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Home Brew Analog Computer System

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GK:
A geofiz trip put me out in the middle of nowhere again for several days, but I'm now back in the shed. The timebase board is finished and works just as planned. Got it wired to a scope with more channels this time! (A DSO for now, until I finish calibrating two of my Tek 1A1 plug-ins for the 551 mainframe).
The two rotary switches (time [1s, 2s & 5s] and five-position multiplier) which select one of the 15 calibrated compute time settings (from 1mS to 50S) will be double pole types, with one half of each switching a diode decoding matrix and MPSA44 HV transistors to display/indicate the timebase setting on three Nixie tubes (and two neon lamps in bezels to indicate either ms or S), which I have salvaged from an old stuffed "panel" meter (along with a suitable transformer to supply the anode potential).


SeanB:
You need a new slip indicator. I got quite good at knitting them out of a big ball of bright red wool i bought at the sale section at a haberdashery. What chopper were you flying over the sand.

GK:
Robinson R44 Raven I. I actually drove a ~6 tonne truck/mobile lab out there, battling sand dunes. When things didn't go to plan (as usual), instead of sitting around in the 40+ heat with sand up my arse, I managed to hitch a free seat on the chopper out to a hotel room for the night. Touched down right in front of the pub!
   

FenderBender:

--- Quote from: robrenz on February 15, 2013, 12:42:25 pm ---Awesome work there GK :-+ Makes me feel electronically inept :'(

--- End quote ---

I'd say...

Yikes, I'm still trying to understand class-b amplifiers...

GK:

--- Quote from: GK on March 01, 2013, 08:00:56 am ---A DSO for now, until I finish calibrating two of my Tek 1A1 plug-ins for the 551 mainframe.
--- End quote ---


Done! Well, almost. The 1A1's are still way out of calibration, but I have fixed all of their faults and they are functional. Also spent the entire afternoon tracking down faults in the 551 mainframe, before I could calibrate it properly. My long run with ancient Tek gear and no dodgy electrolytic capacitors has come to an end. One "125MFD 350WVDC", of the -150V regulated reference supply, suddenly decided to go <100nF, giving me huge ripple on all of the regulated rails along with a really funky CRT display. Another PSU electro decided to low impedance instead and burnt out some parallel peak-current-limiting resistors between it and the bridge rectifier. I will have to compile a shopping list and do an electrolytic capacitor blitz on my old Tek mainframes one weekend  :-/O

But anyway, two 1A1 dual-trace plug-ins in a 551 dual-trace mainframe gives a 4 channel scope. The next step is to track down a pair of 1A4 plug-ins on Ebay to make 8 channels.................

 

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