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Subject: FW: Re: LX200: DEC Motor Study
From: alberts@pi.net
Reply To: mapug@shore.net
Date: Mon Apr 22 00:07:21 1996
Rob
The regulator I was talking about was VREG 1 on the main board (7805), I
have replaced it but it is still getting very hot, so I've put an Heat-sink
to it, while running it on the table. BTW, the regulator on the mini-board
says "78L05" too, and the other comparator IC is a LM339N (not LM2901N)!!
BTW, in looking for a replacement for the, hard to get, L2724, I've found;
ULN 3753W Dual Power Opamp 2 AMP Output SIL 12
ULN 3755W Dual Power Opamp 2 AMP Output SIL 12
would these components make a chance to become a replacement?
I've still the same problems with my LX200, but won't give up, yet!!!!
Regards,
Albert
---------------Original Message---------------
Howard Anderson's analysis stands a good chance of putting us all ahead
of the DEC failure problem...I can hardly wait to see the effects of
his upgrading his LM78105 DEC miniboard regulator...(but mine says
"78L05" JRC not "78105", and it's clearly a capital "L"...is that a
misprint on the labeling for chrissake??? and the reason why I gave
up on reverse-engineering this bloody thing???)
Thank you, Howard, for the detective work and keen insights.
(Albert Schuitema said something about a regulator being extremely hot
on his scope...was that the same regulator IC, Albert?)
By the way, I've been operating my scope routinely with the max slew
speed set to "6" on the "telescope" menu, ever since I noticed how
much arcing there is in the DEC motor commutator at the full speed
slew. That may or may not help the 78105 regulator situation, but it
certainly would help with any possible heat problem in the L2724
motor drivers...those too might not appreciate the 12V to 18V switch
that was engineered by Meade.
Rob Preston
Pittsburgh PA
rapr@med.pitt.edu
----------End of Original Message----------
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Albert Schuitema
Dwingeloo N 52 50'18.6"
The Netherlands E 06 22'26.33"
alberts@pi.net
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