Alembic Guitars Club
Alembic products => Showcase => Series I Basses and Guitars => Topic started by: rv_bass on March 19, 2023, 07:31:00 AM
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I decided to see if I can bring this 73-28 bass back to life. The bass is structurally in very good shape. Looks like there was a minor crack in the headstock that was repaired very well and is very solid. If the front veneer did not show a crack it would be hard to see otherwise. The bridge pickup makes no sound and bridge controls appear non-functional, although I don’t know if it is the pickup, controls, or PF5 card. The neck pickup has sound, volume, filters and trim pots work, the q is not original and not working properly and needs to be replaced (I have a spare new one in my parts box). No RF noise issues. The five pin and 1/4 jack both work as they should. So it is playable with the neck pickup and sounds great. The hum canceling pickup was moved to between the pickups on the front of the bass and batteries moved to a routed compartment on the back, both mods reflecting the modern configurations. There are also screw inserts for the back plate and battery compartment, and I don’t know if the tailpiece is a replacement or original, it is wood with brass plate top. The brass plate on the electronics cavity has a nice hammered pattern and will look nice once polished. Woods look like walnut top and back, mahogany body, walnut and beech/birch neck. I spoke with Mica and she is checking with Ron for his thoughts on how to proceed. I look forward to restoring the bass to full functional electronics again. A couple photos and a link to some quick clips recorded with an iPhone of the neck pickup. I will replace the roundwounds with flatwounds after a little cleaning and lemon oiling :)
https://app.box.com/s/kmtaeltvzkp98qb01bu9q3usn4mmufzd (https://app.box.com/s/kmtaeltvzkp98qb01bu9q3usn4mmufzd)
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That's a worthy restoration Rob. Keep us posted.
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mmmm - that is delicious. Hope that the refurbish goes well.
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8) (all I got to say about that one...)
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Wonderful restoration project!
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Hey rv,
This is excellent news! That bass was hanging there looking sad and lonely so I'm glad it's finding some love and attention. It did feel nice in its raw state so I think it will be a winner once you've brought it back to life. Best of luck!
Jimmy J
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Rob, did you plug the working neck pickup into the bridge pickup card input?
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Keith, as you can see from this photo that Jimmy took when he examined the bass, everything is soldered to the PF5 card, no snap together parts. So I have to think about how to approach this for a bit.
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I did notice that the neck and hum cancelling pickup wires have two wires each soldered to the PF5 card, maybe a positive and negative (ground) wire for each pickup (?). The bridge pickup only has one wire soldered to the card, the second wire for that pickup is coiled around the wire sleeve. It’s the wires extending from and coiled on the wire with the blue shrink wrap in the attached photo. Looks like the card has had a lot of secondary soldering done throughout it too.
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Good luck, Rob. As Keith said, a worthy restoration.
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Rob, indeed some difference with this one's pickups connections. Wonder what Ron thinks of these pics. I really hope that the connection is the issue with the bridge side of things.
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Thanks everyone, it will probably take a little while, but we will see where it goes :)
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You just know somebody somewhere was totally baffled by what they found under that brass plate... and they were probably pretty good wiresmiths. No match for a Wire Wizard.
I'm betting this is going to be a happy ending. :)
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Hey Rob,
I do believe careful removal of the shrink wrap I've circled (and arrowed) below will reveal mini-coax connectors. A way to disconnect and swap pickup inputs. That might be a good place to start.
Also, I think that roughly soldered wire wrapped around the bridge pickup's wire might be connected after all though I can't tell by the picture. Those p/u wires are tiny shielded cables, like mini-guitar cables. A single conductor in the center with a woven shield wire around the outside, plus the clear plastic insulation. It appears they lost the shield connection to the board at some point and wrapped & soldered wire this wire to the sheild to make the connection. Might not have been a successful hack though.
Keep us informed. Exciting!
Jimmy J
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Thanks, Jimmy, I will investigate and give that a try, -Rob
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Good idea Jimmy with swapping the pickup connectors! That should help narrow down the issue.
Rob, good luck! Very interesting project.
