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Infiner

Thunderbird Pro Wiring Diagram

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I searched far and wide for these schematics due to the humming problem, note these schematics only apply to the Epiphone Thunderbird Pro IV and V. I re-wired it exactly as outlined in the following steps.

 

1. The Bass and Treble potentiometers were not grounded at the factory, they should be grounded in series to the volume pot. This is shown in the schematic wiring diagram attached.

 

2. Both of the T-Pro pickups have an extra red wire on them that should be wired to the battery red cable, as they are indeed active pickups. (I suspect based on Duncan Basslines)

 

3. Remove the pickup grounds from the blend pot, solder them to a black cable, cover with shrink tubing, and solder the cable to the volume pot.

 

Notes:

The volume has a 103 (.1uf) capacitor for treble bleed.

The preamp is too big to add another battery in the compartment unless some wood is removed.

There is room for another control pot but a hole needs to be drilled, carefully with a sharp bit.

 

 

 

Here is the wiring diagram for the Epiphone Thunderbird Pro:

post-29984-055017800 1295891969_thumb.jpg

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The preamp bears very close resemblance to the Duncan Designed BEQ-2, as a matter of fact, they might be the same, just thought I would mention that if anyone searches. I did a search for BEQ-2 and some guy is selling one, I look extremely close at the picture several times and try to make out the lettering. I look closer and see that it says RBA-04m, I found the schematic as a search for RBA04m.

 

post-29984-079304700 1295895648_thumb.jpg

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I found a push/pull schematic ( RBA04p ) that switches between active and passive. It looks to me the red and orange wires are swapped when switching from active to passive, with the orange wire going to ground in passive.

 

The MJ300-NI in the wiring diagram is a stereo Switchcraft type jack.

post-29984-079692500 1295895912_thumb.jpg

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What I've done so far:

 

1. I soldered the red T-Pro pickup wires into the main red battery wire along with the preamp brown wire, and hum gone.

 

2. I removed the plastic output jack that comes stock and soldered in a 3-prong Switchcraft jack in it's place.

 

Tip: Signal, Middle: -Battery (Black), Ring: Ground

 

3. I tried the parallel 18v battery mod, which didn't increase volume or affect the scratchy blend pot as I hoped it would. The additional battery did not fit along with the preamp in the control cavity, causing the cover to bulge, which over time will permanently warp. If I remove some wood from between the jack area and the extra blank pot area the battery will fit, but also it will remove some shielding paint.

 

The parallel 18v battery mod:

I disconnected the red T-Pro pickup wires from the main battery and added another battery. I soldered both pickup wires directly to the red wire on the new battery, then soldered the black wire directly to the middle of the jack, where the other battery connects. The preamp brown wire going directly to the old battery as it did stock. This runs the batteries in a Parallel configuration as opposed to the standard serial battery configuration that is normally done. This Parallel mode allows more current (not voltage) to be available to each circuit simultaneously. (see http://en.wikipedia.org/wiki/Series_and_parallel_circuits ) This improved headroom and dynamics of the pickups, but did not increase volume or fix the scratchiness of the blend pot.

 

What I'm trying next:

 

1. For the scratchy blend pot: First write down what wires are located where on the blend pot, be as detailed as possible. Remove the blend pot, and de-solder all connections. Spray with contact cleaner and move the wiper around a bit until it feels clean. Set the blend pot aside for now.

 

We are going to need to solder a black ground wire to the pickup grounds, cover the exposed wire with shrink tube, and then solder the pickup ground wire to the main volume ground, they are not going back on the blend pot.

 

 

Rewire the pot, but do not put the pickup grounds or any other grounds on the blend pot, with the exception of the grounded wire coming from the preamp and going across diagonally. Trying a washer ground instead or no ground at all to the blend pot other than the one that goes to the leads.

 

Here's a nice tutorial on cleaning pots: http://www.michaelshell.org/gadgetsandfixes/fixingscratchypots.html

 

If that doesn't work, time for a new blend pot.

 

2. For the low volume: This might be fixed by placing the grounds to the pickups onto the volume pot instead of the blend pot. Replacing the main volume pot with higher values from 50k to 250k may increase volume with the preamp installed. I came to this conclusion after looking at many active bass schematics which said a 250k pot will increase volume by about 6 decibels. I find this value a little strange for active pickups, the preamp must be affecting volume somehow. Since I only have 500k pots available I'm going to try that. My chicken scratch math tells me this could make it put out 12db, but we will see.

 

3. For the extra Battery: Removing some wood to make room for second battery. Will need a small saw or hack saw blade. Also should repaint shielding paint over cut.

