dim. 26 juin 2016

HP 34970A Data Acquisition Unit - part 3

As explained in the previous post in this series, I've started to sniff the serial protocol between the main board and the display panel so I can replace the failed VFD by an OLED or TFT display managed by an arduino or similar.

Protocol

The serial communication takes place at …

mer. 22 juin 2016

HP 34970A Data Acquisition Unit - part 2

This is quick follow up of my previous blog post on my attempt to fix my recently acquired HP 34970A.

In my hurry to replace the failing FRAM (FM24C04) chips, I also replaced the FRAM chip on one of my 2 plugin modules.

Bad idea: the module then provoques an …

lun. 13 juin 2016

HP 34970A Data Acquisition Unit

I recently "scored" a HP 34970A with the DMM included and 2 plugin cards (HP 34901A and HP 34907A) for less than 200€. The plugins should be in working condition, but the main switch unit was almost "given" with the plugin modules since it is non functional.

front view of the HP 34970A data acquisition unit

It's in very …

mar. 19 avril 2016

Tektronics 2445 scope PSU repair: part 3

After having mostly destroyed the PSU of my Tek 2445, I've decided to be a bit less foolhardy and I've subscribed to the yahoo Tek group. I discovered that such a failure has already been reported there, also after a full recap of the preregulator and regulator of the power …

dim. 27 mars 2016

Tektronics 2445 scope PSU repair: part 2

After a quick repair of the PSU of my Tek 2445, I've started a more systematic replacement of the capacitors.

Tek2445 PSU Caps being replaced.

But I was also a bit worried because of a dirty noise coming from the preregulator area.

After having replaced most of the electrolytic capacitors, the dirty noise became louder …

jeu. 10 mars 2016

HP8904A Multifunction Synthetizer Repair: 10MHz output

After having fixed the PSU of one of my HP8904A signal generator, I discovered that the other unit had its 10MHz reference output dead flat.

I've disassembled the main logic board, but unfortunately, the schematic of this later A2 board (as it is referenced in the servce manual) is notavailable …

jeu. 10 mars 2016

HP8904A Multifunction Synthetizer Restoration

What Is This About

I have a couple of HP8904A multifunction synthetizers for years (bought them on ebay around 2007 IIRC). One of them is working properly, but the second one had very inaccurate output levels, generating a non-symmetric signal when output level was set above 5V or something like …

jeu. 10 mars 2016

Tektronics 2445 scope PSU repair: part 1

I've recently took my good old Tek 2445 scope from the cellar (along with my {tag}HP8904A signal generator), and it showed signs of tired PSU: unstable display, noise, then the typical noise of a capacitor failure.

Here is the beast:

My old Tektronics 2445 scope

And some pictures of its womb:

The main analog board. Top view of the scope.

The PSU consists …

« Page 2 / 2