80's PRS Standard 24 - wiring issues?

Discussion in 'PTC - PRS Tech Center' started by Brainofjon, Aug 26, 2019.

  1. Brainofjon

    Brainofjon New Member

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    Hi all!
    Old time lurker here, finally joining the PRS family :)

    I've recently acquired my 1st core PRS, an 80's standard 24 that has been in my wishlist for years. These come with the blue wafer rotary pickup selector, sweet switch and stamped T&B pickups. It's beautiful and plays great. It took me a few days to be able to plug it in though, since I wasn't at home; so when I did, the first thing I detected was that, while the tones coming out of it were pretty good, there was a noticeable volume drop on certain pickup combinations (specially in the middle position).

    At first I thought it might be the pickups height, but still, I couldn't balance them out nicely.
    So I opened the control cavity to inspect the wiring, and, since I didn't know what to look specifically, I tried to compare it to a couple diagrams I've found online and some other pictures of guitars of the same era.

    This is how mine looks like:

    [​IMG] [​IMG]

    these are other pics found online, same era guitars:

    [​IMG] [​IMG] [​IMG]

    And the Wiring diagram until 1989

    I could't figure it out exactly, since there's not much info online and I'm not an expert (I've wired a couple guitars some time ago, but the rotary switch is a bit intimidating, heh)... but, fr om what I see, the wiring looks wrong (or modified). I didn't know how to read the rotary/wires on the sheet, but I assume (by comparison with pics) that it's being displayed using the top point of view, when looking at it installed on the guitar cavity.

    I also run some quick tests:

    1. From what I've found, the rotary wiring changed a few times during the early days. I've found these Diagrams online: 1985-1989 / 1989 / 1991
    so, I started by tapping the pickups (like this guy does on this video at 7:40), to confirm the pickup/coil combination matches any of these sheets. No luck (I think).

    2. I've also measured the resistance with a digital multimeter. The 8 position (the quieter one) has also the lowest value.

    I put together this chart, using what I got so far.

    [​IMG]


    I'm going to mail the shop to see if they have any info about it, but I wanted to try and get some input on the forum first.

    My goal is to confirm the pickups are alright and eventually, if the wiring is wrong as I suspect, reverse it to stock if possible.

    The volume pot is a bit scratchy at some points, but appears to work fine other than that. The sweet switch does what it's supposed to do, no issues.

    Can you tell by looking at it if it was modified or if it's wrongly connected? (I could take better pics if needed)
    I will greatly appreciate any input or guidance! If you have any rotary connections hi res pics or pickup readings, that'd be awesome.

    Thanks!
    Jon
     
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  2. Collywobbles

    Collywobbles New Member

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    As you picked up wring changes by year. I can answer your question for the first two wiring versions – so up to nominally around serial 6000 for normal wiring (I believe options were available as an upcharge).

    I’ve also listed some resistance readings I’ve taken on various guitars.

    Good luck!

    ’85 to mid ’87

    10 – treble PU
    9 – both pickups together out of phase aka ‘power out of phase’ (NB the early wiring is different to the later power out of phase wiring)
    8 – both pickups in parallel, in phase
    7 – inner (slug) coils of both humbucker pickups in parallel
    6 – bass PU


    Mid ’87 to circa mid ’89

    As above except

    9 – both pickups out of phase BUT one coil of the neck pickup out of phase against BOTH coils of the treble pickup (my experience is this is a much hasher sound than the original out of phase wiring)
    8 – inner (slug) coils of both humbucker pickups in series (replaces previous both pickups in parallel, in phase, wiring)

    Post circa mid ‘89

    This version is the same as the mid ’87 to circa mid ’89 wiring , EXCEPT position 9 power-out-of-phase changes. However I’ve not owned a guitar with this wiring, so I’m not 100% sure what power out of phase changes to.

    Simple multimeter test

    A simple was to check what you have is via a multi-meter reading resistance across a guitar lead. Make sure the volume pot is turned all the way up to ten otherwise you’ll get false reading. Sweet-switch position doesn’t matter. It’s not 100% but will get you close plus if you know the readings of the treble and bass pickups as you can assume the two coils of each pickup have the same number of turns and are therefore half the resistance of the pickup and then work out theoretically what the various wiring options should give you in the 9, 8, and 7 positions and then compare that to what you have. Or just use the readings I made as a guide.


    Readings taken using the above method:

    V1 wiring from a very early production 1985 Custom
    10 – 9.54 (treble)
    9 – 16.94 (power out of phase)
    8 – 4.31 (both in parallel)
    7 – 2.17 (strat sound)
    6 – 7.74 (bass)
    (I've owned 7 guitars with this wring and they've all been very close)

    V2 wiring from a mid 1988 Sig
    10 – 9.69 (treble)
    9 – 13.52 ( MODIFIED power out of phase, just one coil of bass against both coils of treble)
    8 – 8.83 (2 coils in series)
    7 – 2.30 (strat sound)
    6 – 7.99 (bass)
     
    #2 Collywobbles, Aug 26, 2019
    Last edited: Aug 26, 2019
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  3. Brainofjon

    Brainofjon New Member

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    Hi @Collywobbles,
    thanks a lot for all the info. Your readings are pretty different from mine, except from the 'single coil/strat' sound, which I seem to have in position 8 instead of 7. This supports the idea that the wiring is modified (not sure if intentionally, since I don't seem to have the neck or bridge pups individually).