Just for reference - I am aware of at least a couple of threads that have photos of other PF-5 circuits:
https://club.alembic.com/index.php?topic=4619.msg55306#msg55306
https://club.alembic.com/index.php?topic=8342.0 - Maybe take this with a grain of salt, as I'm not sure if this was completely "stock".
[links changed to current Club]
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Really rooting for the restoration of #28!
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Thanks, guys, and thanks for the photos as well, very clear examples :)
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Good luck with the restoration! I hope it turns out to be something simple affecting the bridge pickup.
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I switched the pickups and can confirm that both pickups work, which is great since I prefer the sound of these older pickups over the newer ones. The other positive confirmation is that the electronics cavity is 1 3/8” deep, which is the same depth of my other 70s era Series basses. So, a PF6 card mounted on the back of the brass plate will fit in this bass. What is preventing the bridge pickup from making sound is still unknown. Next step, follow up with the mothership. :)
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Thanks for the update. That's great news that both pickups are alive. That's going to be a sweet bass when you get it all dialed in.
Jimmy J
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Rob, that's the best possible news. RW can easily suss out that circuit.
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Great to see you bringing this one back to its full glory and excellent news that both pickups work. May not be as involved a restoration as originally thought.
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Question for the group:
Should I have a local luthier lightly professionally sand and re-oil the finish to remove built up residue and smooth it out with a fresh oil finish, or leave it with its historic “mojo”?
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Rob, I'm not sure a professionally done cleaning would detract from the value.
After all, it is #28. It will always have the value of a very low number Alembic.
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Thanks, Kenn, that’s kind of what I was thinking too.
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That would be a difficult choice if I was the owner. There is beauty in either choice.
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I vote for leaving the mojo, for the time being at least. I can imagine this being a good time to have it done, while you're having it restored so taking it apart and cleaning everything? I personally lean more toward "the dirt keeps the funk" school, but a lot of that is laziness on my part! (And I do wipe down and clean my instruments periodically) (And how much "mojo" is on there?)
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The body is not bad, I was just thinking a nice smooth even finish would look nice and really make the nice grain pattern come through. The neck has some build up on the back and I will probably clean that up and smooth it out a little. Otherwise it is in very good shape. But we’ll see, I might leave it as is as well. :)
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I wonder if this bass was a couple of years in the making…
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Very unlikely. The date codes are stamped by the potentiometer manufacturer. The minimum order for custom pots means that the date codes can trail the serial numbers for many years.
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Ah, thanks for the insight! Pretty cool to see one with ‘71 on it though :)
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My 73-32 has the internal hum canceller setup with the battery compartment in the front middle between the pickups . I suspect this bass has had some modifications in that regard ?
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My 73-32 has the internal hum canceller setup with the battery compartment in the front middle between the pickups . I suspect this bass has had some modifications in that regard ?
I don't know when the batteries officially moved to their under-the-bridge location so this does seem like a mod. Or possibly even a prototype test of that design move? Because the routing of the battery compartment on the back, and cover for it, do look like factory work. More mystery in the history. Can't wait 'till you get this bass going again, I think you're gonna love it!
Jimmy J
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I think it has more to do with when and the quantity of parts purchased than time to build the bass.
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Regarding things like the battery location, consider that serial numbers traditionally are assigned as the last thing in the build. Something may have been started, set aside for customer's work, then picked up again at a later date. There are also some times when the serial number isn't the last item done in a build. It means that you really can't use the serial number as a hard and fast "before or after this number" declaration.
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My 73-32 has the internal hum canceller setup with the battery compartment in the front middle between the pickups . I suspect this bass has had some modifications in that regard ?
I don't know when the batteries officially moved to their under-the-bridge location so this does seem like a mod. Or possibly even a prototype test of that design move? Because the routing of the battery compartment on the back, and cover for it, do look like factory work. More mystery in the history. Can't wait 'till you get this bass going again, I think you're gonna love it!
Jimmy J
Wolf, I think you are right.
