be extreme.
And don't forget the relay in the transmitter can do this. Cleaning the contacts may help.
73
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Post by 238 on Jul 22, 2021 8:25:13 GMT -5
I am going to recheck the tubes & sockets. i have triad another transmitter same thing. Jim/238
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Post by 2600 on Jul 22, 2021 22:47:43 GMT -5
As a rule, any tube that makes any noise at all when you tap it or rock it a little bit in the socket has a problem. Should be steady as a rock and dead quiet in response to that kind of disturbance.
Today's "crackle" when the tube is disturbed will turn into tomorrow's "went dead".
73
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Post by 238 on Jul 28, 2021 21:51:34 GMT -5
Have run it off & on for 3 days. It has lost the receive twice. If you bump it in between V5 & c25 it will come back on. That is the 6ba6 & the 7-25 cap. The receive just drops down lower, acts like you turn the volume down. Jim/238
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Post by 2600 on Jul 29, 2021 0:13:51 GMT -5
Molesting the parts and wires on the chassis underside below those parts with a plastic tool tip might zero in closer. You're looking for something that responds directly by cutting out when you touch it.
73
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Post by 238 on Jul 29, 2021 8:26:02 GMT -5
When i bumped it an it came on, i took the bottom off, but could not get it to go off. I have went over it several times with a plastic stick but never got it to come on. Next time it goes off i will check that area again. Any chance the 6ba6 could have a short inside, even if it checks go in the tube tester? The receiver was rebuild in 2012 by fixr. All the if transformers & 6ba6 tubes where changed. First time i have hooked an ant to it in two years, but have never had a problem with it before. Jim/238
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mattbee
Mudduck
Tram & Browning Enthusiast :)
Posts: 38 
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Post by mattbee on Jul 29, 2021 10:59:59 GMT -5
Jim,
Obviously intermitting problems are the worst!
I have read where you stated you check all the tubes, make sure you take some fine emery-cloth and clean the pins real good as well.
Also unplug the two Nuvistors and try plugging them back in & out a few times, making sure they are making a solid connection and are lined-up correctly going back in. I've previously have seen those cause a drop in receive when not making a solid / good connection.
Good Luck,
Mattbee
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Post by 238 on Jul 29, 2021 20:34:00 GMT -5
Ran it most of the day, never did quit. Not sure if i checked 6ds4s, but i will. Just waiting for it to quit. Jim/238
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Post by 2600 on Jul 29, 2021 23:34:40 GMT -5
You could swap that 6BA6 for one of the other two. If the problem follows the tube, that's the problem. And if it's something in the radio near that socket, the choice of tube used there won't affect where it's sensitive to being disturbed.
A tube that checks good might be. You didn't run it in the tester as long as you do in the radio, I'd guess. If it takes that long for the fault to appear, the tester doesn't have a chance to catch it.
73
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Post by 238 on Sept 19, 2021 22:48:47 GMT -5
Finally found the problem with the receiver. It is C25 the variable cap. I can bump it an it comes back on. If i touch the bolt that holds it in place it will come & go. Not sure if i should spray cleaner on it or not. I am going to loosen the 2 little bolts up tomorrow, probably where it gets it ground. Jim/238
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