[Central-Electronics] Compiled Responses from my questions

[Larry A. Walker]

Hello Larry:

Congratulations on the 100V.  The serial number should be on the back, as I
recall.

There is no "preferred" receiver for use with the 100V.  The 75A-4 was often
used simply because many of the receivers of the time did not have a crystal
controlled front end and were therefore not stable enough for tune and
forget stability.  Later receivers are all fine, but often are smaller than
the 100V.

I use a Collins 651S-1 receiver sometimes, which is a bit smaller but sounds
great.  At this point in life, you use whatever gives you a glow.

About the only thing you need to check is the batteries in the limiter.  The
original are mercury and will have been replaced.  Nick Tusa has a website
for 100V users and you will want to visit it.

73,  Colin  K7FM



Larry,

Congratulations - the 100V's are wonderful.


Cannot locate a serial number. Can you tell me if there are serial numbers
and where they would be located on the unit.

If the label is missing from the rear of the unit, near the RF out
connector, it is doubtful you will be able to find out the serial number.
Maybe others know but I sure don't.


Was there a preferred receiver to use with this unit or was it "receiver de
Jure". Some have say the 75A4 was the optimum. Just wondering!

Yes!! The 75A-4 is the best "mate" ... same time frame, etc ...


Anything else I need to know? Any perferred way to light this off short of
powering it up into a dummy load?

Oh, yes!

1. Remove all tubes, clean the pins and sockets with DeOxit. And the
switches.

2. Check the HV electrolytics. They are probably bad - leave the cans in
place and use newer, smaller units mounted under the chassis.

3. Replace the small "Chemtronic" white colored electrolytics - I bet every
single one of them is bad. There is one across the relay coil in the final
cage, a couple in the audio limiter, and a few in the audio circuits. Get
'em all.

4. Oil the fans - if they remain noisy you will have to replace the
bearings.

5.  If the VFO feels "lumpy" you will have to remove, clean, relube, and
maybe replace the bearings within the dial mechanism. If the VFO is nice and
smooth you are lucky and there is nothing to be done!

6. If carrier suppression is terrible remove the plug in "Mod Diodes" module
and replace all the 6uf electrolytics within.

7. Remove the plug-in Audio Limiter and see if the small original batteries
are in place. If so, I suspect you will see lots of ugly corrosion. Clean it
up and replace the batteries and Ge diodes with back to back (cathode to
cathode) 3.6v zeners.


Tnx in advance for any help/info you can give me. It was a fanasy in my
youth and now a reality. Licensed in 1955 as K0IET (now KW4A).

Same here! I dreamed about this stuff. I was licensed in 1954 so we're the
same "vintage."
I now have a number of 100V's, 200V's and the very rear 600L linear. They
are wonderful.
Here are photos of my toys:

http://www.isquare.com/personal_pages/hardware-23.htm
http://www.isquare.com/personal_pages/600L.htm
http://www.isquare.com/personal_pages/hardware-26.htm

My station: http://www.isquare.com/personal_pages/hardware-14.htm

Have fun with the 100V - let me know when you're on the air and we'll talk
CE to CE.

73, Bob
W�YVA
Great Falls, VA



Hi Larry:
Congratulations on the 100V; I think it's the best there is for vintage SSB.
My favorite B/A set-up is a 200V driving a BTI LK-2000, with a 75A-4 for a
receiver.  I do have a KWS-1, but the 200V is so much easier to handle, and
a lot more flexible. Of course there are a number of good receivers, but the
A-4 is a great match.
Vy 73,
George Maier - K1GXT



Larry ...

I restored a 100V 3-4 years ago, and love it -- great radio.

There are generally only a few issues with these (other than the run of the
mill stuff -- checking caps, resistor tolerances, etc.)

The first is the SSB clipper/limiter stage.  Some of these were modified to
use standard 1.5 volt batteries -- works but it's UGLY.  Some may still
have (probably long dead) mercury batteries in place.  In either case, you
need to look at the circuit board inside the limiter can and make sure it
hasn't been damaged from leaking acid out of the original mercury
batteries.  Nick Tusa has a simple fix on his 100V website --
http://www.tusaconsulting.com  - using zener diodes.  Series connected
1N914s or similar will also work to set the limiting level.

The second is the smoothness of the PTO tuning.  Many unrestored
100V PTOs have a "gritty" feel to them, which is just the result of needing
to be relubricated.  They require special tools to get the bearings apart
safely (without losing all the ball bearings).  Again, Tusa will do a swap
of
your PTO with a refurbished PTO for a reasonable price ($165 or so).
Well worth the money.

You will also want to make sure that the caps in the "MOD CAPS" plug-in
are ok.  It is probably worth just replacing them if the originals are still
in
there

I'm still fighting a problem with a little audio hummmm in the mic preamp
stage of mine.  In fact, the next project on my list is to go back in there
and float  the filament connections at the socket of that stage above
ground with a the ground side connected to a common audio single-point
ground at the mic connector.

Enjoy ... Grant/NQ5T



Fine Larry, the serial number should be in the back of the unit on a stick
on tag. The only matching receiver which was the 100R was only done as a
prototype and there is only one in existence.  The collins 75A4 or the 51J4
are a good cosmetic match.
    Fern

Larry-
Yes,  the relay coils are available...$65 which includes postage/handling.

The serial number tag was simply glued on and many sets lost them over the
years.  No big deal really as there were three runs of 100Vs and 1 of 200Vs.
Each run had 500 sets.  Most of the changes were in run #1, then things
settled down.

73..Nick



Larry:
Almost forgot....
The serial number tag is always on the rear apron of the chassis on CE
products.  I don't have a handy photo of my 100V or 200V from the back, but
I've attached a picture of an MM-2 just to show you what one looks like.
I've also attached a photo of my 200V + 75A-4 rig.  The Ten Tec PM-3 is now
an Elecraft K2, and what a radio that is !!!   The Johnson T/R switch has
been replaced by a regular Advance coaxial relay, it was easier to deal
with.  I highly recommend Advance relays, if you can find them.  Actually,
anything is better than Dow Key !!!
Vy 73
George - K1GXT
PS - If you ever get a 75A-4, drop me note.  I've developed some really
great AGC mods, that I'll publish soon in ER.