Fender Blues DeVille Pwr XFMR + Amp Rebuild
- Thread starter CJ
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CJ
Well-known member
CJ
Well-known member
Thats looking great CJ. The tinned waxed wire and tag strip stand offs looks really convienient and fast to do ,its a soldering gun job from start to finish really. Do you expect any noise gremlins ,or do you have the layout down well enough not to worry ?
It gives a lot of freedom for component placement ,and with no potential leakages or incidentals that could occur on the single plane of a pcb. It would be cool to hear what it sounds like before the owner takes it away .
It gives a lot of freedom for component placement ,and with no potential leakages or incidentals that could occur on the single plane of a pcb. It would be cool to hear what it sounds like before the owner takes it away .
CJ
Well-known member
it is pretty quiet, got the CT on the heater and doubled up on the uF.
had a slight osc at hi freq but that went away as soon as the nfb line was installed.
had a slight osc at hi freq but that went away as soon as the nfb line was installed.
CJ a link to something that might be fun to build.
https://www.diystompboxes.com/smfforum/index.php?topic=114210.msg1059856#msg1059856
The first post schematic has a few changes that are noted in the thread I also posted a stripboard layout in the thread.
There is a nice youtube that someone did of their build of theirs in the thread.
I like to use Si more than Ges in fuzzes and adjust for the Sis.
Based off the supa/mark 2 fuzzes using close to the correct Ge biasing points with NPN Sis.
https://www.diystompboxes.com/smfforum/index.php?topic=114210.msg1059856#msg1059856
The first post schematic has a few changes that are noted in the thread I also posted a stripboard layout in the thread.
There is a nice youtube that someone did of their build of theirs in the thread.
I like to use Si more than Ges in fuzzes and adjust for the Sis.
Based off the supa/mark 2 fuzzes using close to the correct Ge biasing points with NPN Sis.
CJ
Well-known member
thanks Gus! I will build that! i got 10 of those blue boards for like 6.99 so gonna get some 2222's for sure.
cj
cj
CJ
Well-known member
we built a daughter board for the solid state reverb circuit for this amp and it hummed like a banchee, don't know why, circuit looked ok, so we ripped the board out and went for the old school blackface reverb from the 60's.
problem is, the tank is a 4BB3C1B, if you know your Accutronics numbering system like i don't, then that should ring in at 150 ohms and 2250 ohms in and out.
we know the stock Fender rev xfmr ratio and turns count, don't need to change the primary, that is still gonna be a pair of 12AT7a plates which uses a 20 K wind from Fender,
but what about the 8 ohm secondary that needs to be 150 ohms?
well, orig turns are 4950 : 99 = 50 :1 turns and 20K : 8
keep the 4950 turns on the primary and re-compute sec: 20K/150 = 133.33 Z ratio, take sq root for turns ratio: 11.54
4950/11.54 = 429 turns, add a few turns for core loss and call it 434 T.
so 4950 T : 434 T
no room for big wire like the 8 ohm wind uses so we go with #29 and it fits.
a good xfmr should have half the window full of pri wire and half with sec wire. something about current density. this one came out well balanced with #42 and #29>
problem is, the tank is a 4BB3C1B, if you know your Accutronics numbering system like i don't, then that should ring in at 150 ohms and 2250 ohms in and out.
we know the stock Fender rev xfmr ratio and turns count, don't need to change the primary, that is still gonna be a pair of 12AT7a plates which uses a 20 K wind from Fender,
but what about the 8 ohm secondary that needs to be 150 ohms?
well, orig turns are 4950 : 99 = 50 :1 turns and 20K : 8
keep the 4950 turns on the primary and re-compute sec: 20K/150 = 133.33 Z ratio, take sq root for turns ratio: 11.54
4950/11.54 = 429 turns, add a few turns for core loss and call it 434 T.
so 4950 T : 434 T
no room for big wire like the 8 ohm wind uses so we go with #29 and it fits.
a good xfmr should have half the window full of pri wire and half with sec wire. something about current density. this one came out well balanced with #42 and #29>
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CJ
Well-known member
> a good xfmr should have half the window full of pri wire and half with sec wire. something about current density.
I'm sure you know this. For lurkers:
Yes, current density should be about-the-same in pri and sec.
But for small iron and particularly audio iron, Resistance should be low both sides. Winding pri in 90% of area and sec in 10% of area gives low pri resistance but huge sec resistance. Giving each half the space makes both pretty low and generally gives lowest total pri+sec (allowing for turns ratio), thus best performance.
This runs afoul when you need HV insulation in one side but not the other. Then you may lean toward 40% space for LV, 60% space for HV, and that 60% is a third paper so the actual HV copper is similar to LV copper. Total resistance is some higher but it doesn't leak-across, arc-over, electrocute the user or yell "smoke" in a crowded bar. If resistance is also critical you just buy a bigger window (larger core size).
I'm sure you know this. For lurkers:
Yes, current density should be about-the-same in pri and sec.
But for small iron and particularly audio iron, Resistance should be low both sides. Winding pri in 90% of area and sec in 10% of area gives low pri resistance but huge sec resistance. Giving each half the space makes both pretty low and generally gives lowest total pri+sec (allowing for turns ratio), thus best performance.
This runs afoul when you need HV insulation in one side but not the other. Then you may lean toward 40% space for LV, 60% space for HV, and that 60% is a third paper so the actual HV copper is similar to LV copper. Total resistance is some higher but it doesn't leak-across, arc-over, electrocute the user or yell "smoke" in a crowded bar. If resistance is also critical you just buy a bigger window (larger core size).
