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Bizarre Riverhead Phantombass Active electronics problem. I need a hero!

Discussion in 'Pickups & Electronics [BG]' started by neutralomen, Dec 8, 2020.


  1. neutralomen

    neutralomen

    Jan 31, 2018
    Hey everyone. I officially have a headscratcher 80s style.
    I'm starting an 80s cover band focusing on alt pop/new wave/synthwave kind of stuff, and I began my search for period instruments with the right vibe.
    I was lucky enough to find an old Riverhead Phantombass at a pawn shop. It needs a shim, and I may even get the decals remade and have it totally refinished. not sure yet.
    Anyway, the reason for this post is, something very bizarre happened under the hood.

    It's got an active 4 band EQ. Main volume works, and the selector switch works which, from the sound of it, is a series/single coil splitter. Here's where it gets odd. The active EQ is dead. the knobs are completely unresponsive. You'd think in an active bass, you either get the full signal, or no signal. I don't think this model had a passive mode.
    In any case, my luthier and I popped open the back and were both bewildered.
    There was obviously some major tampering. Neither of us know what we're looking at. He's usually great with electronics but because this is a rarebird with what looks to be proprietary circuitry, we couldn't make heads or tails of it.

    First of all, the battery compartment is empty, and there isn't even a PLACE for a battery to be installed. No 9 volt plug or anything. That was very strange. So this is definitely a passive bass now.

    Second, you can see that many of the wires have been cut. I have no idea what I'm looking at, but my guess is, this was crudely converted into a passive system by bypassing the circuit board altogether.

    I reached out to riverhead which is not a phillipino company that makes Fender clones for the domestic market. They don't have old wiring diagrams for these.

    I'm hoping to get this circuit restored. I can't even do a tone roloff now so this is has kind of turned into a mark hoppus bass.

    Alternatively, the old catalog actually points out the bands for the eq, so I could potentially have this gutted and have a custom preamp and circuit made to approximate the same 4 band eq. I'm not precious about keeping this all original, but I'd like to if possible.

    Anyone have any leads/can tell me what I'm looking at?

    Thanks so much.
    20201208_201416.jpg

    20201208_200556.jpg 20201208_200655.jpg 20201208_200758.jpg 20201208_200736.jpg 20201208_200746.jpg 20201208_200706.jpg
    I know some of these are hard to see. I did the best I could to get a camera under there and flash.
     

    Attached Files:

  2. Crater

    Crater

    Oct 12, 2011
    Dallas, TX area
    Yes, it's pretty obvious the preamp was "bypassed" by soldering that white jumper wire from the input to the output.
    Lots of basses don't have a separate battery box, the battery is simply installed in a space in the control cavity. The space above the preamp board in photo #2 appears to be such a space. And the black rectangle covered with electrical tape appears to be a 9 V battery snap. ??

    If you want to restore the original preamp, it's possible as the circuit board appears to be in good shape. It might still even work, but may have been abandoned and bypassed because a tone control became scratchy, or they just didn't like using batteries in their bass. But it will be simpler and quicker to replace the preamp with a modern one. I have an EMG BQC with stack knob bass/treble and mid/mid frequency knobs.
     
  3. neutralomen

    neutralomen

    Jan 31, 2018
    Wow thanks for the reply.
    I would need this professionally done as, while I'm a decent setup guy, I know JACK about electronics. This looks very complex and bizarre to me, but i'm sure to the trained eye it's a standard thing.

    If I did go the route to restore it, how would I go about it without a wiring diagram? I did contact Riverhead and they said they'd reach out to japan to see if they can find old documentation. Fingers crossed there. Anyway, assuming I either find a wiring diagram, or the technician who fixes it doesn't need one, what channel would I have to go through to get this restored?

    Second question, if I decided to just get a modern preamp installed, I'm sure I'd need some custom fitting or whatever for this particular cavity, and again, i'd need it professionally done. Who would I send it to? Which sites/builders offer these kinds of services?

    Thanks so much in advance for any advice.
     
  4. rojo412

    rojo412 Sit down, Danny... Supporting Member

    Feb 26, 2000
    Cleveland, OH.
    That cavity is big enough to fit a number of modern preamps, so I don’t think you’d need to do anything but gut it and put something new in. The BQC is a good pick for having the same look, but it’s a 3 band with a mid frequency sweep, which is likely even more capable in some respects than a 4 band.

    That said, I’d personally love to see if this thing still works. You clearly have the IN, OUT, GROUND, and POWER + spelled out on the board, so that makes it a lot easier. Here's basically what you'd need to know:

    Screen Shot 2020-12-09 at 11.11.28 PM.png
    Remove that white jumper wire. You may also have to take the screws out of the body to detach the preamp board to access the back.

    The switch does appear to be controlling the function of the pickup coils, and I see it going out to the board.

