It is a totally reversible mod though, and the bias ballance pot still functions too. I did add a bias ajustment pot because the bias was very cold and needed to be set correctly. The hum has gone and it's as good as new with an almost brand new set of valves. Not to worry too much though, it's a great sounding and very serviceable amp now, even with a shiny new choke. That was even more disappointing because the transformers and the rest of the circuit were basically original. I temporarily replaced the choke with a 1K, 5 Watt resistor and the hum disappeared, confirming the choke was indeed faulty. Vintage Fender MusicMaster 1973 short scale bass guitar works great 1,399.00 100. The oscilloscope picked this up as a sawtooth wave instead of smooth DC. It turned out to be the choke that was not doing it's job of filtering the ripple voltage out of the HT feed to the screens and the reverb transformer, which supplies the gain "boost". The usual servicing/overhaul, including a full recap, did not improve things as I expected, so it was time to trace the fault. I payed way too much under the circumstances. Not everyone is honest and forthcoming about any shortcomings their beloved amps may have, and photos can be a bit fuzzy/vague. When I pulled the master volume boost switch out, the noise jumped up suddenly to an unacceptable level. Never mind that, but there was more than the normal background valve amp hum (Twins are usually very quiet). The legs were not there and it had no casters, only "glides". I was a little disappointed when I went to pick up this Ebay win as it had clearly been recovered. Photo Credit: Our sincere thanks to Richard Beattie for allowing us to use photographs of his amplifier.Another Fender Twin needing a bit of TLC. Yes it’s a smaller amp but the sound is great, it doesn’t take up an enormous amount of room and doesn’t do your back in every time you lift it. however, the quality is now very appreciated by serious musicians and it has kept its price well. The MMB was originally sold by Fender as a beginner’s bass amp. They stick to the familiar Fender branding with an open back cabinet, black Tolex, silver grille cloth, ‘Made in the USA’ raised chrome logo, the silver control panel with blue lettering and the iconic red jewel light. These are rapidly being appreciated as fantastic little 12 watts, 1×12” valve combo amps. The CBS-era Fender ‘Silverface’ Musicmaster Bass amps (MMB) were manufactured between 19. Nothing has been messed with on this amp, all parts and components are original, even the power cable. Chassis has never been unbolted and removed, no circuit tampering or re-capping. We have over 30 years of experience so one of our team will always be happy to help and advise. Fender Musicmaster Bass tube combo amp born in 1972 according to the 72'/72'/ 71' Schumacher transformer codes and the 72' speaker date code as pictured. If you have any queries about replacing your valves please get in touch. Replace the Valves on your Fender Musicmaster.
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