90's Gibson Thunderbird Bass Pot Values / awful sound when Tone knob is on

fatherted · February 11, 2022, 10:09:29 AM

Hoping someone can point me in the right direction on this one, I've got a 90's (from what I can tell) Thunderbird Bass and it's been always been a bit off, in terms of tone/sound.

Apologies for the super long first post, but might help with the diagnostics:

I discovered the 3 point bridge was bent and broken when I took it off, the bolts had been the only thing holding it on. It crumbled into 3 pieces.

I upgraded it to a hipshot bridge and the sustain on it is amazing now, it was almost non existing before.

Next I took a look at the internals, I can't seem to find the correct values of the pots online, but what I had was:

Neck Pickup Pot - reading 241K Linear taper , must of been 250K
Bridge Pickup Pot - reading 236K Linear taper , must of been 250K
Tone Pot - reading 367K Linear taper, not sure what it would of been 500k?
The cap on the tone pot read 0.019uf and was replaced with a Mallory .047 Capacitor @ 630 volt

I took these measurements with just the pots - nothing else connected.
It looks like the previous owner might have put these pots in and I was just wondering if anyone could confirm the proper values. I can find wiring diagrams and it is hooked up properly, but nothing solid for pots values.

I had some spare CTS good quality pots kicking around and played around a bit, I found that that the pickups seem sound better with Linear and the tone with an Audio taper. (just my opinion wasn't that bad with all audio taper either)

After all that I still find with the tone knob enabled (anything past 0-2 really) the bass sounds good but is picking up a "twang" sort of sound into the amp like too much treble or something, this is just mainly on the A string, if you play it open it sounds awful. The string height is easy to adjust and I've raised it and still get that noise.

If you turn the tone completely off, all that noise is gone, but the bass doesn't sound as good. Any help/advice would be greatly appreciated, this is the only Thunderbird I have access to and can't compare it to anything similar.

4stringer77 · February 13, 2022, 06:43:29 AM

Hi and welcome. That's odd that you're only getting a twang from the A string. I've got an early 90s Les Paul bass with the same pickups and they we're horribly microphonic when I cranked up the volume in band rehearsal. I was going to ditch the original pick ups for something aftermarket. Haven't gotten around to it since having my first child. There are a bunch of different avenues for replacement Thunderbird pickups. Could be the ticket to getting your bird soaring again. Best of luck.

Alanko · February 15, 2022, 04:35:35 PM

Try replacing the strings first? I had one string on my Telecaster that was buzzing in all positions. I bit the bullet and restrung the guitar and the issue disappeared.

fatherted · February 16, 2022, 07:08:27 AM

Thanks for the replies, I've been looking at how to test if a pickup has turned microphonic as far as I can tell it's a the bridge pickup that causes the noise combined with the tone being cranked up.

I found some more pots, but before busting out the soldering iron I took Alanko's advice and swapped out the strings just to be on the safe side, but no luck. Still a good idea to rule that out though.

fatherted · February 27, 2022, 08:48:28 PM

Still working on this one any recommendations if I was to change out the pickups? I was thinking the EMG Passives.

Basvarken · February 28, 2022, 07:46:36 AM

Quote from: fatherted on February 16, 2022, 07:08:27 AM
Thanks for the replies, I've been looking at how to test if a pickup has turned microphonic as far as I can tell it's a the bridge pickup that causes the noise combined with the tone being cranked up.

Tap on the casing with the back of a screwdriver. If you hear the taps amplified it's microphonic.

Quote from: fatherted on February 27, 2022, 08:48:28 PM
Still working on this one any recommendations if I was to change out the pickups? I was thinking the EMG Passives.

I'm always impressed by the sixtes repro Thunderbird pickups, by EY guitars.

They also have modern Thunderbird replacement humbuckers:

https://www.eyguitarmusic.com/Eric-Custom-Thundbird-Bass-PickupBridgefor-Gibson-Thunderbird_p_2636.html

And even replacements for the Jim De Cola humbuckers as used in a 2015 Thunderbird (and EB and RD from the same era)

https://www.eyguitarmusic.com/Eric-Custom-Alnico-5-RodThundbird-Bass-PickupNeckfor-Gibson-Thunderbird_p_2742.html

fatherted · March 03, 2022, 05:41:24 AM

I tried the test with the screwdriver and yea it picks up the tapping with a pick or a screwdriver, unless you turn the tone pretty much all the way down. Heck you you can hear the guitar strap creaking from the back of the guitar.

Going to go ahead and order the modern Thunderbird replacement humbuckers from EY guitars and have a go. Their Neck pickup comes as a 9K resistance and the Bridge comes in 9.5K or 14K Ohm.

I've reach that the bridge pickups on thunderbirds are usually a bit higher resistance than the neck. I'll test both of mine once I get them out, but has anyone tried really upping the bridge pickup to something like 14K? I'll probably start with the 9/9.5K range first as I imagine it's closer to the orignal specs.

4stringer77 · March 03, 2022, 12:08:31 PM

Yup, that was the deal with my LPB as well. Hope the new pick ups work out for you. Make sure to check back once you've completed the swap. Interested to hear how it goes.

fatherted · March 08, 2022, 05:56:46 AM

Pups have been ordered. 9K and 9.5K Hopefully 9.5K was the way to go for the bridge pickup. The store page for the bridge pickup said that some customers complained that 9.5K was too low of an output so they created the 14K. Figured I'd start with 9.5K as I am trying to cover up some noise instead of making it louder.

Old Pups came out, they tested @ 7.7K for the Neck and 7.8K for the Bridge.

godofthunder · June 05, 2022, 05:37:35 AM

I always put the higher value pickup in the neck position as I don't really use the bridge pickup much.

fatherted · July 20, 2022, 05:01:03 PM

I've been through x2 sets of up pickups through eyguitarmusic now. The first batch that look like the original pickups, didn't fit as the bottom of the pickups are not flush like the original. there is a bunch of stuff sticking out. Contacted the seller, I shipped them back for a refund as advised, and I ordered the other kind they had from 2015 and up.

The new ones came in, didn't sound very good, but 1 was horribly microphonic while the other was okay.

Any other suggestions?

4stringer77 · July 20, 2022, 05:52:01 PM

Lollar, Thunderbucker ranch and Seymour Duncan make t bird repro pickups. I think there are some emg options too.

4stringer77 · July 21, 2022, 07:18:16 AM

Turns out Thunderbucker is going out of business and I'm not seeing t bird pickups on the Seymour Duncan site so it looks like Lollar and EMG might be the only other players left in the field.

Dave W · July 21, 2022, 07:21:01 AM

Quote from: 4stringer77 on July 21, 2022, 07:18:16 AM
Turns out Thunderbucker is going out of business and I'm not seeing t bird pickups on the Seymour Duncan site so it looks like Lollar and EMG might be the only other players left in the field.

The Seymour Duncan TBird pickups are from their custom shop.

https://customshop.seymourduncan.com/thunderbird-bass/