Maybe upping that again would clean it up? But, remember it had a 1k5 cathode bias resistor, now its 330ohm. I could swear it wasnt as crunchy when I got it but with all the hum it had its hard to be certain. Can I hit the 6AQ5's with all that? Might increase headroom. What about higher voltage? My PT puts out 352v on the screen but I dropped it down to 293v via a limiting resistor. Any values that can be altered for more clean headroom? I've already got a JBL in there but it starts getting crunchy at 11 o'clock. Now that noise is no longer an issue, I'd like to tweak it a bit for later breakup / more clean headroom. Well I might as well keep my mega-thread going cause now its all fun stuff! Again, I'm not well versed on transformer wiring so this may be out of my reach and over my head.īut if theres a way to check that each wire is were it should be I would like to. Could that be the issue or did the tech who installed it screw something up with the wiring? He's the guy that put the 1meg resistor inline with the pilot lite I presume. The PT has very thin wires, unlike any fender unit I've ever seen. Can I use acetone on a q-tip to clean the tube sockets? I really thought it was the tubes, but tried 4 nos GE 6aq5's and that didnt change things.I've cleaned and re-tensioned the pins.If my pot cleaner is conductive,that would be a bummer. It's a low hum that comes on instantly when the amp is switched on and gradually gets louder for five seconds, kinda the same amount of time it takes the tubes to light up. My hum is not affected by volume/tone adjustments. My amp appears to have lived inside somebodys house all these years, its in quite good condition with no rust anywhere. The only thing i really not sure of (thinking about it now) is whether or not the the schematic had 6V6s or if it was the 6BQ5(EL84) version.Īll the ones I found online that with the mains drawn the way Im describing have 6BQ5s, and the amp I was working on had 6V6s.Thats an interesting link! How on earth would you be able to tell if your wax impregnated board had retained moisture and become conductive? But Im pretty sure I remember it looking like original Fender. Is it possible you're working drom the "unofficial" schematic? And thatcthe creator's example had one of those batshit bare wire fuses but it was mistaken for a piece of wire? The single Fender layout diagram I found did not show anything either. But a third "unofficial" schematic seemed common that was NOT official Fender, that did not show anything. I found two official Fender schematics one of which showed a "CSA Thermal Protector" & the other which showed a regular fuse. But they also look a good bit different from any official Fender schem I've seen, compared to others of thecsame period. Have any of you run into this on this model?ĥ4144Now that's cheap and dangerous of the bean counter.Įdit: seems all of the "homenade" schematics show 6AQ5s.
#Fender musicmaster schematic full
The mains current didn't exceed much more than ≈500mA at full output, so I chose a value of 1A/slow.
The cap was removed, and installed an inline cap from the live to the power switch.īefore choosing a value, I ran the amp into clipping at full power, while monitoring the mains current draw. Inside, there was the typical 70's fender tag strip with one of the legs of the incoming mains coupled to the chassis with the blue radial cap. Apparently, fender installed what appears to be a thermal fuse in some other/later models. It has a UL sticker on the back panel as well. I double checked on the schematic and confirmed that it was designed and built without one, which is crazy to me. I mean, there was no mains fuse at all, and there never was in this amp!!.
Not like, the fuse was missing from the fuse holder. So, after replacing the mains power cord with a new molded plug, I went to check the fuse and. One of the other routine checks I make, particularly in vintage amps, is confirming the fuse value and rating is the one specified. More often than not, it's a disaster and it gets replaced–as this one did. We see this a lot, and I always check the condition and wiring inside. The molded plug end had been replaced by an old 3-prong replacement with screw terminals. We had a 70's Musicmaster Bass amp that came in for general cleaning/service (dates to '79, it looks like).
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