Jimmy, I was also thinking the battery placement on the back and the hum canceling pickup on the front may have been done at the factory. They are both very well done, and the battery compartment rout appears identical to that on 74-59. -Rob
…making progress
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It would be interesting to see if there are screw holes (or filled ones) for a different tailpiece under the currently installed one. The earliest one like it I recall seeing is on guitar #74-53. 74-52 is a short-scale bass with a moustache-type. I would have expected this bass to have one similar to what was on #73-27, a simple bar-type. (it was eventually changed too)
*like Mica said too, this bass may have been in production a while. Perhaps well into '74, and the tailpiece among the last pieces of hardware to go on. Hard to say.
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All great comments and thoughts! At 50 years old I’m sure it has been through a lot! :)
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Wondering about the core wood. Does this grain look like walnut or mahogany, or something else?
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If I am not mistaken, I seem to recollect that when Alembic so beautifully resurrected my 73-32 ,it was mentioned that the core wood on that instrument may be "OAK". Mica, might that be the case here as well, with 73-28 ? :)
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Wolf, I don’t think it is oak. Below is a photo of 74-59 lighter oak core wood on the left, next to 73-28 darker core wood on the right.
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I’m leaning towards the possibility of the battery and hum cancelling pickup relocations being done at the factory. Below are photos comparing the battery covers and cavities for 74-59 and 73-28, they appear identical, even the plates are identical size with screw holes line up perfectly (the photo of the plate alone is actually the 73-28 plate on top of the 74-59 plate).
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Not oak. Cherry?
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I'm guessing #73-28 is a;
mahogany core, schedua top and back, and walnut and birch neck layup. The headstock face could be a couple things... Califorina Claro walnut maybe? It looks a lot like McVie's #27, whatever that stuff was. Totally different logo.
Agree, the routing work done is 'factory'... man, this bass has stories.
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I think the top is walnut; core walnut, mahogany, koa, other? Back walnut, mahogany, schedua, other? Neck walnut and either beech, birch or maple. Would be cool if there was an actual record for 73-28 :)
But 73-28 looks a lot like 73-43 and the ad online for 73-43 says body woods schedua and mahogany, so Greg may be right.
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I'm guessing #73-28 is a;
mahogany core, schedua top and back, and walnut and birch neck layup. The headstock face could be a couple things... Califorina Claro walnut maybe? It looks a lot like McVie's #27, whatever that stuff was. Totally different logo.
Agree, the routing work done is 'factory'... man, this bass has stories.
Wow, so this bass was right after McVie’s? Cool :)
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Update on progress:
We have been testing all of the circuit solder points. So far all very good. We have found three minor issues so far that are easy to fix:
1. The volume pot wire for the bridge pickup was detached from the board. We soldered it back in place and now everything works fine for the bridge pickup and controls, sounds great.
2. Found a broken resister associated with the neck Q switch, we will replace that Wednesday night. So once the resister and Q switch are replaced the neck pickup controls will be fully functional (hopefully).
3. The neck Q switch that someone replaced at some point is falling apart, we will replace that Wednesday night as well.
Everything else seems to be working fine. So by Wednesday night if all goes well it will be back in full working order.
I will provide another update later next week.
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Sounds good.
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Good progress!
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Excellent report!
You're gonna like this bass.
Jimmy J
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Update: Success! :)
We replaced the broken resistor tonight and after testing found that the neck Q switch that was previously replaced works fine. So all it needed was reconnection of the bridge volume wire and broken resistor replacement. It now works perfectly. Can’t wait to try it at practice this weekend :)
P.s. I think I will leave the finish as is for that 50-year vibe :)
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Excellent news Rob! Agree about the finish, the body isn't damaged and it has a kind of patina that only comes with age. Looking forward to your observations about the sonic qualities after rehearsal this weekend.
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There ya go! "Air gaps" don't work well in this type of circuitry. :o
I would hope you'd eventually get a replacement switch for the mismatched one. In my mind that would finish off the resurrection of this bass. I also dig the finish and am glad you're going to leave it as is. You're doing a great job bringing it back to life!
Jimmy J
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Glad all worked out. Let us know how it sounds in the mix.
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Nice, congratulations!!
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#73-28 plays on. 8)
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Thanks,everyone, I’m pretty psyched!
