I thought I asked here before I start messing with my amp.
I have an Ceriatone OTS and while reading several threads here, I think some of my voltages are a bit high.
PT prim 219 (wall voltage)
PT sec 695
Heaters 6,3
plates
V1a 201,3
V1b 202
V2a 200,3
V2b 209,1
PI1 313
PI2 301,5
6L6 454
bias 38mV
So my first question is are those a bit high or I'm imagining things. You should consider that wall voltage was 219V when I measure this. During summer time wall voltage can go up to 230V (even more sometimes).
I'm currently using 220V primary setting on the PT. I could go to 240V setting and that would probably reduce everything for about 10%. Right?
So should I do that or should I rather play with my dropping string (I use 3K3, 22K, 2K2 ), considering my heaters voltage is fine?
mcinku wrote:I thought I asked here before I start messing with my amp.
I have an Ceriatone OTS and while reading several threads here, I think some of my voltages are a bit high.
PT prim 219 (wall voltage)
PT sec 695
Heaters 6,3
plates
V1a 201,3
V1b 202
V2a 200,3
V2b 209,1
PI1 313
PI2 301,5
6L6 454
bias 38mV
So my first question is are those a bit high or I'm imagining things. You should consider that wall voltage was 219V when I measure this. During summer time wall voltage can go up to 230V (even more sometimes).
I'm currently using 220V primary setting on the PT. I could go to 240V setting and that would probably reduce everything for about 10%. Right?
So should I do that or should I rather play with my dropping string (I use 3K3, 22K, 2K2 ), considering my heaters voltage is fine?
What is the smartest thing to do?
Any ideas?
The voltages depend on the iron used, in your case it seems the CTS has a PT that puts out more than your average Fender Twin type of transformer. There is nothing wrong with that, I myself prefer my only amp which has a Marshall style PT and puts out about 475V on the power tube plates -- and higher voltages throughout from there on down to V1.
The only thing I think is that 38mV (I take it you are measuring that across a 1 ohm resistor and that you actually mean that the power tubes are drawing 39mA a piece) with 454V on the plates is a bit higher than I would use. To get 12.5W or 15W per tube (half power at idle, depending on the type of 6L6 you use) you would need between 28 and 33mA per tube. At the end of the day, if the plates are not glowing red when you play the amp at volume, you are not likely to blow anything up. But since you mentioned the line voltage can go up to 230VAC, then I would back off on the idle current.
mcinku wrote:
V1a 201,3
V1b 202
V2a 200,3
V2b 209,1
PI1 313
PI2 301,5
6L6 454
bias 38mV
So my first question is are those a bit high or I'm imagining things. You should consider that wall voltage was 219V when I measure this. During summer time wall voltage can go up to 230V (even more sometimes).
I'm currently using 220V primary setting on the PT. I could go to 240V setting and that would probably reduce everything for about 10%. Right?
So should I do that or should I rather play with my dropping string (I use 3K3, 22K, 2K2 ), considering my heaters voltage is fine?
What is the smartest thing to do?
Any ideas?
Per Nik's measurements, these are considered typical for the design:
Given that, your measurements seem to be reasonable. Try going to the 240 setting if you want to see if you can hear a difference. Just check the heater voltage, but a little low (say 6V) won't hurt and may even help tube life and tone. Other than that, if you like the tone I don't see a need to alter voltages. You could certainly experiment. Perhaps consider a regulator though, if your wall voltage range is considerable.
Given that the power tubes have 454v on them, according to a chart I have, with a plate voltage of 450v, 33ma is around 50% disapation, 40ma is 60% and 47ma is 70%.
But the chart is probably the actual bias current with the screen current taken into consideration.
Voltages look very close to ideal. The preamp plate voltages will vary greatly with the choice of tubes so I wouldn't adjust the dropping string until you've settled on your preamp tubes.
I wouldn't go to the 240V tap. It will lower your overall voltages BUT will also lower your heater voltage.
Just for the record I use Tun-Sols all over and that bias voltage is measured across a 1 ohm resistor.
Maybe I can utilize that unused ground switch, so I can switch between 220V PT setting in the winter and to 240V for the summer when the wall voltage goes up.
Maybe I can utilize that unused ground switch, so I can switch between 220V PT setting in the winter and to 240V for the summer when the wall voltage goes up.
Maybe change the mains switch to a 3 position on-off-on switch?
