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

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.



I know some of these are hard to see. I did the best I could to get a camera under there and flash.

 

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.

 

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!

 

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.

 

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!

 

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

 

oh I see. well they also put enormous strings on it and jumbled up the saddles lol. it was a cryin shame

 

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.

 

and they make good stuff? again I'm totally ignorant to the preamp market.

 

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?

 

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.