2203 V1?

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revolver1
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2203 V1?

Post by revolver1 » Mon Oct 09, 2017 1:44 pm

Looking at a lay out I have for a 2203 downloaded from the forum and looking at 2203 gut shots I see the shielded cable from the input jack socket has the 68K resistor on the other end connected to pin 7 of V1.

The other shielded cable connects to pin 2 of V1 and is routed to the preamp pot.

When following the down loaded kit instructions the connections of these two wires at V1 are reversed. Is this ok?

danman
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Re: 2203 V1?

Post by danman » Mon Oct 09, 2017 6:40 pm

IIRC, the first way that you described is how Marshall originally ran the wiring to V1. The second way is suppose to be slightly quieter I believe. I have always followed the original layout so I can't say if there is any actual benefit to changing it.

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neikeel
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Re: 2203 V1?

Post by neikeel » Mon Oct 09, 2017 6:42 pm

Normally V1b is the preferred first stage so the grid from the inputs should go to pin 7 and the 0.68uF/2k7 cathode to 8

the 10k cathode is pin 3 and grid is pin 2. Normally only ground the pot/input jack end unless 'hot shield'.
Neil

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Re: 2203 V1?

Post by revolver1 » Tue Oct 10, 2017 2:44 am

Thanks for the replys fellas.

I do wish the instructions had mentioned it was a deviation before I soldered that nice nos imported resistor in there.

I guess the noise factor comes from crossing the shielded wire but if it was done at 90' and being shielded I can't imagine there would be cause for concern?

I was going with a star ground scheme so grounding of the input jack and pot would be to separate points (not a pot bus). The shielding of each wire is only grounded at one end ie the respective jack and pot, the other end is heat shrunk.
Is this OK?

revolver1
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Re: 2203 V1?

Post by revolver1 » Tue Oct 10, 2017 4:41 am

Has any one got experience with both methods? What's the preference and why?

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Re: 2203 V1?

Post by d95err » Tue Oct 10, 2017 10:22 am

revolver1 wrote:
Tue Oct 10, 2017 2:44 am
I do wish the instructions had mentioned it was a deviation before I soldered that nice nos imported resistor in there.
I doubt there is any significant difference between using V1a or V1b as the first stage. Replacing that NOS resistor with a modern metal film resistor would probably be much more signifcant (in terms of reduced noise).

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neikeel
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Re: 2203 V1?

Post by neikeel » Tue Oct 10, 2017 11:51 am

d95err wrote:
Tue Oct 10, 2017 10:22 am
revolver1 wrote:
Tue Oct 10, 2017 2:44 am
I do wish the instructions had mentioned it was a deviation before I soldered that nice nos imported resistor in there.
I doubt there is any significant difference between using V1a or V1b as the first stage. Replacing that NOS resistor with a modern metal film resistor would probably be much more signifcant (in terms of reduced noise).
Depends if it is a NOS Piher CF or a cc. The Pihers are probably the best all round resistors I use, but I generally avoid carbon carbon comps.
Neil

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Re: 2203 V1?

Post by revolver1 » Tue Oct 10, 2017 12:52 pm

I'm using all piher for this one.

I've started a kind of build journal with pics over in the 100w master vol section now I've finally sussed out the picture thing.

I have a bit to do on the board but should have some more bits to up load by the end of the week.

As it is I've re ordered all the parts to redo it so I have the option. But im just trying to figure which is the best method, as in why V1b is preferred?

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neikeel
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Re: 2203 V1?

Post by neikeel » Tue Oct 10, 2017 1:02 pm

Why do y need to re-order parts - I'm confused?
Neil

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Re: 2203 V1?

Post by revolver1 » Tue Oct 10, 2017 1:47 pm

Not a big deal really but I feel because the 68k resistor lead is trimmed so short that the resistor must have seen a lot of heat.

Also not sure I have enough shielded cable to 're do it. There's enough length on the resistor lead but probably not quite enough for the other lead.

Just a little frustrating as I felt I had done a nice job of it then clocked the differences when I looked at the other lay out. Also collecting all the parts has taken patience and time... You know how it is.

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