Tag Archives: Review

Understanding and repairing the power supply from a 1969 analog computer

via Dangerous Prototypes

Ken Shirriff writes:

We recently started restoring a vintage1 analog computer. Unlike a digital computer that represents numbers with discrete binary values, an analog computer performs computations using physical, continuously changeable values such as voltages. Since the accuracy of the results depends on the accuracy of these voltages, a precision power supply is critical in an analog computer. This blog post discusses how this computer’s power supply works, and how we fixed a problem with it. This is the second post in the series; the first post discussed the precision op amps in the computer.

More details at righto.com.

A look inside a Marconi signal generator

via Dangerous Prototypes

A closer look at a Marconi Instruments signal generator @ jaeblog:

Recently I got a Marconi Instruments 2019 signal generator, capable of generating signals from 80Khz up to 1040Mhz. It can also modulate these signals with AM, FM and more. This instrument is from the mid 80s and is, as far as I can test, still in good operational order.
A signal generator capable of generating over 1Ghz is pretty impressive, especially in the 80s, so let’s have a look inside this unit and see how it’s made.

Capacitor plague? Inside an HP 8620C sweep oscillator and HP 86245A RF plugin

via Dangerous Prototypes

p-topcoverremoved-600

A teardown of the HP 8620C and HP 86245A by Kerry Wong:

I just picked up an HP 8620C sweep oscillator with an HP 86245A 5.9 GHz to 12.4 GHz RF plugin on eBay. This time around though, the unit does not work. While it was advertised as a working unit I could not get it powered on and there was no sign of life whatsoever. So before I start troubleshooting and repairing the unit, I thought I would do a quick teardown to see what’s inside and if I could spot anything obvious that was out of the ordinary.

More details on his blog here.

Check out the video after the break.

Teardown of an HP 8671A microwave frequency synthesizer

via Dangerous Prototypes

p-HP8671A-600

Kerry Wong did a teardown of an HP 8671A microwave frequency synthesizer:

I recently bought an HP 8671A microwave frequency synthesizer on eBay. This synthesizer can generate signals from 2GHz to 6.2GHz with an unleveled output of more than 8dBm. It is a nice complement to my HP 8642B signal generator and Wavetek 907 signal generator. Using these generators, I can now generate signals of pretty much any frequencies under the 12GHz range. A video of this teardown is linked towards the end of this post.

More details on his blog here.

Check out the video after the break.

Inside a PM1A color analyzer

via Dangerous Prototypes

PM1A-600

Kerry Wong did a teardown of a PM1A color analyzer:

As I mentioned in one of my posts a few years back, a color analyzer from the 80’s can be a treasure trove for the hobbyists. And at the very least, it is a cheap way to get yourself a photomultiplier along with the supporting circuitry to do experiments with. For instance, you can utilize the fast response time of a PMT to do accurate speed of light measurement in a lab setting like I showed in this experiment back in 2015.
I just bought another one off eBay, and this time it is a Beseler PM1A color analyzer. By the look of it, it is probably a cheaper version of the Beseler PM2L I did a teardown and reverse engineering with before.

See the full post on his blog.

Check out the video after the break.