24 Nov
2025
24 Nov
'25
3:04 p.m.
Another test would be to disconnect the output and see if that runs the
device cooler. Maybe the load, while not a short, is simply too great for
the device.
But I am leaning towards the inputs containing spikes that need to be
dissipated as heat in clamping diodes. A decent CRO on the device input
pins while it is out of circuit will show that as well.
Kindest regards,
Doug Jackson
em: doug(a)doughq.com
ph: 0414 986878
On Tue, 25 Nov 2025 at 09:52, Peter Coghlan via cctalk <
cctalk(a)classiccmp.org> wrote:
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.