 

4. If none of the above works, remove the preamp and wire them like standard bass actives, will need 25k or 50k or 100k pots for this. Four controls: two volumes, a main tone, and a tone circuit bypass would be my choice here. Not a complete cutoff switch that would be wicked on speakers and amps, a tone circuit bypass eliminates the tone circuit completely, like wiring the pickups straight to the jack and ignoring any pots.

 

5. Funds and time permitting, EMG Thunderbird Pickups with something like a BQS eq system. The Thunderbird Pro can accommodate 5 control pots, although one hole needs to be drilled, carefully with a router and a good bit. This would be the most wicked and ideal situation but they aren't even out yet, and well... expensive!

 

 

On second thought, I think I'm just going to chuck the preamp, forget cutting wood, and wire them like standard actives, with two batteries. The only minus I can see here is I will need a pickup selector or a blend.

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2. Both of the T-Pro pickups have an extra red wire on them that should be wired to the battery red cable, as they are indeed active pickups. (I suspect based on Duncan Basslines)

 

Hi there!!!

 

Just a question for you... If these red wires (I have already wired them following your advice) are not wired means that the pickups can work as actives or passives? AFAIK an active pickup needs a battery for its pre-amp. If not attached, the pickup would be "in passive mode", isn't it?

 

Working in that mode, a good mod should be adding an on/off switch for pickups/EQ. What do you think?

 

Thanks.

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Hi there!!!

 

Just a question for you... If these red wires (I have already wired them following your advice) are not wired means that the pickups can work as actives or passives? AFAIK an active pickup needs a battery for its pre-amp. If not attached, the pickup would be "in passive mode", isn't it?

 

Working in that mode, a good mod should be adding an on/off switch for pickups/EQ. What do you think?

 

Thanks.

 

Yes that's correct they work in a passive mode, if the red wire was wired to ground, or signal instead of battery, that might remove the hum as well, although they appear to have the capability to switch between active and passive on some other schematics I have, which I can't upload because I have used all my upload space. It is not unusual for bass pickups to switch between active and passive, Bartolini has bass pickups that can do this. The reason they can do this is because the bass string is much larger and generates a stronger magnetic flux than a guitar string is capable of.

 

Switching between preamp and direct pickups is a possibility. It is a simple task of connecting the switch between the pickup and volume at the output, and the pickup and the EQ preamp.

 

I just want to make a note that the scratchy fader pot can be replaced with a 3 position switch, like a Les Paul has, a much cheaper alternative to buying another expensive concentric pot from an overpriced online dealer. If you wire the bass like a Les Paul the balance of the pickups can be adjusted by two separate volume knobs. There a tons of schematics for this configuration, although I might try using 25k pots, more like EMG wiring, or Seymour Duncan Blackout wiring, or if you want to get really weird use the pots from the EQ with the center detents in them for tone pots. It's probably best to wire it like the regular Epiphone Thunderbird, which there are more schematics for anyways.

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which I can't upload because I have used all my upload space.

You can use as many pics as you want if you host them elsewhere (photobucket etc), info on how to do this is in the DIY thread pinned to the top of the Epi Lounge.

 

http://forum.gibson.com/index.php?/topic/51292-the-d0-it-yourself-thread-look-here-for-tech-related-questions/

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Great info, thanks!

 

My only question is why don't they come wired from the factory the way you describe to minimize hum?

 

They actually knew about this problem and offered people a free repair service if you sent it back to the store you bought it from. They would then offer you to trade for a fixed one the store already had, or they would send it back to the manufacturer for you. The trouble is, not many knew about the warranty repair service, so a there are a lot of T-Pros are still out in the wild that have electronics issues. I'm not sure the exact years the T-Pro had these issues, I'm thinking the earlier models when they first came out. So if someone is selling them for a steal, you might know why, because it hasn't been fixed yet. Although it's often cheaper to get a used broken one, and throw in an EMG BQS or Bartolini system, than to buy one new. I won't even get into the neck dive issue, that's been addressed in many articles on the web. Bottom line is, if you want the sound of a T-Bird you are going to have to really want it, and be able to pay for it's flaws. The T-Pro is like the hot chick at the bar, she sounds sweet, but costly to maintain!

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Infiner - I went ahead and linked this thread in the "Do-it-Yourself" Sticky.

You've put a lot of effort into the research. It's in the Guitar Wiring Diagrams

section as a "Stand-Alone" topic.

 

This thread had come up before, but at that stage it seemed to be still in an

experimental/under development point, so I just waited. :rolleyes:

 

Now, others can easily pull it up, comment, etc. Any changes/additions to THIS thread

will automatically be pulled up if clicked on in the DIY, and now this thread won't "get lost".

 

[thumbup]

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You can use as many pics as you want if you host them elsewhere (photobucket etc), info on how to do this is in the DIY thread pinned to the top of the Epi Lounge.