    I finally understood the diagrams (i think), so I'm going to take out the rotary later today, take some notes and see what needs to be modified in order to revert it to stock.

    Thank you!
    Jon
     
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  4. Collywobbles

    Collywobbles New Member

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    Some pictures of v1 wiring in case they help. Casually looking at your wiring it doesn't look like it's been messed about. I'm not electrically minded but like you spent quite a while working out what was going on when I first got some early PRS. One thing I wonder is if there is some sort of short - possibly where solder has burnt through the insulation. The other possibility is just one wire being moved. My '88 Sig had one wire moved when I got it giving exactly the same sound / reading at positions 9 and 10 (writing this I now recally why I spent so long going through the wiring diagrams).

    EDIT: The other possibility is from day one it was wired wrong or had some special order wiring.

    [​IMG]

    [​IMG]

    [​IMG]
     
    #4 Collywobbles, Aug 26, 2019
    Last edited: Aug 26, 2019
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  5. Collywobbles

    Collywobbles New Member

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    And the wiring diagram I found most useful.

    [​IMG]
     
  6. Brainofjon

    Brainofjon New Member

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    Thanks again for everything, this is super helpful.
    Just by looking at your pictures, I can clearly see that your wiring matches the diagram. If you look at mine, keeping the ground/hot out connections as a reference, the red and black wires are connected to other pins.
    I'll try to take it out tonight and see what's going on with the wafer bottom and middle levels... hopefully I'd just need to re-position the pups wires only.
     
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  7. Brainofjon

    Brainofjon New Member

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    I've finally took out the rotary for a detailed inspection... and this is what i've found:
    [​IMG]
    *The magenta numbers point where the wires are actually soldered to.

    So, every pickup wire is in the wrong pin (except for the Bass Black, #6). The other wafer connections seem to be ok, according to the 1985-89 diagram.
    There's some solder residues on some unused pins, that actually match the places where some wires should be, so this was definitely modded at some point.
    I don't find any logic on this wiring... but who knows.

    I'm gonna try to reverse it, wish me luck! :eek:

    By the way, @Collywobbles, just curious, which combination on the 8th position do you like best/find more useful on your guitars, 'treble+bass' or 'series single-coil'?

    Thanks,
    Jon
     
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  8. Boogie

    Boogie Zombie Two, DFZ

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    Series single coil is a very useful option but you usually have to use a 3-way toggle to get treble+bass. I like the latter but prefer having individual volume controls for each pup to blend. Personally, I’d lean toward the former.
     
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  9. Collywobbles

    Collywobbles New Member

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    If I was starting from scratch and had a choice I'd go with the V1 wiring. From memory V2 has a capacitor across rotary row 2, so I'm not sure if that changes anything if your guitar started as V2 but both together like a Les Paul would be my choice. But both pos 8 V1 and V2 are useable sounds. In contrast I don't like V2 power out of phase as much as V1. You can always change pos 8 if you don't like it once you re-wire your guitar. Your guitar looks Electric Blue, a 1987 colour, so as a guess it could have be V1 or V2 originally, but prob V1 (look for the little capacitor on the middle wafer row, if it has one then it was almost certainly V2 originally). I'm half thinking of putting some Throbaks in my '88 V2 Sig and will re-wire it V1 if I do.
     
    #9 Collywobbles, Aug 29, 2019
    Last edited: Aug 29, 2019
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  10. Brainofjon

    Brainofjon New Member

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    Hi @Boogie, thanks!
    Actually, I think that the original position 8 on the rotary switch (until 1989) was Treble + Bass.

    I've rewired yesterday to V1 and, I think, it sounds GREAT now!
    I've measured the combinations again and got this:

    pos10: 10.78k
    pos09: 18.16k
    pos08: 5.09k
    pos07: 2.75k
    pos06: 8.78k

    Now those readings make sense and are pretty similar to the ones you posted.
    phew, I was a bit intimidated by the rotary, but fortunately it went well and I feel like I've learned something new and that's cool!

    Thanks a lot for the info, it was super helpful!
     
  11. Collywobbles

    Collywobbles New Member

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    Super - nice to have been able to help as I think the Forum is as much about sharing info as it about posting pictures. When I was trying to find out about the early wiring and pickups the old Birds and Moons Forum was a big help, so I feel I've repaid my debt a bit:)
     
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  12. Boogie

    Boogie Zombie Two, DFZ

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    Yes, but the difference is that when the version 2 rotary was released, getting both humbuckers together wasn’t possible unless you replaced the rotary with a 3-way toggle. Sure, you lost the innovative single coil versatility (unless you added switches/push-pulls) but you got the beautiful bridge+neck combination back. Then David Grissom gave us the 2 volume version so you could sculpt that combination. :D Many people wanted the option of getting both pickups when they took it away. I was one.
     
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  13. gush

    gush She said "huge bag of dibs".

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    Those 80s prs guitars are sweet. I've got an 89 cu24 that I just love. I get pleasure just thinking about the fact I own it!
     
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