Recapping a Falcon PSU with an Exxos kit

[Badwolf]

I'm hoping to record video of my attempts to resuscitate the Falcon motherboard I bought off Asci.

As a bit of a forerunner to that and a tech experiment in what works from an audio-visual point of view, I've put together a short* video of me recapping my Falcon PSU.



Conclusion so far is that the second camera isn't good enough and the audio is marginal, but let me know what you think.

I assume changing through-hole electrolytic capacitors is old hat to most guys on here, but I hope it might be useful to anyone who is a bit nervous about getting the soldering iron out or working with mains voltages.

Drama ensues when it turns out I'm short a capacitor & I get to see more filth than an adult movie producer.

Cheers,

BW

* Not at all short.

[exxos]

Drama ensues when it turns out I'm short a capacitor & I get to see more filth than an adult movie producer.

Great video. Sorry you short of a cap.. will send one out.. I've checked the other kits and the 680 is in those, so not sure why that bag got missed :(

What the electronics load you have there btw ?


Odd you're not seeing any spikes. Are you limiting bandwidth or anything on your scope ?

falc5a-min.png

That is why I suggest people recap as those spikes will eventually kill stuff.. Mostly seems to be the Videl, which is "first in line" ...

[Badwolf]

Drama ensues when it turns out I'm short a capacitor & I get to see more filth than an adult movie producer.

Great video. Sorry you short of a cap.. will send one out.. I've checked the other kits and the 680 is in those, so not sure why that bag got missed :(

Ah, that's kind, thanks. I wasn't going to raise it as an issue as I'd had the box sitting on my shelf for months and was my fault for not checking it earlier. :cheers:

What the electronics load you have there btw ?

It's the Dave Jones design from EEVblog 102.

Screenshot 2021-06-16 at 09.38.48.png

Odd you're not seeing any spikes. Are you limiting bandwidth or anything on your scope ?

That is why I suggest people recap as those spikes will eventually kill stuff.. Mostly seems to be the Videl, which is "first in line" ...

No filtering turned on, but I was at one volt per division. You're down at 10mV per div. I never wound it in that close. I could re-run the freshly capped version with the resolution cranked up to see how that looks.

Ta,

BW

[Badwolf]

Thanks @exxos! A Spanky new 680uF/25V cap arrived in the post this morning.

When I get this fitted I'll run a few more of those scope tests and see how things look now. :-)

Cheers, :thanksyellow:

BW.

[Badwolf]

I finally got around to fitting the missing capacitor and doing some better measurements.

Turns out my shed is noisier than your average teenager on a bus!

[exxos]

I finally got around to fitting the missing capacitor and doing some better measurements.

Turns out my shed is noisier than your average teenager on a bus!

You can turn on the bandwidth limit to like 1mhz or something. The PSU switches no where near that. It helps no end to filter background noise out. LED lighting and other switch mode close to the scope can cause problems, you pretty much have to turn everything off in the room in fact .

When I developed my PSUs I had a 400hz spike which drove me nuts for ages. Turns out, it was coming from the fan I was using to cool the load resistors with :lol: :roll:

You can also use the vmin vmax under the measure menu to automatically tell you the figures..

Also you didn't seem to mention ripple either. You need to get down to 50mv / div and fiddle with the time / div until you see a sine wave, which is the ripple. I've probably got images of it on my site somewhere.

[Badwolf]

Also you didn't seem to mention ripple either. You need to get down to 50mv / div and fiddle with the time / div until you see a sine wave, which is the ripple. I've probably got images of it on my site somewhere.

Yeah, I had considered the noise so overwhelming that it wasn’t worth pursuing. Also, since finding my ‘before’ figures were so corrupted by the bloody voltmeter employed as a current indicator there was no meaningful comparison, so I concentrated on characterising anything dangerous or weak.

The problems of doing this the first time. ;)

Ta for the replacement cap!

BW

[Steve]

Hey BW just noticed we have the same scope, did you do the free upgrade to 100mhz? :)