I'm so stupid... Was: Head Cleaners

From: Brent Hilpert <hilpert_at_cs.ubc.ca>
Date: Wed Jun 30 04:26:51 2004

Tony Duell wrote:
> True story (although I am ashamed to admit it). I was sorting out a
> Commodore 8250LP (slimline model, double sided drives). And I could not
> get a reliable read signal.
>
> I checked all the components in the head amplifier, the head switching
> diodes, the head select signals, and so on. I then remembered to clean
> the heads. Worked fine after that...
>
> -tony


I've had an inclination for some time to start a thread along these lines: tales told at one's own expense. Of course, one can't make such a suggestion unless one is willing to put up one's own tale. So here's one at mine (I'm willing to follow up with another if this catches on at all):

Back around 1981/2 when the CompSci department here was much smaller, I filled in occasionally to do some hardware repair and support when I'd had enough of sitting and doodling with little green characters on a screen (aka: programming). Our TI-990 [1] - being used for OS development - needed some new boot PROMs burned but the PROM burner was being flaky, burning erratic bit patterns and such.

I decided to tackle this and proceeded to haul out our newly-acquired sophisticated multi-channel logic analyser, an oscilloscope, a DVM, arranged it all around the rack-mount computer and prom burner with it's guts hanging out, pulled a terminal over so I could control the burner via the computer, connected up multitudes of probes and pods, sat myself in the middle of it all and started turning knobs, flipping switches, and bringing up pretty traces on all the screens.

I looked like a real rocket scientist, surrounded on three sides by all this hi-tech equipment ... but I wasn't getting anywhere. I decided to take a break and go for lunch.

When I returned, the other hardware guy informed me the PROM burner was fixed.
He had taken a screwdriver and made a minor tweak to the 5 volt logic supply level.

(I was going to do that ... really I was...)

[1] As much as I recall, I still think the -990 was a rather neat machine architecture, the stack-based work-space registers making for simple process switching and nice compiler code generation. Some RISC characteristics way before RISC.
Received on Wed Jun 30 2004 - 04:26:51 BST