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Prostheta

Aria Pro II SB-1000 bass electronics restoration

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This is definitely a bit left of centre for our usual fare. People that know me a little beyond ProjectGuitar.com will be aware that I've been a big Aria Pro II (and Japanese instruments in general) for many years. To the point that I have fallen into being a go-to guy for the SB-1000 in terms of electronics and the stuff that makes it what it is.

So anyway, I get an email reference that a guy is looking to restoring the electronics on his 1981 SB-1000. That's what I do. He drops round, we have coffee and have a nice afternoon discussing the job and all manner of other things. His bass needs a bit of physical restoration work, but is fundamentally in original condition. Not bad for a 35yr-old bass!

Come up to the lab and let's see what's on the slab:

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By this point, I'd taken off the strings, nut and spent time degunking the fingerboard....

 

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I know that you'll love this even though it doesn't have magnets, @curtisa. The cover is a neat and perfect Rosewood inlay....

 

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The frets are fairly worn in the lower region as you'd expect. I'm thinking that it could possibly do with a refret, however we'll see how the remaining wire levels out once the rod is relaxed and the neck acclimated. Either the existing gunk was more resistant to my charms than your average common-or-garden gunk, or that's residue from a glued refret. I've also noticed a couple of light cracks in the Ebony.....

 

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Now this is where the problems really lie. The SB-1000 (both 70s and 80s variants) had odd electronics and pickups of a very specific size. Unfortunately, when something goes in those, most owners tended to rip the lot out and replace it with something like an EMG or Bartolini. Fundamentally, that alters the tonal character that SB-1000s are known for, so that's heartbreaking for me. In this instance, the pickup was an EMG-P4 with what looks like an old EMG BTC system. Nothing of the original electronics remained. ^_^

 

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Well, at least the modification didn't involve truly invasive surgery like I've seen on some. A couple of shims to block up the gaps at either end and a bit in the floor to raise it up. I'd already pulled off the foam rubber....

 

IMG_8077 -1.jpg

Careful work with a hammer/chisel, inspection lenses and tweezers removed all evidence of the offending infills.

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Most importantly there, the original threaded inserts for the pickup still remain. The pickup is fitted using M4x35mm machine screws instead of crappy wood screws. Another reason why I love the upper end of old Aria Pro II stuff. They didn't cut corners and produced fine instruments. Weird choices sometimes (we'll get to that) but fundamentally sound.

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This is where the fun is (don't you agree, @Norris?).

IMG_8078 -1.jpg

 

Normally this is populated with (left, clockwise) a DPDT switched jack socket, an active 6-position rotary varitone, active/passive circuit switch, always-on LED monitor, plus dual value volume and tone controls. The cavity at the far right housed the differential preamp (another speciality part which only I make) plus 2x PP3 batteries.

Pretty hefty circuit all in all.

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The missing MB-1E pickup is being replaced by a reproduction part made by Veijo Rautia, coincidentally also here in Finland:

http://www.rautiaguitars.net/aria-pro-ii.html

It always seems that either Veijo or myself get all of the resto queries. Unsurprising since these are unique and loved basses. The pickup itself is a hot dual ceramic humbucker encased in a plastic case and encapsulated in epoxy. When they fail, they fail.

Two original pickups, both non-functional. I dissected these many years ago now so this is old stuff. One was configured differently, for a different Aria Pro II bass....these also made their way into Westones of the same era IIRC, although packaged differently....

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Underneath the plastic case (this is not easy). Note the copper tab and what I think is conductive paint from the inside of the plastic case? (@curtisa: thoughts on this?)

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Two "king big" ceramic bar mags. Both cracked which is why this pickup was non-functional, or at least....probably having happened from whatever hit it (check the case above):

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Gutspill:

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Essentially, kind of a "double J" humbucker, however the poles are evenly spaced. The bobbins interlock beautifully. Each pole was cut to an exact length to create a radius.

 

IMG_4726.JPG

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So this is what a populated 80s SB-1000 should look like:

The thing in the electrical tape is original, surprisingly. It consisted of a thrown-together PCB designed to blink the LED. Not monitor the battery condition or indicate anything other than that the batteries were not dead. I think we can improve on that.

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Now there's the beast of a varitone. Sounds great, but it's like a Fabergé egg to construct.

