Started my first scratch build. Bassman AA165

[1blueheron]

So I started cutting metal and punching holes.  The chassis is from a Conn organ and the Transformers and tubes are from a Baldwin Organ.  I think the signature by "Flo" is really cool.  assume she was the original assembler at Conn in 1961.  I left it.  The top will get a fresh coat of silver metallic paint after all the cutting and drilling is complete and before I start wiring.  These pics are just trial fitment.

I have added an extra small bottle socket in anticipation of either adding reverb or high gain to the normal channel at a point in the future.  The transformer has the current for it so I figure why not future proof.  I will plan an expansion area on the board as well.  I would have 3 unused triode sections to play with.

I have pilot holes drilled for the control panel and hope to get them drilled out soon.

I left the original terminal strips in the chassis but may remove them if they aren't useful.

Please feel free to criticize comment or make suggestions.

[1blueheron]

Transformer cutout was done with a sabre saw using a fine metal cut blade and edges finished off with a file. 

[Slimtim]

looking good man.DAMN thats a huge hunk a iron for a 50 watt pt.

[sluckey]

I wanted to mention those noval tube sockets before you start wiring them. Those wafer sockets are notorious for developing poor connections to the tube pins. Even worse if the tubes will be pointing down.

[1blueheron]

 
I have heard they are not favored.  What causes them to develop bad connections?  Heat?  When I tried to pull the tubes from these, they were so tight I was afraid the tubes would break getting them out.  I'm not crazy about them, but they were free.  Is it a huge mistake to leave them in or just a "not recommended"...?  These tubes will stay pointing up.

[sluckey]

I would just get some Belton sockets and not think twice. Besides, some of those tubes will benefit from tube shields.

edit... spelling error

[DummyLoad]

I have heard they are not favored.  What causes them to develop bad connections?  Heat?  When I tried to pull the tubes from these, they were so tight I was afraid the tubes would break getting them out.  I'm not crazy about them, but they were free.  Is it a huge mistake to leave them in or just a "not recommended"...?  These tubes will stay pointing up.

inferior by design and construction + heat burns phenolic resulting cracks so part itself & connectors become weakened. those sockets were prevalent on 'throw away" radios & electronics.

as already stated: you need shields on at least the first 3 preamp tubes. unless you like RFI, buzz & hum...      


--pete

[PRR]

Those phenolic-wafer sockets were the absolute CHEAPEST type for years.

Suitable for $9.98 radios on 30-day warranty.

I have seen them still be OK after 30 years, but I do not like them.

[1blueheron]

Got my order form Doug last night so I now have the new Belton sockets, all my input/output jacks, pots, and grommets.  Belton sockets line up pretty good with the holes I had for the wafer style sockets so that is a big relief.  Still working on my board layout.  Debating where to put the space for future  gain stage or reverb mods. 

[SILVERGUN]

My unsolicited 2 cents...
Put the reverb in now. You won't not like it.
I personally would not spend the time scratch building a Fender amp without Fender reverb.

It'll take a little combobulation but nothing like building a boat.

[1blueheron]

I have been working on my board layout and have it pretty much complete except for the modified normal channel....

So here is what I have come up with.  I want to build the bassman pretty much stock and get it working first.  Then after it is up and running without issues, come back and mod my normal channel for a high gain "Lead" channel that could easily be put on a footswitch.   

I read through a lot of threads and stumbled across Dummyloads K10 hack which uses a 6AU6 as a preamp.  I kinda like the idea of a small pentode pre-amp and figure it should easily be able to overdrive the normal channel.  So what I did was steal Pete's preamp scheme and graft it in the design as best I know how.  I am certain I probably made some mistakes, perhaps the whole idea has some severe flaws but I've got thick skin and can take the criticism.

I suppose I may need a way to control the gain and may need to add a pot if it can't be controlled sufficiently by the guitar volume /tone knob.

So waht say the experts on this hairbrained scheme of mine?  I am also considering the fact that if I like this, I could leave the circuit wiring in a 6205 in place of the 6AU6 to gain back my 5th socket for something else later on.  I guess I could also use a 5654?  Thoughts?

[1blueheron]

Guess my idea isn't very original, Looks like Fender is basically doing similar in the MTG tube distortion pedal using a 6205.  Has nyone been able to get a schematic on that pedal yet or reverse engineered?  Also see someone has used it for "The Werewolf" pedal? 

[PRR]

> * Baldwin Bassman 6AU6 mod.jpg

You need a cap and resistor into V3A. (As drawn, V3A grid connects to the +100V on the pentode plate, which won't be good.)

[sluckey]

Schematic is too small.

[1blueheron]

PRR,

I believe I see what you are saying.  I either need the tone/volume control section in the k10 mod,  or an RC network as shown in the werewolf drawing between the plate of V2 and the grid of V3A.  Does this look better?  Maybe a 1M pot would be best solution as a gain control but it all has to go on the V2 side of the DPDT switch so as not to affect the clean bypass circuit?

Is C3 needed in this case?

Sluckey,

I have enlarged the scheme below and will fix the one in previous post, sorry I forgot to super size my happy meal.