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Thread: marshall valvestate 8100 pot value help!!!!

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    marshall valvestate 8100 pot value help!!!!

    ok i have NO idea whatsoever as to how to read an amp's schematics sheet (wiring diagram or call it what you may...to me its the damn paged whriten in antient egipian...) i need to get the pot values so i can restore this head to its former glory!!!

    if ANYONE knows how to read it, and can tell me alternatives for pots... per say a 100k pot is neaded but a 10 kj(something) would work as well,

    PLEASE IM IN DIRE NEED OF HELP HERE!!! i atached the "scroll of secrets" onto here and i am at the mercy of some one's kindness :'(
    Attached Thumbnails Attached Thumbnails valvestate80_80w_8080_8100_8412.pdf  

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    you gotta feel what you play...in order for others to feel what they hear ;)

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    Supporting Member Jazz P Bass's Avatar
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    Marshall 8100 potentiometers

    Here you go.
    Please keep in mind that I do not have the amplifier in front of me.

    I would assume the potentiometer designations (looking at the front) are from left to right.

    Log = logarithmic (A taper)
    Lin = Linear (B taper)
    VR = Variable Resistor

    VR 1: 220K Lin
    VR 2: 100K Log
    VR 3: 4.7K Lin
    VR 4: 22K Lin
    VR 5: 1Meg Log
    VR 6: 1Meg Log
    VR 7: 22K Lin
    VR 8: 220K Lin
    VR 9: 100K Lin
    VR10: 100K Lin
    VR11: 22K Lin
    VR12: 22K Lin
    VR13: 10K Lin

    Are you really going to change all the pots?
    Why?

    Here is the 8100 parts list from Parts Is Parts.
    Attached Files Attached Files

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    Last edited by Jazz P Bass; 11-12-2010 at 12:40 AM.

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    well i have to change them even if i dont want to.. this amp was stored for a few years by a family member of mine (WHO HAPPENED TO LIVE BY THE SEA) so you can imagine the kind of RUST and corrotion damage it suffered.... even the wood cassing for the head paid the consecuences, i have NO IDEA whatsoever what else it needs.... also the first switch from clean to crunch was completely broken... i have no idea as to what kind of swich i could use (or if i could create a bypass by using another tipe of switch, id love some advice on that one too....)

    also i live in a city wich is very DAMN LIMITED thats why i have to get creative with most of my stuff...most of the time i manage very well but IN THIS Particular case it was a kick in the low spot if you get my drift....

    are there alternatives wich can be used for pots? (since i took the head to a local electric shop and the "tech" installed 2 pots that he swore would do the job, now i get weird sounds from the head)

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    you gotta feel what you play...in order for others to feel what they hear ;)

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    Lifetime Member Enzo's Avatar
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    Yes, they are in order across the front of the amp starting with VR1 next to the input jack.

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    Supporting Member Jazz P Bass's Avatar
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    Unhappy

    thanks!!! i had a lucky break accompanied by a REAL kick in the NU#S... i was able to come do a concert at another city and the transmission of my truck went to hell, so i got stranded but due to that i came across an electronic store that sold some of the pots... i got a few others with a slihtly higher value... would this change the sound or damage my amp?

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    CRAP

    well.. i installed the pots, the clean chanel works REALLY DAMN GOOD!!! but i cant get the DIST chanel to work, i also had to remove the Crunch switch (on the clean chanel) i have NO idea if the tube in the preamp is working (again im not electronically savy) i have no idea if the DIST chanel isnt working because of the missing switch :s

    any thought's on the issue?

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    I have similar case. I need to replace all pots in Marshall Valvestate S80. Guitar-parts doesn't seems to have all required values. They even don't have any photos nor ducumentation (to check the dimensions). What manufacturer it is? There is a logo - it looks like letters "dp". They are 17mm diameter and 20mm shaft. I need most of the values listed by JPB.

    Mark

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    Lifetime Member Enzo's Avatar
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    The manufacturer might not even be available to you. Well unless you want to order several thousand.

    I would have guessed 16mm, so if your normal suppliers have no 17mm pots, look at 16mm ones.

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    I'm just curious what the manufacturer is. There are many companies that sell Marshall parts but if you check the pot's values that you need (and the length of shaft), they don't have it. This is a great oportunity to make business.
    I asked about the pots on Marshall forum but my post didn't appear until now (most probably it's still under moderation).

    Mark

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    Lifetime Member Enzo's Avatar
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    COmpanies like Alps or whoever that make pots for commercial amp makers do not get the parts off the shelf, they make then to order for the OEM. If you get one of their catalogs, you will see under for example 16mm pots, a chart for you to make up the part number for what you want. Each digit in the number means something, just like each digit in the number of a reverb pan means something.

    SO when Marshall wants a 10k 16mm pot they sit down and specify 16mm, shaft (plastic or metal, split or solid shaft, or D-shaft, knurled or smooth), shaft length, threaded panel bushing, no support side brackets, resistance, taper, style of terminal (pc mount, solder lug, whatever), and probably other stuff I forget.

    These choices generate a part number like PHA16R10KAFBNCX. I totally made up that particular number, but you often see such charts on data sheets.

    Here is a line that Mouser carries. Look on page 2 of this data sheet. There is an example of exactly this number generator.

    http://www.bitechnologies.com/pdfs/p160.pdf

    And same for ALpha, which Moiser also carries

    Untitled Document

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