Jimmy, I have an extra new Q switch with paddle shaped toggle for Series in my parts box and may install that in the future. The objective this phase was a do no harm approach to getting it up and running. Replacing a Q switch on a PF5 is a little different than a PF6, with greater potential to mess up the connections between components on the board. I’ll enjoy it for now and think about that switch replacement for the future…”and the band keeps playing on…” :)
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Yes indeed, the main thing is it is making all the right sounds!
I think the switches for the PF-5 were a bit different in that they had long lugs - maybe called "through-hole"? - which, along with the trimpots, are what held the board in place. See the pic below which I grabbed from that other thread. I bet these boards were assembled on a rig which held those four components in place while the board was soldered to them. That makes it a bit trickier to replace just one of the four parts... But it can certainly wait because it's time to play music!
Carry on and enjoy that axe!
Jimmy J
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I’m going with Koa top and back, the grain pattern and all those tiny dark spots are characteristic of other koa instruments I have seen (including Mission Control and 75-A013). But, I still don’t know what the core wood is, the distinct grain lines don’t seem typical of mahogany to me.
Update, Greg set me straight, I’m going with mahogany core :)
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Looks like the original hum canceler was embedded in the neck and exposed when the battery cavity was routed on the back. It is non functional and has one located between the pickups now.
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I would like to have been a fly on the wall in the shop when the plunge router hit that thing. I'm kind of wondering if it was an accidental. Like maybe they tried to move the battery box to the back of the bass per a customer request, accidentally hit the hidden hum-canceller, and therefore, had to locate it between the pickups.
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Holy cow! Yeah, no joke - that is NOT what you want to see when you finish routing.
I suppose it's possible that they knew all along it was going to be "sacrificed" to get the battery cavity in the standard location, but if not, ouch.
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Wow, how about that? It's like an archeological dig and you've unearthed the humbucker from when the Romans were building basses. :D
I can't imagine that was done on purpose so it must have been quite a surprise and perhaps a disappointment when it happened. But maybe they were planning to move the coil to the front anyway so... That bass has some history!
Jimmy J
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The interrupted cut probably necessitated a router bit resharpening.
But yeah, that is really a cool find!
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The PF5 wires are quite old and very brittle. Each time I reconnect a wire another one would pop off when I reinstalled everything in the electronics cavity. The bass has had quite a bit of modification to this point by others, so the bass will be updated with a new PF-6 and associated wiring harness. I plan on using this one a lot, so it needs to be reliable. I will then take my time and restore the PF-5 by replacing every wire on it with new wires, restoring the PF5 functionality and reliability for future use.
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Note to those considering replacing Q switches in older Series I basses that have the PF card mounted on the back of the cavity plate.
The new Q switch design with snap on connectors are taller than the older Q switch components that have soldered wires, the result is the plate mounted PF card will not fit with the newer snap on connector Q switch components. It looks like the new snap connector Q switches are designed for Series basses with the PF card in a separately routed compartment on the back of the newer Series basses.
You can make it work with a little imagination though :)
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With all of the mods and surprises by previous owners and my current restoration efforts, I’m going to call this one my 73 Custom :)
One more step remains, converting the pickup wires from coaxial to Molex two-pin, found these photos for guidance…
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rv,
You know that Alembic has coax to Molex adaptors right? But you might as well go all the way with your Custom machine! Note that in the two pics above the shield is in different positions. I believe the lower picture is correct; shield on that side when looking at side of the connector with holes.
Jimmy J
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Thanks, Jimmy, I have seen pictures of the connectors and will look into those as well. Thanks also for pointing out the differences in the images above, noted :)
I’ll post photos of the restored bass once completed and tested for functionality.
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I am happy to report that this evening I finished resorting this bass to full functionality. I had to add a little to its history of modifications to get the new Series I electronics to fit, but it works perfectly now and is a pleasure to play. I will plug the extra original holes in the front of the bass with abalone-topped wooden plugs. It’s a beautiful bass brought back to life. :)
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So cool to see this one back up and running. 8)
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Wow! Great work rv!
That center board with the resistor array looks like a custom piece which makes the wiring harness more modular. What's the story, is this the current factory package? It also puts the Q switches in a vertical line instead of the 2 o'clock position relative to the tone controls. But that just adds to the custom-ness of this lovely historic axe. Very cool.
