> -----Original Message-----
> From: Doug Jackson via cctalk <[email protected]>
> Sent: 24 November 2025 23:04
> To: General Discussion: On-Topic and Off-Topic Posts <[email protected]>
> Cc: Doug Jackson <[email protected]>
> Subject: [cctalk] Re: Hot Video Shift Register on VT100
>
> 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.
I think I can try this, the DC012 it drives is socketed.
>
> 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.
I guess CRO means Cathode Ray Oscilloscope? Not sure what you are suggesting I
try here?
>
> Kindest regards,
>
> Doug Jackson
>
> em: [email protected]
> ph: 0414 986878
>
>
>
>
> On Tue, 25 Nov 2025 at 09:52, Peter Coghlan via cctalk <
> [email protected]> 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.
> >
