Help!!! No treble

[Rob W]

Hi all! I finally got my L-1000 conversion completed by my luthier just before closing time on Saturday on my way to a gig. He got it done just in time for that gig, but we didn't have time to work out any of the bugs. We only did a super quick test through a tiny guitar amp (that's all he had handy at the moment) and I suspected that the treble control wasn't doing much. I got to the gig and through my big rig, it was super obvious that yeah, the treble does nothing and seems to be all the way off (I compared with my L2000 to match tone). Heck, luckily it was a Country gig, so a little extra dark wasn't a deal breaker and I used it all night anyway. Still sounded pretty awesome! Anyway, he's going to try to figure what went wrong but he's closed until tomorrow, so in the meantime, if anyone has an ideas what's gone wrong.. This circuit is completely new to him also

His wiring looks super cleanly done (although some of the pots are facing a different direction from many of the old body cavity shots floating around). Following and matching 5 or 6 different old circuit pics and the attached diagram (the white wire from the pickup is missing on this diagram, but it's meant to go to the switch where the other white wire is), it looks like he got everything right that I can see (other than a few arbitrary different coloured wires - but they seem to go to the right places). I don't see any obvious broken connections or shorts.

Any ideas what might be amiss? Could it just be a bad pot or something?

Another related question, some of the other block diagrams I've seen show a resistor on the treble control and have the connections to different terminals, yet I haven't seen photographic evidence of a real example of this. All of the pics I've seen floating around here have no resistor and are wired up just like mine. Even Paul Gagnon's schematic show the resistor, yet I've not seen it on any actual pics.

[Rob W]

By the way... the finished look!

[Ken Baker]

On the treble pot you show what I assume is a capacitor labeled 75K / 100. If that is indeed a treble cut cap, it should be 0.047µF (or 473K). You could use a 0.1µF (104K) for extra treble cut. I don't know what 75K is all about but that is not a proper capacitor code, which would be three digits plus a letter tolerance identifier such as K. Here's a chart. I'd verify that cap's value.

Edit to change my comment about the "75K" cap.

Also, the free soldering lug on the treble pot should either be grounded or grounded through a 6.6KΩ resistor. Either way should be fine, though the resistor is used in the original circuit.

Ken...

[Rob W]

Thanks, Ken. No, I'm not actually using that weird 75k cap (I can't remember where I found that diagram, but it seemed otherwise to be the most straightforward looking diagram that seemed to match most closely the pictures of actual L-1000 circuits I've seen here). I do in fact have the .047 uf cap supplied by G&L.

I feel like I haven't seen any pictures with the resistor, but if that's the missing piece, that looks like an easy fix. That free lug on the treble pot is indeed connected to nothing at the moment. I'll give it a try tomorrow.

Thanks again

[Ken Baker]

Look at the drawing I linked above labeled "original circuit".

And also note that I mis-read the drawing. The correct value of that resistor would be 6.8KΩ, which is a standard value.

Ken...

[Rob W]

After trying a few things, it turns out that it was a bad capacitor. After swapping the cap and grounding that free terminal, it finally works! The treble control is now functioning although I still feel like the instrument is lacking a tiny bit of top end but maybe that's just my imagination. At least I generally prefer a little darker sound. I'll A/B it with my L-2000 (neck pickup only in parallel) and see how they compare. I guess that's truly the only setting they share.

Anyway, overall I'm super happy how this turned out in the end. I suspect this will now be my number 1 bass. I just love the punch, warmth and clarity. Thanks for all of the help!

[Ken Baker]

Great!

Thanks for letting us know.

Ken...

[Rob W]

Okay, I guess I was a little premature with my proclamation that it's completely fixed. It's *better* but not quite fully functional. With the new .047 uf capacitor and grounding that free terminal on the treble pot, the treble control now works somewhat but as I suspected, when I A/B with my L-2000, there's a noticeable lack of full treble. I'd say that with the treble all the way up, it still sounds like the treble is reduced to what sounds like a maybe 40%-50% level at best. It will fully roll off to zero from there. Just one other change from the original pics I posted, we moved the white wires to the left terminal of the treble pot instead of the right (if the terminals are on the bottom) to match the wiring diagram that you suggested we reference. The right terminal is now grounded to the casing (no resistor though) I can post a pic of the update if you want.

Having said that, I don't hate the sound. As it is, it's about how I would probably dial it in anyway 90% of the time, especial in parallel mode. However, I'm sure that it should be capable of more top end, so I know it isn't quite right. It would be useful in OMG mode to have a little more top as well.

Any ideas what could be drawing this last bit of top end out of the circuit?

[Ken Baker]

Any ideas what could be drawing this last bit of top end out of the circuit?

On the bass pot is what we call a swamping cap - usually .001µF. In your drawing, it's labeled ".001 K / X 5 F". This cap "swamps off" a bit of extra treble. There's no control over it other than removal. Lift one of its leads (making sure it doesn't short to anything) and see if that gives you what you're after. If it does, clip it completely out and call it good. If you don't like it out of circuit, solder it back in.

Ken...

[Rob W]

So, in other words, you'd say that amount of treble is normal for an L-1000? I really have no real example to compare it to around here. Although there are a decent number of G&L basses in Canada (and I own a bunch of them!), I've literally never heard a real L-1000 in person. They're exceedingly rare in these parts.

As I said, I'm pretty okay with the amount of treble as it is, but I guess I wasn't expecting that overall, the instrument would be that much darker sounding than say, my L-2000, L-2500 or Kiloton so I thought maybe something was still slightly amiss. If that's normal, then I guess I'm good.