High voltage working, then not working, and all I changed was input voltage.

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2 months 3 weeks ago #11218 by rezin8
I sent Ian a couple emails, but then I found the forums, so I thought I'd just try here rather than bothering him directly through email.

I found an old Modular Rev 2 clock in a box of projects that I'm seriously behind on and since I have a bunch of free time right now, I thought I'd give it a shot. I was able to get the low voltage circuit put together with no problem, and then the HV circuit. I took a quick video of it working to mess with a friend of mine showing it outputting significant voltage on just 5.5v, 0.5A input.

Here's that video of it working:


After I took that video, I switched power supplies and set the other one to 12v. After that the HV circuit stopped working. Now it won't work no matter how much I put to it. I thought that maybe I blew the MOSFET, so I desoldered it last night and tested it, but it seems to test OK.

Now, no matter what voltage I put to it, the LV circuit works fine, but the HV circuit won't work. Here's another video I just took showing what I see:


I looked at it last night with my thermal camera and the only thing I see other than the MEGA that's getting toasty is (I think( D1, the UF4007 on the LV.

I've tried to connect the BTN pin to ground on front panel header while powering up in order to reset to factory defaults, but that hasn't changed anything. The manual says the LED should blink 10 times or something, but I'm not seeing any blinking, it just sits there blue like nothing's happening.

Can anyone think of anything else that I can do to troubleshoot this circuit?

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2 months 3 weeks ago #11221 by rezin8
I went ahead and hooked a scope up to the gate on the MOSFET (after changing the MOSFET). Document says I should be seeing a square wave, looks like I'm seeing a sine wave. Now I really have no idea what I've done...

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2 months 3 weeks ago #11223 by rezin8
Update on the troubleshooting. I figured it out. Seems that the IC was fried. I was able to pull another IC out of an Arduino Uno I had laying around. I hooked the scope up to the mosfet and noticed that it wasn't getting a nice square wave, so I figured that it wasn't getting the proper signal from the Arduino. I grabbed an Uno, flashed it with new firmware, swapped chips and the HV circuit came right up. When I went to flash the old chip, the Arduino IDE couldn't speak to it. So, no idea why it fried, probably something to do with a cheap power supply, but at least I have it up and running now. Thanks!

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2 months 3 weeks ago #11224 by Ian
Thanks for the update!

It's really unusual that a controller takes a hit.

Was the waveform there but bad, or just not there? If it was not there, I'm wondering if there was a problem on the firmware: but it's pretty unlikely as the HVD pin (High Voltage Drive) uses a particular pin on the controller because it is able to use a 16-bit CTC, so that has never been changed on any revision or version.

I understand from the mail exchange that you are trying to re-flash the controller, and I'd be really interested to know if it is indeed a hardware error.

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2 months 3 weeks ago - 2 months 3 weeks ago #11227 by Ty_Eeberfest
Hey Rezin8! Thanks for posting all the detailed info, I haven't been around the last few days but if I had I'd have jumped into the conversation. Glad to hear you got it working.

That sine wave, as well as the "bork wave" in the video, interest me. I don't know how the chip could put out either of those waveforms. What I'm wondering about is amplitude. Were those signals just noise, i.e. millivolt level stuff that the scope locked on to when auto-ranging? Or did they have significant power to them, i.e swinging from rail to rail?

Look into it later when the dust is clearing off the crater.
Last edit: 2 months 3 weeks ago by Ty_Eeberfest.

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2 months 3 weeks ago #11231 by rezin8
Ty, you can see in this video that it's millivolt level stuff. The controller wasn't putting out anything.

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