Tektronix 5000-series Plugin Mod for 500-series Mainframes

After getting a cheap PS5010 in good shape from eBay, I needed to make it work on my TM500 mainframe. Since TM500 modules can be used on TM5000 mainframes, I thought the reverse should be also possible. I found some references on the web and newsgroups, but no details on how to do it.


Here is a comparison of the TM500 and TM5000 mainframe interfaces:






Part of the modification consists of fitting this circuits in the TM5000 module:

* +33.5VDC to +26VDC regulator, less than 500mA. This is done with a LM317.

* -33.5VDC to -26VDC regulator, less than 500mA. This is done with a LM337.

* +11.5VDC to +8VDC regulator, about 1A. This is done with a LM317

* PWR signal generator. This is a TTL compatible signal that comes from the switched TM5000 power supply and goes high (5V) when all DC voltages have stabilized. The signal is generated with a PIC12C508A that simply waits 2secs after power up and drives the base of a PNP transistor low so that it puts +5V on the PWR input on the PS5010 module (pin 6B of the interface). This is the simple program running in the PIC:




All four circuits are very simple, with almost no need for capacitors since the PS5010 boards already have them:




All three regulators need cooling and they are placed on an already-built-in heatsink (which luckily had some free space and holes !) between other TIP31 and TIP32 transistors used for the power supply outputs (SMD resistors and cap on the new PCB are difficult to see):




The 8V regulator is put in place by removing a fuse and inserting the fuse wire between two squares of the project PCB. For the other two supplies, two traces need to be cut in order to insert the regulators. Notice the clean cut to open a sandwiched track between pins 6 & 7 and the other one (pin 12), that needed just a light scratch on the surface:




This is where the daughter board connections go (the 8V regulation handles more current, and thicker cables are used):




Everything fits nicely between the boards. This is the back of the module without covers:




And finally, here it is, running on the TM500 mainframe:




Note that the 500-series mainframes have no GPIB and there no slot to accomodate the smaller GPIB connector on the back of the 5000-series plugins. The GPIB contacts PCB has to be cut in order to fully insert the modern module in the old mainframe. Someone told me there was no need to do this since the entire GPIB (processor) board could just be removed, but there is much more circuitry in there than just GPIB extension, so it needs to stay in place. I know, it's a pity but I had abslutely no plans for upgrading to an expensive 5000-series mainframe.


Roberto Barrios, EB4EQA