Need some help with this argon laser - Page 1
Forum section: electronics / general

author: bobhaha
author_rank: Contributor
timestamp: August 04, 2012, 08:33:20 am
content: So I've pretty much exhausted google, looking for schematics for this argon laser I purchased.It's a LaserPhysics 50s-488 single line argon laser.It seems to be having problems producing the low side voltage to heat the cathode. The high voltage "striker" seems to be working fine.The low side voltage is estimated to be around 3VAC at ~20A. I've checked the board over for blown fuses, burnt out resistors, bulging caps etc.. and it all seems fine.There are two FET's that I have already changed out, that seems like they control the lowside voltage... but that has not changed anything.What would be the next step? What do you recommend I try looking at?Here are some pictures of it....These components had scorch marks below them...I changed out those FET's but still no good...-Adrian

author: amyk
author_rank: Super Contributor
timestamp: August 04, 2012, 01:01:55 pm
content: Is the tube OK?If you can't find a schematic then just trace out the relevant portions. It looks like double-sided and no SMD so it shouldn't be too hard.

author: bobhaha
author_rank: Contributor
timestamp: August 04, 2012, 01:50:54 pm
content: Yup, tube was tested... works fine.The board is 3 layers I believe... this could be a bit of a challenge for me... From those pictures, what would be the first place to sniff around? I'm not sure how I can test the torrid or the small transformer on the lowside... I can get a resistance reading from them... but other than that... I don't know what else to look for in them.

author: aargee
author_rank: Frequent Contributor
timestamp: August 05, 2012, 06:26:20 am
content: Looking at the last photo, your problem may be all/partially caused be the carbonisation of the PCB layers.You may have resistance paths set up within the board and there's the fault, no matter which components you replace.

author: bobhaha
author_rank: Contributor
timestamp: August 08, 2012, 04:59:27 am
content: Bump... any ideas?

author: Psi
author_rank: Super Contributor
timestamp: August 08, 2012, 05:15:07 am
content: Create an account athttp://www.photonlexicon.com/forums/and ask thereThey have quite a few people who specialise in knowing everything there is to know about all models of lasers.I would be shocked if they didn't have the circuit diagramThat forum really is a compendium of all laser knowledge and experience.

author: Things
author_rank: Regular Contributor
timestamp: August 08, 2012, 06:43:47 am
content: lol, hey boobI believe the board may actually be 4 layers, not 3. Would be kind of a bummer if a trace on the inner layers has burnt out.

author: Gall
author_rank: Frequent Contributor
timestamp: August 08, 2012, 10:32:08 am
content: That's unlikely. Burning inner traces usually cause visible bubbles. Surface leakage probably.Regardless of anything you may check the DC operating point and gate and drain signal magnitude. Are they Ok?Is source going to ground?

author: Sionyn
author_rank: Frequent Contributor
timestamp: August 08, 2012, 11:07:14 am
content: Alex is your man though haven't seen him here for months