    - make sure the output of the volume is connected to the IN of the preamp (it looks like it is)
    - make sure the OUT to the + (tip) connection of the jack (looks like it is)
    - run the GROUND to a ground (it probably already is)
    - connect the red wire of a battery clip to the "+" tab (a new clip is a great idea)
    - run the negative of the battery to the "RING" connection of the jack.

    That should at least see if it makes noise with the preamp getting power. From there, you could diagnose further.
    After peering at this, it looks like the white jumper and the cut battery connection and lame clip are the only issues. A soldering gun, a clip, and a tiny bit of patience may be all it takes. And if you were in Cleveland, I'd just tell you to stop by!
     
    getbent and Crater like this.
  5. neutralomen

    neutralomen

    Jan 31, 2018
    Wow I REALLY appreciate the detailed response. Regrettably I don't know the first thing about soldering let alone something complicated like this.

    It's good to know this is salvageable though. As I said, i'm open to a new preamp system too, but because of the double stack knobs I think i'll go with a 4 band if I go that route.

    I'm in the New York Area, but do you run a shop, or are you saying you'd look at it just as a private person?

    I'm definitely going to need some professional help here so any leads/services/websites would be really helpful. I can ask around with local techs and luthiers too but it stumped the couple I showed it too. Nice to know some of you out there really know your stuff!
     
  6. rojo412

    rojo412 Sit down, Danny... Supporting Member

    Feb 26, 2000
    Cleveland, OH.
    If you’re in NYC, my good friend @rogerbmiller may have some leads for you on techs.

    As jobs to learn some soldering go though, this would be pretty simple. Looks like most of it is connected. You could basically snip off that white wire and solder 2 leads for the battery clip. If it doesn’t actually work right, that would require the harder stuff, but this is the start.

    I do actually do a lot of tech work and build basses full time. I’ve definitely helped out friends of mine with similar issues for usually little more than a beer or something, that’s how simple this looks, to me at least.
     
    neutralomen likes this.
  7. rogerbmiller

    rogerbmiller Gold Supporting Member

    Sep 16, 2003
    NYC

    Hey OP I have a couple of really good techs in NYC I can steer you to. If you are interested hit me with a PM.
     
    neutralomen likes this.
  8. neutralomen

    neutralomen

    Jan 31, 2018
    Update*
    I reached out to some people, hoping to hear a reply. Thanks everyone so far for all your help.
    Some good news. I thought the neck needed a shim. Turns out, the knucklehead who owned this last did a lot more to this bass than wreck the wiring. I took a caliper to the strings. they were SUPER thick. The low E was .130. The truss rod was pinned and the neck was practically getting pulled off. I restrung it with good ole' 45-100 and the neck is beautifully straight and the frets are astonishingly level.
    THEN, the G was still too high but the saddle was bottomed out, so I still thought I needed a shim. Upon further inspection, I realize mr. knucklehead took the saddles off at some point, and replaced them, not noticing there are two tall saddles and two short, and one of the tall saddles was on the G. I removed the bridge, lubed up all the old screws, put the saddles in their right places, set intonation, and wham. This thing is a KILLER player. Like, it's an excellent bass.
    I REALLY hope I can get the wiring fixed.

    PS Any Riverhead owners who might come across this, is it possible for you to open your cavity and reverse engineer a wiring diagram for me? i'd be happy to pay you for it. Thanks everyone, and please continue to feed me leads or advice if you can.
     
    Matt Liebenau likes this.
  9. Crater

    Crater

    Oct 12, 2011
    Dallas, TX area
    Basses' wiring is usually not unique, there tend to be "standard" wiring schemes that are used over and over. So you don't necessarily need the "factory schematic" to get this thing working again. It would also be very helpful to know the exact resistance value of the volume control. It may be stamped on the back, or may be printed on the front, which would require you to remove the knob and pot from the bass to see it. Or of course it could be checked with an ohm meter. Volume controls can either be on the input of the preamp or the output.

    Since that preamp is so old, it would be pretty simple to reverse-engineer it. It clearly uses a single-layer circuit board, with lots of room between the components. If you take a clear, well centered photo of both the top and bottom of the circuit board, someone can invert the photo of the circuit traces, and transparently overlay on the photo of the component side. Once that's done, someone who knows what they're doing could trace the circuit out. It's not horribly difficult, but it does take time.

    Having said that, it will probably be simpler and easier to just install a modern preamp/EQ unit. It won't change anything externally on the bass, nor should it require any routing or carving inside the cavity. A modern preamp is likely to be quieter and have a longer battery life than an early 80s one. It's really up to you what's more important - having it 'all original' or just getting back in service with a minimum of time.

    I suggest removing the screws holding the preamp and gently flipping it back so we can see the controls and wires underneath. There should be enough slack in the wires to allow you to do this.
     
