AAARGH! Laser stopped! SORTED!! WOOHOO!

[Darren Null]

Symptoms: Laser stopped firing about an hour into a (3hr) job. I rebooted the laser and it fired for a few minutes, then cut out again. Now it seems to have stopped doing that.

Possible causes...I really don't know. It's 28 deg C outside, so heat might be a factor....sticking a big fan to blow air through the laser duct didn't seem to have much effect though.

Please help if you have any ideas.

Thanks.

NOTE: Mirrors clean, beam aligned. The 'go' lights on the control panel and the laser indicate that it's firing, but it's not. It could be the capacitor that went last time, but I would have thought that if that was the problem it would go all at once and permanently.

[Rodne Gold]

Sounds like it might be heat related.
1) clean all fans , ducts and the tube fins of all dust
2) check motherboard fans as well , use a soft brush to remove any dust on drivers
3) Remove and reseat any dodgy connections , check the ribbon cable connections
4) make sure its not a dodgy interlock magnatic switch
5) Go into diagnostic mode , try fire from there , put the paper right at the hole the laser exits the tube - see if it fires?
6) Remove and reseat firing plug into tube
7) check power supply fuses , all fuses
8) There should be diagnostic lights on the motherboard , I think you got Gcc - check em and their meaning (cant be more help here)
Maybe you lucky and it comes right , otherwise time for a deeper inspection or sending the tube away.....
Whats the lifespan of the tube so far?
What make is it?

[Darren Null]

It's a 2002 Synrad 48-1

I'll go through those parts of the list that I haven't already done. Thanks Rodne...I'm panicking too much to think clearly.

[Darren Null]

>1) clean all fans , ducts and the tube fins of all dust
Done. There wasn't a great deal of dust there.

>2) check motherboard fans as well , use a soft brush to remove any dust on drivers
All fans working; none of them were especially dirty...cleaner now

>3) Remove and reseat any dodgy connections , check the ribbon cable connections
All important-looking connections removed, cleaned and replaced.

>4) make sure its not a dodgy interlock magnatic switch
It's not. One of the really good things about the GCC machine is a 'door open' light.

>5) Go into diagnostic mode , try fire from there , put the paper right at the hole the laser exits the tube - see if it fires?
All the lights on the control panel says it's firing, but no beam.

>6) Remove and reseat firing plug into tube
Done.

>7) check power supply fuses , all fuses
Yep. Fuses OK, power supply to the laser giving it a steady 32.1V

>8) There should be diagnostic lights on the motherboard , I think you got Gcc - check em and their meaning (cant be more help here)
3 lights:
Power- (machine switched on) working normally
Laser- (laser firing light) working normally
Door open- working normally

Also on the back of the laser are power (working) and laser firing lights (working normally and in tandem with the one on the control panel)

All is as it should be, just no beam.
-I'm pretty sure it's not a gassing thing because it stopped suddenly.
-It was a capacitor on the RF board last time...I would have thought that a cap would go all at once and not come back, but I could be wrong there.
-Thinking about it, I'm not convinced it's heat. It's only 10W; it worked through August last year (when it hit 40 deg C regularly); the fans are all working perfectly and none of them were particularly gucked up; also there was no improvement when I put a bloody great fan on the end of the laser duct.

Deeper inspection time?

[Dan Hintz]

Unless there is a power surge, caps will tend to slowly deteriorate over time... if they're heated (through too much power, etc.), they'll leak their electrolyte, reducing capacitance. Eventually, they just cannot provide enough capacitance to do what you want... and depending upon where they are in a system (such as in a power supply regulation section), the slow reduction in capacitance can often end in one final (and catastrophic) throb of pain. YMMV...

[Darren Null]

It was the capacitor again. Thanks for help.

It was a pretty catastrophically-failed capacitor (photos later when I have time); but there must have been melty bits inside passing current through for a brief time, hence the sputtering ending.

I'm back in the game again. Yay!

[Howard Garner]

It was the capacitor again. Thanks for help.

It was a pretty catastrophically-failed capacitor (photos later when I have time); but there must have been melty bits inside passing current through for a brief time, hence the sputtering ending.

