Ever notice there's rarely a convenient place to connect your Ground Probe to?

[nevetslab]

Ampeg SVT-CL sent over for service. Randomly turning off. Newer unit, Power Tubes have Base Clamps (that don't work well, too loose!). I removed the preamp and power amp chassis from the cabinet. I had already set this amp up previously, finding Tech Flex sleeving instead of the traditional stiff garden hose sleeving between Preamp and Power Amp harness wiring.

Chassis' stood up on end, re-connected and warming up. Moved my DMM over, getting ready to have a look at it's ailments. The Cathode resistors of the output stage all have piles of RTV on the resistor leads, so I can't clip my ground lead onto those (my usual ground test point when I'm measuring voltage across those resistors). Scanning the horizon for what I already knew....no other place to hang a ground probe....and my eyes spot the feedback wires' PCB plug NOT plugged into the output PCB assy. Why would THAT not be connected? Plugged it back in.

Anyway, lacking any other simple place, I had to move eight boxes out of the way on the shelves to get to the parts drawer where my solder lugs are stored (parts shelves still unmanageable since moving back into this small shop space!). Installed the solder lug on the chassis grounded front PCB support standoff adjacent to the location of the power tube cathode resistors. Connected the DMM, switched out of S/B, briefly saw GRN bias LED's lit, then tubes 1-3 went RED, Protect fired. But I had just enough time to see around 400mV across V3 power tube cathode resistor....40mA

[Enzo]

I used to keep a big old #70 plug stuck into a hole in my speaker/load patch panel. I could plug it into a jack, and clip my ground to the edge of the hole in the shell.

[g1]

I could plug it into a jack, and clip my ground to the edge of the hole in the shell.

Same approach, but I have a switchcraft 1/4" plug with the shell removed and just clip onto the ground lug.

[Leo_Gnardo]

I used to keep a big old #70 plug stuck into a hole in my speaker/load patch panel. I could plug it into a jack, and clip my ground to the edge of the hole in the shell.

Similarly, I have a couple 280 plugs I keep handy, with short maybe 2 inch insulated wires sticking out the back, with half an inch of bare wire showing on each. I can clip lead them to load resistors and scope probes that way. Or, like you do, plug one in and either put negative probe on the shell or clip lead probe to grounded wire. Those plugs come in handy every day.