Discussion in 'Amplitude Modulation' started by KA4KOE, Jun 7, 2017.
OK what's left to check?
That should explain the high grid current meter reading. You can adjust the sensitivity of the O/L relay. With full 1 kw (broadcast) out, the normal plate current is about 600 mA. The tripping threshold would be higher than that. Whatever you normally run in amateur service, the tripping threshold should be set to 25% or so higher. Since there is no protective bias in the stock Gates circuit, it depends entirely on the O/L relay for protection of the final tubes.
I added protective bias to mine so I could use it on CW, but that's a whole other story.
Maybe the finals are pulling 600+ mA (PA plate out of tune) but the meter reading way off.
A series of wondrous blunders have all been resolved. The grid current meter had me on a wild goose chase. Once I had that fixed, the balance of the troubleshooting all made more sense. She's tuning up nicely and now I'm doing some more testing. But high voltage is holding nicely!
THANK YOU EVEYBODY!
(You guys don't want to know what was wrong, do you?? LOL)
Why was the HV tripping out? Explain please becuz darn tootin' we wanna know.
2 primary causes:
#1: 240V was on the wrong terminals on the HV transformer giving me 3100V instead of 2300. That threw EVERYTHING off!
#2: The tank circuit had one capacitor incorrectly wired.
I knew it was going to end up being something goofy. On the bright side, it revealed a lot of the other issues that are now fixed. AND I got the fans going, pilot lights, and the roller inductors up top are nice and smooth now.
She's running like a champ now (the transmitter - not the XYL, W3TKP). I'm about to give it audio. Nice and quiet on 1450AM - no hum - just a strong quiet carrier.
That transmitter must have been originally designed for 1000w/500w operation, or at least that's where the plate transformer came from. The 1000w-only and the 1000w/250w versions' stock plate transformer is 3100v only, with 250w achieved by switching the transformer primary voltage source to 120 volts instead of 240.
Glad to hear Phase I of the mission is accomplished.
Did you pull one of the terminals off the HV rectumfryers to get it at low power per the manual?
It was wired for those two power levels.