HL2 accidental over-voltage

[Allen Finne]

Hi guys,

     Pulled a bone headed move this evening. I had moved my HL2 to the bench to use as a driver to an amp I am repairing. I managed to apply +30v to the input from my bench supply. I noticed front LEDs briefly lite and go out. When I investigated, I discovered my error. 

Positive pin of input power connector to chassis ground is showing pretty much a dead short (couple ohms). In chasing the voltage path, I suspect D12. I can't find it. Where is it physically located? 

Further initial troubleshooting,  F1 shows continuity, next stage is Q1, it shows a couple ohms between the drain and gate which I would expect if D12 was shorted. If it turns out D12 is not shorted ( not failed or failed open) then Q1 becomes the suspect. Any other thoughts or tips are welcomed.

Allen

w5sqk

[Allen Finne]

I located D12, hard to miss once you pull the board out of the case and turn it over. ;)

Removed D12, dead short. HL2 now appears to power up normally & Thetis sees it. I'll order a replacement for D12 tomorrow. I am cautiously optimistic that was all the damage, we'll see once I have D12 replaced and it back in its case.

73

w5sqk

Allen

[Graeme Jury]

Hi Allen,

You obviously have not taken out any of the power supplies which most of the radio is protected by and any of the caps should be able to withstand a few microseconds of over voltage so it looks like you are a lucky lad (we deserve a bit of that sometimes).

Enjoy your HL2, Graeme ZL2TE

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[Allen Finne]

The good news is I put the Hermes back in its case minus the TVS and all is working. The TVS is on order and I'll get it in when it arrives. Good news is the  <$1.00 part saved the Hermes from my inattention.

[Steve Haynal]

I'm happy to hear it was a simple fix!

73,

Steve

kf7o