'67 100 watt board layout

5150loveeddie · Post by **5150loveeddie** » Sat Aug 13, 2005 11:50 pm

Billy Batz wrote:no. More high end less gain. 270k has less resistance between the mixer and the unused/opposite channels volume pot ground. In other words the volume controls are more interactive with each other.

Your the man Billy, thank bro!!!!!!

Billy Batz · Post by **Billy Batz** » Sun Aug 14, 2005 12:57 pm

If you keep the unused channels volume at 10 then you probably wont even notice any gain difference since at that point it would theoretically be 1.47M vs 1.27M. If you keep the unused channels volume off then you only have 270k vs 470k to ground and obviously the 470k will give you a larger signal. If you keep the same value bypass cap you can check out the sticky on calculating RC time constants.

Guest · Post by **Guest** » Tue Nov 08, 2005 7:59 am

wdelaney72 · Post by **wdelaney72** » Thu Jan 26, 2006 11:39 pm

Billy Batz wrote:I read an article somewhere specifically about those mixer resistors. It said you can date marshalls by the presence of 470k mixers because they started in early 67. If the amp has 270k that doesnt mean its pre 67 because they still showed up in amps after the 470k's but the 470k's started being used at a specific ttime.

Clay Finley's document which is posted in another thread references dating by 470K mixer resistor.

Metal Handles · Post by **Metal Handles** » Sun Jan 07, 2007 11:41 am

Two questions.

1- could anybody post a diagram of the jumpers/buss wire connections/and whatever other connections are needed "below the board"?

2- help me with the diode on the far right of the board. I can only find pictures having it bend left to the top of the adjacent 10uf can, is that a better way to connect the diode so that the choke, OT center tap and red lead from the HT fuse can have that corner turret separate to be soldered to?

Flames1950 · Post by **Flames1950** » Sun Jan 07, 2007 11:54 am

Dan's layouts showed the connections under the board -- get the '67 layout from the "Layouts by Bily Batz" sticky at the top of the Marshall (?) forum......

And on #2, yes, bend the diode over so you have the extra turret to use as a junction point.

Metal Handles · Post by **Metal Handles** » Sun Jan 07, 2007 12:14 pm

Thanks again Flames.
A couple more easy ones. (for anybody)

1- just to the left of the first 10uf can George has a single 8.2K resistor. Billy and Dan's layouts both show dual 10k and 8.2k. Which is preferred and why?

2-do I connect the negative feedback wire (from the 8 ohm tab on the ohm selector switch) to one end of the 27k resistor that the other end connects to the right tab of the presence pot?

Billy Batz · Post by **Billy Batz** » Sun Jan 07, 2007 3:21 pm

Metal Handles wrote:1- just to the left of the first 10uf can George has a single 8.2K resistor. Billy and Dan's layouts both show dual 10k and 8.2k. Which is preferred and why?

Because my layout is made for both the earlier 67 style amps with the 2" OPTs and the later 67 and 68 amps (12 series). The vast majority would have 2 resistors or at least space for 2 resistors (one may be bypassed by a jumper wire.) The resistors only add together for a higher resistance. Nothing special but the early 67 amps with 2" OTs probably would mostly have the single resistor there. In fact I just use one myself. I can buy a 5W or 7W 18.4k or 20k but I mostly just use 10k there.

2-do I connect the negative feedback wire (from the 8 ohm tab on the ohm selector switch) to one end of the 27k resistor that the other end connects to the right tab of the presence pot?

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Yes. The other end connects to the presnce pot and the PI tail a couple spots over (as a jumper wire on the board). YOu can use the 8ohm, 4ohm or 16ohm tabs. Whatever you want. 8 or 16 is probably the most common and original. 16 would be the 'cleanest'.