[Collins] Help with 75A4 parts location

[Dr. Gerald N. Johnson]

Checking parts list and schematic, I see how the picture is of no help.

C102 is 1 mf 200 volts, while C115 and C116 are 0.1 mf 400 volts. That
means about 5 times the volume of dielectric in C102 so it should be by
far the largest capacitor in that stack. One end of each of these
capacitors goes to ground. C102 connects to the junction of R53, 68K 1/2
watt, R76, 100K 1/2 watt and R77 180K 1/2 w in that same vicinity.

C115 connects to the other end of R77 plus R97 15K 1/2 watt that isn't
located by the picture that I found. So a wire probably leaves the
terminal strips.

C116 connects to R94, a 2.5K 10 watt resistor that is not on those
terminal strips, probably only to a wire.

If these are color coded black beauties, I'll have to dig a bit to find
the color code, but the third ring from the end should be one digit
greater on C102 than on C115 and 116. The first band should be brown,
the second band black, the third might be green for 0.1 mf and blue for
1 mf. Capacitor color codes have never been as reliable as resistor
color codes. Especially the multiplier. Since I've never met one of
those molded paper and oil capacitors that wasn't leaky, I haven't saved
any to have a sample to look at the color code. Its possible there are 3
digits plus the multiplier, not two like a resistor, then C102 would be
brown black black green and the others brown black black yellow.

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

On 11/5/2010 8:24 PM, John King wrote:
> If you have access to the under chassis of a Collins 75A4, i need to
> ask you to assist me with the location of a specific capacitor in my
> 75A4.
>
> I have the manual with the parts location pictorial, but the part is
> sandwiched with several others so that the pictorial does not help.
>
> I need to locate the physical attachment points of C102,a 1MFD @
> 200wv. capacitor. I know the general area it is to be mounted, but I
> need to know what terminals on two terminal strips it is mounted on.
>
> If you can assist, it will be greatly appreciated. Please email me
> directly. Thanks for looking for me. 73, John, K5PGW
>
>
>
>