![]() That way you can eliminate a crucial thing right off the bat.Īre you using a variac or other means to bring the voltage down to 110vac? So if you have any other working tube amps you can pull tubes from make a note about what sockets they were pulled from and try them in the Bandmaster. It was a new tube but was bad from the get go. That was what the problem was, a bad tube. On a whim I changed the tube in the socket. I triple checked everything until my eyesight started failing. When I turned it on and it warmed up, I got a huge BUZZZZZZZZZ! I had made one wiring mistake, corrected that, got the voltages where they needed to be and took it and connected it to my amp. Here is an example, a couple days ago I built a Tube Buffered Effects Loop. The ticking of the tremolo seems to ring a bell with me, it may have to do with the ceramic discs in that section, not real sure.īut of course the best thing to start with is new tubes to eliminate them from the troubleshooting. So you have to go by how the circuit is wired. Leo was famous for being frugal and would use up the old tube charts before printing new ones for updated schematics. Sometimes the Fender amps have an incorrect tube chart on the cab. So it is considered safe to go to the next higher value that is available today.Īlways keep the same voltage or one step higher, never lower on the voltage rating. Often times you won't find the same value caps that are in an old amp. Your photos are very clear but are very BIG! I'm sure one of the members is very experienced with that circuit. Thanks for your help and for this great forum! Voltage on plates of 6L6GC tubes (JJ) = 408V (schematic says 440V) Voltage on plates of V4 PI (12AT7)= Pin 1 = 218V and on pin 6 = 214V (schematic says 230V on pin 1, 225V on pin6) Voltage on plate of V3, vibrato (groove tube 12AX7) = Pin 1 = 356V! and on pin 6=404V(schematic says 280V on pin 1, 380V on pin6) Voltage on plate of V2 (GE 7025) = Pin 1 = 258V and on pin 6=260V(schematic says 260V on pin 1, 275V on pin6) Voltage on plate of V1 (GE 7025) = Pin 1 = 237V and on pin 6=259V(schematic says 260V on pin 1, 265V on pin6) Secondary windings on PT before rectifier and measured to ground = 2X 355VAC (schematic says 2X 320VAC) (pin4-5 on one tube goes to pin 9 on the other and visa versa) I noticed that the "polarity" of the heaterwires is not respected. (could be because I connected it to a 8Ohm speaker instead of a 4Ohm)Ĥ. The tremolo makes a lot of ticking noise.ģ. The datecode tells me it is made in week 45 1965.Ĭhoke: Again according to the sites mentioned above:Ħ06-5-47 (= Woodward Schumacher week 47 of 1965)Ģ. The "022848" number confirms it is a Bandmaster OT.Īccording to the same sites as above this PT is also a Woodward Schumacher.Īn original Bandmaster PT (when refering to the number "125P7D that is stamped on it). ![]() ![]() When I look at this site, and this site,, it should be made in week 45 of 1960 or 1970. I did found out that it is a Woodward Schumacher tranny. the wires that are coming out of this transformer are a lot brighter in color than the other wires in the amp. First two are 100uF the others are 20uF) (schematic says 70uF and 20uF) there are new (at least they are not original) Elko's in the powersupply. It already came with a 3 prong powercord.ī. To bad it didn't work properly when it arrived.įinally I have some time to check things out.Ī. Last year I bought a 1966 (maybe 1967?) Fender Bandmaster (AB763) via Ebay. ![]() First of all, HAPPY NEW YEAR! And thank you for this great forum!
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