Re: Desoldering Station for JUNO-106 Chips, etc

On Tuesday 02 May 2006 05:30 a poster that claims to be Wes wrote:

I responded once and apparently the post went to newsgroup post graveyard.

You might check the setting on your newsreader! Here, have another look.
===============
I'm having one heck of a time desoldering an 80017A VCF/VCA chips in one of
my JUNO-106's. Here's a picture of somebody else's used chip:
http://www.heartsofmusic.com/images/80017A.JPG

I've had this problem fixed a couple of times back in 1990 on two of my
three JUNOs. I was living in St. Paul and there was a reputable
repair shop in the Twin Cities called The Good Guys. As awesome as
the 106 is, trouble with the 80017A is well documented. There are six of
these proprietary chips on the Module Board. The only method to
troubleshoot this is trial and error. If you take an ohm meter and check
across various leads, all six will appear to be the same.

Even the well reputed Good Guys had to use the one at a time trial and
error method of troubleshooting. One of them told me when I went back in
the shop with him. This common trouble was not one of their favorite to
chase down. <w> It's plain to see on the backside of the PCB where
the Good Guys technician was marking his one-by-one removal
replacements by bending over one pin each time.

When my wife was a technician at the FAA she had a really expensive
desoldering station that would suck that solder right out! I've told her I
plan on buying a similar station for our home. Since I'll be doing a lot of
this kind of work on my JUNO's and it will be worth the money.

Anybody have a favorite desoldering tool (a REALLY good one) or method that
might do the job?
===============


If a repair shop/person claims that it takes a trial and error process to
find the offending 80017 in a Juno 106, then it is time to find a
competent repair facility. A repair charge to replace a 80017 should be
between 1 and 1.5 hours labor + part. That would include calibrating the
offending voice also.

That was about sixteen years ago. They /were/ quite competent. So much so
that they were referred by an article in Keyboard Magazine. (I'd found
them /before/ the article.) My memory is probably off about whether the
tech said "trial-and-error" was used. I do *not* want to probe at the
module board in a powered up state. The service manual doesn't indicate
where to test with oscilloscope or anything at all about this problem.

The 80017 rarely fail, though it is one of the problems for a 106.

Are you telling us that the 80017 chip is not the cause of the infamous 6th
note off trouble?? /That/ trouble is very common. I should know.
Besides, the internal wiring doesn't allow for access to the back off the
PCB while powered up.

Does it
warrant purchasing a desoldering station?

Being someone that's been soldering since 1968, a desoldering station is
something I've wanted in my Christmas stocking for a while.

Well, if you have 3 106's (which
I am not sure about the purpose of so many) and have soldering skills,
maybe.

That's amazing that you wouldn't know why a person would want more than one
JUNO-106. Astounding, really. More oscillators, filters and envelopes =
bigger real-time layering, sound and polyphony.



It would take about two repairs (as described above)to pay for it.
Generally, the problem with some DIY'ers is they create more problems than
what they started with, so there is always the chance that it may cost you
money. One mistake and you run the risk of a repair that may exceed the
value of the instrument.

True. I've done my own repairs on my Moog and Rolands for years.

Why do you plan to do a lot of this type of work on your 106's? Are you
planning on swapping out all the 80017's? A known working part is always
better than an untried new part.

Because my JUNOs are getting old and I don't live near any smug techs in
Ohio. :-P I live in the rain forest on the west coast.

If you have a favorite desoldering station you'd like to recommend instead
of getting uppity, please share. ;)



Wes Taggart
Analogics
http://www.analogics.org/



--
Respectfully,

Ru Drisi
heartsofmusic.com

Music is the shorthand of emotion.
- Leo Tolstoy

.

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