Just got a dead V3 working, replaced OT, re-cap, new 7027A's, few other things. I notice my PS V's are high. Get 551V on the plates, a volt or two less on the screens, and -64V bias. Both 7027A's are pulling around 27mA, so at 551v that puts them at less than 15 watts dissapation. That is quite cold is it not? Max Diss rated at is 35 Watts.
My wondering is do I want to try to pull the bias V back closer to the -54V on the schem, or is running cold a desirable thing given the plate and Screen V's are so high? The data sheet I am looking at puts Max plate V at 600v, so I'm good there, but Max screen grid at 500V, which is about 50v lower than where this amp is at. All the PS resistors measure within tolerance out of circuit.
I am thinking about putting a bias pot in it, but am unsure where the best place to put it would be.
What to do, what to do.....
Here is the Joe Piazza version. The Ampeg drawing that is inside it shows plate node at 500v, screen node at 490v, and bias at -54v.
http://schems.com/manu/ampeg/v3poweramp.pdf
My wondering is do I want to try to pull the bias V back closer to the -54V on the schem, or is running cold a desirable thing given the plate and Screen V's are so high? The data sheet I am looking at puts Max plate V at 600v, so I'm good there, but Max screen grid at 500V, which is about 50v lower than where this amp is at. All the PS resistors measure within tolerance out of circuit.
I am thinking about putting a bias pot in it, but am unsure where the best place to put it would be.
What to do, what to do.....
Here is the Joe Piazza version. The Ampeg drawing that is inside it shows plate node at 500v, screen node at 490v, and bias at -54v.
http://schems.com/manu/ampeg/v3poweramp.pdf
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