Does anyone knows how to adjust the air gap. Tubes are. Pairs of 4-440 on a RCA BTA 1R2
I have spark gaps on my 4-1000A plate modulated rig. They are on the Heising reactor and both sides of the mod xfmr. This was how the iron came stock.
I use a seat-of-the-pants method to set the gaps as taught to me by the Tron. Basically you set them closer and closer until they begin to arc during normal voice speech. Then back them off until they arc only when there is an unusual problem, like an audio pop or transient. You also watch the T/R key-up and un-key sequence to see that they arc only occasionally.
Keying transients are another subject, so if you have an arcing un-key problem, don't set the gaps too far apart to compensate. Fix the arcing the best you can. A 100-200 watt 5K power resistor across the mod iron during un-key using a vacuum relay will quench and dissipate most collapsing magnetic fields. I use the scheme here.
The gaps are really a failsafe device to keep the high voltages from arcing over the mod iron windings. Occasional gap arcing will not hurt a good transformer, though excessive arcing can put a load stress on it, just like a low resistance short.
Bottom line is that you want to hear the gaps arc only occasionally during robust operation - and for good reason.
T
