Overheat cap and MOSFET with no HV

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1 year 4 weeks ago #7974 by TechGuy03
I've got the modular board here... Bought 1 full kit and 1 partial kit.

Side note... I may just opt to buy remaining components from you folks for the 2nd partial kit.

Anywho... Finished the build.
Couple of comments: the silkscreen is not the best. I feel labeling component values on board would be useful, though I see how it does force one to read the docs.

The PROBLEM:
When plugging in my supply(12v 1a)
1) I see no more than 40v DC on my HV
2) C1 heats up
3) L1 heats up
4) Q1 heats up
5) VCC to ground is 5.01V
6) VIN to D1 has no drop
7) red LED lights up

Could a bad cap be causing all of this?
Any suggestions?

Thank you

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1 year 4 weeks ago - 1 year 4 weeks ago #7975 by BS_Jim
A couple things come to mind. Is the "-" stripe on C1 facing the tubes? Is C1 a 2.2uF/400v capacitor? Is the banded end of D2 also facing the tubes? In an earlier version of the kit there were two different types of diodes and putting the 1N4007 in D2 would not work. I think all Ian's recent boards just use UF4007's for both diodes.

If all polarities are correct and D2 is the correct type, I would start by removing the opto-couplers from their sockets and retesting the HV. It should now read around 360v because of no load.

Where to go next depends on your results.
Last Edit: 1 year 4 weeks ago by BS_Jim.
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1 year 4 weeks ago #7976 by TechGuy03
Caps are all in correctly
. D1-3 are not mixed up(2 uf4007 and 1 Schotty diode)

Ill try removing optos though I tested this without tubes and report bsck

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1 year 4 weeks ago #7978 by BS_Jim
I just discovered the "modular" board was slightly different from the "All-in-one" and "classic" boards that I've built. I was wondering why you had 3 diodes.

So D2 should have the banded end toward the edge of the board instead of forward.

If you have an old neon tester for electrical outlets (or an NE2 neon lamp and a >100k resistor), you should try lighting it from the 170v test point. This will let you know if you have HV under load and eliminate any weird readings some DMM's show with switching noise generated by the boost circuit.
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1 year 4 weeks ago #7979 by TechGuy03
Are you suggesting I have HV but the DVOM is giving poor readings? I can see that being possible.

my real concern is that C1, L1, and Q1 get blazingly hot. Within 10 seconds, you can't handle them without getting burned.

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1 year 4 weeks ago #7980 by TechGuy03
I believe I discovered the issue...
I made an oversight on the caps and assumed they were all 220uf...(I thought the 2.2 Jim wrote was a typo).
A 35v cap does not like being fed 170+... Ill fix this and hope I did not cause any more harm

So C1 has a 220/35v, it should be 2.2/400v
C3 has a 2.2/400v, it should be 220/35v

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1 year 3 weeks ago #7981 by BS_Jim
Yeah, the 35v cap would be the problem. I would recommend that you don't re-use it. It will more than likely be leaky now.

Let us know how it goes.

Jim

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1 year 3 weeks ago #7982 by TechGuy03
I didn't even try to salvage it, I did remove and relocate the 400v cap though.

Everything is great now. Clock is set up and appears to work great.
Thank you Jim!

I am hyper sensitive to the noise produced by the buck circuit. Any safe recommendations to reduce the noise?
9v power supply? Firmware settings? Added cap?

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1 year 3 weeks ago #7983 by BS_Jim
Try doing a factory reset to re-calibrate the mosfet on-time. It was calibrated while charging a leaking cap.

Jim

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1 year 3 weeks ago #7984 by TechGuy03
To my understanding, the calibration doesn't take place till you break out of the first time run loop. (Press button at 88:88:88) is this correct?

Nevertheless, I did try a factory reset with little to no change

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