Something interesting has arisen after the failure of the mains fuse (500ma) on my "champ" style amp using 1 6v6 output valve.
I measured the current draw as 178ma (after stabilising) by removing the fuse & fitting the ammeter in series to get a current reading.
Now this equates to around 43w power consumption on what is nominally a 5w amp, although I would think a 6v6 can go a fair bit higher depending on the output transformer's capability.
The meter I'm using can read ac current & seems to be accurate (although as I sold my pro gear last year when I retired from testing/inspections it has been about a year since I was able to check it properly)
I have heard of a "rule of thumb" with valve amps that is a 3-1 ratio input-output power. Although the 2 commercial amps I have declare a ratio of more like 6-1 on the specification plate.
Checked around adverts & similar amps seem to declare broadly similar power consumptions as I am getting.
Since replacing the fuse the amp has run for about 6 hours without any problems
It's an Ampmaker kit with a couple of "mods" to the ht & smoothing that has run for around 250/300 hours without any problems
This arose after I mailed Barry at Ampmaker to see if there had been other instances of the mains fuse failing, he seems to think however that the current draw should be around 15/16w although he seemed surprised that I chose to measure the current across the fuse terminals, he however is going to try for himself when he has time (xmas rush)
Thanks if you have managed to read this far & would be interested to hear what you think.
Ideally if you have a 5w amp by looking at the spec plate, or even better by measurement if you have access to an ac ammeter
Cheers
Dick.