using new technology on old machines. Was: PDP-12 Restoration at the RICM

Mark J. Blair nf6x at
Mon Jun 15 15:27:43 CDT 2015

> On Jun 15, 2015, at 11:54 , tony duell <ard at> wrote:
> Why not do it properly first time? What is the rush in bringing up a classic computer? And for a test,
> use the TTL pulse generator you have on your bench.

I don't have one. I have a lot of test equipment, but mostly for RF work. If I needed to generate TTL pulses, I'd probably pull out a microcontroller development board of some sort, because that's what I have sitting around.

> Or even an NE555 astable (yes, with a decent capacitor
> it is stable enough for a baud rate generator, I've used it). Heck, I've worked on machines that used a 
> 2 transistor astable multivibrator for the baud clock. Surely you have 2N3904s in the spares box?

No, I have neither 2N3904s nor NE555s in my spares. I could replace an M1 Carbine trigger spring on the spot, or a HMMWV taillamp housing, or most of the tubes in a 1950s US military vehicular radio, or an AR15 recoil buffer, or an Enfield Mk. 2 firing pin, or countless other things. I could test a diesel engine injector for pop-off pressure and slobber, or pull diagnostic codes from an M923's antilock air brake system, or check a transmitter for spurs up to 2.9 GHz, or measure a TTL clock frequency to within 50 parts per trillion absolute accuracy. But I don't have a TTL signal generator. Not everybody has the same junkbox, background, interests, equipment or capabilities, so not everybody will do things the same way that you do. Should I criticize you for not having SAE grade 8 hardware on hand, or Bristo wrenches for working on a Collins PTO, or spare Packard connectors for a post-Korean vintage US military vehicle, or the right kind of grease for an M1 Garand bolt, or the special screwdriver for the tiny little center-drilled screws in a telephone patch plug, or an M1 carbine gas piston plug wrench, all of which I have on hand? (No, I shouldn't, and I wouldn't.)

> Incidentally, if certain horologists heard you would use MDF in an antique clock, you would be
> going home with a pendulum rod shoved where the sun don't shine ;-)

Well, maybe I'd educate them that Underwood and Remington Rand didn't just make typewriters before they got that pendulum rod in very far. ;)

Mark J. Blair, NF6X <nf6x at>

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