After Tony's suggestion that I test our faulty LK201s with a VT terminal, it
turned out that both worked fine with a VT420. So I thought I'd give our
LK401s a try as well. And it actually turned out that one worked! The other
still didn't. I opened them up and connected them to the VT, and after a
while, I noticed that a small (14 pins DIL?) Motrola IC called LC74750P was
much hotter on the faulty board. I established that the fault was on the PCB
by connecting the working one to the keyboard matrix of the faulty one. The
74750P was only pleasantly warm in the functioning keyboard, whereas it got as
hot as a Pentium processor after a while on the faulty PCB.
So I thought I just had to nip down to the shop and get some standard TTL (it
does begin with a 74...) chip and solder back (in a socket =). No such luck.
The clerk couldn't find the chip in store, in any catalogue or any databook.
He suggested that it might have been made as a batch only for DEC.
Does anyone know what kind of chip this might be, and if it's available
anywhere?
As for the LK401, the PCB contains three ICs:
1 ? 74750P (???)
1 ? i8051 (microcontroller, does this have some on-board ROM which prevents
drop-in replacement?)
1 ? AMTEL something or other. Could it be a ROM?
--
En ligne avec Thor 2.6a.
Die Malerei ist stumme Poesie, die Poesie blinde Malerei.
--- Leonardo da Vinci
Received on Thu Oct 04 2001 - 22:40:33 BST