Consider restoring my ’77 2203, the last crusade…

Info for maintaining and tweaking your amp to perfection.

Moderator: VelvetGeorge

hotguit
Senior Member
Posts: 285
Joined: Sat Aug 18, 2007 12:31 pm
Just the numbers in order: 7
Location: somewhere in Europe - Italy

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

Post by hotguit » Thu Aug 11, 2011 9:07 am

catalin gramada wrote: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
hi
Yes, lowering 10K is not a good idea imho, you are right
let me know your mod.
you suggest to lower 2,7K first gain stage's cathode res. to 1.5 k right?
and add a 330u cap where? please can you explain me?
thank you
hot
LIFE IS TOO SHORT FOR A BAD TONE!!

catalin gramada
Senior Member
Posts: 182
Joined: Sun Feb 08, 2009 1:54 pm
Just the numbers in order: 7
Location: everywhere in Europe

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

Post by catalin gramada » Thu Aug 11, 2011 4:00 pm

Hi
that's right 1K5 instead 2K7 and 330u in paralel with 0.68(keep both caps on board)-you can solder 330u directly on 0,68 terminal in respect of polarity (minus to ground).
Catalin
Catalin

hotguit
Senior Member
Posts: 285
Joined: Sat Aug 18, 2007 12:31 pm
Just the numbers in order: 7
Location: somewhere in Europe - Italy

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

Post by hotguit » Thu Aug 11, 2011 4:50 pm

catalin gramada wrote:Hi
that's right 1K5 instead 2K7 and 330u in paralel with 0.68(keep both caps on board)-you can solder 330u directly on 0,68 terminal in respect of polarity (minus to ground).
Catalin
ok, now i understand.
what do you obtain increasing the first cathode's cap?
more gain? insane gain? no oscillation?ùand what about the tone?
Thank you
hot
LIFE IS TOO SHORT FOR A BAD TONE!!

catalin gramada
Senior Member
Posts: 182
Joined: Sun Feb 08, 2009 1:54 pm
Just the numbers in order: 7
Location: everywhere in Europe

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

Post by catalin gramada » Thu Aug 11, 2011 8:18 pm

you will raise the amplification in tension but second stage will clip as same so the tone will became more crunch and bit compressed on the entire frequency range keeped the 2203 character.also more low and mid-low add but bigger slope resistor in tone stack help to keep it under control. the voltage over v1 plate will keep in a distinctive shape(can mod from last 10K rail resistor but will affect the voltage over whole rail) no worries for oscilation I don't see any reason for and anyhow didn't hapened to me.Btw.due to new configuration must "deal" with pot between stages and 1nf bypass cap can or cannot be the happiest choice in this position...
it is easy mode to tune a 2203.don.t know how you like but pretty simple to try it
Catalin
Catalin

User avatar
Did J
Senior Member
Posts: 165
Joined: Tue Nov 09, 2010 4:23 pm
Just the numbers in order: 13492
Location: Remember Paris

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

Post by Did J » Sun Aug 14, 2011 10:31 am

catalin gramada, hotguit,
I remember a very interesting and usefull thread about that subject from Neil you can take a look:
http://forum.metroamp.com/viewtopic.php ... +5#p298400" onclick="window.open(this.href);return false;
It's about Blocking Distorsion on 2203. And to follow this you also should read some Randy Aiken's tech info on his website.

It might be a serious complement to answer your questions in this one:
http://forum.metroamp.com/viewtopic.php ... 15#p360179" onclick="window.open(this.href);return false;

Did J

catalin gramada
Senior Member
Posts: 182
Joined: Sun Feb 08, 2009 1:54 pm
Just the numbers in order: 7
Location: everywhere in Europe

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

Post by catalin gramada » Thu Aug 18, 2011 2:43 am

Hallo Did. thanks for info. but I did not suppose the mod just I did it and have nothing in common with subject above.the amp (reissue 2203)work pretty fine , no oscilation , no blocking distorsion even with 4vpp at input from a pair of emg 81 :whistle:
Catalin

User avatar
Did J
Senior Member
Posts: 165
Joined: Tue Nov 09, 2010 4:23 pm
Just the numbers in order: 13492
Location: Remember Paris

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

Post by Did J » Thu Aug 18, 2011 4:05 am

hallo catalin, I was thinking about Neil wrote:
"Trying to add a bit more gain to 2203 front end.

I have tried lowering the 10k on V1 to 4k7 but whenever gain is over 5 there is a volume drop and a microphonic squeal

Then tried 8k2 - better but still craps out with gain over 8, unfortunately it looks like I am stuck with the 10k (did not bother even trying 2k7 with bypass cap - I was going to try 4k7 with a 0.47uF )." :scratch:

Anyway, I'm going to do some mods when I get ready to do it...

Did J

catalin gramada
Senior Member
Posts: 182
Joined: Sun Feb 08, 2009 1:54 pm
Just the numbers in order: 7
Location: everywhere in Europe

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

Post by catalin gramada » Thu Aug 18, 2011 4:24 am

don't do it !it's a kind of lsd or something...you will became addicted. :D
Catalin

User avatar
Did J
Senior Member
Posts: 165
Joined: Tue Nov 09, 2010 4:23 pm
Just the numbers in order: 13492
Location: Remember Paris

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

Post by Did J » Sat Nov 27, 2021 9:50 am

It's been a long hiatus on the board since the last thread. So I'm back in the community.
My 2203 shows proudly ten years older and is still working like a charm, what a journey !

Best

danman
Senior Member
Posts: 1099
Joined: Tue Sep 10, 2013 9:09 pm
Just the numbers in order: 13492

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

Post by danman » Mon Nov 29, 2021 6:28 pm

Welcome back! Sadly, traffic has really fallen off here over the past few years. There may only be on or two new post a week these days. It's a shame because this place was really hopping a few years back!

User avatar
Did J
Senior Member
Posts: 165
Joined: Tue Nov 09, 2010 4:23 pm
Just the numbers in order: 13492
Location: Remember Paris

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

Post by Did J » Thu Dec 02, 2021 2:59 am

I have some projects that I'm considering to share : 1987 & 2204.
More later...
Best

Post Reply