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Hi,
I got a Mesa Express 2 25 for maintenance and retubing. All voltages check against the schematic floating around however I measured lower output power in both 25W and 5W mode. The only thing that doesn't check is point E where bias voltage is around 1.5V not 3V but I guess that's normal considering the 230V PI anode voltage.
I'm well aware that this amp can't produce 25 or even 20 Watts but I didn't expect to measure only 12 Watts before clipping (400Hz sine wave FX loop Return). In SE mode it puts out only 1 Watt before clipping and then the sine starts taking strange shape.
In 25W mode the anode voltage sags to around 340V on power tubes' the plates and 260V on the screens (before clipping). I measured all components and everything looks OK. By the way that 20 Ohm cathode resistor is actually 120 Ohms.
I would appreciate your comments on this.
I got a Mesa Express 2 25 for maintenance and retubing. All voltages check against the schematic floating around however I measured lower output power in both 25W and 5W mode. The only thing that doesn't check is point E where bias voltage is around 1.5V not 3V but I guess that's normal considering the 230V PI anode voltage.
I'm well aware that this amp can't produce 25 or even 20 Watts but I didn't expect to measure only 12 Watts before clipping (400Hz sine wave FX loop Return). In SE mode it puts out only 1 Watt before clipping and then the sine starts taking strange shape.
In 25W mode the anode voltage sags to around 340V on power tubes' the plates and 260V on the screens (before clipping). I measured all components and everything looks OK. By the way that 20 Ohm cathode resistor is actually 120 Ohms.
I would appreciate your comments on this.
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