I'm back in the game again. Yay!

I would look at installing a different capacitor. Use the same capacity value and type, up the voltage rating. This may give it a longer life next time.

Howard Garner
former electronics tech

[Richard Rumancik]

I think the cap he is talking about is part of the RF circuit in the Synrad laser tube. I would stick with the one that Synrad suggested.

Darren, it could be that the tube was tuned for a different voltage than 32V. This was a long outstanding problem. Synrad would tune at 30V and OEMs would run them at 32V which apparently stresses the RF circuit. So it could be a mismatch that caused the second failure.

Unless you know at which voltage it was tuned there is not much you can do except have spare caps on hand. If you KNOW it was tuned at 30V (sticker on the tube?) then I would try dropping the voltage to 30 or 31V. But it might reduce output by a bit.

[AL Ursich]

Glad you found your Capacitor Problem. I was a Sony Service Tech for a few years and got a whole bunch of overtime at the Philadelphia Service Center fixing Capacitor Problems. Some bad Capacitors got into the system and new Computer Monitors needed to have about 6 capacitors on the main board replaced. There were hundreds of Monitors to be fixed.... They became "B" Stock after the replacement not sold as new "A" Stock because of the work done. They went to outlet centers.

So I was curious as I had spent 4 years at the San Diego plant, 2 as a Maintenance Mechanic on the CRT manufacturing line. Keeping the PLC or Program Logic Controllers working running the conveyors, Fanuc Robots, RF Generators, and other equipment working. A cross between an Electronic Tech and Grease Monkey when it came time to lubricate conveyors. Then I did 2 years in the Calibration lab doing calibration and repairs. The Calibration Lab picked up test equipment in about a dozen high tech Sony Labs and I learned allot. My interest was Component testing and learned that samples of all parts were tested and evaluated on a regular basis. Bet this is where the bad capacitor problem was first found.

Fast Forward 2 years and I am now in Philly near my home working at the Bristol, PA Service Center. Overtime was available for Techs interested in replacing Capacitors in Monitors in another Sony Building, they had 2 at that time. I lived within walking distance from Sony and loved Overtime. I was already overpaid from my fast San Diego advancement.

Then the Capacitors we needed went out of stock and we were out of work..... Then I remembered my friends in San Diego and made a call.... I knew they saved bags of hundreds of Capacitors after only testing a few. I found they had hundreds in storage of the GOOD ones we needed. I let the parts guys know and soon we were back to work and finished the project.

I contacted my Buddy in San Diego and he shared with me the story of the bad capacitors and a web site with the story..... Here is the story of the "BAD" Capacitors.....

---------------------------------------------------------------
In September (2002), "Passive Industry Components Magazine" published a story that exposed the reasons behind the unusually high failure rates. They reported that the failures were directly related to the use of faulty electrolytes in the manufacturing process.


Industrial espionage?

The story describing how the electrolytes came to be faulty reads like a lot of fiction. It begins in Japan, at a major capacitor manufacturer. A materials scientist for the Japanese company resigned and went to work for a Chinese capacitor manufacturer. While there, he reproduced one of the electrolytes used in his former employer's premium (low-ESR) aluminum electrolytic products.
Staff working with the scientist then defected, taking the secret electrolyte formula with them. They used the formula to manufacture their own electrolyte, which they subsequently flogged to major Taiwanese capacitor manufacturers at bargain prices. Unfortunately, their reproduction of the formula was flawed and the rest is history.
A bad case of the squirts

So how does the faulty electrolyte cause early failure? Here we can only speculate. Some stories have stated that the flawed formula causes electrolysis, which in turn generates lots of hydrogen. Eventually, gas pressure ruptures the can or breaches the rubber end seal. We are inclined to think that since the electrolyte is used in low-ESR capacitors, the typically high ripple currents and resulting heat causes decomposition of the electrolyte. Either way, the result is the same - the capacitor eventually leaks or ruptures.
Apart from eventual self-destruction, leakage from these capacitors can also damage nearby components and circuit board copper, as the electrolyte compounds are quite corrosive.
Symptoms

When these capacitors fail, the signs are generally quite obvious. The top of the case may be split open or "bulged" upward and/or the can may be dislodged from its base (the rubber seal). There may also be an unpleasant smell and signs of electrolyte leakage nearby.
Even more obvious is the muffled explosion followed by the blank screen. Thankfully, we've heard that this failure mode is quite rare!
However, before catastrophic failure eventuates, all kinds of annoying symptoms can occur. These can range from intermittent boot failures to lock-ups in Windows. Eventually, the affected PC will refuse to boot at all, perhaps even before the culprits have showed themselves!


