Thunderbird Pro Wiring Diagram

[tommy87]

Did somebody try to connect original pickups in parallel mode(shielding and white wire together and red wire as the signal one)? How does it sound? Since the impedance of single stock pickup is 7k, then impedance in this way should be 1/3,5k+1/3,5k)=1/?.....1,75k. Isnt this value too low and signal too weak?

[Antoniof]

I had a TBird pro  with a great hum noise issue. After I've read this forums (and others) I came up with, what I think is the correct solution. Here I share with you

1) The wiring schematics in the page are correct

2) I don't think the preamp is the SD BEQ-2, just another two band preamp. I remember searching for it with the part number and finding it ,,,but not at SD

3) I don't think that changing the volume pot for 250K would yield aa 3dB volume gain (much less a 6dB gain with 512K). If you look closely at the schematic, you see you get the signal straight from the preamp output pin when the volume is maxed. Howeve rthere might be a small increase  in volume depending on the amplifier input impedance

4) The pickups are PASSIVE with an active preamp (as this is the most common configuration on active basses). There's no such thing as ACTIVE/PASSIVE pickups. EVERY BASS (and guitar for that matter) than can work both as active/passive, is a passive pickup/active preamp combination, changing to passive simply bypasses the preamp. One of the the wiring diagrams in this thread confirms this.  The RED WIRE in the pickup is for coil splitting, you can definitely check this with a multimeter, it's NOT FOR POWERING THE PICKUP. However, as the noise is picked by the pickup coils, running a current through them might mitigate the problem.

5) The correct approach is to properly shield the pickup cavities   with copper foil, o painting it with conductive painting.  (in my case the preamp cavity was painted with conductive paint, but you could check yours)

6) Note that it also has to be properly grounded, all pots bodies bust be grounded, and if you use copper foil or paint with conductive painting, this is already done

Hope this is useful

             Antonio

 

[Mcontour]

Hello folks,

 

 I’m working on one of these basses for a friend. It is the full active model. 
 

When I plug the output cable in, sound comes out of the bass for about 2 seconds and then fades off to nothing rather quickly. The battery is minty fresh. 
 

Anyone have any tips on solving this?  I thinking of verifying all the wiring is per the diagram in this thread, and then maybe replacing the module if I don’t find any discrepancies. 
 

Thoughts?

 

 Thanks. 
 

Michael

[Mcontour]

What I meant to say is that the pickups are passive and they run through the module.  No option for passive/active.

[Mcontour]

Hello again, Folks.

Hey, I'd really really appreciate your help on this....I want to purchase a replacement premap module for this bass.  I called Epiphone directly and they told me that I'd have to go to a dealer and have them order it.  I went to (large) dealer and they tell me that their Gibson/Epiphone support person is not responding to the inquiry....multiple tries over 3 weeks.

I'm at a loss on this....how can I get a replacement preamp?  

Thanks in advance for any support you can provide.....really.

 

[AleX33]

Hi, did you find a solution to change the preamp ?

I buy a T-bird bass with this hum issue et would like to replace the preamp with the original one.

Edited August 14, 2022 by AleX33

[UXBASS]

I had this exact problem, and solved it by desoldering the red wires from the back of the volume pots and adding heat shrink to them.

First I tried replacing the preamp with 500k volume pots and a 250k tone pot and 0.047 cap. That did nothing. Then I started shielding everything! That includes the back of the scratch plate, pot cavity, and pickup cavities; all connected to ground. It didn’t work. Finally, I disconnected the red wires and as of by magic the bass was perfect.

I feel stupid for not reading the whole thread first! Oh well. One day I may put the preamp back in, but for now I’m good. I had bought this bass for nearly nothing, so I presume the seller was lowballing the price due to the buzzing. I’m glad I could fix it with just a soldering iron. I’m shocked the factory let the basses out in this condition

 

[UXBASS]

I’m so thankful for this post, 11 years after it began.
 

Recently I bought a thunderbird pro V and had this very problem. I cannot believe the red wire was soldered to ground in the factory! Why didn’t the designers utilise the series/parallel system? 

So I’m looking to go Volume, Volume, Darkglass Tone Capsule to replace the shoddy factory preamp. To accolade the three band EQ I will drill out the third traditional pot cavity, use reflector knobs for the top three pots and keep the lower two as black metal. This was the lower two are camouflaged!

I’ve also changed the tuners for lightweight ones to reduce the neck dive.

[UXBASS]

On 3/13/2021 at 5:59 PM, Mcontour said:

Hello again, Folks.

Hey, I'd really really appreciate your help on this....I want to purchase a replacement premap module for this bass.  I called Epiphone directly and they told me that I'd have to go to a dealer and have them order it.  I went to (large) dealer and they tell me that their Gibson/Epiphone support person is not responding to the inquiry....multiple tries over 3 weeks.

I'm at a loss on this....how can I get a replacement preamp?  

Thanks in advance for any support you can provide.....really.

 

Years later, I can tell anyone thinking of upgrading a T-Bird Pro to get a Darkglass Tone Capsule. Running just a blend, no volume, the three EQs allow for incredible tone-shaping. The original two-band EQ is useless garbage by comparison!