What is up with the 2553 reissue 50 watt amp?
This amp I have here has at least 3 resistors and 2 caps in the start of the preamp section so far that do match the schematic numbers, and as such there locations!
For example on my amp here ( board stamped 2553) R 25 the 68k resistor off the input Jack as read from the schematic is the first gain stage plate load resistor in the amp in front of me!?
This amp has more gain hiss then I have ever heard in my life on the lead channel, it had tons of hum also until I replaced that first grid wire with a sheilded lead, and yes the hiss is not from that first tube!
2553 issue
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Stevem
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2553 issue
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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JazzGuitarGimp
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- Location: Northern CA
Re: 2553 issue
It sounds to me like you have the wrong version of the schematic!!! Is there more than one version floating around on the net?!!! That's the first thing that comes to mind, anyway!!!
Lou Rossi Designs
Printed Circuit Design & Layout,
and Schematic Capture
Printed Circuit Design & Layout,
and Schematic Capture
Re: 2553 issue
Check the reissue of your schematic.
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The Ballzz
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Re: 2553 issue
I've seen so many "after the fact" re-writes of Marshall schematics by well meaning folks that re just plain wrong that it's hard to know what's correct and what isn't. Not to mention multiple factory modifications and re-writes!
Gene
Gene
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Stevem
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- Joined: Fri Jan 24, 2014 3:01 pm
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Re: 2553 issue
I went to the Dr Tube site and found nothing that matched it so I am just dealing with it!
I have to check my Groovetubes schematic CD and look if that has anything on it in the Marshall section.
A buddy of mine just picked up another 50 watter like this and a 100 watt model so next week I will pry those open and see what they have in regards to layout matching!
Thanks all!
I have to check my Groovetubes schematic CD and look if that has anything on it in the Marshall section.
A buddy of mine just picked up another 50 watter like this and a 100 watt model so next week I will pry those open and see what they have in regards to layout matching!
Thanks all!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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The Ballzz
- Posts: 369
- Joined: Thu Oct 24, 2013 7:22 pm
- Location: Las Vegas, NV
Re: 2553 issue
Check here:
http://www.classictubeamps.com/SchemMarshall.html
but you'll want to check/compare several from different years, etc,!
HTH,
Gene
http://www.classictubeamps.com/SchemMarshall.html
but you'll want to check/compare several from different years, etc,!
HTH,
Gene
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The Ballzz
- Posts: 369
- Joined: Thu Oct 24, 2013 7:22 pm
- Location: Las Vegas, NV
Re: 2553 issue
The Ballzz wrote:Check here:
http://www.classictubeamps.com/SchemMarshall.html
but you'll want to check/compare several models from different years, etc,!
HTH,
Gene
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Stevem
- Posts: 4587
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: 2553 issue
Well it seems this 50 watter was from the first year of production in May of 87.
It's very upsetting to see all the 1/4 watt resistors they use in this, it's a crime!
Through signal testing I found out something interesting about the lead channel, this amp will pump out 97 watts peak and the lead channel drivin by a only a little .152 volts will drive the amp to that 97 peak watts with the lead volume at between only 4 or 5 dependant on how strong V1 is!
Since the amp uses diodes for clipping opening up the lead channel volume past 5 makes for nothing but more hiss to the point of being a issue!
I did go head and change out / shot gun a bunch of resistors in the signal path(I did all the plate resistors last year) and got a bit of improvement from that but nothing big !
It's very upsetting to see all the 1/4 watt resistors they use in this, it's a crime!
Through signal testing I found out something interesting about the lead channel, this amp will pump out 97 watts peak and the lead channel drivin by a only a little .152 volts will drive the amp to that 97 peak watts with the lead volume at between only 4 or 5 dependant on how strong V1 is!
Since the amp uses diodes for clipping opening up the lead channel volume past 5 makes for nothing but more hiss to the point of being a issue!
I did go head and change out / shot gun a bunch of resistors in the signal path(I did all the plate resistors last year) and got a bit of improvement from that but nothing big !
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!