24 Nov
2025
24 Nov
'25
3:42 p.m.
-----Original Message-----
From: Peter Coghlan via cctalk <cctalk(a)classiccmp.org>
Sent: 24 November 2025 22:41
To: General Discussion: On-Topic and Off-Topic Posts
<cctalk(a)classiccmp.org>
Cc: Peter Coghlan <cctalk(a)beyondthepale.ie>
Subject: [cctalk] Re: Hot Video Shift Register on VT100
Yes, I did think of doing this, but I don't like the idea of breaking a
track for this purpose if the outcome is uncertain. I guess maybe even if
this does work the circuit was presumably designed to work fairly hot,
although perhaps the revision added the inductor to reduce the heat?
I will consider it though, but I am not too sure what kind of part to use.
If I have read it correctly the revised print set says "BEAD, FERRITE
.1380DX.380LG", I am not quite sure that this means, although I am sure I
can get ferrite cores. Does that description mean anything to anyone?
Sorry if I wasn't clear in my earlier reply, but there were some
answers inline. The summary is that Vcc looks fine, there does not
seem to be any short on the outputs of the shift register and the chip
seems to be working correctly. It just gets hot and I wonder if this
could be due to the CLK input being a bit spikier on the VT100 than on
my VT102? Could this be why later revisions of the VT100 introduced an
inductor on the DOT CLK output from the DC011?
Perhaps one way to test the hypothesis would be to insert an inductor like
those used on the later revisions in the DOT CLK output and check whether
a) everything still works and b) the shift register runs cooler?
Regards,
Peter Coghlan.