Film-Tech Forum ARCHIVE: Kinoton FP23 Exciter Lamp

This is topic Kinoton FP23 Exciter Lamp in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Mitchell Dvoskin (Member # 751) on 06-03-2003, 01:01 PM:

I have just burned out the second exciter lamp in 3 months of limited use on my Kinoton FP23X. Being that this is now more exciter lamps than I have burned out in my life, a put a volt meter between the the "hot" point on the exciter lamp cover and the center base of the bulb. It reads 15 volts, the bulb, which I obtained directly from Kinoton USA in Boston is marked 6.5 volts. Either they sent me the wrong bulb (correct base), or the Kinoton exciter lamp power supply is not happy camper.

My question is, what is the correct exciter bulb (same as the one in the FP20), and if I have the correct bulb, is there any way to adjust the the power supply. The power supply is mounted on the same board as the projector controls, so I don't want to tamper with the wrong component.

Any suggestions would be greatly appreciated.

/Mitchell

Posted by Fabrice Dubourg (Member # 1635) on 06-03-2003, 04:58 PM:

you should read the voltage of our exiter supply with a lamp on it.
the voltage with no load can be different of the voltage with a lamp light on if you've got an old exiter supply.
with 15 volts, your lamp can't work 3 months.

Posted by Gordon McLeod (Member # 33) on 06-03-2003, 11:32 PM:

Since it is a regulated supply the load should not affect it
It should operate around 6v

Posted by Leo Enticknap (Member # 534) on 06-04-2003, 01:42 AM:

I just tried looking on Kinoton's website to see if it would say what the correct voltage for an FP-23 exciter bulb should be, but clicking on 'support' asked for a username and password which I don't have.

I once had a similar problem with an FP-20: the output level from the cell would fluctuate wildly for a few days (we were needing to reset the gain on the CP-45 daily using the Dolby test film) and then the bulb would blow. The culprit turned out to be the power supply unit. I can't remember what the (correct) exciter voltage was but 6 sounds familiar.

Posted by Michael Schaffer (Member # 1204) on 06-04-2003, 03:36 AM:

The support section on the website is for their own technicians only so that they can download material wherever they are.

Posted by John Anastasio (Member # 607) on 06-04-2003, 04:49 AM:

Sounds like the voltage regulator in your power supply has gone south.

Posted by Fabrice Dubourg (Member # 1635) on 06-04-2003, 06:36 AM:

forget my last post, i was thinking about old version of FP28!

Posted by Larry Shaw (Member # 388) on 06-04-2003, 11:22 AM:

The 23X, which is a very old machine, has an unregulated DC exciter supply with an AC backup. The supply is a full-wave bridge followed by a simple R=C circuit. The correct bulb is rated 6.5V, 1.48A.

*First, is the AC-DC exciter switch in "DC"?

*Second, what is the DC voltage at the bulb socket with the bulb lit? If the voltage thus measured is too high (above 6.5V), lower it via the potentiometer marked "5" on the PCB schematic, located near terminal 7/8 on the diagram. This pot controls both the DC and AC backup supplies.

Let me know if you have further difficulties.

Posted by Mitchell Dvoskin (Member # 751) on 06-04-2003, 07:34 PM:

Thanks Larry,

Yes, I do indeed have the correct bulb, and the switch is in "DC" mode.

I re-measured the voltage under load (bulb on), and it reads 7.25 volts. That is definately more believable.

I found the potentiometer on the schematic, although it was not marked "5". What I could not find was a potentiometer anywhere on the circuit board.

unless you are refering to the gizmo that appears to be a variable resistor.

which is marked (on the board) as 5.5V Gr2 on 1 side, and 9.5V Si2 on the other (15W 2.5 Ohm).

I do not want to move the setting on this and then find out I screwed up the power for the relays or something other than the exciter lamp voltage.

/Mitchell

Posted by Larry Shaw (Member # 388) on 06-04-2003, 07:49 PM:

Mitchell,
I can't find a PCB layout drawing for the 23X right now, but from the schematic and my reccolection that 15W variable resistor is the one you want. If you're worried, make a mark on the ceramic coating of the resistor to either side of the adjustment band. In this way you would be able to reset the resistor if required. Then just loosen the adjustment band screw, slide it a bit, tighten the screw, and test. Repeat as required.

Posted by Mitchell Dvoskin (Member # 751) on 06-04-2003, 09:11 PM:

That fixed it. Thanks Larry and everyone who responded.

/Mitchell

Posted by Jeff Taylor (Member # 443) on 06-06-2003, 01:58 PM:

Mitchell: Perhaps not totally "kosher", but there's no law that you have to run an exciter at 100% rated voltage. More than likely you can cut it down a bit and have no ill effect on sound quality while dramatically extending lamp life.

Posted by Steve Guttag (Member # 268) on 06-06-2003, 08:09 PM:

Not to throw too big a monkey wrench into the works...there is another exciter lamp that one can use that would probably load things down a bit better ...the 7251C. It is a 5V 4A lamp and is listed on most of the FP 20 and FP 23 books right alongside of the 6V 1.48A lamp. I prefer the 7251C since its filiment is wider and seems to illuminate the slit a bit better.

Steve