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Peavey Mace VT series head, the one with 6 x 6L6GC for 160 watts RMS.
Came in with several problems and didn't produce any sound, but the 6 amp main fuse was not blown. Kept amp on the LBL and first got the preamp working. Preamp now produces strong signal from PREAMP OUT on rear panel. Equally strong signal from the LINE OUT.
Lots of hum and AC ripple, so moved to the power supply board and replaced the 100/350 main filters at C6, C7, C8, C9, also replaced the 1000/35 at C14 and C16 and the 10/160 at C11. Power supply seems stable. Found a couple loose pins on two of the molex connectors and tightened those.
On the power tube board several of the 100/5W were open so I replaced them all at R29, R31, R33, R35, R37 and R38. Then with all the tubes installed, measured in the neighborhood of -40V bias at pin 5 of each power tube socket, give or take a couple volts on a couple sockets. All this with the amp still on the LBL.
Cautiously played the amp while still on the LBL and get moderate outout from the power amp while keeping the volume control down. (160 watts RMS into a 70 watt speaker). Seemed pretty much normal for the volume I dialed in. Noticed when I dug in the power indicator lamp would dim and then go completely out until I quit playing.
Noticed some low hum, so I tested all the old stock Sylvania 6L6GC tubes on tester for grid leakage and shorts and all tested fine with strong readings. Measured current draw at each power tube via bias probe and current draw at idle was quite low, definitely not too much at idle.
Took the amp off the LBL and the fuse blew pretty quickly once I put a tone at the input and raised the volume to about 35-40 percent. Put amp back on LBL and with all tubes pulled, all six tube sockets have 499V at pin 3, 497V at pin 4, and -60V at pin 5.
Added tubes back one at a time and predictably the voltages dropped accordingly. With all six power tubes in the bulb glows dim, definitely not bright, to be expected with six hungry 6L6GCs. Plate voltage is now 397V and the tubes are drawing ~7 mA of current. I've done nothing to rectify the blown fuse, so I won't take the amp off the LBL until we can sort that out.
Any ideas what to check next? The replacement electrolytic capacitors are definitely oriented correctly.
Came in with several problems and didn't produce any sound, but the 6 amp main fuse was not blown. Kept amp on the LBL and first got the preamp working. Preamp now produces strong signal from PREAMP OUT on rear panel. Equally strong signal from the LINE OUT.
Lots of hum and AC ripple, so moved to the power supply board and replaced the 100/350 main filters at C6, C7, C8, C9, also replaced the 1000/35 at C14 and C16 and the 10/160 at C11. Power supply seems stable. Found a couple loose pins on two of the molex connectors and tightened those.
On the power tube board several of the 100/5W were open so I replaced them all at R29, R31, R33, R35, R37 and R38. Then with all the tubes installed, measured in the neighborhood of -40V bias at pin 5 of each power tube socket, give or take a couple volts on a couple sockets. All this with the amp still on the LBL.
Cautiously played the amp while still on the LBL and get moderate outout from the power amp while keeping the volume control down. (160 watts RMS into a 70 watt speaker). Seemed pretty much normal for the volume I dialed in. Noticed when I dug in the power indicator lamp would dim and then go completely out until I quit playing.
Noticed some low hum, so I tested all the old stock Sylvania 6L6GC tubes on tester for grid leakage and shorts and all tested fine with strong readings. Measured current draw at each power tube via bias probe and current draw at idle was quite low, definitely not too much at idle.
Took the amp off the LBL and the fuse blew pretty quickly once I put a tone at the input and raised the volume to about 35-40 percent. Put amp back on LBL and with all tubes pulled, all six tube sockets have 499V at pin 3, 497V at pin 4, and -60V at pin 5.
Added tubes back one at a time and predictably the voltages dropped accordingly. With all six power tubes in the bulb glows dim, definitely not bright, to be expected with six hungry 6L6GCs. Plate voltage is now 397V and the tubes are drawing ~7 mA of current. I've done nothing to rectify the blown fuse, so I won't take the amp off the LBL until we can sort that out.
Any ideas what to check next? The replacement electrolytic capacitors are definitely oriented correctly.
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