The rest of the story can be found here. http://www.siliconchip.com.au/cms/A_30328/article.html

The thing is that there are THOUSANDS of the BAD Capacitors out in the Repair Parts system and unless you know all the brand and style of Capacitors out there you might easily see them show up in a Laser Power Supply.... You just never know....

Last winter our old Ford Tractor started to not want to start when it snowed and we really needed it to plow the SNOW.... Some days it started some days it didn't.... 6 months my Step Father change parts in the Ignition system. I told him to change the Condenser at the mechanical points for the spark plug coil. He did... With another from Ford.... Then another from Ford Tractor Parts..... I told him to go to NAPA and get one from them.... Guess what.... No more problems..... I would imagine that Ford Tractor just happened to get a bad batch of LOW BIDDER Capacitors or Condensers in tractors.....

So it "IS" possible that you have been lucky enough to get 2 "BAD" Capacitors...... I also think the 30 Volt / 32 Volt reason is VERY Valid too...

Just my 2 Cents and a very long story.....

With being a Electronic Tech since 1972 and being a Retire Navy Electronic Tech fixing Radars and Analog and Digital Computers I really get into the route cause of why electronics fail.... I taught a few tricks to the young guys fixing Play Station's too..... They were fun to fix... Things you did not learn in School...

Another story....

We have all seen Crimp on connectors on wires.... A Classic Find for me was a Radar with low power. I suspected the first oscillator tube was putting out low power and it was. The Tech had replaced it with no fix. He even at my request cleaned the 2 heavy wires for the Filament Voltage inside the high voltage box. He wire brushed the crimp connector and screwed the wires back on the tube. Tests showed that something was still bad. What I found was due to the heat of the tube a film of black carbon had formed between the wire and the inside of the crimp terminal. I had them clip off the wire and attach a new crimp terminal. Problem fixed.

Now the clipped wire... Between the wire and the crimp connector there was about 20 meg of resistance due to the carbon... Re crimping the connector would have shattered the carbon and re established connectivity... But it was a lesson that I taught other sailors working on the aging equipment. I was a Mobile Technician my last 4 years. I went to fix the equipment when the sailors on ships couldn't find the problem.

WOW.... Where did all that come from.....

The Readers Digest Version should have been.... "Hey, Good Job fixing the bad CAP!!!!"....

AL

[AL Ursich]

Since I am on a roll tonight and I am willing to bet that the Electronic Oriented Creek reader is interested in the Laser problem and is reading this.

While in the Navy I had found out about the Fluke Multi Meter Recall as my meter was on the list. Two years after retirement and working at Sony I got the job in the Calibration lab. Along with that was a bunch of Schools paid for my Sony, my favorite was the Fluke Electronic Calibration Schools.

On a break in class I brought up the story of the recalled Fluke meters and the instructor told us the story. After the final design was made for the Fluke 77 series and seven models, Fluke Series II, Model 21, 23, KIT-23, 70, 73,75, and 77.

A new Engineer was given the task of finding components on the final design that were not needed and could save Fluke Money.... He found a few and deleted them without asking the Designing Engineer.

Off to production went the project.

A few years later a few Electrician's and Technicians were DEAD and it came back that a Fluke Meter was involved....

What had happened was the person had placed the positive or RED lead on a Voltage source ABOVE 300 volts AC or DC.... Then placed the black lead on the other side of the circuit. The meter would sometimes read ZERO VOLTS.... "Hey is the power turned OFF.... Let me check?... OK.... It's OFF...... ZAP.... DEAD.....