 

http://forum.gibson.com/index.php?/topic/51292-the-d0-it-yourself-thread-look-here-for-tech-related-questions/

 

 

Well I will think about the other schematic later I'm anxiously waiting for some tools from Stewmac. I really should be sleeping, but I'm tracking my package, and no it hasn't moved.

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Infiner - I went ahead and linked this thread in the "Do-it-Yourself" Sticky.

 

[thumbup]

 

 

Thanks much appreciate that, I'm just here to share what I've learned by poking around with my soldering iron, and multimeter. I only hope to save the next person that works on one of these some time, as I spent quite a while scratching my head.

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hi there,

 

is there any new progress in your project? i have a t-bird pro iv too, and i want to fix the humming problem. but i have some questions:

 

- if i solder the 2 red wires from the pickups together with the red one from the battery along with the brown one, whats about the energy consumption of the system?

- does the consumption stop when no cable is plugged in?

- what is the easiest way to fix the humming? did the grounding of the treble and bass potentiometers helped?

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hi there,

 

is there any new progress in your project? i have a t-bird pro iv too, and i want to fix the humming problem. but i have some questions:

 

- if i solder the 2 red wires from the pickups together with the red one from the battery along with the brown one, whats about the energy consumption of the system?

- does the consumption stop when no cable is plugged in?

- what is the easiest way to fix the humming? did the grounding of the treble and bass potentiometers helped?

i have tried solder red ones to battery + and ground literally everything with paying attention not to make any ground loop but it didnt solve my problem with humming :( the hum i get sounds like 50hz, that we have in electric network here in slovakia. does anyone know how to get rid of this?

 

by the way, it sounds to me like its a shielding problem, cuz the hum changes as i am moving, but since there is this "special" shielding paint everywhere, it should be fine. one more thing comes into my mind, that maybe pickup holes arent shielded, so i am considering a brand new shielding of whole t-bird at the moment and dont rely up on the manufacturer..

Edited by tommy87

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it seems that the red wires thing don't work for me, too...All that i get was scrachy balance pot.

did it scratch before you've connected red wires? i dont remember that.. i shielded pickup holes, but didnt have chance to test it well yet, so im courious if it helped or not, but i didnt notice any noise during this concert tour, we will see in the noisy training room

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did it scratch before you've connected red wires? i dont remember that.. i shielded pickup holes, but didnt have chance to test it well yet, so im courious if it helped or not, but i didnt notice any noise during this concert tour, we will see in the noisy training room

I connected all the red wires as you instructed and the buzz got much quieter but I did get a scratchy blend. I disconnected them again and the buzz came back and the scratch went.

 

So I can confirm that the scratchyness in the blend pot did go away when I disconnected the red pickup wires again.

 

A ground wire between the bass, treb, an volume had no effect for me.

 

Found these Aguiler wiring diagrams, one of which (page 1) looks just like my wiring EXCEPT there is no ground connection between the volume and blend. Maybe that's our problem? I'll cut mine and see if that works.

 

http://www.aguilaramp.com/pdf/support_wiring_obp2.pdf

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ok, so while we left pickups passive, there is no problem with scratchy blend pot. but this annoying noise is there in both cases, even with everything grounded, what i've tried. when the trebble pot is lowered to minimum, the noise is gone too. so the last thing that comes to my mind is to make the guitar, for this purpose, passive, so bypass whole electronics and battery circuit. i'm pretty courious if it will be humming even with this diagram too. if yes, then it's pickups where is the problem, if not, the electronics is noisy, so change will be the best way..

 

edit: yesterday i tried to bypass the electronics and my bass remained deadly quiet after that. So the verdict sounds that we've got s shity electronics in there. im gonna order some new parts and completely rebuild my t-bird to passive, i didnt like so much trebble and bass after some time anyway. what i want is to make 1x volume pot, 1x balance pot and 2x tone pot, for each pickup separatelly. there is option to buy one push/pull pot and make it switchable between power supplied and non-power supplied pickups. so this is my next job as soon as my next sallary will come :P

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Quiet!!! Finally!!!

 

Disconnecting the ground from the blend did NOT work. But I noticed that the red signal wire and the brown power wire were wrapped together!?! Anyone should know that you always keep signal and power separate! I separated them and moved the power around away from the signal wire and my hum is completely gone!

 

So what I have at the moment:

 

I have put everything back to the way it was when I bought it

The red pickup wires are not connected to anything.

There are no new ground wires run anywhere.

I separated the brown and red preamp wires (just cut the black wrap) and moved them away from eachother.

 

Hum GONE!!!

 

To those others who have solved this issue by re-soldering and fiddling around, did you separate those wires as well?

