Check the laser FAQ...Sam's Laser FAQ!
While waiting for a suitable tube for my HGM-20, I recently acquired a Omnichrome 543-300A-NORN laser head (yes, this is an addiction).
Applying an Oudin coil, the tube clearly ionizes and is vacuum intact.
Base on documents I found searching the web, it appears this head uses a Model 170B or 176B power supply. I have neither one of these, however, I do have a model 171 power supply.
Apparently, the 171 PS is for the Omni-643 head. What is the different between the 171 and 170B power supplies?
Does anyone know if a model 171 power supply will work with the Omnichrome 543 laser head?
Last edited by turbohead; 02-05-2014 at 17:13.
Check the laser FAQ...Sam's Laser FAQ!
Phil Bergeron( AKA 142laser)
Interesting that your 171 doesn't work on the 543, but the 176B does. As I use a 176B for my 643 ArKr, and I've been told that the PSU will also work with a 543, and the PSU for the 543, for the 643.
The way it's been relayed to me, is that they are completely interchangeable.
100% interchangeable They're pretty much the same PSU, and the same head, with just a different gas, or both.Originally Posted by Master Manual
I received a reply from Dale at HHR-Lasers:
"The 171 will run the Omni 543 if it is set up for 220 volt input. If it is only set up for 120 volt input it can only run the 532 head. Both the 543 and 643 require 220 volt input. Unfortunately, while basically the same supply, it can not be converted over easily. Look at the sticker on the front or back. It tells the volt input and the head it will drive."
There are four pins different on a 220V or 110v head. They are the interlock and fan power. A 220v head wont interlock a 110v supply.
A 110v supply will not drive a 543 or 643 series tube in most cases, the rectified line voltage is not enough to overcome the voltage drop of the tube.
Hook it up and try it, if the PSU has a 220v sticker.
After satisfying the interlocks on the DB25 and the fan, filament voltage is present, however, the fan on the power supply does not turn on. After a warm-up period, the high voltage igniter starts and the tube briefly starts. When the tube starts, the fan on the power supply turns on. However, after about a second, the tube turns off and the power supply fan turns off. The cycle then repeats; filament on, warm-up, igniter, brief light, power supply fan on and then off again.
I can only conclude that since the power supply states it is for the 643 head, the 543 head is not compatible or the power supply is faulty. The next step is to check the FETs and transistors in the power supply.
Last edited by turbohead; 02-05-2014 at 20:14.
I un-soldered and checked all of the FETS, resistors and diodes on the large heat sink. All of the components check good.
What interlocks do you currently have jumpered?
It is normal for the PSU fan to not turn on until power is going to the head. I noticed the same with mine.
I turn the key all the way to the right for a second or 2, then back to on. Then flip AC on, all red lights go out, fan PSU turns on, then the head fan also turns on. This whole time, while there is a connection between the head and PSU, with no switches, or key turns, there will be a green light on the head on as well.
When running (before I had a fan hooked up the the P3) I had the interlock on the fan jumpered, and 6 pins on the P2 jumepred.
For the fan, I mapped out what pins on the connector matched up to the interlock pins on the umbilical. If you have a circular 7 pin connector. Using the following schematic, you can map out what each of the 7 pins do. Also sent Sam the info, I believe it'll be on the FAQ, if it's not already.
1 & 3 --- 115VAC Hot & Neutral
2 --- 230VAC hot
4 --- GND
5 --- Nothing. If you notice, this is the pin with no metal inside the connector. Just plastic. This pin is referenced in the manual, though I do not remember under what condition it will actually serve a purpose.
6 & 7 --- Interlock (jump these two)
As far as the remote DB25, the 170, 175, and 176 all have the same getup. I have the following jumpered.
1 & 3 --- Beam Interlock *
6 & 18 --- Current control using the PSU's pot **
19 & 21 --- Safety Interlock ***
* - This interlock prevents the laser head from receiving HV without a solid connection with the umbilical, as well as the fan. If a connection is breached, and then fixed, lasing will begin again once the 35 second warm-up finishes.
** - This is one of two potential shorting procedures to use the pot for current control. Shorting 7 & 18 (light control) results in a similar outcome. However, the latter method resulted in me reaching a full 9.48A at about a quarter turn. Leading me to believe I was getting full lines with only 25-30% power. Using 6 & 18 allowed me to only reach 9.48A after completing almost a full cycle with the pot wiper.
*** - Similar to the beam interlock. Prevents the master power relay from activating unless power cables are firmly in place (including the fan connector(s)). Also requires the head cover to be in place. If deactivated, then reactivated, lasing will commence again once the 35 second warm-up is gone through yet again.
If you suspect an issue with the current, or would like to monitor it, jumpering pins 9 & 11 will allow that.
I slipped some metal strips, bent them at a 90*, then slipped them in the connector. This allowed me to clip my DMM probes to them to meter. When metering, 100mV = 1A. Ranging from 0 - 1.2V.
The goal with this post was to include every possible bit of info that I needed when trying to get mine to work. I hit several walls when getting this one to lase. From interlocks not working until I removed, and replaced them. Also keep in mind that depth doesn't matter if you're not making contact with the walls.
Again, not trying to insult anybody's intelligence, just trying to cover all the bases.
I think that just about sums it up...
Last edited by SoulFeast; 02-11-2014 at 14:28.
Thank you very much for the complete information above! Knowing that the power supply fan does not turn on until the laser is operating is valuable information since otherwise it indicated to me that the power supply was faulty. Unfortunately, the high voltage ignitor on the laser head stopped working and I need to diagnose which component is faulty. Probably the trigger SCR. Once I get the ignitor working again, I will definitely apply all of the information you provided.
I got lucky and won an auction on ebay for an Omnichrome 171B power supply. The back of the power supply listed the 543 laser head. After receiving the power supply, I jumped the DB25 pins as instructed above. After a 30 second warm-up, the laser fired up! It just goes to show, you need the proper supply for the laser head. Thank you for everybody's input on this topic.