I have success finally on the conversion. I did start with trying to make another 7603 from the salvaged parts, but too many things were wrong with various items, so I decided to try the R7613 to 7613 switch after all. It turned out to be quite easy structurally, except that I had to give up the original fan cooled power supply unit (which is essential in rack-mount I think), so the end result is convection cooled only. It is possible to mount a small DC fan onto the internal structure to get some circulation and flow on the pass transistor heat sink assembly, where most of the dissipation is from. I'm doing some burn-in testing and assessment of temperature rise, then I'll decide if I need to add some fan help. This unit will never be used toward the higher specified temperature (up to 50 C) extreme, so I'm OK with reasonable lab/garage conditions. The real 7613 and my 7633 are fan cooled, and the covers are solid. With this one, I'm using the 7603 type perforated covers for regular convection cooling of the cabinet, and I'll probably modify the cover that goes on the back over the heat sink assembly to get easier flow. It will run hotter, comparatively, but I think it will be OK, and quieter too.
Mechanically, I had to drill only two holes in metalwork - one in the handle spine for a clamp to hold the CRT's Alden connector, and one in the 7603 style cross bracket that supports the CRT socket end so I could flip it around to fit the longer assembly. I used a salvaged 7603 transformer/rectifier section (with the optional signals out back end) that was good, and the low voltage regulator assembly from the R7613.
I found out quickly that the hardest, most tedious part is rewiring all the interconnecting cables. On the attempt at making a 7603 first, it was a PITA to hunt through my limited stock of Tek harmonica/ribbon cables. Somewhere I have lots more but couldn't find the missing box. Even with plenty of pieces, it takes a lot of work to sort out the lengths, conductor counts, and plastic housing color codes if you want them as original. When I decided to do the R7613 teardown I made some notes on certain parts of the wiring, but I should have done more and thorough work. I went through extra grief to keep it as modular as possible, and managed to take the whole CRT side out as a unit to minimize its local rewiring. This involved cutting and bending the rack chassis apart in certain spots, which also made it a one-way trip for this project - no going back to the original if I should fail the conversion.
So here was the left side guts assembly with cables hanging every which way, and the rest of the sections sort of separated, and sort of connected to each other, but removed from the chassis, and a lot of mystery cable ends that had to be pulled and noted for re-hooks, or would need to be figured out. I kept the pieces together as much as possible so I could gradually move the cables into the new scope chassis. The left side CRT module slid right into the top chassis section, and there are plenty of extra holes to accommodate the different mountings needed around the CRT and front control panel, so it was a breeze to install it. I made the mistake of keeping a dubious salvaged 7603 main interface board in place rather than transplanting the (known to have been working) one from the R7613, thinking it would save some time. I paid the price later. After that it was mostly the tedium of figuring out where all the cables went at each end, and whether they were long enough to reach, and gradually putting the remaining big pieces and their cabling into the chassis. I had to build some new cables from various pieces on hand, and tried to keep the color coding original, but couldn't get them all.
The time finally came to fire it up, and the screen lit up just fine, but there was some kind of vertical failure showing compression so the traces would hardly move up and down, and the readout was miniaturized. After some connector checking and more study and measuring I couldn't find anything to blame, so figured it was time to change that main interface assembly. Sure enough, putting the original one in as I should have fixed it right up. Then everything seemed to work except the right vertical readout was gibberish. I went on a wild goose chase with all sorts of grief trying to figure out what happened, then finally found I had made a mistake on one of the cables I made for the readout board - two wires were swapped.
Now it all seems to work, and will need checkout and some adjustments. The focus seems kind of crappy, but actually better than it was when it was in the rack chassis. I'll probably be starting a new thread on some of the issues that I find.
Ed
