Xpantastic!

If your xpander is not plugged into anything (e.g. the wall) while unsoldering the battery, I it shouldn't matter if the iron is grounded or not because there will be no circuit to complete!  Just make sure your xpander's not plugged in, and its chassis isn't touching the same ground that the iron's grounded to (like the chassis of another plugged-in device) and you should be OK.
 
MHO,
Randy

--- On Sun, 9/7/08, Tony Cappellini <cappy2112@gmail.com> wrote:

From: Tony Cappellini <cappy2112@...>
Subject: Re: The Status of my Autotune & DAC Tests was Re: [xpantastic] Re: It's official- my Xpander is sick
To: xpantastic@yahoogroups.com
Date: Sunday, September 7, 2008, 12:11 PM






> 6.6 V seems very strange for the memory power supply. The battary
> might need changing.
The Service manual reads that this should be 4.4 V with power on, and
2.xV with power off.
With power off, the voltage reading is correct.

I will probably change the battery too, since it's been about 10 years
after it was changed last.

> If you are re-flowing the + side of this circuit ( M+5V) you better
> make sure you have an un-grounded soldering Iron. If not
> the +Mem supply will be shorted to ground and then the MEM will be
> lost.

I will have the solder tech where I work do all of this for me since
he does soldering all day long.
I dont trust myself soldering on pcbs. He has a nice temperature
controlled iron with many removable tips.

> Hope I caught you in time.
I havne't heard of an ungrounded soldering iron before, but I assume
you mean that the iron should not have the ground prong of the
power cord connected. This is easily done with an adapter.

> I notice in the Xpander schematics D4 exsists twice. One is a diode
> at the top edge of the board the other is an LED for the LFO. Now I
The D4 I'm referring to is on the Processor board-not the voice or pot
board. This is how the service manual refers to it.

> If this is shiny brown, this may be soldering flux. This should
> always be cleaned off the circuit board.
> After about 5 - 10 years this will eat the solder and cause problems

It doesn't look like flux too me, and is far enough away from where
the solder flux would have been when it was soldered.

> Well, I be talkin about U811 the main DAC which feeds the voice
> board. The MP7614C-4 was mad by EXAR and is obsolete per their web
> site, and the HS3140C-4 was made by SIPEX and is also obsolete.

I googled for this part, and many hits were found on websites that
specialize in getting rare parts.
They want orders of $100 or more.

It might not be a bad idea for us to do a group purchase of these, if
we could find a supplier who would sell us a small order.

> I suppose with digging you can find this part out there somewhere
> (repair shop or part house which specializes in obsolete parts but
> you will pay quite a bit).

I wish there was a cross reference online that would tell you which
commercial devices also used these components
It would be much easier looking for an appliance than a chip.