Electronic Fluorescent Lamp Ballast

[Toasty]

Re: Electronic Fluorescent Lamp Ballast

The circuit is not exactly like yours. I was trying to show where C10 (Cr) goes.

L represents the coil (looks like a transformer next to C10) on TG1.
B just represents a connection point. Same with A.

M1 & M2 are the "transistors" which are running in a multivibrator arrangement with no "true" frequency control but rather crudely determined by C9, the coils (L2, L3) on the first board, the multi-position slide switch, and a few resistors and the 2 smaller electrolytic caps on TG1.

By adjusting the frequency, the light output is varied.

Is the lamp easily removed? If you can do so, measure across the ends for any resistance. If you get it on both sets of pins, at least it would mean the heater filaments are good.

MJE 13003 datasheet attached.

Did you ever get voltage measurements as suggested back in the beginning?

.

[mysterfxit]

Re: Electronic Fluorescent Lamp Ballast

The bulb is currently not installed. Do you mean test the pins on the bulb? The first thing we tried was new bulb.

I'll try getting the voltage on the electrolytic caps, resistance on the bulb pins, and desoldering and testing C10 tomorrow night.

Do I test the voltage on the electrolytic caps with the power connected?

Which brings me to another question I was going to ask the forum. At what point to do I need to be REALLY careful working with capacitors?

[Toasty]

Re: Electronic Fluorescent Lamp Ballast

Bulb was swapped, so no need to check it then.

Voltage test with Power connected - Yes.
Resistance test of C10 - No power and make sure the voltage has dropped off to zero on the 2 big electrolytics before you do any work on the boards.

You always need to be careful working around any circuit that exposes you to mains power such as this one does. The entire circuit is not isolated so you have the potential of being shocked or injured if you contact any connection with your body.

If you are unsure of what to do or how to properly test the circuit then I suggest the trash can for the unit and go buy a new one. Safer and you'll live longer.

Toast

[mysterfxit]

Re: Electronic Fluorescent Lamp Ballast

I understand. Thanks.

As far as the voltage on the big caps. Does it just dissipate over time or do I have to bleed it off somehow?

I'm pretty comfortable working with electricity. I work on household wiring all the time. And unfortunately have been shocked a few times. Most recently when a ceiling fixture I was working had the hot shorting to the box.

[Toasty]

Re: Electronic Fluorescent Lamp Ballast

The voltage bleed-off may be rapid or slow. It depends on the circuit and should be monitored. Let it drain on its own.

[mysterfxit]

Re: Electronic Fluorescent Lamp Ballast

OK. I desoldered C10 and it still tested 0 Ohms.

Testing the electrolytic capacitors with the power on I got:

(2) 22uf 250V (big ones) - 160V
(2) 4.7uf 250V (medium ones) - These would measure 100V then slowly drop to 90V and stay there. A couple of times when I measured them they spiked higher.
(2) 4.7uf 50V (smallest ones) - I got nothing. 0V

[Toasty]

Re: Electronic Fluorescent Lamp Ballast

Let's be sure here. 0 (zero) ohms means the same reading as shorting the meter leads together, correct?

If that is correct, the cap is shorted and the problem.

The 2 smaller ones won't read because the tube isn't firing.

Spiking is the unit cycling, trying to fire, I would think.

[mysterfxit]

Re: Electronic Fluorescent Lamp Ballast

Yes. The same as shorting the meter leads.

There are only four on mouser that match the specs. So it appears my choice comes down to 17 week or 21 week lead time

[Toasty]

Re: Electronic Fluorescent Lamp Ballast

Should work. You may have to modify the board to fit the cap. Leads are 15mm apart and overall it's 18mm.
Drilling a small hole and bending the lead over to get to the foil trace is likely. What's the spacing to the second hole?

http://www.mouser.com/ProductDetail/...4niCR02Szqo%3d

DigiKey may be cheaper because they'll do 1st Class mail in an envelope:

http://search.digikey.com/scripts/Dk...name=P10505-ND

That one has longer leads, 20mm spacing, so it may just work as-is.

.

[mysterfxit]

Re: Electronic Fluorescent Lamp Ballast

Ah...higher voltage..thank you so much! I'll order it right away

[Toasty]

Re: Electronic Fluorescent Lamp Ballast

Updated, read further.

[mysterfxit]

Re: Electronic Fluorescent Lamp Ballast

Thanks. I haven't placed the order yet. I was holding off an order for a bunch of electrolytics for a subwoofer amp to combine with this one.

It turns out some of those are backordered as well so I'll have to find replacements, maybe I'll get the one you posted from digikey with the backordered stuff from the other project since I won't have to modify anything to fit.

[mysterfxit]

Re: Electronic Fluorescent Lamp Ballast

I got the new capacitor in the mail yesterday, soldered it in, and the lamp is working again!

That new part is huge compared to the old one. The leads were a lot fatter too and I was worried it wouldn't fit, but it did.

Thanks for all your help!

[Toasty]

Re: Electronic Fluorescent Lamp Ballast

'nother one off the Honey-Do list!!

[cmj21973]

Re: Electronic Fluorescent Lamp Ballast

Congrats on fixing it.

[GeX]

Re: Electronic Fluorescent Lamp Ballast

Congrats mysterfxit, you did it, I think your wife is happy now

[RJARRRPCGP]

Re: Electronic Fluorescent Lamp Ballast

Essentially:



Where Cr is C10 and C1 & C2 are C5 & C6.

Why 2 caps (C1 and C2) and 2 transistors instead of one? (M1 and M2)