View Full Version : TH and TL terminals on a DC power supply.

Mike Lysov
06-28-2017, 5:20 AM
Hi guys,

I have a question which is raised by my friend who is going to help me to install a new DL-300 DC tube into my current system that is designed to run two DC GSI tubes.

Currently it is wired from a PWM2 port on my laser control(UTC200P by Microtrend) to two power supplies I have for the GSI tubes. A db25 connector is used for it and both power supplies I have or at least their extra case enclosures has DB25 port on each. Until I open these enclosures for both power supplies I cannot say exactly but I am sure they are just metal cases with all connection ports sitting on them and they are wired inside to the same type of a power supply as new ones.

DLT 300 I have bought is a double tube combined inside a metal enclosure design so it also runs from 2 power supplies.

The new power supplies we are going to use do not have the same DB25 connector port so we will need to cut off DB25 connectors at the end of each cable and connect each wire to a relevant pin. I believe the PWM wires should go to the IN terminal on my new power supplies.

He is asking what is a difference between TH and TL terminals on a HV PS. Knowing that TL is for low level control and TH is for high level control does not help him to understand what they are for. He understands PWM well so it is just these two terminals he has no idea what they are for.

He is very good with anything related to CNC, electricity and electronics but he never has done anything with lasers and he does not understand that bit.

Mark Canada
06-28-2017, 11:19 AM
Depends on if your controller outputs a high or low pulse for when the laser should be active. Check your laser controller's manual. If you connect it to the wrong one, your power will get lower as the controller tries to set it higher, and higher as it tries to set it lower (ie: PWM is inverted).

If it gets hooked up wrong, you wont damage anything - just swap the connection if its not behaving as expected.

Mike Lysov
06-30-2017, 12:00 AM
Thank you Mark. I have no information about the controller apart from it is UTC200P and it is working with G-Code.

My laser manufacturer won't supply too much information about wiring and electrical diagrams and it does not seem to be happy to help at all.

I can only be sure the new tube will work as the whole system is set to work with two GSI DC exited tubes and they have the same power requirements as the Yongli tube I have bought. My friend will come with all the electrical measurement tools including an oscilloscope so will check all signals.

The only wiring diagram I have for connections from the controller to HVPSs is attached to this message.

Also is it normal that Yongli cannot tell me what is a maximum operating current for a warranty purpose for their DLT-300 tube?

The only thing they say on the manual about the tube power requirements and they are repeating the same on Skype in my conversation with them
"maximum starting voltage is 40kv and maximum current is 40mA" and the only information I have about their HVPSs is below

DLT-280 laser specially equipped with high voltage power supply
(including 2 sets identical power supplies), can provide DC for A 0 ~
40 ma, 10 kv ~ 30 kv DC high voltage power supply.

They have a basic diagram for wiring their tube to their HVPSs but it looks like a standard one for any DC tube.

Both the tube and a HVPS documentation I have cover two models of their tubes DLT-280 and DLT-300 and they say both models have the same specification apart from output power and that's why text I quoted above mentions DLT-280 model.

Does it mean that I can still hit their tube with 40mA current and they will honor their warranty?
Otherwise I guess they would say something like RECI do not exceed 32mA otherwise you will kill your tube faster and you won't be covered.

Dave Sheldrake
06-30-2017, 12:30 AM
40mA is going to kill the tubes very quickly, the combined resonator EFR's that run from one supply only pump 40 and that's to get 260 watts peak.

Treat them like 2 separate tubes for current as in effect that's what they are, so a 280 watt is 2 x 140 watt, look up the max Q for a 140 watt SPT and run by that :)

The peak output of the PSU is 40mA, not the run current

Mike Lysov
06-30-2017, 4:57 AM
Thank you Dave.

I think the same about 40mA. It is not the right number but that's the only one they specified everywhere and confirmed many times.
They say their tube runs on 40kV maximum but their power supply they say 10-30kV, I can guess that for the tube specs they put combined voltage from two power supplies. Even though it is not combined physically as each tube runs from its own power supply which are not connected together so they cannot double voltage in any way. So that part is fine.

regarding SPT 140W I cannot find it anywhere on their website, google search is not helping either. Can you please tell me what is that number for their 140W tube.
I can set it to 32mA as for powerfull RECI tubes but it can be even 35mA. if I set it lower than I can I will loosing on processing time.

Dave Sheldrake
06-30-2017, 9:09 AM
How long are the tubes Mike? that will be the best guide to current,

I would best guess they are 150 watt tubes but you lose a certain amount in combining hence why they are calling them out as 2 x 140 as that is likely to be the top stable power they supply out of the combiner, if the tubes are 1650mm long they are 130's stable, 160's peak, if they are 1850mm long they are 150 stable, 180 peak.

32mA is a good safe level for both with a strike of 35mA , you could go to 35mA but will lose life and increase heat output by quite a bit (cooling requirement)

Mike Lysov
06-30-2017, 9:19 PM
I can only guess by the size of the metal box which is 1850mm in length that the tubes inside are the same size as a GSI 140W tube and close to 1600mm.
I would have opened the case and measured them if it had not had warranty stickers.

The picture below shows it with a cover removed but it won't tell us how long they are. However it gives an idea of its design inside.

32mA maximum seems ok, If I do not get the exact number I will just stick to it.

I have just found one page with DLT-280 model where Youngli says working current is 35mA
https://yllaser.en.alibaba.com/product/60223431621-802567980/Yongli_CE_FCC_ISO_260W_10000hrs_co2_gas_laser_dlt_ 260.html

It is just not on the table with specs on that page. It is located in Quick details section above it. The table says maximum working current is 40mA

On the other hand there is another page for DLT-280 from them that says that 35mA is a maximum operating current, not working one
https://yllaser.en.alibaba.com/product/60077187346-802567980/DLT_280_I_CO2_laser_tube_with_CE_ISO_certification _co2_laser_tube_280w.html

Dave Sheldrake
07-01-2017, 12:54 AM
they look like 1650's, I'd be very loathed to run them above 32mA per tube

Mike Lysov
08-02-2017, 3:23 AM
It has all gone well. We installed the DLT-300 into my laser, set the current to 32mA top with resistors. It gives 265-270W of power at the maximum and not exceeding 32mA. It makes really thin kerf and by the look much better than two GSI tubes combined. I will see how it goes in terms of lifetime but at this point I am very impressed.

For those who is going my way with the same tube ask ahead about location of all connectors. On Yongli pictures all connections are at the back of the tube but mine has come with water and ground connections on the right side. That made it quite difficult to install and we had to drill a few big holes in my laser wall just to run hoses and wires inside its bed compartment and back to the tube. Also the tube is very long and we have had to cut of the side of the tube compartment to fit it in. We knew that from the beginning so it was not a big drama.

Repared Synrad tube and RF are giving me the most headache now.
We have tested it with any possible electronic tools and guy who was doing it has 45 years in electronics development and fault analysis. Even he could not find what's wrong with it. I think I have no option left rather to send it back to Synrad and ask them at least to fix their repair. I cannot believe that repaired set did not work straight after repair then started working and did it for less than 2 months before it stopped working again.