First, as a good practicer and enforcer of the RTFM principle, I looked into the service manual of the scope. What i found was interesting, how to test the main board and power supply : where is GND, 3v3, 5V and 12V rails.
Except for that, nothing really useful for my project.
Second, using the published photos of the TDS3GV found on the EEVBlog forum, the ref for the chips were easy to get. An unknown connector, some TTL, a VGA driver, a classic MAX232 and a GPIB controller. Easy to see how it work:
- 7 x 74LCX245 Tri-states bidirectional transceivers
- One 74LC00 quad NAND and one 74LC08 quad AND, probably managing the address selection for the chips
- One ADV7120 probably for driving the VGA port plus it's impedance matching components and bypass capacitors
- One classic MAX238 for the TTL/RS232 serial port plus some caps for the integrated step-up
- A big chip labelled TNT14882 who seemed like a GPIB controller/driver with filtering caps and inductances for the GPIB lines
- A 40MHz quartz
- Some caps, resistances, ... don't know why
- An unknown 100 pins connector
The block diagram of the cards was easy. Next, finding all of the chips datasheets.
TTL chips : no challenge. But i didn't know the LCX familly. To summarize : it's the family of 3v3 chip, with low noise, high speed and 5v I/O tolerance. I'll keep them in mind for sure.
ADV7120 : a sub 15$ 5V driver to transform 3x8 bits colors to a proper VGA signal. Good guess and the data sheet confirm the impedance resistors. But .... it seem the scope use only 4bits per colors ... will have to check that.
MAX238 : Same here, no challenge. But can't find the expansion port pins just by looking at the photo.
TNT14882 : This one was ... tricky to get. The only information i could come across was a commercial brochure that confirmed it was a GPIB controller. The National Instruments had the full datasheet but ... like always, when you need old information, you can't get it because it's too old and someone removed the file on the web server ... I was doomed. Some time later I found this datasheet in a dark corner of the web on an anonymous FTP. Don't know who put it here, but you have my thanks !
For the unknown expansion connector, i had what i need just in front of me : the matching female connector. Time to get the caliper and some drawing paper. After all measurements and a lot of mouser browsing i nailed it : AMP 1-1734099-0
A note about the measurements : If i can't put my hand on cheap connectors (Mouser, Digikey are a no go for me : VAT and import taxes add 40$ on every commands) i will be able to make my tests using a 1.6mm PCB with 1.27mm spaced tracks. It match the female connector perfectly ! But i would prefer using the male connector for reliability and longevity especially for some Rev&Dev.
Luck was here, as some days later, someone sold there old stock on ebay : including shipping, 25$ for 11 connectors. Lucky me !