EEVblog #468 - Uni-T UT513 Insulation Resistance Meter Teardown

[larry42]

My UNI-T UT502 always has voltage on the output connection - regardless of the "TEST" button. Which is not good on a 2500V tester (Have to switch to DCV to prevent getting shocked). Anyone got a schematic for me to try and fix this UNI-T P.O.S.?

Followup from myself: I had hoped that my faulty UT502 might have a similar relay that was either incorrectly wired, or the wrong "form". Unfortunately there's not safety relay in the UT502, from what I can tell.

[larry42]

My UNI-T UT502 always has voltage on the output connection - regardless of the "TEST" button. Which is not good on a 2500V tester (Have to switch to DCV to prevent getting shocked). Anyone got a schematic for me to try and fix this UNI-T P.O.S.?

Followup from myself: I had hoped that my faulty UT502 might have a similar relay that was either incorrectly wired, or the wrong "form". Unfortunately there's not safety relay in the UT502, from what I can tell.

Just for completeness I'll mention that I fixed the UT502 - the was a solder bridge on Q4 right out the box, causing the "test" button to be ignored, and hence the HV output was always present.

The UT513 looks like has has better construction.

[JuanPC]

1500 Volt Bug Zapper Racket Power Mod,.

[ilanko]

Hi Dave,
Way not blasting Fluke 87-V Digital Multimeter http://goo.gl/FKZYrL with 5k volt ?

[mboensel]

They used a special power adapter and plug for isolation? God I hate having to keep track of those! Why couldn't they just use a little inverter to provide their own isolation to whatever adapter you use? There can't be much cost difference between the external transformer and an internal one - throw in a couple $0.03 transistors and you have yourself an inverter!

Old video and old comments, but I'm optimistic.

Could you explain what you mean by isolation? Isolation from Mains Ground?

Also Dave at 8:11 says "Linear adapter higher isolation voltage" when referring to the input. Could someone explain or point me in a direction? Thanks