12.000 Finished!!

Sral68 · Post by **Sral68** » Mon May 18, 2009 3:44 pm

I have a question. On the 67/68 layout there is a white wire going from the pt to the 27k resistor on the main component board. As far as I can see, this is also the point were one sends a blue wire to the bias on the standby switch.

I've looked closely on Ricky Lees pictures but I can't see this wire. Also there's no white wire on my PT. On the 68 layout the same wire is called the bias tap.

Studying SDMs draving of the 1959 this seems correct.

I will post som more pictures of my progress tomorrow.

Sral68 · Post by **Sral68** » Tue May 19, 2009 2:28 am

Here is a link to the layout Im talking abaout:

http://home.comcast.net/%7Ejbjdav26/195 ... 0PPIMV.JPG

Sral68 · Post by **Sral68** » Tue May 19, 2009 2:05 pm

Heres were I'm at presently:

Sral68 · Post by **Sral68** » Thu May 21, 2009 6:47 am

Looking at the layouts I see that I've wired the cap board wrong. The Yellow wire to the PT need to be moved to the minus side. The red wire leaving the board need to be moved from the rectifier to the + side of the last cap.

Omn · Post by **Omn** » Thu May 21, 2009 7:37 am

The two blue 95 VAC bias wires from the PT; one is grounded, the other goes to the triple standby toggle switch.
That is; your blue IS the white on the layout from SDM.

It will blow your mind when you are finished. Just take your time...
Good luck, sral!

Sral68 · Post by **Sral68** » Fri May 22, 2009 8:55 am

Thanks for the feedback. My build is moving along slowly.

By the way, I see that I wired my capboard after Leledukes pictures. They deviate from the 67/68 layout. Is this an altenate way of doing it?

Sral68 · Post by **Sral68** » Fri May 22, 2009 12:43 pm

I was wondering about grounding the cap on the board. I understod that Ohm grounded the tone pots to a lug under the board. Is it ok to run the ground from the cap to the same ground lug?

Roe · Post by **Roe** » Fri May 22, 2009 1:35 pm

Sral68 wrote:I was wondering about grounding the cap on the board. I understod that Ohm grounded the tone pots to a lug under the board. Is it ok to run the ground from the cap to the same ground lug?

that may lead to noise. I recommend larry style grounding

Omn · Post by **Omn** » Fri May 22, 2009 6:07 pm

I grounded the buss wire from the tone pots to a "dedicated" (drilled an extra hole) lug between the main board and the pots. The cap from the main board is connected to that buss wire.
But I guess you are talking about the power board. The black wire from the diode closest to the fuse is connected to a lug by the phase inverter. Together with a wire from the presence control.
Not saying I am doing the right thing..., but it works. Fine.

Anyway, as Roe points out; Larry is always the way to go.

Sral68 · Post by **Sral68** » Sat May 23, 2009 3:20 am

Hi!

I was thinking about the cap on the mainboard. I see from Leledukes pictures that he has grounded the tone pots and the cap on the mainboard in a similar fashion to what you describe Ohm.

From what I understand the cap on the board is part of the v2 circuit. Following Larrys star grounding, should the bolt be placed before you get into v3 territory following a line from the input jacks to the PT?

Is it ok to incorporate parts of Larrys groundig solution or do you have to go all the way?

Roe · Post by **Roe** » Sat May 23, 2009 7:28 am

you could simplify larry's grounding by running grounding points for (v)1 & (V)2 together, and also 4 (screens cap and bias circuit) and 5 mains together. I believe larry suggested this in an earlier tread

thousandshirts · Post by **thousandshirts** » Tue May 26, 2009 3:26 am

Sral68 wrote:Is it ok to incorporate parts of Larrys groundig solution or do you have to go all the way?

You don't have to go all the way, but don't tell Larry

Sral68 · Post by **Sral68** » Tue May 26, 2009 4:21 am

Hi!

I just read trough the instructions for the 50 watt kit. It seems to have a similiar layout to the 67/68, with the cap on the mainboard. I think I'll go with grounding the busswire and the cap on a lug near the choke (ala Leleduke) and ground the presecense to the cap near the fuses. The bias grounded to the tonepots busswire.

Thanks for the input.

Sral68 · Post by **Sral68** » Wed May 27, 2009 1:03 pm

Hi!

Are there any pros or cons for using the 1.5k recistors, one between pin 5 on the power tubes, instead of the solution presented in the 100 watt instructions (one 5.6k on each tube socket)?

Using the 1.5k recistors give more room for the boards

neikeel · Post by **neikeel** » Wed May 27, 2009 1:07 pm

The 5k6 on each tube should give better prevention of PO than just the 1k5 on the outer tubes.

Seems to be more of an issue on clones (lead dress?) and tweaked Superleads. Less so on Superbass, early original Marshalls and when lead dress is immaculate (usually

)

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