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DIAC Bilateral Trigger

I have a 56-70V Bilateral Trigger DIAC (basic data @

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?Name=HT60-ND) which I would like to test. I found what appeared to be a thorough discussion of this device someplace on the web (can't find it now though) but being an EE dropout it's all above me. Is there a fairly simple way to do this with basic test equipment such as a VTVM, DC power supply, signal generator &/or oscilloscope? Thanks for any ideas.

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bicycle6228
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"bicycle6228" schreef in bericht news: snipped-for-privacy@e34g2000vbm.googlegroups.com...

For a simple, static measurement you need a resistor of 47k, a voltmeter and an adjustable power supply that ranges from 40-80Vdc. Put resistor and diac in series and connect to the power supply. Connect the voltmeter cross the diac then slowly raise the voltage. At some point between 56V and 70V the diac will trip and the voltage on the meter goes down. Then you can lower the voltage until the diac blocks again. According to the datasheet (at least the one I have) the voltages need to be between 56V and 70V mentioned already and may differ for about 4V as a maximum.

BTW Why do you need this information as you seem to lack the knowledge to do something with it?

petrus bitbyter

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petrus bitbyter

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Wow; thanks a ton for the response- exactly what I was looking for.

Here's the scenario: This DIAC I'd like to test is in an AC/DC converter associated with a Klipsch Promedia 5.1 amplifier. The circuit, if you're interested is described and diagramed here:

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The circuit suffered a fairly massive failure of several parts, including a power FET and a pair of zener diodes in close proximity (both physically & electrically) to the DIAC, so I'm concerned about its condition. I will perform your test and replace the DIAC, depending on my observations, along with a laundry list of other casualties. Thanks again for your reply.

Reply to
bicycle6228

berichtnews: snipped-for-privacy@e34g2000vbm.googlegroups.com...

Wow; thanks a ton for the response- exactly what I was looking for.

Here's the scenario: This DIAC I'd like to test is in an AC/DC converter associated with a Klipsch Promedia 5.1 amplifier. The circuit, if you're interested is described and diagramed here:

formatting link
The circuit suffered a fairly massive failure of several parts, including a power FET and a pair of zener diodes in close proximity (both physically & electrically) to the DIAC, so I'm concerned about its condition. I will perform your test and replace the DIAC, depending on my observations, along with a laundry list of other casualties. Thanks again for your reply.

Oops. I made a big mistake! A diac that trips, keeps conducting until the current falls below the hold level. So the voltage that makes a conducting diac block again will be way below 40V. It will be around 1V as the hold current is only about 25uA.

After this measurement you need to connect the diac in reverse and repeat. Now the trip voltage needs to be within +/-4V of the first measurement.

If your power supply cannot go low enough, you may connect a 5M potmeter in series with the resistor. Start measuring with the potmeter on 0. When the diac trips lower the voltage and then increase the resistance of the potmeter until the diac blocks again.

petrus bitbyter

Reply to
petrus bitbyter

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