I suppose you think that's funny! Inject a signal into the EL84 indeed. You didn't say that would by-pass the volume control and 4kc/s blasting through a ten inch speaker a foot from my lug-hole was not pleasant.
Seriously, with the other valves, apart from the (thermionic) rectifier removed the hum was negligible; no worse than that out of my Roberts RB26.
I then tried injecting again via a 1 meg resistor and this seemed to produce a 'clean' tone. However, if I left the ground connection off the tone was accompanied via a load hum but I don't know if that's to be expected; I can't think why that would work at all as the sig gen is battery powered and doesn't have any sort of earth connection.
I've also spotted another Hunt's capacitor which I'll deal with when I get a replacement tomorrow. It may be innocent but certainly won't be helping.
I don't really do logical approaches as I've always tended to work largely on instinct. It's certainly sound advise which I'll try to heed. Substitution isn't really an option as I don't have a spare valve and, tight-fisted Tyke that I am, am loathe to buy one on suspicion. I'm more inclined to put it aside for a bit and hope for inspiration to strike or another set turn up which can be borrowed from.
By the way, thanks for the link to the web-site with the valve data last week. That's well worth knowing about.
I've also managed to cut my grass so that just leaves my mate's b/day cake to make, along with seeing why my AVO's 250VAC range is u/s - Chris very kindly sent me the data on that.
All the best
Joe
Seriously, with the other valves, apart from the (thermionic) rectifier removed the hum was negligible; no worse than that out of my Roberts RB26.
I then tried injecting again via a 1 meg resistor and this seemed to produce a 'clean' tone. However, if I left the ground connection off the tone was accompanied via a load hum but I don't know if that's to be expected; I can't think why that would work at all as the sig gen is battery powered and doesn't have any sort of earth connection.
I've also spotted another Hunt's capacitor which I'll deal with when I get a replacement tomorrow. It may be innocent but certainly won't be helping.
I don't really do logical approaches as I've always tended to work largely on instinct. It's certainly sound advise which I'll try to heed. Substitution isn't really an option as I don't have a spare valve and, tight-fisted Tyke that I am, am loathe to buy one on suspicion. I'm more inclined to put it aside for a bit and hope for inspiration to strike or another set turn up which can be borrowed from.
By the way, thanks for the link to the web-site with the valve data last week. That's well worth knowing about.
I've also managed to cut my grass so that just leaves my mate's b/day cake to make, along with seeing why my AVO's 250VAC range is u/s - Chris very kindly sent me the data on that.
All the best
Joe
