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...

Fri Jun 29 2007, 04:10PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

The wattage does not really matter, 1/4 watt should be fine. You could use the 2 150K resistors from the PFN (R5 and R6 on the 2nd schematic) in series if you don't have anything laying around.

Also after looking at the schematics of the PFN, you also need to put diode D4 of the PFN (from the 2nd schematic) across the cap as well, (the side of the diode with a line on it going towards the 1 mreg resistor).

EEYORE

Fri Jun 29 2007, 06:09PM

Registered Member #99 Joined: Thu Feb 09 2006, 06:10PM
Location: florida, usa
Posts: 637

I used to have one of these. They can be pushed pretty well without breaking...I forgot what the maximum Joule's into the flashlamp was, but Im pretty sure it was over 100J. I used a bunch of photoflash capacitors in series/parallel. These type caps have enough inductance as to not wreck the flashlamp. No resistors or inductors are needed! I used both a MOT with variac to charge the caps, as well as tried a CCFL power supply.(Worked better). You may want to take out the q-switch as pushing the energy will likely destroy it. I beleive I pushed 1000volts on the lamp (My DMM wouldnt allow any higher DC voltages).
Have fun and BE SAFE!These things WILL blind you if you mess up!
Matt

Will1234

Mon Jul 02 2007, 04:39AM

Registered Member #846 Joined: Tue Jun 19 2007, 08:04PM
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Posts: 40

I just read your responses (last 2) after trying to power everything up a few hours before. Needless to say, I wasn't successful but did manage to keep the smoke from leaking out anywhere. One thing I kept re-thinking and the more I re-thjought the more uncertain I was. Is the + connector of the cap the one the came through the metal housing 'on top' and the negative the one that whos wire ran up the outside of the casing. Or, is it even polarized.

"If not, you need to add a resistor in series with it, if it is going to complain if you try to draw >30a from if you would need a .5meg resistor (you are dropping 1300v at 30ma, so use v=ir), which will need to be able to dissipate the full 40w that supply can put out (at least for short periods of time)." Does the wattage of this resister apply?

Concerning the short created during discharge, would there be any value in using the vacuum switch to steer the current? In its normally closed state it would discharge (instead of a slow bleed) the cap and when open charge it via a momentary switch.

The Q-Switch, keepiong in mind that I know very little about a whole lot, isn't the Q-Switch in use a dye switch that triggers based on optical energy levels? If so, other than literally burning it up with optical energy, is electrical energy my main concern? I'll give the your additional instructions a go ASAP. And as always, I really appreciate your help....!

...

Tue Jul 03 2007, 04:04PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

The cap is not polarized.

For the charging resistor, I would use a resistor rated for at least 10w (a string of 10 1w 50K resistors would work great)

You could use the vacuum relay as you describe, if you have it you may as well use it. You best bet would be to connect the cap to common terminal, and the HV supply to the normally open terminal, and the discharge resistor (R1 from the 2nd schematic would be perfect) to the normally closed terminal. Then to charge it you would hit one switch to open the vacuum relay (that would be the 'arm' switch) and then power up the charging supply (charge switch), and then when it is charged you let go of the charge switch, and fire the trigger coil.

The q-switch physically is made up of to 2 pieces of glass plate (antireflection coated for 1064nm) with a die that is normally opaque to IR, until you hit it with enough light, then it becomes clear. So when you fire the flashtube it begins to force the Nd ions in the YAG rod into an excited state, but since there is this opaque q-switch in the cavity the laser can't lase. That is until it gets hit with enough light that it bleaches, greatly increasing the 'q' of the cavity, allowing it to start lasing. But at this point the rod has a huge amount of charged Nd ions ready to fall back to a relaxed state, so you get a very high power pulse (several megawatts peak power).
Likewise, yes you can only damage the q-switch by too much optical power (you start to turn the die into something else when you hit it with megawatt pulses of light). Unfortunantly, the military designed the q-switch so that it can just take the light from a 700v shot, so when we hit it with almost twice as much energy with a 900v shot we run a serious risk of damaging it. On the bright side, it is not impossible to remove it, and once you have the only thing you risk is exploding the flashlamp, which doesn't happen until you are running several hundred joules of power.

Will1234

Tue Jul 03 2007, 11:08PM

Registered Member #846 Joined: Tue Jun 19 2007, 08:04PM
Location:
Posts: 40

Concerning the Zener D4, is it across the trigger cap with the line toward the lead with the resistor?

Main cap. ===== Resistor ========+== Trig CAP ==+=== Other side of cap out
| |
+---- || Zener --+

Like this?

Will1234

Tue Jul 03 2007, 11:14PM

Registered Member #846 Joined: Tue Jun 19 2007, 08:04PM
Location:
Posts: 40

Well, so much for the text spacing. Does the zener straddle the trig cap? What about the diode on the main cap to inductor black lead labeled "2"? Should all connections to the inductor be bare lug to wire or hop on the other end of the diode?

...

Wed Jul 04 2007, 04:33AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

If you want to make ascii pictures, use the code tags, and if you want to add to a post use the edit button.

In any case, yes the zener 'straddles' the trigger cap.

As to the big diode, I believe it is to protect the cap from voltage reversal, however from what I have seen there is very little reversal (if any-that pfn was designed very well), and the cap isn't polarized in any case. You can safely ignore it. If you do chose to leave it in place (I can't imagine it is hurting anything) it should be safe to connect the lamp to the wires from the diode. Although IIRC the diode had some plastic on the leads that would need to be removed to solder to it.

Will1234

Wed Jul 04 2007, 11:59PM

Registered Member #846 Joined: Tue Jun 19 2007, 08:04PM
Location:
Posts: 40

I'm going to put together a diagram of how everything is currently connected that will hopefully expose any flaws. From what I have read and what you have told me this can't be as hard as I am making it. I get the cap charged, pull the power and hit the button with nothing to follow and the cap immediately starts counting down to 0 volts. Tried without pulol power as cap charge increased with same result. I'll upload it ASAP.

W

Will1234

Thu Jul 05 2007, 09:55PM

Registered Member #846 Joined: Tue Jun 19 2007, 08:04PM
Location:
Posts: 40

Attached is a jpg and Visio file in case you have Visio. What am I missing?

W

Will1234

Thu Jul 05 2007, 10:40PM

Registered Member #846 Joined: Tue Jun 19 2007, 08:04PM
Location:
Posts: 40

There is one thing that seems odd to me but may be normal. I'm running the 24VAC wall transformer through a full wave bridge rectifier and as expected shows up as 24VDC and is then sent to the power supply. If I disconnect the power supply from the cap and leave it free standing I can reverse a 200V 5W Zener and get a stable 735 volts out of the power supply. If I then connect the power supply to the cap and turn everything on the voltage at the cap climbs to 735v and continues to climb until shut off. How can this be?

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