[Collins] Re: 75S-1

[kiyoinc at attglobal.net]

Did a little more playing with the 75S-1.

It has a little AC hum in the speaker.  It's not bad but
I can hear it if the room is quiet.  The hum does not get
louder when I turn up the AF gain.  

Does this mean that C59 the HV capacitor, is getting soft?  It
shows as a multi section cap on the schematic, the aluminum can
that's sticking up between the audio transformer and the power
transformer.  

I've never tried to hog out and refill an aluminum capacitor.

I don't know if I can find 3 40 uF caps that'll fit in there. I
hate to just add 3 caps to the bottom of the radio and bypass
the cap. 

What are good caps for this application? 

I found the instructions for setting the PTO spread.  You guys
are right, it's in the manual.   I just read past it.

Odd thing is that the 0 to 100 are within 300 cycles but 100 to
200 is about 1500 cycles off.  I should put this on a counter
before I make any changes. 


I didn't come up with that boatanchor philosophy, I read it
here, just up the thread.  


I've stopped buying new radios.  I have an ICOM IC-720A with CW
and AM filters and the ICOM power supply. 20 years ago, I paid
full price for it, used it for a few hours before putting it on
the shelf. I paid about $2,000 when that was real money.  

When I brought it out again, the relay contacts had corroded
and other problems manifested themselves.  

I have a friend who just got an ICOM 756 Pro II.  I urged him
to refurb a boat anchor but he had an itch for a new radio.  

Frankly, I'm afraid of the new radios.  I've been inside the
720A, cleaning the contacts of the TR and stepping relays.
It's built in layers with sub-assemblies connected with flimsy
looking ribbon cables.  If the 720A fails at the component
level, I probably won't be able to fix it.

On the other hand, 30 year old Heathkits are easy.  Everything
is out in the open.  No microprocessor, no integrated circuits,
mostly common parts.

The 75S-1 should be nice to work on.  The seller explained the
PTO drive, inner ring, pinch wheel, it sounds just like the
Heath LMO.