Marshall Silver Jubilee - Circuit Changes

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Marshall Silver Jubilee - Circuit Changes

Post by Samsquantch » Tue Dec 17, 2013 1:09 pm

Hi, everyone

New to forum, but noticed that actual, technical explanations are found here. Now, fair warning, I am a complete layman when it comes to the technical side so my input in this regard will be limited, but wouldn't mind at all if the thread develops into a technical discussion that may help others down the road.

Long story short, I had an early circuit Silver Jubilee - with a serial number in the 5XXs, that was manufactured in May of 1987. While the amp was great, I did notice three issues (in descending order of significance, at least to me) - a) a relative/perceived lack of bass (some say thinness); b) a effects loops that degraded the signal; and c) volume discrepancy between the channels. These issues appear fairly common.

Now, there appears to be a lot of conjecture about the differences in the circuits, but a lot of it appears unsubstantiated. From what I understand, there are two primary schematics out - pertaining to pre and post S/N 3100. In addition to this, there were at least 4 revisions indicated on the PCB - Rev. A, B, C and D. The latter circuits purportedly resolved (at least) the bass/thinness issue. There are some claims out there that the last circuit, purportedly employed as early as S/N in the 2700s, sound noticeably better. That said, other posters have claimed that the 2555SL ( a reissue, which logically would have been based on the revised circuit) also suffer from this thinness.

Some posters have reviewed the differences between the schematics and have found the difference to be minimal and unlikely reflective of any resolution of perceived thinness. This is coupled with the total lack of info in terms of the various revisions - namely, exactly what changes occurred with Rev. B, C and D. Interestingly, Rev. D was purportedly in place well before the time of the S/N 3100 schematic change.

So, is there any consensus on these revisions - when they were employed and what they did? Is there a real understanding of the differences between pre/post S/N 3100? Was there a PCB issue as another poster claims?

Any help is appreciated, but a definitive assessment of things would be great. Thanks all.

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