    Last edited: Dec 14, 2020
  10. TNCreature

    TNCreature Jinkies! Supporting Member

    Jan 25, 2010
    Philadelphia Burbs
    Did you get that at the pawn shop on Long Island? I almost bought it. (Might even be my old bass)
    I owned the exact bass in the 80s in NYC and was considering buying it out of nostalgia.
    When I owned it, there was no battery box.
    I sold mine because there was something wrong with the preamp, and I blew a speaker while using it. (No direct evidence but I got rid of it). It would put out sizzling squeals of pain.
    I hope you get it sorted, it is the right bass for the gig you are planning!
     
    Last edited: Dec 14, 2020
  11. neutralomen

    neutralomen

    Jan 31, 2018
    I DID get it at the pawn shop in long island. If it was your bass, either you or the next owner really abused it lol. as I said in an earlier post, the tall saddles were in the wrong spaces and the strings were way way too thick causing the neck to bow like crazy, not to mention the gutted electronics. fortunately I was able to restore it to an excellent played grade instrument minus the preamp issue.
    a lot of bassists do this btw when it comes to super thick strings. a single truss rod flatsawn 1 piece neck is not designed for these 50-125 suspension bridge coils some of y-all call strings :). I'm lucky the neck wasn't permanently damaged. this is a bit of a digression, but just a reminder, it is an electric instrument so the size of string doesn't really do much besides add tension and potentially damage the instrument. to the extent it does change tone/support a more a aggressive playing style, only use them on modern graphite reinforced laminated quartersawn necks! I'm sure most of you already know this but it came to mind because this poor boy was screamin!
     
  12. neutralomen

    neutralomen

    Jan 31, 2018
    thanks for the great advice. I'm totally open to just getting a new preamp for reasons you stated. I'd at least want to keep these original components unharmed so it could be restored if need be for collector purposes
     
  13. TNCreature

    TNCreature Jinkies! Supporting Member

    Jan 25, 2010
    Philadelphia Burbs
    I never abuse my basses.
    But if it was my bass, the inference was that whoever owned it next may have disabled the preamp rather that fixing it.
     
    Last edited: Dec 14, 2020
  14. neutralomen

    neutralomen

    Jan 31, 2018
    oh I see. well they also put enormous strings on it and jumbled up the saddles lol. it was a cryin shame
     
  15. neutralomen

    neutralomen

    Jan 31, 2018
    a question for the thread. if I do decide to get a modern preamp which I'm starting to think I should, i imagine I'll need a custom one built? something that will fit these particular stack knobs and be a 4 band, 1 volume, 2 stack knob layout. can anyone either direct me to a good preamp that fits this description or a good service or site that custom builds them?
    sorry I'm just new to this segment of the market.
     
  16. rojo412

    rojo412 Sit down, Danny... Supporting Member

    Feb 26, 2000
    Cleveland, OH.
    Audere makes that setup. You can get it direct from them.
     
    neutralomen likes this.
  17. neutralomen

    neutralomen

    Jan 31, 2018
    and they make good stuff? again I'm totally ignorant to the preamp market.
     
  18. rojo412

    rojo412 Sit down, Danny... Supporting Member

    Feb 26, 2000
    Cleveland, OH.
    People love their preamps. They are very well made and allow for maximum transparency from the pickup itself.
    I think there are a bunch of threads and reviews on here you can search through.
     
    neutralomen likes this.
  19. neutralomen

    neutralomen

    Jan 31, 2018
    Another update: It never ends with this thing! If you look at the photos you'll see the volume knob isn't original, and it was replaced at some point. It's not a set screw. it's a push on and it was REALLY jammed on there. I can't get it off to measure the pot for when I replace the system. I'm worried about applying too much force for fear of caving in the rear mount control cavity. For all I know it could be GLUED on. I guess I'll have my luthier get it off safely. Even if he destroys the knob and the pot it's fine. Any tips on removing these things safely?
     
  20. neutralomen

    neutralomen

    Jan 31, 2018
    Yet another update: As I prepare this for its restoration, I reached out to Riverhead for some restoration decals. They said they'd look but probably don't have it. I work as a visual artist, so I had the means to just go ahead and make them!

    I'm going to get water decals made of these(they still need some cleanup but I am trying to replicate that imperfect ink look). And I'm getting this refinished. I may either have them color match the pearl or go for a solid white. What do you guys think? My printer is not high enough resolution for these, which is why the test print looks pixelated. the image itself has alpha information to make it look smooth to the naked eye. I still may have to make vector drawings for these. Not sure yet. 20201218_020935.jpg 20201218_023717.jpg
     
    Last edited: Dec 18, 2020
    Heavy Blue likes this.
  21. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
    Feb 28, 2021

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