Hi _g. post_

Thanks for the speedy, and informative, reply. Your info was very
helpful.
I am not aware to what BAMA refers - could you give me a heads up? It
seems as if Google should have noticed a treasure trove of Weller tech
sheets like you are inputting.

I also need to do a little confessing. I wrote my original post late
at nite - that accounts for some dis-information. Secondly, I skirted
the truth a little in order to get to the heart of my inquiry. All that
did was to confuse you. So, as Paul Harvey says, here is the rest of
the story.

My base is an EC2002M-O power unit. The back sticker displays the
COOPER logo prominently, so I would guess that the base dates from
after the 1980's. It was originally paired with a EC1201A pencil, but I
loaned the unit to a technician and when it was returned several months
later, he said he could no longer find the pencil. I have a
non-functioning EC1503A pencil, so I was trying to get the station back
in working order by repairing the EC1503A pencil. This lead to my
inspection of the base-unit connector and the discovery of the sixth
pin in the Tyco/Amphenol base-unit connector. (I no longer have the
EC1201A pencil, so I can't determine if it had a sixth pin.) (By the
way - I thought I was pretty observant, but I completely missed the
fact that you pointed out - that two of the pins in the connector -pins
3&4- are gold, while the other four are silver.)

Your link to the cooperhandtools manual was helpful, but it does not
illustrate the sixth pin in the center of the connector. Mine has a
(silver) sixth pin in the center of the other five pins. This pin has
a blue wire which connects to the circuit board. I spend quite a while
with a lope to confirm that this pin connects to the PIC MPU IC on the
circuit board. The schematic of the PIC MPU says that the pin (pin17)
is an I or an O pin depending on the programming of the chip. I have
no way of referencing the program code, so I can't determine whether
this is an input or an output, but I would guess that is is used as an
input since there is a 10K (I think) resistor in series with the lead.
(i.e.,base connector pin 6 to blue wire to circuit board to 10K to pin
17 of the PIC processor.) One unsupported quess is that this is an
input and that it is used to implement a software zero-crossing
detector to control the TRIAC turn-on point, but, this seems like a
really round-about way to make the connection for a zero-crossing
signal. If you have any ideas, I would really appreciate hearing them.

I guess my real question at this point is, do you think fixing the
EC1503A pencil (replacing the RTD) is a way to go here? Do I need to
worry about the center pin at all? My other soldering station is a
cheapo Unger, and I really miss the Weller.

Thanks - MashBrain