Biasing amp, measuring plate voltage. Blown fuse. Quick sanity check please!
Hi everyone.
Yesterday I received a socket probe that I ordered to measure plate voltage on a DRRI 65’ to calculate total dissipation %, I already owned (and used) an idle current probe. I am also familiar with DMM usage.
I ask for assistance because, when attempting to measure the plate voltage via the socket probe, after flipping amp out of standby, the transformer hummed aggressively and popped the 2A fast-blo fuse on the back of the amp.
Now, this probe is pretty stupid simple to use and verified all my leads were connected correctly before and after the fuse blew. Probe was clocked correctly, tube was clocked correctly and both were fully installed.
Quick run down of instructions provided with probe:
- Connect leads to DMM to COM and Voltage ports.
- Set DMM to 300-600v DC or auto-range if available.
- Install probe and tube clocked correctly
- Turn amp on for 60 seconds on standby, and then flip off standby.
- Take read.
Is there anything I’m missing here that would cause this?
The only thing I have concerns with is the permissible use of “auto range” on the DMM. my DMM starts reading in mV, is it possible this is the cause?
Either way, after replacing the fuse on the back, the amp appears to be functioning normally. Is there anything I should keep an eye out for the may be damaged? I know there’s a possibility the transformer, rectifier, traces, and screen resistors took a hit, but nothing seems amiss right now.