Hey gang, I recently got a pair of Tek 1731 and 1721 waveform monitor + vector scope. However, they have a bunch of problems:
- The waveform monitor (1731) won't turn on. There is a clicking sound coming from the main transformer, and no lights turning on.
- The vectorscope (1721) doesn't always turn on, sometimes it comes on after a while, there is a clicking sound in this one too.
- Some of the vectorscope knobs are broken, but relatively easy to fix. There is an interesting rotating control for the phase, which is a sort of strange 3-way potentiometer. I'll post pictures when I perform the repair on this one.
For now I'd like to concentrate on the 1731 waveform monitor. Here are some links I've found, which have been useful, but not 100%:
I own the 1731, which is the PAL version (1730 is the NTSC version). The serial no is E202089. The reason I'm mentioning the serial number is because the second link in the list above is a fairly complete manual, but it's for "SN B070000 and above", which means it's a different schematic for the PSU at least. The component numbers don't match.
The third link, which is a scan, corresponds, there is some text near the end that explains how the power supply works, and the component numbers match, but unfortunately there is no schematic or troubleshooting steps.
Btw, the power supplies are identical on the 1730 and 1720 series, so a manual for 1720 would work too, as long as it's not for "B0X0000 series and above" like they are on the tek site.
So I need either help fixing it, or a manual scan. I've found some manuals on ebay, but they're for >$50, and I paid about $75 for both devices. I know I got ripped off, but it's more fun to fix it than to send it back.
Anyway.
I've measured the voltages at +5, +15, -15 and +40V, and they're around 1V, so 10 times as low. I've taken a look at the PWM chip and its +Vcc looks like a 10Hz spike on the scope. On the other device (1720), which eventually turns on, the supply for the PWM chip is a constant 12V, and the PWM output looks like 50% duty cycle, I guess a few hundred kHz. I've read somewhere that the clicking is actually the supply going into some sort of undercurrent protection mode and shutting down and turning on again.
I've replaced most of the electrolytics caps too, btw.
Anyway, I'm attaching some pictures, and if anyone can help with some troubleshooting, that would be great.
Thanks!