[Collins] Restoration of Collins 20V-2 Ser.# 260

[Dr. Gerald N. Johnson]

I looked at the schematic at the other site on line. The simplified 
schematic shows the circuit breaker is at the line and no plates 
supplies should work including the lamp if the breaker is open. No 
filaments or controls if the filament/heater breaker is open. That's the 
way it should be wired for safety. Any variations are unsafe and 
probably not from the factory. One variation I can see happening in the 
field is the indicator lamp being rewired from one line to neutral so 
they can use an easier to find 120 volt lamp accompanied by having 
jumped on circuit on the breaker because it has failed. Opening one side 
of the 240 will turn off 240 volt loads BUT it makes working on the unit 
hazardous because while those transformer supplied loads are off, 
there's still 120 volts to ground on all the primary wires. The relay 
breaks both. Some airconditioner outdoor units are wired with one 
contact breaking the 240 volt circuit. After that relay died from bug 
attack, the replacement breaks both sides to make it safer, but I'm sure 
the double pole relay costs more.

My question is whether the plate voltage is off with the breaker off or 
is still on? If the lamp is still on and still is a 240 volt lamp, it 
would appear the breaker wiring has been modified or jumped because the 
breaker failed or was worn from too many operations. Using a breaker as 
a switch works but can make the breaker more sensitive as many manual 
operations wears a square edge rounded inside the breaker.

73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association.

On 9/29/2014 5:53 PM, Keith Sorensen wrote:
> Greetings,
>
> I am in the process of bringing a very nice 20V-2 back to life on the
> original Freq. of 910 KHz, I do plan to convert to 75M next but want to get
> solid results on original Freq. first.  I am finding a few problems with
> wiring inconsistencies in the primary HV circuit breaker S107 to K102
> contactor. The original schematic (fig. 7-7 main schematic) was taped to the
> back door dated 61/62 and appears to be the original. Does anyone have the
> complete manual for down load that matches this year? I have the information
> provided on the web site, but this is a later revision. My set has the
> original Mod trans 4 terminal. The Plate on light remains illuminated after
> the S102 20 amp breaker trips.. The schematic indicates the lamp should drop
> out with the main plate breaker tripped; I have to open K102 by pushing
> plate off to extinguish the plate indicator lamp??? Thanks for your
> comments..
>
>
>
> Keith
>
> KE7GPO
>
> Radiorm1 at comcast.net
>
>
>