Yamaha RBX 270 -- HELP!

[voodoorat]

So I got a used Yamaha RBX270 (PJ bass) on the local used market for $50. It didn't have any strings on it (kinda suspicious) but I figured if there was anything wrong with it I'd be able to fix it and that the bass was probably pretty decent. A buddy of mine picked it up and he didn't ask any questions. I stupidly didn't test the electronics before I strung it though and was pretty disappointed when it made no sound. I opened it up and saw the wiring was crazy--the tone and the neck pickups were hooked up to each other as expected but not to the bridge--the bridge was hooked up to the bridge volume pot which was hooked up to the output jack (actually, the pickup wasn't hooked up to the volume pot which is why neither pickup worked but that was an easy fix once I realized what was going on).

So today I dug into it a little more, was going to fix the wiring but ran into a snag and found out why (sorta) the wiring was so weird. What I thought was the tone pot is a pickup blend dual pot. So the original wiring was that, a master tone, and a master volume. I think I'd prefer to have the two volumes and a master tone but I can figure that out later. The bigger problem is that the P-bass neck just doesn't seem to work at all. I hooked it up to the bridge volume pot to test, and even directly to the output jack, and no input. I can measure resistance across it though with a multimeter, about 8k. The pickups are totally sealed so I can't see what's going on inside there but I'm trying to figure out what could break a pickup like that. There's no output at all but electricity flows from hot to ground. Is there any way to tell what's going on in there? I can buy a new P pickup but I'd rather not if I don't have to--I only spend $50 on the bass and those pickups should be decent, I'd be reluctant to spend what it would likely cost to buy the same one.

I don't see how I can repair the existing pickup but it's weird, anybody ever seen this kinda thing?

[LightWingStudios]

"Once bitten, twice shy babe".

[andrewsrea]

If I have this right, the Yamaha RBX 270 is a 'P-J' pickup configuration? This would mean the 'P' neck pickup has 8K resistance, measured from the leads in the control cavity?

If I have this right, than your pickup should be okay. I suggest taking a spare 1/4 inch jack and soldering the neck pickup leads to it, just to test for sound. Do the same for the bridge pickup, if you are not sure if it works.

When you are sure they work, wire it like this: https://www.google.com/search?q=p-j+bas ... FN1_TUznaM.

If one of the pickups does not work, more than likely you'll need new ones. I have found the pickups on the lower price point instruments are not typically made to be rewound.

To which pickups break all the time, typically due to tight machine winding and occasional thin spots in the coil wire. [mention]golem[/mention] and I were in the local Music Go Round and he asked to play an expensive Fender Custom Shop Strat. Low and behold, it had a broken neck pickup.

I can wind you a vintage P bass pickup with nice Alnico 5 magnets for $50, delivered. Or, their are scads of inexpensive new and used on the internet.

Hope it works out for you!

[golem]

[mention]andrewsrea[/mention] speaks the truth. If my experience with his humbuckers and single coils are representative, I don't think you can find better pickups for the price.

[Chad]

[mention]andrewsrea[/mention] is a really good winder... Ive tried out his pickups in an agile 3100 that I bought locally in St Louis and they were really great PAF style pickups!

[voodoorat]

If I have this right, the Yamaha RBX 270 is a 'P-J' pickup configuration? This would mean the 'P' neck pickup has 8K resistance, measured from the leads in the control cavity?

If I have this right, than your pickup should be okay. I suggest taking a spare 1/4 inch jack and soldering the neck pickup leads to it, just to test for sound. Do the same for the bridge pickup, if you are not sure if it works.

When you are sure they work, wire it like this: https://www.google.com/search?q=p-j+bas ... FN1_TUznaM.

If one of the pickups does not work, more than likely you'll need new ones. I have found the pickups on the lower price point instruments are not typically made to be rewound.

To which pickups break all the time, typically due to tight machine winding and occasional thin spots in the coil wire. @golem and I were in the local Music Go Round and he asked to play an expensive Fender Custom Shop Strat. Low and behold, it had a broken neck pickup.

I can wind you a vintage P bass pickup with nice Alnico 5 magnets for $50, delivered. Or, their are scads of inexpensive new and used on the internet.

Hope it works out for you!

huzzah! yeah, i figured i must have something wrong because it didn't make sense that the pickup didn't work when it was sealed, so i held the two wires up to the tip and sleeve of a guitar cable and tapped it and it did something. i got it all hooked back up and both pickups work although i screwed something else up in the wiring when i put it back together--the blend works fine but the master tone and master volume aren't doing quite what they should be. i'll try to track that down later though, just happy it's making noise and both pickups work.

thanks!

