Tweet
I have a client's Ampeg SVT-CL Bass Amp on the bench, which came back to me from repairs in April, which then had shut down during shows. I had replaced power tubes, driver tubes, cleaned up some solder joint issues, and other routine service, since it hadn't been serviced since 2017. It came back a couple weeks ago, once again it shutting down during a show.
This morning, I had powered up the amp, now both chassis removed from the cabinet to check connections in the preamp, and again have a look at the power amp chassis wiring. All seemed nominal, but after having left it in Standby Mode, powered up for a bit over an hour, when I switched out of Standby, it didn't light up. No difference in AC Mains Wattage consumption. And the Heater/Bias Power Xfmr on the chassis was VERY HOT. I powered down for an hour and tried again. Xfmr core was now only moderately warm to the touch. It powered up without any issues this time. I powered back down, removed the hold-down clamps & power tubes, removed the power tube cover, and then unplugged the wires to the power tube PCB. The right angle 1/4" female Fast-on Terminals vinyl covers were quite dark from years of heating (these connections being the source of the 6.3VAC into the amp's Heaters).
I slid the covers back, checked the fit of the terminals to the blades of the power tube PCB, and they felt on the loose side. Closed the contacts down a bit to get a nice tight fit, so you really have to push them on firmly to get them into place. (Yeah, I know soldering them into place is best). I've now had the amp running under Burst Pink Noise for an hour and a half & counting, pulling 250W AC mains during burst, and 210W at idle between bursts, and haven't yet had the power amp shut down as it had earlier.
Has anyone out there found their Ampeg SVT-VR or SVT-AV thermally shut down during operation? I've never seen any mention of there being resettable internal thermal switches in the Heater Pwr Xfmr.
This morning, I had powered up the amp, now both chassis removed from the cabinet to check connections in the preamp, and again have a look at the power amp chassis wiring. All seemed nominal, but after having left it in Standby Mode, powered up for a bit over an hour, when I switched out of Standby, it didn't light up. No difference in AC Mains Wattage consumption. And the Heater/Bias Power Xfmr on the chassis was VERY HOT. I powered down for an hour and tried again. Xfmr core was now only moderately warm to the touch. It powered up without any issues this time. I powered back down, removed the hold-down clamps & power tubes, removed the power tube cover, and then unplugged the wires to the power tube PCB. The right angle 1/4" female Fast-on Terminals vinyl covers were quite dark from years of heating (these connections being the source of the 6.3VAC into the amp's Heaters).
I slid the covers back, checked the fit of the terminals to the blades of the power tube PCB, and they felt on the loose side. Closed the contacts down a bit to get a nice tight fit, so you really have to push them on firmly to get them into place. (Yeah, I know soldering them into place is best). I've now had the amp running under Burst Pink Noise for an hour and a half & counting, pulling 250W AC mains during burst, and 210W at idle between bursts, and haven't yet had the power amp shut down as it had earlier.
Has anyone out there found their Ampeg SVT-VR or SVT-AV thermally shut down during operation? I've never seen any mention of there being resettable internal thermal switches in the Heater Pwr Xfmr.
Comment