Get one with mixer amplifier, fault is the power tubes is not particularly durable, for use, new tubes for any length of time will burn, power tubes model C5200/A1943.gMWservice manual download site
gMWservice manual download site
Disassemble, measuring two C5200/A1943 were damaged, the tubes burned the b-e,b-c junction is not the same. Real painted for ease of maintenance circuit as shown in Figure 1.gMWservice manual download site
gMWservice manual download site
Figure 1 shows that the power output of the power supply only, 50V, is C5198/A1941 (140V/10A/100W) is fully competent, C5200/1943 (edge 230V/15A/150W} is, Furthermore, the adoption of huge aluminum radiators, useless fan helps heat dissipation design, should be sturdy and durable. Remove the transistors all measurements, except for two pairs of output tubes damaged, the others are all good, resistance is also normal; welding diodes opened a foot measurement is also normal.gMWservice manual download site
gMWservice manual download site
So, install a power tube test, D1-D3 ends long welding leads received a digital meter, wrapped with adhesive tape, speaker binding posts to connect an electric wire cross-section of 8 ohm dummy load, and 470 μg/30W DC isolator 8 ω speaker F/400V capacitance as listening to prevent C5200 breakdown using capacitor to protect the speakers. Music test, use tip of each transistor heat, everything is normal; the diode heat when soldering iron when you position it near the D1-D3,gMWservice manual download site
gMWservice manual download site
Voltage from 1.9V began to decline after a few seconds the voltage suddenly rise breakthrough 2V range, quickly shut down. C5200/A1943 had his hand burned fingers can't touch the extent of power tube bias voltage 2V breakthrough has been in a "group bias" hot hot to the touch, this is the reason why loss power tubes. Is no longer necessary to pursue at this time was D1~D3 which had problems, decisive replacement D1~D3, reheating experiment bias voltage drop is no longer increasing, indicating risks to exclude, install the remaining pair power tubes, deliver ease of use.gMWservice manual download site