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Note the values on the pots. These aren't simply concentric pots or dual gang, they're dual value dual gang. The SB-1000 circuit is build on two completely parallel circuits; one active (20k gangs, preamp, varitone) and one passive (500k gangs only) bypassed or switched in with the 4PDT (only three poles used) switch. Ergh.

P1010045.JPG

 

So yeah, they're not simple circuits to work with. Proper ratnesting. For this bass, I'll be going for a scheme which is more or less like you see above, however in the longer term I am producing a PCB-based solution with quick connectors that I can supply to people refitting SB-1000s directly. The bass on the healing bench was lucky because it lives 1-1/2hrs from here. Other people aren't so lucky.

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Other considerations for this are things like the LED flasher circuit. Over time, the supply buffering (mistyped, "buggering" which is actually apt) capacitors in the preamp which smooth out any fluctuations become leaky. As the LED circuit bangs the supply rails with big current spikes, those end up pushed onto the audio as clicks. Nice. I think that a nice "breathing" LED will be better than that. Perhaps even one that switches red/green using the spare pole on the switch....

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I love the look of Arias.  @Norris has a scrumptious one....

But I had no idea that the electrics could be this unique!  Fascinating read so far :)

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....about dual value pots....

They don't exist on the open market. This means that I either need to hybridise a load of dual gang 500k and 20k pots (usual method) or have them custom made with a MOQ of 1000.

Good job I had 5 sets custom-made as a favour then. Beyond this very limited stock, I'm going to move to the hybridised pots mounted on PCBs with quick connectors.

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These are literally a nightmare, Andy. The number of hours that get sunk into them....

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7 hours ago, Prostheta said:

Underneath the plastic case (this is not easy). Note the copper tab and what I think is conductive paint from the inside of the plastic case? (@curtisa: thoughts on this?)

Probably shielding. Easy way to tell (if you still have the pickup) would be to ohm it to the ground connection on the pickup cable.

 

5 hours ago, Prostheta said:

They don't exist on the open market. This means that I either need to hybridise a load of dual gang 500k and 20k pots (usual method) or have them custom made with a MOQ of 1000.

Omeg used to do MOQs of 100 pieces, don't know if they still do. Looks like you can request mixed value wafers on their dual gang product selector too.

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Nice job and great to see another one getting some TLC!

I'm not sure if mine is a very early bass or something, but my pickups are fitted with wood screws - not the threaded inserts. But yes, it's a complete rats nest of wiring, and the varitone switch is a work of art.

Looks in PhotoBucket library...

022_zpsauuzxp2w.jpg

001_zpsgylaid5f.jpg

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Yes - the 70s "batwings" like your own had a number of differences. Bridge placement, varitone function, internal pickup configuration. Easier to work on than these 80s SB-1000s with their crazy component choices!

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12 hours ago, curtisa said:

Omeg used to do MOQs of 100 pieces, don't know if they still do. Looks like you can request mixed value wafers on their dual gang product selector too.

 

I can't spring for that number of parts. It's simply way too expensive for the low number of clients that ask me about these basses. That and there'd need to be a LIN and a LOG model for tone and volume respectively. Omeg doesn't stack up even if I could afford to buy 200 pots!

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Hi, can anyone help please. I have just bought a 1979 SB1000 that has not been played for years and the volume control has seized. From previous comments it does not appear to be a standard pot. Can any recommend where I can buy a replacement?

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A 1979 SB-1000 should be single-gang 20k pots. They're relatively easy to source. You might have to settle for 22k or 25k depending on where you look though. Not sure of specific UK suppliers, however you have Banzai over in Germany:

https://www.banzaimusic.com/Alpha-24mm-Full-Shaft-Standard/

https://www.banzaimusic.com/Alpha-16mm-split-shaft-20k-lin.html

The problem is the splining; the original Aria knobs are unlikely to fit the splining of common pots. This may mean a modification to the knob or replacing it.

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I can't believe that I didn't finish this thread!

I took a load of photos of the bass's new electronics; the switch and varitone all had custom daughterboards for the interconnects. I'm kicking myself now....I think I might have lost a lot when I transitioned from the old desktop machine to this new computer.

Sorry....I'll see what I can find....

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