Restoring a Maverick 250 9 Tube Linear Questions

[743]

I haven't been able to post anything for a couple years due to 2 back injuries then a broken hip, and the slow demise of my wife due to Alzheimer's. Lots of Maverick 250 Posts I looked at but didn't find answers I need. I purchased a new President McKinley and traded my old Magnum 1 for this working Maverick 250 that gave me near 700 watts PEP on CH 38 (I only work SSB, no AM) and SWR went from 1.2 to 2.5. My questions follow. 1: There is a toggle switch in the back that is marked BTL. Is this a switch for turning on/off an RF pre amp? 2: Schematic from CB Tricks shows an ML250 and a MGL250. Don't know what those are?? 3: Schematic shows a 12AQ5 as the antenna relay driver and does other major things but mine is a 6HG5 so I suspect someone did a mod to make it 6V. Would you agree? The 6HG5 would be a sub for a 6AQ5 if one exists. All I'm doing is replacing the electrolytics, the plate choke to which was attached a 4.7nF 3KV Z5U ceramic plate capacitor and I broke off one lead. Made by RMC it's about 1 inch dia. Found lots of the same 4.7nF/3KV caps but none were called plate capacitors. 3: Any ideas (yes it did check mouser and purchased a couple different mfgrs) but I think plate caps have special qualities to assure temperature is high enough so value doesn't change over time. Agree yes/no? Not going to replace the tubes. Had a KL-203P which gives me 100W PEP so for one more S unit I need 400W. Any other ideas I sure would wellcome! Thanks, 743 "The Old Desert Fox" (Just sittin here with my toes in the sand watching the rabbits chase the coyotes)! Not now, I live in AZ and it is way too hot.

[743]

Found the answers to my questions. I have a 6 Vac filament system. D&A (the manufacturer) finally figured why use one 12V tube and series wire the other tubes to make 6 Vac when all the tubes have the same pin out configuration (pins 3&4) for the small tube and pins 4&5 for all the rest of the tubes plus the fact every tube has one filament pin grounded. With the 6 Vac system they used tube sockets that allowed bending of the socket lead to the metal frame surrounding the socket and soldering the lead at that point. All pins now wired in parallel made a nice cost reduction and easier wiring.

[MDYoungblood]

There were a few base amps made the would tie the heater elements of the tubes in series creating a 120v loop, this in theory saved them from buying and installing a transformer, the rest of the tube voltage were controlled by regulators, resistors, and caps. These did work fine but line voltage played havoc with the tubes so the idea was dropped (really they just went out of business).

3's

Greg

[743]

Really just need to find what those glass diodes can be replaced with (don't know what the bottom meter is for anyway but knowing would help as it must be there for a reason, yes?) Was told the screwdriver load was to help with the SWR between the 250 and the radio but my President McKinley automatic SWR that beeps shows hi SWR and doesn't change. 743, "The Desert Fox"