Consider restoring my ’77 2203, the last crusade…

Info for maintaining and tweaking your amp to perfection.

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Did J
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Re: Consider restoring my ’77 2203, the last crusade…

Post by Did J » Wed Mar 02, 2011 1:11 pm

neikeel wrote:I think that is right.
Always try it out first and tweak according to your ears.
The Lar mar might allow you to crank the master volume (where these amps sound their best, IMO).
Let us know how you get on 8)
Ordered Lar/Mar from George, and I'll be back to tell you how the amp will sound with it... for sure!

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Re: Consider restoring my ’77 2203, the last crusade…

Post by demonufo » Thu Mar 03, 2011 4:45 pm

neikeel wrote:They look like original Dagnalls to me............
OK, that's good enough for me. :wink:

It's just that the lacing on the leads doesn't look very "1977" to me, is all. :?
So I like purple, okay!!!!!!

83.7% of all statistics are made up on the spot!

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Re: Consider restoring my ’77 2203, the last crusade…

Post by Did J » Fri Mar 04, 2011 1:16 am

Hi Demonufo, thanks for sharing your expertise on this topic too.
After right back on the chassis, I'm convinced that transformers are stock, in good shape, but no marking at all. Only small white stickers DG appear on them.
Do you mean that the lacing is more vintage than a 1977 built?
About power switch, I've noticed that the blue wire on pin12 looks melted, or maybe it's my imagination...
Anyway, I gonna make the measurements in the next days.

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Re: Consider restoring my ’77 2203, the last crusade…

Post by demonufo » Sun Mar 06, 2011 9:46 am

Did J wrote:Hi Demonufo, thanks for sharing your expertise on this topic too.
I wouldn't use my handle and "expertise" in the same sentence unless there's a big "NOT" in there somewhere. :lol:
Looking closer, the lacing seems right to me (crappy monitor in the workshop compared to this 21" monster). The thing that really throws me is your camera seems to have really vivid colour definition :D , rather than the cheap and cheerful Sony that I have.

Raising one of the B+ droppers to 8K should certainly give you a little more headroom and definition. I actually like them that way, a little more aggressive too. Not a night and day change, but all the same...
So I like purple, okay!!!!!!

83.7% of all statistics are made up on the spot!

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Re: Consider restoring my ’77 2203, the last crusade…

Post by Did J » Sun Mar 06, 2011 10:48 am

... so I like Purple too, my favorite color :wink:

About those pictures, I use a pretty small camera canon ixuss55... not realy huge equipment and works fine !
I'm going to take the measurements in the next few days, but before that I have to spend one more little time to learn how to proceed with the excellent instructions George has wrote for the 2203 kit. And understand exactly why and what I have to do...

Did J

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Re: Consider restoring my ’77 2203, the last crusade…

Post by Did J » Sun Mar 20, 2011 12:34 pm

Well I did the measurements today, here is the voltage chart:
2203 MV XXXXJ Voltage Chart.jpg
(142.08 KiB) Downloaded 1110 times
All the values seem to be 10% more than the George's 100 Watt MV Kit chart, maybe it's logic for this 1977 amp.

The power switch is still illuminated in off position, so I think I have to follow all the power supply wires to see what's going on... More later... :scratch:

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Re: Consider restoring my ’77 2203, the last crusade…

Post by Did J » Sun Jul 24, 2011 1:09 pm

Got all the parts needed for the whole restoration, thanks to UK, US, German and Italian providers :thumbsup:

Before reforming Daly caps, I have to fixe the lighted rocker power switch : the bulb is 'on' all the time. The PT is a Dagnal T3836, not a T4145 specified by the Marshall schematic, but both seem to have the same color code. I think the power switch is wired backwards and the stand-by switch aswell, Hoffman's diagram accredit my thought (http://www.el34world.com/charts/images/mar_switch.gif" onclick="window.open(this.href);return false;)

here is the picture:
Switch IO STB.JPG
(148.98 KiB) Downloaded 1057 times
Power switch:
12/ Orange from PT primary (0v)
25/ Yellow from Mains fuse
11/ Blue from IEC
24/ Brown from IEC

Stand By switch:
12/ Blue wire from diode rectifier
25/ Blue wire from diode rectifier
11/ Blue from PT secondary (HT)
24/ Black from PT secondary (HT)

I have changed fuses, they were wrong value when I inspected them. By the way, I noticed that the Blue wire - common - from the IEC is grounded on V7 :palm: , I have to move it at the right place!
IEC Ground.JPG
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I did some research about rocker switch wiring, at Amp Archives it seems that the '77 2203s are wired as mine :scratch:
According to the Hoffman's diagram my amp is wired backwards, and with SDM schematic I'm between two options listed. I know only one is OK :stars:

