eBay auction for this this Guild Thunderbass head 3 X 12AX7, 1 X 7247, and twin 8417s. Seller says it's been painted black.
Given the paint job and the holes in the bottom of the cabinet, it probably started out life as one of these:
With only one particular concern, the chassis top and bottom are in very good condition: the red box IDs a power resistor where the inner resistive element has come loose from its insulating sleeve; common enough but needs fixed:
For purposes of comparison, you might look at this Guild Quantum currently on eBay. In terms of the Quantum, the Thunderbass is pretty clean. As ever, the caps in the Thunderbass could last 5 days or 5 years but I'd read the lack of rust and minimal coating of tone cheese as suggestive of more, instead of less, remaining useful life. But if you want the amp to sound as good as it could ever sound or you want to gig it, replacing the caps is a necessity ... and the power cord.
This amp, like the Quantum comparable, is fitted with 8417s; a sweet, good-sounding 6L6 variant that is no longer in production. While the 6L6 and 8417 have identical pinouts, the plate/screen voltages in the Guild 6L6 design are 460v/420v but 400v/300v in the 8417 design and 6L6s are biased hotter than 8417s. The Thunderbass has a bias test port and separate bias pots that allows accurate bias and permits the use of unmatched tubes. To run 6L6s in the amp, at least one resistor in the power supply - like the chunky one that's coming apart - would have to be reduced in value to push the screen voltage up and some consideration given to changing the bias resistor. CJ
Given the paint job and the holes in the bottom of the cabinet, it probably started out life as one of these:
With only one particular concern, the chassis top and bottom are in very good condition: the red box IDs a power resistor where the inner resistive element has come loose from its insulating sleeve; common enough but needs fixed:
For purposes of comparison, you might look at this Guild Quantum currently on eBay. In terms of the Quantum, the Thunderbass is pretty clean. As ever, the caps in the Thunderbass could last 5 days or 5 years but I'd read the lack of rust and minimal coating of tone cheese as suggestive of more, instead of less, remaining useful life. But if you want the amp to sound as good as it could ever sound or you want to gig it, replacing the caps is a necessity ... and the power cord.
This amp, like the Quantum comparable, is fitted with 8417s; a sweet, good-sounding 6L6 variant that is no longer in production. While the 6L6 and 8417 have identical pinouts, the plate/screen voltages in the Guild 6L6 design are 460v/420v but 400v/300v in the 8417 design and 6L6s are biased hotter than 8417s. The Thunderbass has a bias test port and separate bias pots that allows accurate bias and permits the use of unmatched tubes. To run 6L6s in the amp, at least one resistor in the power supply - like the chunky one that's coming apart - would have to be reduced in value to push the screen voltage up and some consideration given to changing the bias resistor. CJ
