Test Equipment Anonymous

Ordered this Heath IG-18 THD Improvement Kit. Should arrive by Saturday. Complete write-up once received.

https://www.ebay.com/itm/154285948636

Hmm interesting, that board mounts directly to the back of the meter I think IIRC?

Specmaster wrote: ↑Thu Jan 05, 2023 12:59 pm Hmm interesting, that board mounts directly to the back of the meter I think IIRC?

Yes.

Here's the advertisement from the Heathkit site, with a picture showing it mounted to the meter, and details showing the improved performance.

https://shop.heathkit.com/shop/product/ ... ga-18-1-17.

The modification kit showed up today. The instructions are typical Heathkit very detailed and complete. Nice throw back to those old days. I'll start the assembly this coming week.

Meter board fully populated. Those 3 diodes surprisingly turned out to be Germanium. 0.297V forward voltage drop. That's all I have time for today. Tomorrow the install, modification to the generator itself, and then test.

Meter board installed. There were also some changes required on the main board and also the filter capacitors on the PSU board were upgraded.



Final adjustments were made at 1kHz. Nice clean Sine at 993.5Hz actual. Not bad. I can't tell if the overall distortion has been improved since I don't have the equipment to accurately measure it. But it doesn't really matter. It was a fun little project.

Looks good, and it it is pretty accurate considering how old that design is really, well done.

MED6753 wrote: ↑Wed Jan 11, 2023 3:34 pm I can't tell if the overall distortion has been improved since I don't have the equipment to accurately measure it. But it doesn't really matter. It was a fun little project.

You mean you are going to wimp out and not go down the rabbit hole of ludicrously low distortion oscillators and distortion analysers that can wrestle with them on the noise floor? Very sensible.