Are you waiting on the mini-coax to Molex adaptors or did you change the connectors on the pickup leads?
What a great save! So glad you've put the time, effort, and $ into reviving this bass. I bet it sounds amazing! Also thanks for keeping this thread going, it's been a treat to watch your progress.
Jimmy J
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Thanks, Jimmy and Greg.
The Q switches appear to be a new configuration with individual circuit boards and clip on wire connectors. I assume they are a new design since they are not the same as the 70s versions, but I do not have any basses newer than the 70s so not sure how long these Q switch versions have been around.
I believe they are typically aligned horizontally next to the low pass filter knobs like they have always been. But, the new Q design with the clip on wire connectors and mini circuit boards are taller than the old ones. So, the brass plate cavity cover would not fit if I tried to attach the preamp circuit board to the back of the cover plate as is normally done on the older basses. So, I had to find a way to insert the preamp card into the cavity with all of the other controls (I did not want to rout out a separate preamp compartment on the upper half of the body like on the new basses). The only way I could fit the card in the cavity was to slide it up towards the lower horn as shown in the photo (I also slipped the board into a thin insulating sheath to prevent shorting it out, not shown). To do this, I had to relocate the bass pick up Q switch up between the volume knobs. Now it all fits and works great. So it's my custom 73 bass (maybe a new design, who knows). Also, I changed the mini-coaxial connectors on the pickup wires to the two-prong molex connectors so that they would connect to the new circuit board, that was the last step that I finished last night (not shown in the photo).
The bass has a beautiful tone, it is lighter than others I've had, hangs nicely on a strap, and the neck has a great feel, plays wonderfully. :)
I plan to completely rewire the entire original circuit and harness that came with the bass. If I can do that and get it all to work properly I might consider putting that back in the bass sometime down the road.
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Hey Rob, if you have the clearance inside, a couple of these brass hole plugs might be an aesthetically blending fix for those three vacant holes. They are available in many sizes. For that matter, black plastic ones are too.
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Ah yes, understood! The only way the newer preamp board fit into the Series I models which followed this version was because the pickup volume pots were single-gang and all the components related to the Q-switches were wired point-to-point and tucked down in. With these new small boards and their vertically mounted plugs you've found the only way to pack it all into this main compartment. Excellent puzzle work!
I think rebuilding the original board would be an interesting project too so you should definitely hang on to all those original components. You'd need to source one of those Q-switches with the long solder lugs but I know they're still being made. And we know from your experimenting that the opamps are still operational. Or perhaps I should say "opamperational? :o So maybe someday.
But the main thing is you've literally made this old bass NEW by putting in the current electronics package so we all thank you for doing the good work.
Jimmy J
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I did the exact same conversion on 73-47. I plugged the holes with readily available 1/4 inch abalone dots. They fit the holes perfectly!
Michael
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Congrats Rob; looks great!
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Excellent job and dedication to the task at hand Rob! Such a cool bass, play it in good health.
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Thanks Everyone :)
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Rob, that restoration is nice. Great job!
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Thanks, Paul.
The abalone might need a little touching up, but came out OK for now.
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SO GLAD TO SEE THIS BROUGHT BACK TO LIFE. I SAW IT YEARS AGO AT THE SHOP ON VENTURA BLVD., BUT HE WANTED A LOT FOR IT, AND IT LOOKED LIKE A MAJOR PROJECT. HOPING YOU GOT IT FOR A MORE REASONABLE PRICE, AND IT LOOKS LIKE THE FIXES WERE NOT TOO BAD. IT WAS LIGHT WEIGHT AND FELT GREAT WITH ALL THAT PATINA. CONGRATS!
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Thanks, Trevor. It wasn’t that bad to fix up, and it was actually fun. You are right, the bass is nice and light and sits well when using a strap, very comfortable to play. The neck is like my 67 Starfire, only long scale. It has a sound that I find unique to the early 70s basses too, likely similar to your beautiful fretless. And all of that wear and patina feels and looks good too. I love it :)