Turned out the 4 capacitors that the New Engineer removed caused this problem......

So 4 years after my meter was repaired and a "R" placed after the serial number I go back to the Calibration lab and call up the data base of over 400 Fluke Multimeters.... I find about 20 that were in service but never seen as a problem and were a real hazard as there was a bunch of 480 volt equipment in the plant.... I got all the meters off for repair and hopefully saved someone.

Check YOUR Multimeter..... http://www.hanford.gov/RL/?page=750&parent=748

In trying to find a link to this very old story, I found there have been other Fluke Recalls, one for a delayed reading letting you think there is NO Voltage when there IS..... On newer meters.....

Lets be SAFE out there..... I remember hearing a Navy Friend was killed working on a Microwave Oven and always wondered if a Fluke Meter was to blame?...

Now back to your regularly scheduled Laser Power Supply Capacitor Thread.

AL

[Darren Null]

There is a label on the side of the tube saying 32V, so I'm inclined to leave it as it is. It's a 10W Synrad tube, but GCC market it as 12W so there may be some overclocking in there, or CGG may simply be lying.
The capacitor is one that was recommended last time and it worked for 9 months of abuse. The power supply locally is a bit lumpy, so it may well be that the circuit itself is OK, but a little fragile. I would definitely prefer it if the fuse on the laser went first though...getting the laser out is a bit of a mission, requiring 4 hands in a space where 2 is a squeeze.

Photos then- the circuit; close up of the errant part and a close up of the identical cap I replaced it with, with my awful soldering deliberately out of focus so that nobody is traumatised by the very sight of it. On the plus side, I didn't solder myself to anything this time, so I'm ahead on points I think. I upgraded the cap when I replaced the first one; I don't know enough to upgrade it again and don't want to cause more problems by putting the wrong bit in. I'm told there's a range of military ones that are a lot more robust- I might try to get hold of a couple of those.

[Dan Hintz]

That looks like a film cap (e.g., polystyrene), not an electrolytic, so no liquid electrolyte to overheat. Depending upon the type of film used, there may have been some self-healing going on for a while, but that only lasts for so long... eventually the film breaks down and it cascades.

The difference in tube voltage between 30-32V is minimal... unless you're on the ragged edge of the caps voltage range (which you should never be, even in cheap designs), a couple of volts is irrelevant, so you can ignore that non-issue.

You could go with a higher voltage cap than what was originally in there, but you'll more than likely make some trade-off in terms of other specs. Whether or not those other changes will have any appreciable effect will depend upon which ones change, how, and to what degree. With the quality of components increasing over the years, you'll probably be okay if this is an older design (10+ years).

[Darren Null]

According to the Synrad schematic, it should be a "c3 100pF 500V SILVER MICA", whatever that may be. It was suggested that I replace it with a 1000V, but the guy in the shop just had 2000V, so that's what I got (I bought 2). The first one lasted from the end of Sep '07 until now and I've just used the second one.
The laser is a 2002 48-1 from Synrad.

[Richard Rumancik]

The difference in tube voltage between 30-32V is minimal... unless you're on the ragged edge of the caps voltage range (which you should never be, even in cheap designs), a couple of volts is irrelevant, so you can ignore that non-issue.

Dan, the cap is not tied across the power supply. It is on an RF board. I have it from Synrad that it can cause serious problems if the laser is tuned at one voltage and operated at another. So if Synrad says it is an issue, I would not be inclined to discount it.

Synrad made a mistake in the way they labeled some of their laser tubes. They attached a label indicating the operating voltage was 30-32V. That was true, but it needs to be operated at the same voltage that it was tuned for.

[Pete Thomas]

Darren, that capacitor you installed I believe is not a silver mica as called out the schematic. Dan is correct, based on the capacitor type and the operating frequency you can generate self heating in the part and it will destroy itself.

Just because a capacitor says it is 100pF does not mean it be 100pF all all frequencies. If I were to bet, you will be replacing the one you installed again in another ~7 months depending on usage.

Silver mica capacitors look like this

-pete