Author Topic: testing a 3500V 6.5mA constant current PSU  (Read 1616 times)

0 Members and 1 Guest are viewing this topic.

Offline tolland

  • Contributor
  • Posts: 9
testing a 3500V 6.5mA constant current PSU
« on: August 04, 2014, 08:47:24 am »
Hi,

I have been given a JDSU 380T psu for a Melles Griot 05-LHP-991 HeNe laser. However it blows the 500mA fuse when powered up.

I suspect the power brick has been damaged, but I'd like to test it without the laser attached to determine whether it is the laser or the PSU that is faulty.

It would seem I would need a 3500V/6.5mA=538.5 k Ohm load that can handle 22 watts to simulate the 6.5mA load of the laser.

Is that something I can make up? (bucket of water or something.... ;-)

Cheers,
Tom

« Last Edit: August 04, 2014, 08:51:23 am by tolland »
 

Offline mikeselectricstuff

  • Super Contributor
  • ***
  • Posts: 12069
  • Country: gb
    • Mike's Electric Stuff
Re: testing a 3500V 6.5mA constant current PSU
« Reply #1 on: August 04, 2014, 09:01:08 am »
HeNe PSUs do not put out that sort of voltage/current at the same time.
The 3.5kv is a starting supply, and is very low current. Once struck, the tube runs at around 6-700V.

It is safe to run without the tube for short periods, as this is what happens before the tube strikes.
Chances are it's the PSU. A failed tube wouldn't make the PSU draw excess current unless there is an external short, even then chances are the PSU would limit.
Youtube channel:Taking wierd stuff apart. Very apart.
Mike's Electric Stuff: High voltage, vintage electronics etc.
Day Job: Mostly LEDs
 

Offline mij59

  • Frequent Contributor
  • **
  • Posts: 693
  • Country: nl
Re: testing a 3500V 6.5mA constant current PSU
« Reply #2 on: August 04, 2014, 09:02:30 am »
Hi,

Sounds like nasty stuff.
Before you continue, do some reading on the subject, e.g.
http://donklipstein.com/laserhps.htm#hpsrtc0] [url]http://donklipstein.com/laserhps.htm#hpsrtc0[/url]
 

Offline SeanB

  • Super Contributor
  • ***
  • Posts: 15281
  • Country: za
Re: testing a 3500V 6.5mA constant current PSU
« Reply #3 on: August 04, 2014, 05:17:45 pm »
You could run it with a 4ft flourescent lamp as a load. That will strike and run at around 60-90V when lit. If it is blowing fuses that violently though I would guess the input bridge rectifier, capacitors or something on the primary side is shorted. These power supplies are quite happy to run into a short circuit on the output for a minute or so. open it up and look at the unpotted sections to see the cooked stuff.
 

Online edpalmer42

  • Super Contributor
  • ***
  • Posts: 1679
  • Country: ca
Re: testing a 3500V 6.5mA constant current PSU
« Reply #4 on: August 04, 2014, 07:39:17 pm »
How do you have that power supply wired?

You don't say where you are, but your use of a 500 ma fuse suggests that you live in a 230 V area.  So why do I see a white wire going from the power supply to your fuse panel?  The white wire is only for 115 V power.

I also don't see a ballast resistor.  Is it internal to the laser or the connector?

Ed
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf