Questions about replacing power tubes in HT Stage 100 (older model)
Posted: Thu Apr 08, 2021 10:30 pm
This is the first time I have ever owned a tube amp. I looked, and there's no amp techs anywhere near me (over 100 miles away) and my only vehicle is a motorcycle. Needless to say, I'm not hauling this thing on the back of the bike, taking 2 separate 200-mile round trips to drop off and pick up the head.
I do realize biasing and messing around in there with the amp live can be quite dangerous if you're not careful.
I liked the sound that it had, so I am replacing the tubes with the exact same kind: Ruby EL34BHT matched quad power tubes.
My first question is this:
Given that the tubes are the same brand and model, do I need to re-bias the power tubes, or should the existing bias adjustment be pretty close?
Second:
Assuming one or more power tubes is going bad, can I just measure the existing bias and set the bias to being the same when replacing them with new tubes, or will a bad or going bad tube throw off the mV readings? I considered measuring the bias as it exists now to ensure it is the same after so that I don't need to do measuring and math as per my third question.
Third:
I have read this post: http://www.blackstaramps.com/forum/view ... 093#p24420 and I do understand this procedure, with the exception of measuring the plate voltage (no idea how to do that). Is this really necessary to go that far into it with new tubes if they're the exact same brand and model tubes?
I do realize biasing and messing around in there with the amp live can be quite dangerous if you're not careful.
I liked the sound that it had, so I am replacing the tubes with the exact same kind: Ruby EL34BHT matched quad power tubes.
My first question is this:
Given that the tubes are the same brand and model, do I need to re-bias the power tubes, or should the existing bias adjustment be pretty close?
Second:
Assuming one or more power tubes is going bad, can I just measure the existing bias and set the bias to being the same when replacing them with new tubes, or will a bad or going bad tube throw off the mV readings? I considered measuring the bias as it exists now to ensure it is the same after so that I don't need to do measuring and math as per my third question.
Third:
I have read this post: http://www.blackstaramps.com/forum/view ... 093#p24420 and I do understand this procedure, with the exception of measuring the plate voltage (no idea how to do that). Is this really necessary to go that far into it with new tubes if they're the exact same brand and model tubes?