Back in the late 80’s/early 90’s when I started doing tube amp repair and builds, I learned from an old tube radio and television repair man the quick and dirty way to make sure a tube amp was drained of juice. He was a very knowledgeable old man that had worked in tube repair service from World War II to when he passed away in the 90’s. He used a very large Craftsman flathead screwdriver. While making sure your right hand was on the plastic handle and your left hand in your back pocket, touch the + of electrolytic caps, then drop the screwdriver onto the chassis side wall. Make sure you let go of the screwdriver when you do it. A big spark will snap arc on the big screwdriver if the caps are fully charged. Then double check with a multimeter if any juice is in the circuit from the power tube sockets to the preamp tube sockets. His screwdriver was pitted and black from all the arcing. Of course now, I know better NOT to do that. A draining resistor clip is a safer and better way to drain the circuit. It’s a lot easier on the caps to slowly drain them. Just remember to remove it before powering up the amp.
I like to see your videos showing your work, worthy of respect and affection. Congratulations my dear friend, for your competence, professionalism and dedication, it is very beautiful for a professional to become elusive in his work, characteristic of a patient and dedicated scientist. Again; “Congratulations” by PY4RKO Ricardo Brasil - SA!
I have a RCA AR88 which uses negative bias to control the RF/IF gain control a simple mod is to have a relay to lift the earth terminal on the RF/IF gain control to increase the negative bias on transmit and mute the radio, it is very silent operation and works very well.
What relay are you using? It is quite easy to switch high AC voltage with a relay, switching high voltage DC is more of a challenge. Contacts will burn off or weld together within a relay if the gap is not sufficient and action of the relay not quick enough when switching high voltage DC. There are AC & DC contact specs on relays for a reason.
Another hazard should also be mentioned: the same high voltage in the stand-by circuit is also present in one of the screw terminals in the back of the case (at least mine has it). You may want to add a caution to the installation procedure.
Why would they switch the entire B+ in order to simply momentarily mute the receiver? I can understand doing this as a standby mode but it seems a little brute force for a mute. Why not just ground the audio going to the amplifier? Even for experts, routing that voltage outside the receiver, I would think, would be a bad idea because it can introduce any number of problems and make the rig less reliable and more susceptible to damage itself or to other devices not to mention safety. I know I’m not thinking of any novel ideas, they must have had a reason for doing what they did. What was the thinking behind this kind of design?
Hello old man . I am really enjoying this video in my mind I think it’s all good looking and I can’t seeWhich condition best I have ever seen Real I want to get some radio like you thank you so much bye\(//∇//)\
That National is a gem. I haven't seen one that clean in a long time.
I think "kerbammy" is the medical term for lights out buddy. Very nice solution you designed Terry!
Always the BEST Electronic Music Intros here! Pure Gold! THANKS!
Thanks Terry perfect timing on this video as I’m just starting to scratch the surface of what it involved with HAM radio.
Back in the late 80’s/early 90’s when I started doing tube amp repair and builds, I learned from an old tube radio and television repair man the quick and dirty way to make sure a tube amp was drained of juice. He was a very knowledgeable old man that had worked in tube repair service from World War II to when he passed away in the 90’s.
He used a very large Craftsman flathead screwdriver. While making sure your right hand was on the plastic handle and your left hand in your back pocket, touch the + of electrolytic caps, then drop the screwdriver onto the chassis side wall. Make sure you let go of the screwdriver when you do it. A big spark will snap arc on the big screwdriver if the caps are fully charged. Then double check with a multimeter if any juice is in the circuit from the power tube sockets to the preamp tube sockets. His screwdriver was pitted and black from all the arcing.
Of course now, I know better NOT to do that.
A draining resistor clip is a safer and better way to drain the circuit. It’s a lot easier on the caps to slowly drain them. Just remember to remove it before powering up the amp.
Ah, safety. Makes so much sense to have this in a transceiver!
I like to see your videos showing your work, worthy of respect and affection. Congratulations my dear friend, for your competence, professionalism and dedication, it is very beautiful for a professional to become elusive in his work, characteristic of a patient and dedicated scientist. Again; “Congratulations” by PY4RKO Ricardo Brasil - SA!
Great video - excellent solution!
I have a RCA AR88 which uses negative bias to control the RF/IF gain control a simple mod is to have a relay to lift the earth terminal on the RF/IF gain control to increase the negative bias on transmit and mute the radio, it is very silent operation and works very well.
What relay are you using? It is quite easy to switch high AC voltage with a relay, switching high voltage DC is more of a challenge. Contacts will burn off or weld together within a relay if the gap is not sufficient and action of the relay not quick enough when switching high voltage DC. There are AC & DC contact specs on relays for a reason.
Another hazard should also be mentioned: the same high voltage in the stand-by circuit is also present in one of the screw terminals in the back of the case (at least mine has it). You may want to add a caution to the installation procedure.
emf can be scary !!!
What about converting the radios to use TELEFUNKEN Space Charge Vacuum tubes and a B+ of 54V and a H+ of 1.5-3V.
Why would they switch the entire B+ in order to simply momentarily mute the receiver? I can understand doing this as a standby mode but it seems a little brute force for a mute. Why not just ground the audio going to the amplifier? Even for experts, routing that voltage outside the receiver, I would think, would be a bad idea because it can introduce any number of problems and make the rig less reliable and more susceptible to damage itself or to other devices not to mention safety. I know I’m not thinking of any novel ideas, they must have had a reason for doing what they did. What was the thinking behind this kind of design?
Hello old man . I am really enjoying this video in my mind I think it’s all good looking and I can’t seeWhich condition best I have ever seen
Real I want to get some radio like you thank you so much bye\(//∇//)\