[voodoorat]

since it had the one dual 250k pot and i don't have any spares, i found this and wired it up like this:

i must have mis-soldered something though because while the blend does what i'd expect the other two seem almost reversed. i'll open it back up later and see if i can track it down but i'm happy i can do it without buying any new parts, the pots and pickups all work.

[andrewsrea]

since it had the one dual 250k pot and i don't have any spares, i found this and wired it up like this:

image.png

i must have mis-soldered something though because while the blend does what i'd expect the other two seem almost reversed. i'll open it back up later and see if i can track it down but i'm happy i can do it without buying any new parts, the pots and pickups all work.

I was hoping that was the case!

Some folks really like the blend feature. My Tobias has a blend and my Jazz bass has no selector switch and two independent A250K volume pots and a A250K tone. I like them both and it is pretty much what you get used to. I am a guitarist and prefer on guitar, the les paul 4 knob set up and am constantly tweaking as I play. For bass, I am a find a tone and volume for the song and hold the pocket. So, either suits me.

I am pretty sure your volume is a B250K and that blend pot is a dual linear B250K. So, if you ever wanted to convert to the two volume and a tone, you can just use one 'layer' of the dual as an individual volume for the bridge pickup and wire it like I suggested. But that is only if you want to experiment. If you like it with a blend and it is working, you may want to leave it as is.

[voodoorat]

thanks again, opened it back up today and sussed it out. everything is working as expected now except i managed to hook up the jazz pickup to the "left" side of the blend and the p pickup to the "right" side. minor annoyance though and not worth switching it, at least not now. the only other annoyance is if the tone is bright i can hear a bit of a buzz when i'm not touching the strings, which makes me think there's still something that's not grounded. it's a bass though and i don't really turn the tone up past 8 or so where it's audible so it's more of a technical annoyance than a practical one (kind of like the pickups being backwards).

oh, my problem before was some sloppy solder (tiny almost-invisible sliver) that was bridging something on the dual pot and the master volume was backwards (although i'd wired it up the diagram, but i reversed it and it works now).

[andrewsrea]

^ So the 'P' pickup should be hum cancelling, by virtue that the two independent coils of it are RWRP even though they are under different strings. So if it hums with just the 'p' pickup, you do have a grounding issue. Most likely not having a ground wire going from the control cavity to under the bridge, which grounds the bass strings.

The 'J' pickup is single coil and not hum cancelling. Some people experience added hum when this is blended in with the 'p' pickup or on its own. This is normal and unavoidable. Shielding the pickup cavity may eliminate 20% to 30% of it and will also create capacitance (rob some high end from that pickup). I used to be a believer in shielding. But now that I understand how your body is a great big shield from behind the pickup, I believe the marginal improvement at a loss of high end isn't worth it.

[Gear_Junky]

They are good basses, IMHO really worth a decent pickup, something like Toneriders. I get it why someone wouldn't want to invest in a $50 bass. Me, I always upgrade pickups. Toneriders are hardly more expensive than good strings (a set or two) and are definitely good. I had an RBX 160 back in the 90's (just a P-pickup version of this bass). 24-fret neck, right? It's a good bass, discover the full potential!

[voodoorat]

They are good basses, IMHO really worth a decent pickup, something like Toneriders. I get it why someone wouldn't want to invest in a $50 bass. Me, I always upgrade pickups. Toneriders are hardly more expensive than good strings (a set or two) and are definitely good. I had an RBX 160 back in the 90's (just a P-pickup version of this bass). 24-fret neck, right? It's a good bass, discover the full potential!

yeah 24-fret p/j and honestly i like the neck shape a lot. i'm not much of a bassist but it's a comfy shape. the finish has definitely seen better days, almost wonder if it wouldn't be a good test bed for my first attempt at a strip and refinish. although it doesn't look awful. shape takes a little getting used to visually. maybe i'll see about sprucing it up with some of those toneriders. thanks, [mention]Gear_Junky[/mention] .

[Gear_Junky]

My RBX 160 was my first new bass that I bought back in the 90's, as I was getting serious about playing bass. I didn't know anything and it was that weird shape that sold me on it - it looked like a bass, like some of the more pricey basses, not like a guitar with 4 strings (to me then). I also recently talked to a guy who was also into music back then (and now) and he still has the same bass and also a Yammie guitar and he said how he tried all the expensive guitars at the store when he was able to afford them and nothing was as comfy to him as the Yamaha necks. Yamaha is one of those brands that make millions of "workhorse" instruments and equipment for the regular people, the Honda Civic of musical instruments. Your bass is more like the Accord or Prelude, only very old and run down