Here is the Unicord schematic redraw by Brian, the one I would like to follow:
2203_pwr by Brian Wallace 12.25.05.gif
2203_pwr by Brian Wallace 12.25.05.gif (11.75 KiB) Viewed 3527 times
So before I rewire the switchs, what do you suggest ? :worthy:

PS: sorry for my accent ;-)

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Re: Consider restoring my ’77 2203, the last crusade…

Post by stef » Mon Jul 25, 2011 10:10 am

I've recently changed the original power switch (with 5 pins)..my amp is a 1978 1959.. original transformers...

Image

Image

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Re: Consider restoring my ’77 2203, the last crusade…

Post by Did J » Mon Jul 25, 2011 12:11 pm

... Hey Stef, thanks for the pictures. So Red Rocker switch into my amp wasn't wired correctly, fatal inversion :evil:
Here is the schematic I made for record:
2203 Rocher Switch Wiring -- Did J.pdf
(20.47 KiB) Downloaded 131 times
About Standby switch, following the Hoffman diagram the blue wires to diodes are soldered on silver terminals, on yours and mine they are soldered on copper terminals. Is it a big deal to invert the conections?

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Re: Consider restoring my ’77 2203, the last crusade…

Post by stef » Mon Jul 25, 2011 12:35 pm

Did J wrote:
About Standby switch, following the Hoffman diagram the blue wires to diodes are soldered on silver terminals, on yours and mine they are soldered on copper terminals. Is it a big deal to invert the conections?
My STB switch is original. I don't feel the need to mess with it. Had a gig 3 days ago with this new power switch and everything sounded good

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Re: Consider restoring my ’77 2203, the last crusade…

Post by Did J » Thu Jul 28, 2011 12:41 pm

... Red Rocker power switch wiring = FIXED.

This morning I did some mesurements on the PCB board and :shock: ...

R23: 4k56 (NF resistor) -> PCB indicate 100k, think it is OK with schematic
R26: 83k8 (bias resistor) -> PCB and schematic indicate 47k

VR1: 318k3 in place of 1M (pre amp vol.)
VR2: 25k57 in place of 1M (master vol.)
VR8: 4k16 in place of 22k (presence)
2203 PCB Board Components.pdf
(148.75 KiB) Downloaded 145 times
The Marshall factory lady 'Avelene' did some mistakes in 1977, maybe she was in love, the lights were weakish or the warehouse was empty, whatever she was I have today 2 resistors with wrong value and 3 pots aswell :bang: Well I'm completly f****d up... Why did you do that Avelene ? Nevertheless with a so charming first name baby !

So last, I have to take a major decision : pull up the PCB and swap in a Brian's board or leave the PCB and change the wrong value resistors? Working on this PCB is a lot of pain and I'm not confident with the result. Plus, I have 3 pots with wrong value too...

As you can imagine, I need advice on that point :help:

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Re: Consider restoring my ’77 2203, the last crusade…

Post by demonufo » Thu Jul 28, 2011 2:10 pm

You can't measure a lot of the components 'in circuit', as other parts of the circuit will have an effect on what you are trying to measure. Use the colour codes to decipher the values. If unsure, the only way to really measure most components is to remove at least one end from the circuit.
So I like purple, okay!!!!!!

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Re: Consider restoring my ’77 2203, the last crusade…

Post by Did J » Fri Jul 29, 2011 11:35 am

... ok I realise that I make a mistake myself :oops:

I'm very sorry Avelene
flowers.jpg
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Re: Consider restoring my ’77 2203, the last crusade…

Post by hotguit » Wed Aug 10, 2011 5:31 pm

in my 1980 jmp 2203 i only changed slope res from 33K to 47K; better mids and highs.
I also lowered the 10K to 4,7K but it is not a good idea; maybe putting a 0,1 or 0,22 cap across it...
suggestions? (i'm after Acdc tone)
hot
LIFE IS TOO SHORT FOR A BAD TONE!!

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Re: Consider restoring my ’77 2203, the last crusade…

Post by catalin gramada » Thu Aug 11, 2011 6:48 am

for me those resistor _10K_ is forbidden if I think in terms of shape in 2203. better to adjust cathode bias values in 1.st stage and also voltage rail over v1 plate.
I like to use here 1,5K instead 2K7 and put 330u over 0,68 (don't remove 0.68) and 300V on the rail. just a sugestion.
I enjoy 47k in tone stack too :D
Catalin
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