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I own a Thunderbird PRO-V (NO) aswell and found the hum unbearable. Even though I didn't try any of the mentioned methods, I found the solution by accident when I touched the potentiometers without the caps on, and found out that only when touching specific ones (volume and treble) the hum goes away, then I tried connecting those with a metal object (without me touching the object ofc.) and voila the hum was still gone. Then I just attached a new wire inside. [tongue]

 

I soldered a new wire on the housing of the treble potentiometer (GND) and the other end to the housing of the volume pot. (GND) Eliminated the HUM entirely, and theres no cracking or whatsoever!!! [thumbup]

 

Just wanted to share my discovery with all you dissatisfied Thunderbird players in hope it works for you too. :)

here's the proof :)

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Hi together,

 

at first thank you for the work you already put in this thread. it helped me very much to investigate the hum-problem.

 

and now - maybe surprise for some of you :)

the T-Pro Pickups are definitely not active! if you make some measurements, you find out very fast that the resistance of the pickup from white wire to screen wire is around 7k, and from white to red 3.5k resp. red to screen around 3.5k.

 

This shows we have a primitive mode selection available (coils in series or parallel). The parallel mode works when you short the white wire and the screen wire as + and use the red wire as - .

 

This also solves the "mystery" with the scratching blend potentiometer. When you connect the red wire to battery, you bring a DC in the circuit. Each potentiometer scratches when you control a signal and also DC is flowing through it. When you ground the red, then you use the pickup in single coil mode, because you short the second coil of the humbucker.

 

I came to this because I started with the hum problem like most here. Some days of investigation brought a clearer sight to principles. Nevertheless, without this thread I wouldn't have had a good starting point.

 

The last two posts show that there a several problems with shielding. None of them worked for me. BTW, it doesn't matter when you have a battery + near a signal line. You have problems when you have AC cable near signal. So I think, both solutions helped by accident.

 

When all is cleaned up with electronics , nevertheless the circuit is still a bit noisy, but not much more then other ones. If you open the highs, you have a pretty shhhh....

 

also the pickups are hmmm - even they are humbuckers.

 

What I did finally: I made them passive, using 2x 500k for volume and 250k for tone combined with .047 C.

Now I have a hole - I guess I will put a switch in it, either to switch the pickups from serial/parallel or the classic way for pickup selection.

 

The sound in passive mode is much more dynamic from my point of view. Direction goes a bit to precision / rickenbacker but darker.

 

To be honest - the bass is a complte shielding problem. I cut the connection between bridge and ground, because I hate when i touch the strings to be shield. This has a simple reason. When you play, you sometimes touch it and sometimes not. When you are in studio, you get this difference and it is more noticeable then a soft but constant hum.

 

I guess, the finish is somehow static. when I rub the back of the neck or the plastic of the pickguard, I get noises.

 

Nevertheless - I like the sound of the bass - even more passive - and every single coil bass is worse relating hum :)

 

Sorry for my English....

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Hello,

 

it is me again with some additional news. After the last change I got relative fast that even with the correct 5-string pickups (NOT the known-as-faulty-ones, at first I had a model with those)) the B-String and also the G-String were thinner as expected. Not very strong, but for me nevertheless a noticeable difference. So I asked me why.

What Pickups are build in ? If you compare to standard five string pickups from Seymour Duncan or EMG with soap bars, you see the 4-string types are 3,5" (89mm) while the 5-string types are 4"(102mm). But our 5-string Thunderbird has 3,5" pickups. Those 3.5 pickups are given with a max string space of around 68mm. That fits - but what does this mean ? The G- and the B-String are at the ends of the bar then. With a 5-string pickup you get a magnetic field of nearly 80mm, that means also the outer strings are lying pretty in the magnetic field, not on the edges.

The question for me is, why uses epiphone such a strange measure for the t-bird pro V string ? The older t-birds have wider pickups, around 96 mm. This could also fit for a five string. But in the newest generation the pickups became smaller instead....... very bad idea.

The other thing is, it seems my pickups are microphonic. The hum is noticable, even in passive mode and too much for humbuckers.

 

Finally I decided to throw them away. The bass itself really has a nice tone. I ordered a set of Seymour Duncan passive 5-String soapbars SSB-5.

At work I have a friend who did the necessary routing for me. It is very very narrow, but it fits. The wood still has 2mm reserve on each side now :)

 

The sound now is complete different of course - even with the old bad original strings the B now is really fat, also the G is not thinner anymore. That is the V-String T-Bird Pro as it should have been from the beginning. Really a pity to make such a weird construction (electronic, pickups) , as the base idea of the t-Bird pro was really great.

Of course no hum anymore. I guess I will try the old active electronics later, but for now I am complete happy with the Seymours in passive mode (2x500k A, 1x250k A, 1x0.047 uF).

 

Best regards

 

Sigi

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