Sanken STV3H-Y Testing and Installation??

Juan9568

Member
Hi guys, I'm finishing the rebuild of my new F2624 Board.


I got from eBay these new STV3H-Y as a replacement but I don't know how to test them with the multimeter. I tried in diode mode but I can't get a reading, not even with the originals...so I don't know if they are dead or I'm doing something wrong.


Any help???
 
In diode test mode with red (+) probe on the anode and black (-) probe on the cathode (yellow dot) you should be reading about 1.4V of forward voltage.
 
Your meter may not have enough test voltage to start them conducting. The diode test range on your meter is expecting one P-N junction to test, an STV3 is 3 junctions, which gives some meters problems. You could try the 'ohms' range but cross check any readings you get with the old diodes before drawing any conclusions from the readings you are getting.

You could set up a very simple test circuit using a 9V battery (for example) and using a series limiting resistor (- important), and then reading the volt drop across the device when it is conducting. Measuring the volt drop across the limiting resistor (which can be a variable resistor), will allow you to calculate the current.
 
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Still, I don't get any reading. Not even in ohms range...could it be my meter?? I have a cheap one DT830D :(
 
or the battery, or dirty probes, or meter fuse, or wrong probe terminals, or you're just near the south pole in the midst of a solar flare :dunno:
It's all more likely than all of these diodes gone bad at once.

haha I mean that maybe I need a pro meter to test these diodes? cause 2 of them are new the other 2 are the original ones but none of them give me a reading. Meter is new (but cheap), everything else is new, black probe in COM, red probe in V/Ohm/mA Fused...fuse is fine too
 
Well, John gave you a pretty good reason in #4 why this may not work. I don't think you need a pro meter, but if the battery is good you definitely need a better meter. If it's any consolation, I've purchased dozens of Sanken STV-3HY's from the same German seller. They all came neat and tidy in their blue cardboard boxes and the amount I found bad was a flat zero. In fact... I never found a stock one that went bad either.
 
Too bad you aren't in the US, I would ask you to send me the old ones. They very rarely ever fail.
 
STV3 diodes are not a failure point, I have never actually seen one fail all all the years I have been around electronics...
 
Neither have I. Even on units with the amp torched all the way back to the VAS stage.
 
Best way to test (IMO) would be to get a 9 volt battery and an 8.2K resistor, and measure voltage drop. Should be 9 volts in reverse direction (no current) and 1.3 (or more based on my reading, not my experience) in the forward direction. Meter should be in volts measuring mode. I've never had occasion to change these. We used to keep them as replacement for the little bead 3 diode bias diodes. YMMV
 
Just use your meter guys, its very simple, diode test function, the STV3 has a forward voltage of about 1.4V....Easy, job done.
 
I've noticed that the "diode" function on some meters only works up to about 1 to 1.2 volts. The 9 volt battery method posted above is a better way to check them.
If you use a 1K resistor, allowing more current flow through the device, the voltage drop on the STV3 will read higher (about 1.6 to 1.8 volts)

Myself, I use an oscilloscope with a curve tracer.
 
I've noticed that the "diode" function on some meters only works up to about 1 to 1.2 volts. The 9 volt battery method posted above is a better way to check them.
If you use a 1K resistor, allowing more current flow through the device, the voltage drop on the STV3 will read higher (about 1.6 to 1.8 volts)

Myself, I use an oscilloscope with a curve tracer.
Any quality meter can read an STV-3 diode, of not, get a better meter, or replace the battery....
 
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or replace the battery....
Quite right, the difference between an exhausted but still apparently working battery, and a new battery, in a multimeter, can be the difference between being able to test 3 junction diodes and not. :thumbsup:
 
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