[guitarshark]

Hi,
I've been checking out this site for about a year, but never posted anything before...
There are a few oddities about '76 and '79 T-Birds that I wanted to address.
First of all, every Thunderbird in this series that I've owned (I've owned eight of the beasts since 1980 as well as five '64 reverse IVs, one non reverse IVs, two non reverse IIs, (one of the non reverse 'Birds was factory natural mahogany,looked like the back of a Les Paul gold top) and two Epi Embassies) has had the pickups wired in SERIES instead of parallel as the '60s T-Birds were.
This makes for an incredibly muddy, blaring tone with both pickups on that I find useless. Why Gibson did this I'll never understand.
I suppose it's sacrilege these days, but since I'm skilled with a soldering pencil I rewired the '76 and '79 I currently own in parallel and they sound fantastic!
These basses date to the era when Gibson was using 100K and 300K pots. I took the original pots apart, swapped the tracks for 500K CTS tracks and reassembled them. Also made a big difference.
The other anomaly concerns '79 T Birds only...both of the two '79s I've owned had pickups that read really LOW, in the 3-5 K range Both basses had very loud, normal output. I've also had '70s EBs with mudbuckers that read stupidly low like this, yet had full output. I seem to recall reading a post on here regarding this topic a while back. Someone said that Gibson probably used a heavier gauge magnet wire, this would yield a low impedance but high inductance, hence strong output.
So...if anyone out there thinks they have defective pickups in their '70s Gibson, you probably don't.
Gibson was likely experimenting with this idea to gain some of the advantages of low impedance pickups without the inconvenience of active electronics. In those less sophisticated days, very few (if any) players were measuring their pickups' DC resistance, so there would have been no need to explain or even mention this in any of their literature.

Happy new year,

Bill

[doom]

Yes that is interesting. I have two '76 Thunderbirds and one of them is refinned. When I got it I noticed that when I dialed both volumes up full the bridge pup seemed to overvoice and cancelling out the neck pup making the bass sound very thin. I noticed it had been wired in parallell. Once I rewired in series it sounded like my original Sunburst (in fact better). I thought it was due to the bridge pickup measuring a higher resistance I figured it had higher output thus cancelling out the neck pup. Interesting to see you managed to get a good sound wiring in parallell.

[guitarshark]

It's the other way around...parallel is the more usual way a 2 pickup bass would be wired, i.e., as an example, a bass with two 8K ohm pickups would read 4K with both pickups full on in parallel. In series they'd be 16K ohms, twice the resistance of each pickup, very hot and midrangey.
These '76 and '79 T-Birds came from the factory wired in series, which is unusual. It's really too much for two humbuckers, way over the top. Parallel wiring will be brighter, cleaner, and a more even response.
The neck pickups on these basses read lower that the bridge pickups...my '76 has a 6 K neck pickup and a 10K bridge pickup. It's a similar ratio on my '79, although the overall numbers are lower.
The neck pickups on these usually have a 3 conductor wire and the bridge oickups have a regular Gibson braided lead. With the stock (series) wiring one of the neck pickup's 3 wires goes to one of its volume control's lugs and the other wire goes to a different lug on the same pot.
Naturally, the shield goes to ground.
It's a pretty strange arrangement.
I have a pic of the stock Bicentennial Bird control cavity, not sure how to post it yet, though

[doom]

Since I knew they are supposed to be wired in series I thought the cancelling out came from the pickups being matched for this wiring. I've even seen those who had ca 6.5k neck and 14k bridge pups compared to the new 'birds which I believe is about 9k each.

[guitarshark]

Oh, OK, I see...
I think it's the discrepancy between the bridge and neck pickups that are responsible for your problem. Oddly, my '76 with the 6K neck PU and 10K bridge in parallel sounds quite balanced. 4K is a lot of difference, too. Usually the bridge pickup beig 1K hotter makes for a good balanced pair.
'60s T-Bird pickups are aroud 10K, by the way. They are very different in construction and sound from either the '76 3 screw TB pickups or the T bird + units.

[doom]

Maybe the height adjustment made a difference in my case as well. I don't remember how the pickups were set up at that time.

[jules]

Hi Bill, and welcome!

sounds like you've had some great basses. Do you have any pics you can post to illustrate the wiring differences? I would like to check my '79...

Does anyone know.... how tricky would it be to create a mod that allows you to change from parallel to series? Would be nice to hear the diference instantly without changing any other variable

[guitarshark]

Thanks...yeah, I've had a few nice basses. Had a beautiful '65 EB-3 about 10 years ago that I had no intention of selling, but you know how that goes. (Have a '67 now with the skinny neck and narrow knob spacing but still with the handrest...paid way too much for it, but you how that goes as well, no doubt!)
Interesting story about '76 'Birds...they were available until mid 1981 at a local store, I think they were ordering them from a distributor that still had them in stock. So even at a time when the '79s were discontinued, I was buying MOS '76s in sunburst or black for $500.00! I bought 3 this way...don't have any of them anymore, though.

Back to the T Bird parallel/series thing, I guess a switch coud be installed to do that, but it would have to be a pull pot to avoid drilling a hole in the bass. I think it's need to be a double or possibly triple pole switch to accomplish this. Personally, I'd never use the series mode anyway, as I mentioned before, I found it to be pretty useless.
The pic I have of the stock T bird wiring isn't from mine, I lifted it from ebay. I can take a pic of the parallel wiring as I have it now, no problem.
Bill

Stock '76 Thunderbird wiring (pickups in series)


Modified '76 Thunderbird wiring (pickups in parallel)

[jules]

My '79 is in series too. I've examined just two 1990s thunderbird control cavities, and both had the parallel wiring.

I wonder what was so special about the 70s ones.

Anyone looked at an Epiphone or an Orville?

[guitarshark]

I think the series wiring was something Gibson was experimenting with in the '70s. Rippers have series/parallel switching, for example.
The '70s T Bird pickups are odd beasts as far as design goes too, I've head them referred to as a "sidewinder' humbucker, never took the covers off one, so I'm not sure exactly what that means. The design of the pickups might be why Gibson wired them in series, although, as I've said, to my ears they're way too hot in series. By the way, do the pickups read low DC resistance in your '79 Bird?

I would bet that the Epis are wired in parallel. Never played an Orville or even seen one in person.