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High Voltage
- Thread starter kopcicle
- Start date
and on a completely related note
"Do the name Ruby Begonia strike a familiar note"?
So a brief explanation is in order. Operating the radio one afternoon there was a comment from a local on 10m "what happened to ya"?
Turning to the radio and external watt meter I saw a jump on PTT then a fall to nothing. One more attempt to transmit and I heard a soft near imperceptible "phhhhhzzzt". Trying again and looking through the top cover I saw a brief arc on key up. Having been a welder most of my life the arc was very familiar but did not belong in my radio. Further inspection revealed the damage.
C(2)87 shown above with a wart on it and on the schematic as C287 is inline with the neutralization wire from the PA board.
It's something we all see from time to time, the upstream leg of C287 developed an insulating ring of shmooze around the upstream leg and the subsequent open caused the HV to jump across the air gap to the capacitor.
Fortunate that this is at the exposed edge of the board and only a small amount soldering gymnastics were required to replace the part.
"Do the name Ruby Begonia strike a familiar note"?
So a brief explanation is in order. Operating the radio one afternoon there was a comment from a local on 10m "what happened to ya"?
Turning to the radio and external watt meter I saw a jump on PTT then a fall to nothing. One more attempt to transmit and I heard a soft near imperceptible "phhhhhzzzt". Trying again and looking through the top cover I saw a brief arc on key up. Having been a welder most of my life the arc was very familiar but did not belong in my radio. Further inspection revealed the damage.
C(2)87 shown above with a wart on it and on the schematic as C287 is inline with the neutralization wire from the PA board.
It's something we all see from time to time, the upstream leg of C287 developed an insulating ring of shmooze around the upstream leg and the subsequent open caused the HV to jump across the air gap to the capacitor.
Fortunate that this is at the exposed edge of the board and only a small amount soldering gymnastics were required to replace the part.
Attachments
High voltage you say? This guy experiments with high everything..
https://www.youtube.com/user/Photonvids
https://www.youtube.com/user/Photonvids
Hmmmm. 3 capacitors in series. A 47pf, 10pf variable and the 5 pf fixed.
The way I remember it, AC and DC voltage are divided between series capacitors in a proportion inverse to capacitance. Of those 3 capacitors the 5pf will get more RF and DC voltage both across it than the other two. Does suggest that scrimping on C87's breakdown-voltage rating could be the whole root of the failure.
73
The way I remember it, AC and DC voltage are divided between series capacitors in a proportion inverse to capacitance. Of those 3 capacitors the 5pf will get more RF and DC voltage both across it than the other two. Does suggest that scrimping on C87's breakdown-voltage rating could be the whole root of the failure.
73
“High Voltage”. “Sufficient Amperage”
Are those the secret password challenge answers to the boys-only Raccoon Roaster Club
(Man, I’m never gonna stop laughing at that one).
Are those the secret password challenge answers to the boys-only Raccoon Roaster Club
(Man, I’m never gonna stop laughing at that one).