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sweep tube box chatter.

space cowboy

space cowboy

Quack Quack
Oct 16, 2012
1,368
453
93
Michigan
it happens when unkeying on ssb. the relays start chattering and won't stop until the tune or load knobs are turned. it happened once or twice, occasionally, and happens more often lately, but not all the time now.
am was fine, now it's doing a fading chatter for a sec or so then unkeys.
no problem keying up. and the audio it puts out sounds normal and peaks where it has been.
any thoughts?
 

wavrider said:
put a rectifier diode across the relay coil IE anti chatter diode
Click to expand...

Those diodes are usually called snubbing diodes and are usually used to cancel the high voltage created by the magnetic field collapsing in the relay coil. It prevents high voltage spikes from feeding back into the circuit and taking out solid state stuff. What bothers me is the fact it continues until either the tune or load control is changed.


space cowboy said:
it happens when unkeying on ssb. the relays start chattering and won't stop until the tune or load knobs are turned. it happened once or twice, occasionally, and happens more often lately, but not all the time now.
am was fine, now it's doing a fading chatter for a sec or so then unkeys.
no problem keying up. and the audio it puts out sounds normal and peaks where it has been.
any thoughts?
Click to expand...

That sounds to me like you have an issue with the amp self oscillating. You could have tubes going bad or other problems causing self oscillation like component value changes etc.
 
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i had same problem with a transistor mobile amp i changed the coax length between the radio and amp the chattering went away,,,,,,i dont know if this will help you or not,,, but ya never know,,,,,,73s midnight special
 
Not sure if this is on topic or not but I am looking for a simple DIY build of a sweep tube amp. An old friend of mine had a home brew single sweep tube amp that gave him about 25 to 30 watts out. I'll build a small one at first, then on to bigger things! Any guide to a good direction??

Thanks! mechanic
 
wavrider said:
http://www.physics.unlv.edu/~bill/PHYS483/relay.pdf

Scroll down to flyback diode. Good read and may explain some of the chatter you are experiencing.

Flyback, snubber, anti chatter, the nomenclature is many names, the results are all the same no matter what name it is called
Click to expand...


Yes but the diode across the relay coil is to shunt the induced high voltage from the magnetic field in the coil collapsing and protect other components from the voltage spike. The diode across the contacts keeps the contacts from arcing and burning up when switching an inductive load. The big question is why does it continue until the TUNE or LOAD control is adjusted? Sounds like oscillations to me. If changing the length of patch cord from the radio to the amp solves the issue that would prove that theory as it in effect changes the input impedance/tuning (because we all know that 11m amps are NOT 50 ohms input) thereby solving the oscillation problem. I had a 2m VHF amp do that exact same thing a long while ago. It even took out the front end of the HT that was driving it. When I unkeyed the relay would sometime chatter but usually stuck on and would show a couple watts out with no drive. The solution was to very slightly retune the input circuit lower in frequency and the output side a little bit higher. Or vice-versa I can't remember which way was which.
 
Captain Kilowatt said:
Yes but the diode across the relay coil is to shunt the induced high voltage from the magnetic field in the coil collapsing and protect other components from the voltage spike. The diode across the contacts keeps the contacts from arcing and burning up when switching an inductive load. The big question is why does it continue until the TUNE or LOAD control is adjusted? Sounds like oscillations to me. If changing the length of patch cord from the radio to the amp solves the issue that would prove that theory as it in effect changes the input impedance/tuning (because we all know that 11m amps are NOT 50 ohms input) thereby solving the oscillation problem. I had a 2m VHF amp do that exact same thing a long while ago. It even took out the front end of the HT that was driving it. When I unkeyed the relay would sometime chatter but usually stuck on and would show a couple watts out with no drive. The solution was to very slightly retune the input circuit lower in frequency and the output side a little bit higher. Or vice-versa I can't remember which way was which.
Click to expand...
Does seem like oscillation
 
Sometimes if the amp is too close to the transceiver a feedback loop starts and will not quit until the amp changes or the radio changes to break the feedback. Leaky Coaxial cable can cause this too.
 
looks like it was the tubes. I must have swapped out the tubes somewhere along the line. it's supposed to be el-519's but was 6kg6 tubes. I swapped back the original tubes (they were in the 6kg6 boxes) and it's working fine again.
I'll have to see how long these tubes hold up. they were starting to chime when broadcasting thanks to me unknowingly overdriving the box. I remember turning down the radio, but not swapping out the tubes.
 

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