Military projector amp - last edited 9/26/22 - layout help needed

[yello]

I should grab a photo of the switch and the turret board. Convoluted and hard to get to mess of wires. This is an instance where deciphering from the schematic will be way easier than from the real world amp....

There are quite a few rotary switch types. As long as you can find the type of switch, the rest is a matter of confirming with the schematic what connects where. And for the layout, you make that clearer than reality.

You first have to figure out the way the connections work on the switch. There should be 2 common terminals which connect to one other with every switch.

Draw this out... and then figure out which components should interconnect

[Bieworm]

If I can find some time to analyze that schematic I will try to help you out.
But I have a lot (7!!) of upcoming amp projects after this Princeton Reverb I'm building (finishing) right now. And there's this guy who dropped 3 hollowbodies at my place to replace electronics... I'm way busy.. but I'll try to help out.

[Bieworm]

Dayn.. this is not so cleanly laid out, but you can take it from here I guess?

5way switch.png

dayn 5 way switch layout.png

[yello]

Dayn.. this is not so cleanly laid out, but you can take it from here I guess?5way switch.pngdayn 5 way switch layout.png

THANK YOU! This is awesome, I couldn't get my brain to get it this far and its a huge help.

Hope your upcoming projects go well!

[yello]

I was able to find some more info about the tone control rotary switch I am trying to decipher.

First, a clean picture of this part of the schematic:



Followed by a detailed description of what each switch setting is doing and what related parts it is connecting:









It is becoming more clear what is going on, but I need to review it a few more times.

[yello]

So after digesting Bieworm's great diagram, and looking at the detailed circuit info I found, it seems at first glance and reading that when the rotary dial is in the middle "NOR" position, that the extra caps/resistors from other parts of the switch are all bypassed as if not there?

Given I'd like to create a layout that captures only the "Normal" tone position, and basically eliminates that rotary switch, I think it would therefore be hardwired like this:



My lingering question, that I can't seem to deduce from staring at it, is whether the highlighted portion of the switch wiring stays or is eliminate if the rotary switch and its caps/resistors and wiring are removed?

Here is the original circuit pic for reference:

[Bieworm]

NOR bypasses C209, R210 and R212. If you want NOR you might as well delete C209, R210 and R212.

[yello]

NOR bypasses C209, R210 and R212. If you want NOR you might as well delete C209, R210 and R212.

Thanks, sounds like I had it backwards asking about deleting the highlighted wire connection, instead needing to delete the components below it that are bypassed by the wire.

So like this?:

[Bieworm]

Looks correct to me..

[yello]

Looks correct to me..

I appreciate your help sorting it out, I know you are quite busy with the amp and guitar projects! This will help me finalize my layout.

I draw components for layouts by looking at the actual component in the amp. Take good photos of it if it's hard to see.

Currently I'm creating a new layout for this amp circuit, so it can be built on a turret board in a typical amp chassis, not in the original projector enclosure which is crowded and convoluted. That means I'm not recreating what I see in person in my layout, but rather translating the original schematic and original layout, into a totally new (better) layout. Its a great learning process.

[JMPGuitars]

Currently I'm creating a new layout for this amp circuit, so it can be built on a turret board in a typical amp chassis, not in the original projector enclosure which is crowded and convoluted. That means I'm not recreating what I see in person in my layout, but rather translating the original schematic and original layout, into a totally new (better) layout. Its a great learning process.

That's great! And it also means you can do whatever you want.

[yello]

Currently I'm creating a new layout for this amp circuit, so it can be built on a turret board in a typical amp chassis, not in the original projector enclosure which is crowded and convoluted. That means I'm not recreating what I see in person in my layout, but rather translating the original schematic and original layout, into a totally new (better) layout. Its a great learning process.

That's great! And it also means you can do whatever you want.

I will likely mimic the layout sections of the 18w, as that worked out great when I built my ef86 Lite 2p.

[yello]

Here is a question, as I draw up my own new layout for this circuit:

There isn't anything that connects to filter cap C216B - it is connected to filter cap C216A and C216C via a 350 ohm 3w resistor on either side (R240 and R228). What is the point of that? Can I just eliminate C216B and just up the resistor size between C216A and C216C? Would the resistor be 700 ohms 5w? Or 1k or 1.5k 5w? Or does cap size need to change too?

In other words, can I redesign this filter stage to work better and without (what seems to my inexperienced eyes as) extraneous parts?