this a very common problem. this test works on 99% of all 3-500z amps. same thing on 572/B 811A 3cx1500A7 etc. just look at data sheet to get cut off volts and bias volts. the outher part of test is with the tubes in HV applied zero RF in. look at plate current. I had a Zenner short and key amp and tubes runaway . great tip ! the SB 1000 1 3/500Z same bias flop. just one tube. all tube amps have some bias flop. how a tube works. 0 volts full on . just a few use grid bias . same thing. the flop is the grid . 73's
Hi Luke, Thanks for these tips on the SB220. Think I have viewed every video you have uploaded on the amp. Really enjoyed watching you assemble that one from the box. I will eventually get mine put back together. You and the family stay safe. 73 WJ3U
Great video! I would assume that this is the same test for an SB-1000 amp as well? I did test mine and the filament voltage is ok, but bias is 0. Going to check the zener as I key down the tube is glowing like a lantern. Darn thing was working well, too..
So there are a few guys that make a strange modification. They take of the wire from point 3 of the relay, and ONLY feed the relais with 120vdc, then they place the 100Kohm resistor between 6 and 9 (instead of between 3 and 9), so the zener goes from (unkeyed) through the 100Kohm resistor towards the centertap of the fillament transformer. The reason of this (they say) has something to do with "if the cutoff voltage shorts with the fillament voltage" it wil burn out the small transformer, (or something like that) how can this work if the tubes dont get cut off with the 120vdc?????
Hello Sir- Thanks for the great video- my bias flop on my 220 was 0 voltage not 3.5 - Does that mean that the Zener diode is bad? Also I noticed the filament xformer is running hot . Thanks gain
I have a ameritron al 82 that the tubes are trying to run away. I'm in Eastern NC whats the best time to call so I can arrange getting this rig shipped to you.
@electromechanical stuff I watched a ton of his videos and others on that. Seems to me it maybe the high voltage bias but I'd rather pay to have someone to just fix it. Rather then me keep throwing money at it trying to fix it lol
@@swing_king_252 working on them is the part I enjoy the most. Like a ham. The knowledge is my interest. Plus these repair guys are almost extinct those who know seam to think if they teach they'll loose customers to a competitor. Bbi is not accepting orders he's so busy. I'm not waiting a year to get my stuff worked on
You don't explain things very well. Bias voltage is the voltage between grid and cathode. The polarity is important.The grid is usually zero in high power amps or negative compared with the cathode which would be positive if the grid is negative.
this a very common problem. this test works on 99% of all 3-500z amps. same thing on 572/B 811A 3cx1500A7 etc. just look at data sheet to get cut off volts and bias volts. the outher part of test is with the tubes in HV applied zero RF in. look at plate current. I had a Zenner short and key amp and tubes runaway . great tip ! the SB 1000 1 3/500Z same bias flop. just one tube. all tube amps have some bias flop. how a tube works. 0 volts full on . just a few use grid bias . same thing. the flop is the grid . 73's
I still love Irene's knobs.
Hi Luke,
Thanks for these tips on the SB220. Think I have viewed every video you have uploaded on the amp. Really enjoyed watching you assemble that one from the box. I will eventually get mine put back together. You and the family stay safe. 73 WJ3U
thanks bud for keeping it in layman terms ,i love your videos and my sb 220 even more lol
Thank you for bringing it out into the daylight.
Thanks Luke. This was very helpful. 73’s - 64 Baltimore
Very well said. Thanks
GOOD STUFF GIVING TOO MANY TRADE SECRETS AWAY MAN AND SOME STILL DONT GET IT CHEERS
I have 2 of these to work on. Thanks for the info!
Awesome. Thanks for the help..you rock..
awes0me video very very helpful
Great video! I would assume that this is the same test for an SB-1000 amp as well? I did test mine and the filament voltage is ok, but bias is 0. Going to check the zener as I key down the tube is glowing like a lantern. Darn thing was working well, too..
So there are a few guys that make a strange modification. They take of the wire from point 3 of the relay, and ONLY feed the relais with 120vdc, then they place the 100Kohm resistor between 6 and 9 (instead of between 3 and 9), so the zener goes from (unkeyed) through the 100Kohm resistor towards the centertap of the fillament transformer. The reason of this (they say) has something to do with "if the cutoff voltage shorts with the fillament voltage" it wil burn out the small transformer, (or something like that) how can this work if the tubes dont get cut off with the 120vdc?????
Hello Sir- Thanks for the great video- my bias flop on my 220 was 0 voltage not 3.5 - Does that mean that the Zener diode is bad? Also I noticed the filament xformer is running hot . Thanks gain
Need a transfer for 6x3-500ZG. Is EPD still building transformers?
That 5v that same for 1 tube or 3 tubes?
Yep
can you do these same checks with tubes in amp
I have a ameritron al 82 that the tubes are trying to run away. I'm in Eastern NC whats the best time to call so I can arrange getting this rig shipped to you.
Any time between 9-4 M-F probably won't answer but he'll call u back
Sounds like you don't have enough bias. Or 0volts
@electromechanical stuff I watched a ton of his videos and others on that. Seems to me it maybe the high voltage bias but I'd rather pay to have someone to just fix it. Rather then me keep throwing money at it trying to fix it lol
@@swing_king_252 working on them is the part I enjoy the most. Like a ham. The knowledge is my interest. Plus these repair guys are almost extinct those who know seam to think if they teach they'll loose customers to a competitor. Bbi is not accepting orders he's so busy. I'm not waiting a year to get my stuff worked on
You don't explain things very well. Bias voltage is the voltage between grid and cathode. The polarity is important.The grid is usually zero in high power amps or negative compared with the cathode which would be positive if the grid is negative.