Synrad 48-2 losing power

[Ake Daniels]

Hello,
I am from sweden and i have reasently bought a GCC L-25 whith a J48-2S tube from 2002 installed. I am cutting hobbythings out of 4mm HDF sheets. After about 5-10 minutes cutting att 100% power its slowly start losing power and after 60 minutes it cuts only aboute 3mm. If i start at the same spot where i ended cut after a hour it cuts throu nice again. Could it be that the CO2 need to be refilled or can it be a heating problem somewhere? I have been in contact whith GCC and get a tip to check the caps on the RF-boards but they seams to be ok, i mesured the 1000pF caps to 1480pF on my Fluke whithout desolder them, they must have bin changed before because there was burnmark on the inside off the lid. I have tryed to lowering the voltage to the tube from 32.16 to 30.00 at full power but it didnt seems to make any change. The ripple on the Dc voltage is aboute 14mVAC. I have read aboute the important tuning of the RF-card and the caps that tends to blow on this forum, some says that is possible to damage the card if you drive them whith wrong voltage? Does higer voltage make higer laserpower? Is someone sitting on a tuningmanual for the RF-card or som other things i can test/mesure? Synrad says that the tube probably needs a full service but thats out of my budget right now and thats all help i got from them so far. I have a 100MHz osilloscope and i can make a device to provide the right tickle and PWM signals if its nesecery to test the laser.
/Greetings from Sweden

[Kev Williams]

Never had a heat issue with my Synrads, but it COULD be your issue- My glass RECI tube noticeably loses power as the water temp goes up, which mine does because I don't have a refer chiller.

SO, if your tube's heat sink fins are covered with guck and/or the cooling fan's air flow is compromised in any way, that could be the reason for the power loss over time--

[Bill George]

Can not help with your in depth troubleshooting but you are running the machine on the proper line voltage which I assume over there its 220 volts. Are your filters on the tube air intake clean and is the inside of the electronics area clean of dirt? All the fan motors running for cooling? If so, try blowing another external fan on the tube to see if that helps.
If all the about does not fix, I am guessing its time for a tube rebuild.

Some folks on here have changed a RF tube over to a water cooled CO2 tube and HV power supply. Not a job for normal people but you sound like someone who is at home with Electronics? WB0UPD

[Ake Daniels]

Tanks Kev for the tip but i already cleaned all the fins and fans in the machine and it didnt help.

[Ake Daniels]

Tanks for the tip Bill, Yes i am working whit automation and have electronic for hobby. And a change to HV Co2 glass tube
Could perhaps be a way to go in the future. In Sweden we have 230 volts nowdays.

[Mike Lysov]

Ake, I had exactly the same problem but with a 100W Synrad tube installed in Spirit GX. It was going for 2-3 years in this state loosing power if was used for 15-20 minutes. Now it is not even firing.
See my thread at the top. It may not be the tube itself as we checked the tube output just a year ago and it was almost like a brand new. I guess it may be one of the cables that connect the tube with RF unit or RF unit itself.

[Richard Rumancik]

Hello Ake
Sorry I can't guess what is causing the loss of power. You asked about tuning the power supply. I recall that Rodne Gold used to do this in-house with his GCC's. He might have some info but I don't think he has any of these machines anymore. But don't hesitate to contact Synrad as well. They are usually pretty good in supplying info to end-users about their lasers. They might give you the tuning instruactions. You can get a schematic for the RF board as well if you haven't already found one on this forum. It is released to the public by Synrad. Synrad did make at least one change to the capacitor probably somewhere between 2000 and 2002 if I recall correctly as they were having problems with blown caps. Part of the reason for the failure was laser tubes run at the wrong voltage.

As I understand it, the tube will operate between 30 -32 volts. However it is supposed to be operated at the same voltage that was used during tuning. The normal voltage Synrad used in manufacturing was 30V. I think some GCCs were build with a mismatch i.e. power supply set to 32V with standard 30V tubes. This caused the capacitors to blow.

Synrad told me in 2003 that if I reduced the voltage down to 30V (to match my tube) it would reduce laser power but they did not know how much as it is non-linear. I suspect that you can get more power out of the J48-2 by tuning and running at 32V at the expense of lifetime.

[Ake Daniels]

Hi Mike
Sorry to hear that you might have bigger problem then me. I dont know how many Rf-card you got in your 100watt synrad. I have 2 in mine tube and its seems unlikley that all card is going to failur att the same time, i gona check my cables. Have you check your powersupply quality, some electronic might be sensetive if its to much ripple!

[Ake Daniels]

Hello Rickard
Yes i have found the schematic for the Rf-card, i also got the tuning instructinon for Rf-card version IV from Synrad (many tanks) they says that the latest version is VII. Now i hopfully can se if the signal is correct and perhaps starting to tune the voltage and se what happends. I dont have an laserpower meter so i have to use a referens. It's just cuting trough 4mm Acryl @100% Power and 1.8% Speed, 2 inch focuslens, my GCC Firmwareversion is 2.22_01 and the printerdriver version is 3.58 -2D-02 is that normal for a 25watt GCC Laserpro L-25?

[Rodne Gold]

I have never had more than 8 years use out of the many synrad/coherent machines we have had.
Thats why I went to chinese glass based machines , for less than the cost of a synrad tube repair , I got a whole working machine.

In all likelyhood , its one of the RF cards that is failing (drops to 1/2 power) , or on a 14 year old tube , the tube itself
I have 6 dead synrad/coherent sources plus power supplies sitting in my store room...nuff sed...

[Ake Daniels]

Its to bad that a service/refill is so expencive so its cheaper to bye a new Chinalaser!

[Bill George]

And they do not have to be that expensive to repair, its priced high.... because we can. However if you live in the US there was a lower cost alternative and I think it was Evergreen Laser. Not sure if they are still around or not??

[Kev Williams]

I simply couldn't survive with only Chinese lasers, my engraving "styles" (I guess :D) are way more varied than most... As much as I like the Triumph, it's wayyyyyy toooooo slooooow (although I've stated more than once that 3 slow glass = 1 fast metal ;) ), but more than that, it won't engrave glass worth a crap, I have lots of rotary work and a hot-dog rotary, wont cut it, and it won't engrave Cermark onto stainless to suit me, and SS is near half my income. (and I bought it specifically to DO Cermark). It DOES engrave anodized, wood and Romark, and ironcially, cermark on ALUMINUM and brass as well as I could ever hope for.

Many here have had good things to say about some guy who ad's on ebay, very reasonable (compared to Faccchh-tory prices) for refills and total rebuilds, which as I understand is substantially cheaper than a new glass machine...