Repair

I printed the schematics, figured out how to remove the Relay Shelf, and began:

Relay Shelf half-out, probably far enough to work on

• Bias Transformer T203 was utterly toasted... burned and bubbled. Fortunately Peter Dahl / Hammond offer a top-quality replacement - Whew! Nearby components and the wiring-harness appeared miraculously undamaged!
• Bias rectifiers had been changed to silicon diodes, mounted on a terminal-strip. However, the terminal-strip was bent over, shorting at least one (perhaps two) leads to the chassis.
• In a similar vein on the underside of the Relay Shelf, Bias divider resistor R218 was bent to touch the chassis
• Next to this bent/touching resistor, I then saw the cracked-and-broken 10-ohm R232 (limits screen-supply inrush current).
• And, the RF output connector had been changed from the N-flanged original, to a loose-and-sloppy SO-239 barrel (featuring mangled threads which prevented tightening).
• Time-delay thermal relay K202 was only 35-seconds, not 3-minutes as Collins designed (to ensure V101's cathode is properly heated before use).
• Rectifier-filament transformer T202 had cracked-and-broken secondary leads. Because this amplifier had replacment solid-state HV rectifiers, I decided to simply remove the no-longer-needed T202.

Here is a photo of the taped-up schematic, with my annotations and some flags showing the components I decided to replace:

Beyond these quickly-visible electrical problems, I noted that there were some other changes and physical areas needing my attention too:

• The 3B28 rectifiers have been changed to solid-state modules. These modules were mounted to a thin piece of plywood, and look electrically OK... but it is not a thing of beauty
• The 12AL5 dual-diode ALC rectifier-tube has also been changed to a plug-in solid-state diode. This looked tidy. It functionally implements Collins' Service Bulletin SB-3, Nov 1/69 (space-charge standoff voltage from 12AL5 tube)
• The "TUNING" dial had some rubbed/dissolved printing 'way down at the low-end of the dial. The dial functioned, but I knew this would truly annoy me.
• The "LOADING" dial had cracked and been repaired, with a visible glue-line. The repair was very neatly done, but I would find it a constant aggravation simply knowing it was there.
• The 12V filter-capacitors C211A and C211B (a two-section can) looked sketchy: A previous repair fished up into the internals of the can to effect a connection to one of the caps (!), and a scary bare wire snaked through (grounded/conductive) obstacles from the cap to the circuit. It's possible all this did work, but I'd lose sleep if I ignored this area...

Here's a visual summary:

Burned and bubbled T203 Bias Transformer. Bent-over and shorted Bias diodes CR207 & CR208, along with step-start diode CR205

Bent, bruised and shorted R218 (bias switching between CW and SSB)

Questionable C211 (12VDC filtering)

Filament transfomer T202 had broken leads!

Dealing with the Overheated and Cracked R232

Dealing with the RF Output

BIAS Transformer T203, and Associated Circuitry

Screen Supply Overhaul

12V Safety and Control

CR216 and BIAS Multi-Metering

Primary AC Wiring

Dials

Power Supply & Lower Compartment

Tuning & Loading Meter Circuit