I didn't give it a chance to go much over 3/4 of an amp before I shut it off. #Ab763 bandmaster full#I think the problem was the original, dried out electrolytics ( forgot about the bathtub full of electrolytics on top of the chassis) and the current draw associated with powering it up and the caps trying to reform. They cut a new keyway in a tube socket? Why? Now that's one to remember. Maybe use 1N5408's on the HV side, though the 1N4007's should work there too. I'm going to swap them for 1N4007's on the negative bias supply. The diodes look to have been a little warm. Thats why I desoldered the leads from the eyelet board, which is warped and very stiff btw. If that goes fine, look for shorted B+ bypass capacitors. Yeah, but beyond that test all the tubes for shorts- or just pull them all and power up. I have a set on the bench now that the rectifier was installed 180 degrees out.yeah, believe it or not, someone cut a new keyway and the HV was being applied across the filament of the rectifier! You can't make this stuff up. Normally on something like that I would just pull the rectifier tube and if it powers up fine with no tube, then the trans is usually fine and the problem lies with the rectifier or beyond. It's hard to solve an equation if every term is an unknown. Does anyone see anything that I might have missed. I can check the impedance of the transformer windings but there's no reference value for what it should be on the schematic. Other than that it looks used and original. I see new style metal oxide or metal film resistors sprinkled around and maybe one capacitor. Someone has worked on it in the recent past. So, to me, it looks like there's something shorted or leaking to ground in the HV section, after the transformer. Then I checked the output of the three secondary windings, two HV and one negative bias voltage, and they all read reasonable values considering no load. Next I powered up the transformer with nothing but the filaments wired in and still no indication of a short on the primary. I checked for a short on the primary with an ohmmeter and that looked fine. I powered up again thinking (hoping) it might be in the receptacle, broken fuse holder, ground switch, death cap, power switch, anything but the transformer. Next I desoldered the primary and HV leads. When I plugged it in to my Sencore PR-57, as I started raising the output voltage on the Sencore, the current started climbing a lot faster than it should have, I was pretty convinced the odds were stacking up on the wrong side of things at that point. When I got it, based on what the owner told me, I thought that there was a chance that the power transformer was toast. If you are not sure of your abilities to perform these modifications then do not perform them.Īll orders are processed within three business days, however, international shipping may be delayed up to six weeks depending on customs.I just took a look at what I think, based on the QA on the tube chart, is a 1967 vintage Fender Bandmaster Blackface. Tube amplifiers contain parts that operate at very high temperatures and deadly voltages. The modifications to your amplifier are at your own risk and you agree to completely hold harmless the seller of this kit against any and all claims. No Warranty: This kit and the instructions included do not include any warranty of any kind. Super Reverb: AA270, AB568, AB763, AA1069, AA763 (Notify us if you are ordering for the AA763 Super Reverb) The following amp circuits are supported: Included in the kit are high quality replacements for all of the electrolytic capacitors. Use this kit to keep your vintage amp running as smoothly as possible, while also improving tone and reducing noise. #Ab763 bandmaster pro#Recap Kit for your Vintage 1960's-70's black panel and silver panel Fender Twin Reverb, Pro Reverb, Super Reverb, and Bandmaster Reverb Amplifiers.
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