VXI bus, Tektronix and more

If you could publish just once a month, would you miss the opportunity to post on the unique day of a leap year? Here's my February 2024 sum up.

Tektronix VX1405 and plugins.

It turns out that I spent the whole month after a new "toy" I stumbled upon. It's a technology from 1990's that puts together many computer-controlled instruments into a rack. They are controlled via HP-IB (GPIB) and connected with a VXI bus. You can mix the plugins depending on your needs: signal generators, digital (storage) oscilloscopes, voltmeters, ... The configuration shown here has: arbitrary function generator (HP E1445A), two channel oscilloscope (HP E1428A), waveform analyzer (Tek TVS625) and a command module (HP E1406A).

First of all: the thing shown in the picture weights more than 20 kg. It is bulky, heavy, noisy and power hungry (500W). The whole troubleshooting endeavour is described on eevblog, so I'll try to summarize what I've done.

The baby did not give any sign of electronic life. I initially checked the command module and removed the NiCd battery pack with the obvious leak, fortunately contained within the pack. Still no signs. So I checked power supply voltages and +5V, +/-12V were missing.

Therefore I moved my attention to the power supply unit in charge of those voltages and tried to troubleshoot it: a switch-mode high-current configuration without a schematic diagram. It is a very packed circuit. I understood that there are some components that are failing since increasing the temperature the PSU tries to start up. I located the fault in the AC side of the switcher, most likely in a custom part/board so there are very little chances of a succesfull repair. Even the service manual says that PSU are black boxes that must be replaced as a whole.

In the end I gave up: I have learned enough of switch-mode power supplies that now I want to see a working unit on the oscilloscope. I might try to retrofit an external PSU to confirm the plug-ins respond to commands.

Also in February 2024 I received a bunch of Yaesu FT-23R and alike handhelds. Out all of them I got one working with the battery eliminator. I've always dreamed of owning one and now I feel 17 years old when I hold it. It's amazing how heavy and current hungry it is!