B15S Response switch wiring.

[Jatchley]

Any body have some good pictures of what leads go to which pads but on the component side? I have a good schematic and pcb diagram but it’s only as detailed as what pads go to “sw1”. this is probably going to end up with me meticulously tracing the schematic but pictures would help here very much. 

Edit: the story here is I ended up with this amp and it’s pretty much dissembled. I’m starting to restore it

[sluckey]

this is probably going to end up with me meticulously tracing the schematic

I agree. But it will be a very rewarding experience.

[Jatchley]

Attached is also a drawing of how the switch and leads off the switch are wired. If anyone could help me figure out which lead goes to which pad I’d be eternally grateful.

[sluckey]

Here's a more eye friendly schematic. Good luck.

     https://el34world.com/charts/Schematics/files/Ampeg/Ampeg_b15s_revc.pdf

[Jatchley]

If it helps I have updated the switch drawing. My first one was wrong. Oops. I also measured each switch lead to each other and have determined which have continuity to which with the switch in each position.

No resistance continuity:
A+N (Guitar)
M+N (Guitar)
B+C (Guitar)
I+H (Guitar)
J+D (Guitar)
E+G (Bass)
C+F (Bass)
L+K (Bass)
K+N (Flat)

Resistant:
A+N 5.6M (Flat,Bass)
A+M 5.6M (Guitar)
A+E 1M (Bass)
A+J 6.8M (Flat,Guitar) 1M (Bass)
A+D 12M (Flat) 6.8M (Guitar,Bass)
A+K 5.6M (Flat)
D+E 5.6M (Bass)
D+G 5.6M (Bass,Flat)
D+J 5.6M (Bass,Flat)
D+K 6.8M (Flat)
D+M 12M (Bass,Flat) 1M (Guitar)
D+N 6.8M (Bass,Flat) 1M (Guitar)
E+J 100k (Bass)
G+J 100k (Bass,Flat,Guitar)
J+K 1M (Flat)
J+M 6.8M (Bass,Flat) 1M (Guitar)
J+N 1M (Bass,Flat,Guitar)
K+M 5.6M (Flat)
M+N 5.6M (Bass,Flat)

All the rest of the connections test as not connected.

I do know that lead N goes to the Vref of the volume pot. And lead G goes to ground. I suspect lead A and lead E also as ground.

I still do not know the exact number of poles or their spacing. The switch is from the 70s but enclosed by a semi transparent cover. I don’t want to pry it off to see in case I break the switch. It seems fragile.

[Jatchley]

Here is pictures of the switch in each position. can Anyone determine what lugs are tied with what pole? The first picture is bass, then flat, then guitar. There are 2 decks. I’m guessing since the schematic has 6 poles this is a 2 deck 4pole 3 throw?

[Jatchley]

I’ve deduced that lead J should go the the junction of R7 and R8? Since it’s a 100k to ground . And then lead M since it’s the only 5.6M that is on the guitar only setting goes to the junction of c5 and c8? That would mean lead A also goes to a ground point. That makes sense to me because it is black like the other ground leads. Does that seem right? It’s taking a while but I’m working on it. Just need some confirmation.

[Willabe]

I'm not sure you'll get any confirmation. That's pretty complicated. Unless someone who's worked on that same amp see's this thread.

Keep working on it, you might get it working.   

[Jatchley]

Thanks for at least making me feel like I’m not alone In this thing feeling over complicated. 
I’m just trying to provide as many details as I can as I go. I feel like I’m in over my head or something just isnt clicking in deciphering the schematic and how that materializes into the switch. I’ve realized I might be asking for too much with schematics, pictures, drawings, and comparisons and that’s peoples time and energy to an amp they don’t even have. I am posting it in a lot of places though. Multi sourcing help. Once it’s figured out I hope no one will ever have trouble finding the info. I mean it is a vintage B15 the people should know.

[Willabe]

There's 168 views on this thread, so people are watching this.

Switches can be difficult and this switch has 2 decks, 8 positions? That a lot to track down. 

Yes, you might get some help at other forums. Keep at it, I think you'll figure it out. It will take time, but like you said it's vintage B15.

[Willabe]

This might help? It's easier to use this with a layout drawing, but you can use a schematic.

https://el34world.com/Forum/index.php?topic=17701.0

[Jatchley]

Update on this. I have lots more of pictures of the switch,  schematic stuff, my measurements, my most accurate drawing of the switch in this google folder.

https://drive.google.com/drive/folders/1lGR-zIcdd9uI5BQO7URBYE43iGTTHTOX


Also vintage blue responded to my email and said “ it appears to be eight 3-pole switches (only six are used) stacked on a common shaft.  It looks like each ‘switch’ consists of a group of 4 contacts – 1 common contact that gets connected to one of the other 3 contacts in the group, depending on the position of the switch.”

That makes the pin spacing make more sense to me and the cross shaped looking contacts under the semi transparent back on the switch.

[Jatchley]

I’ve determined this.

So here’s an updated drawing of the switch pins labeled with position.

[Jatchley]

So lead K goes through a 5.6M to ground in both B and F positions and has open continuity with lead L in bass position. In the flat position lead K goes through 2 5.6M in series to lead M and is open with with the Vref of the volume pot.

Ohhh I also see Lead J in all positions goes 100k to ground and in the guitar position goes through a 5.6M in parallel with the 100k to ground. And lead D merges with lead J on top of that 5.6M and in bass and flat positions D is 5.6M to ground but in guitar position takes the path of least resistance which is 100k which also true for lead J in all positions.

Ok this is starting to make wayyy more sense.

The path of least resistance.

[Jatchley]

I figured it out. 

A/10
B/3
C/7
D/12
E/5
F/2
G/ ch1 Pcb ground.
H/8
I/9
J/4
K/6
L/1
M/13
N/Vref volume pot on ch1 pcb.

Point 11 is mislabeled on the Ampeg pcb diagram as sw1 when really it goes through the channel 1 pcb then to sw1 this is partially documented when you look at the channel 1 pcb documentation