Dear diy-ers,
I am looking for a method to measure the maximum B+ current draw for an amp with the power supply as shown below.
Could it be so simple as hooking it up to a dummy load and opening the brown wire and putting an ampere meter where the red circle is? After that we dime it and read the meter?
Thanks in advance
I am looking for a method to measure the maximum B+ current draw for an amp with the power supply as shown below.
Could it be so simple as hooking it up to a dummy load and opening the brown wire and putting an ampere meter where the red circle is? After that we dime it and read the meter?
Thanks in advance
Short one side off stand by switch with crocodile lead and put amp meter across other side of standby switch.
Put a one ohm power resistor in the lead you want to measure and use ohms law to calculate the load. If your meter has peak hold on the voltage setting you can read peak and average current.
That is one of two paths the AC of the B+ follows. It is possible to calculate the correction for DC (I assume what you want). Except the correction is different for different types of meters (average, peak, RMS, dumb) It is a whole lot easier to break a DC point, as JMF sugests (altho that floats your meter at high voltage, which may not be necessary).
Put 1 ohm resistors in your power tube cathodes. Get the current in each and add, that's your power stage current. In guitar amps you rarely have 10% more in preampery, but you can measure voltage drop across resistors and do addition.
Why???
Please explain how an ammeter will explode by current passing through it, the very job it was designed to do.
I have done it thousands of times, if not tens of thousands.
Please explain how an ammeter will explode by current passing through it, the very job it was designed to do.
I have done it thousands of times, if not tens of thousands.
If you are that afraid of this method, then wire a fuse holder in series with your meter and clip all that to the fuse holder.
Since you are taking a measurement, presumably the circuit is not malfunctioning to the point of needing the fuse to open.
So what?
You are measuring here, not leaving it there forever, unattended.
And it will be a problem if and only if there is some gross problem would make the fuse blow, not the case here where you are just testing a working amp for, say, 20 seconds.
Speaking of fuses and "booommms", that fuse should be before the rectifier to begin with.
https://www.valvewizard.co.uk/fuses.html
https://www.valvewizard.co.uk/fuses.html
Or just lift one side of the fuse if it's a snap in holder...
My meter is fused anyway... Or use a cheap meter - it'll blow like a fuse if there's a fault... I once blew the chip off of the PCB of a DMM when I had it set up for current but was checking 600VDC with it. Oops 🙂
I think this dummy load is in place of a loudspeaker.
So not DC current but audio.