1967 Bassman build

[Randall]

Here is a before shot of the chassis from the black lagoon.

[Randall]

And here is the chassis , bell covers and 'custom' black choke after rust removal and paint.

[Randall]

"If that's where the Bassman was mixing its channels before, it'll do fine for your modded channel. You needn't add a cathode driver for the EQ stack, just swap out the existing caps for a couple 0.022's, a 33K or 56K slope resistor, and 500 pF or 1000 pF treble cap. Replace the 8200R with a 25K pot for midrange & there you go."

Leo what is your take on the 500 pF or 1000 pF treble cap vs. the 250 (0.00025) cap on the 5F6-A schematic?

[Leo_Gnardo]

Leo what is your take on the 500 pF or 1000 pF treble cap vs. the 250 (0.00025) cap on the 5F6-A schematic?

As you increase the value of the treble cap, you lower the corner frequency at which the treble "filter" operates. Go big enough and you start to bring in more mid frequencies. Could describe it as, the higher the cap value, the more aggressive the treble control becomes. And you can pick an intermediate value, whatever pleases your ears. Or use a switch to select a variety of values. It's all been done before & you can too.

[mikepukmel]

Yes, I have read that article before. I wonder which parts you would recommend. Pretty sure I will put a "normal" bias circuit in it with a 100uF/100v cap. Never understood why you would put a 50v cap in a circuit that supplies -50v.

I am drawn to Leo's idea of a 5F6A in the bass channel. No mid control in the input jack for me, tho. I never have liked that. Maybe in the back though, where there are already two extra holes.

Would a 51v cap be OK?

[Enzo]

Actually a 50v cap in a 50v circuit would be fine. E-caps are rated for "working voltage", meaning a 400 WV cap is fine in a 400v circuit. They also have a surge rating which is a higher voltage. That covers things like power up when the tubes are not warm and the B+ goes high.

What I see as a problem is where Fender specifies a 50v cap in a circuit delivering -55v to the tubes. Both numbers printed on the same schematic.

[Randall]

It's -45v on my print.

[Enzo]

I don't recall the specific model with the "upside down" spec, I wasn't referring to your amp in particular.

[Randall]

Well, we're getting there. Sockets and filament wiring are in, brass control plate almost filled in, board mostly done, filter board almost done. I wised up on this build and will mount the transformers and AC cord last, makes flipping the chassis over and over to get to the other stuff much easier. Waiting on a few resistor values, and then the rest gets wired.

[mikepukmel]

Beauty of a build! Mind if I ask what gauge and type (stranded, solid etc) wire you used for your heater wiring, and if you used the same gauge all across?

[Randall]

I use green 18 ga. solid cloth covered for filaments and grounds, and 22 ga. solid cloth covered for everything else. I use red for HV and preamp plates, yellow for grids and tone controls, blue for cathodes, etc. I like it better than the standard Fender all yellow wiring. Also, grey fiber board, no more black for me!

[mikepukmel]

I use green 18 ga. solid cloth covered for filaments and grounds, and 22 ga. solid cloth covered for everything else. I use red for HV and preamp plates, yellow for grids and tone controls, blue for cathodes, etc. I like it better than the standard Fender all yellow wiring. Also, grey fiber board, no more black for me!

Thanks Randall!

[mikepukmel]

Here is a before shot of the chassis from the black lagoon.

[ATTACH=CONFIG]44201[/ATTACH]
[ATTACH=CONFIG]44202[/ATTACH]

That is one hefty set of transformers!

[Justin Thomas]

Good point.

Randall: You sure that ain't a Twin Reverb OT? My Bassman came with one...
Mike: You should see a Bassman 100 OT!

Justin

[nosaj]

I use green 18 ga. solid cloth covered for filaments and grounds, and 22 ga. solid cloth covered for everything else. I use red for HV and preamp plates, yellow for grids and tone controls, blue for cathodes, etc. I like it better than the standard Fender all yellow wiring. Also, grey fiber board, no more black for me!

Traynors use that color scheme.

nosaj