ASAT Bass Wiring Question

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Re: ASAT Bass Wiring Question

Postby Ken Baker » Tue Jul 12, 2011 8:05 pm

guitarmakermark wrote:The neck pup measures 2.1k, the bridge pup, a feeble 120 Ohms. Ah say, Ohms, not k-Ohms!


He used, I say, he used a Foghorn Leghorn-ism! :o

The tap test which you so graciously suggested, did not show any difference in signal strength between pole pieces, not even on the weaker of the two pups. The tap test did however confirm the finding of the bridge pup being terribly weak.


That's odd. I would have expected a notable difference, one coil to the other, on the bad pickup. Perhaps if you broke out the four leads and measured DCR across the black & white and red & green. If the coils are parallel-connected, I'm guessing that you'd find one coil at 4200 ohms and the other at about 124 ohms. My algebra skills are a bit rusty, so I had my kid run the numbers. I double-checked them using the "reciprocal of the reciprocal" formula and they agree.

The output wire jacket contains four leads plus braid. On both pups, the black and red wires are connected, outputting to the two pots; the green, white and braid are connected (to ground).

1. Does the internal wiring on these pups appear to be parallel, or series? And,


If I make the assumption that the manufacturer followed industry norms (which should not be considered standards), then the black & white leads connect to either end of one coil and the red & green leads connect to either end of the other coil. Because of the way they're connected to the pot (black and red together as hot and the others to ground), this would indicate parallel-connected coils.

2. How do I positively determine the internal wiring scheme in humbuckers? Lastly,


You'd have to lift the coils out of the covers to positively ID the leads. Based on your pics, it looks like they might be glued into place (that blue colored gunk) so this might be tough or not do-able.

3. Is there any hope for these pups??


If I was doing this for a living, or even as a sideline part time job, I wouldn't throw any more time into them. The only exception would be if the pickups were KNOWN collectibles or you're just after the education. I certainly don't think there's enough value there to make salvage worthwhile.

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Re: ASAT Bass Wiring Question

Postby guitarmakermark » Tue Jul 12, 2011 8:23 pm

Ken,

After having posted my questions, I took another hard look at the hand-drawn circuit PDF you or Fred so kindly posted. Studying the diagram, I answered my own question (Hallelujah!!) about the pups in question being wired parallel or in series....they are indeed parallel.

Regarding the odd findings on the tap test, it is possible that because the audible output is so dang low, the differences betwixt coil outputs was just not that evident. I was not willing to turn my amp up enough to really hear the tapping!

In any event, I think we have reached a logical cornclusion....these pups are toast. I agree with you about the time spent....I'm not about to go cracking into that plastic potting in order to resurrect a cheapazoid pup!

I am going to lobby my customer to spring for a set of decent-quality replacements, because he really likes the light weight and balance of this particular bass, counterfeit or not.

On another note....another customer of mine has dropped off his vintage Gibson Les Paul, in for finish repairs and electronic repairs. His pup problem is that the newer humbucker someone else installed obviously is out-of-phase with the o.e.m. humbucker. Hence, my badgering y'all with endless questions on how to go about discerning the different internal wiring schemes. I now feel prepared to proceeeeed on that Les Paul project.

Thanks, Ken, yer a good egg!

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Re: ASAT Bass Wiring Question

Postby deltafred » Wed Jul 13, 2011 2:47 am

Mark

After seeing the photos I am inclined to agree with Ken that it is an internal short in the low resistance one. They look like 2 out of the same batch so should be pretty much identical resistance wise.

If the neck pickup sounds 'ok' (it is never going to sound like a real MM with bar magnets and mild steel slugs) then you could replace the bridge with a similar copy, the cheap option. Otherwise as you say go for a pair of decent aftermarket MM pickups.

Keep us posted on how you resolve it.

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Re: ASAT Bass Wiring Question

Postby guitarmakermark » Wed Jul 13, 2011 9:46 am

Fellows,

I am still considering soldering a resistor into the hot output lead of this weak pup as a last-ditch effort to strengthen the output.

Do you think this strategy might work, and if so, what value resistor might you recommend I try?

If this is not a viable option, then I shall recommend replacement pups, fer sure!

Thanks!

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Re: ASAT Bass Wiring Question

Postby Ken Baker » Wed Jul 13, 2011 11:33 am

'Scuse me while I create an echo. :mrgreen:

Ken Baker wrote:If I was doing this for a living, or even as a sideline part time job, I wouldn't throw any more time into them. The only exception would be if the pickups were KNOWN collectibles or you're just after the education. I certainly don't think there's enough value there to make salvage worthwhile.


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Re: ASAT Bass Wiring Question

Postby guitarmakermark » Wed Jul 13, 2011 12:01 pm

Ken,

Your echoing point is well-taken! However, the owner of this bass is a dear friend of mine, so I don't mind going the extra mile or two.

So, allow me to echo.....is there a particular value of resistor I might try, oh Echoic One??

Thanks!

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Re: ASAT Bass Wiring Question

Postby Ken Baker » Wed Jul 13, 2011 12:33 pm

I deserved that.

I have no clue. The Guitarnuts guy used 47K, so that's probably as good a place as any to start.

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Re: ASAT Bass Wiring Question

Postby guitarmakermark » Wed Jul 13, 2011 12:51 pm

Ken,

Their discussion presumed, methinks, a pair of healthy pickups. In this case, my gut tells me 47k might not cut it.

I have no hope at all of doing the math to determine the resistance value to function as a crutch for this weak pup. Maybe we should ask Fred??

Fred, are you out of bed yet??

I await your responses with bated breath. In the meantime, you may call me "bait-breath!"

Thanks, fellows!

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Re: ASAT Bass Wiring Question

Postby Ken Baker » Wed Jul 13, 2011 4:24 pm

Not much math involved with this one, Mark. You'd be adding a resistor in series between the hot leads and the volume pot. So you'll have your black & red pickup leads removed from the pot and connected to one lead of the resistor, and the other lead from the resistor goes to the same pot lug previously occupied by the black & red pickup leads.

I don't think I'd try anything bigger than 100K. OTOH, resistors are cheap.

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Re: ASAT Bass Wiring Question

Postby deltafred » Wed Jul 13, 2011 4:42 pm

guitarmakermark wrote:
Fred, are you out of bed yet??

I await your responses with bated breath. In the meantime, you may call me "bait-breath!"

Thanks, fellows!

Mark


Dear Bait-breath

Out of bed, I'm not even in yet, it is 01:30 here and I have just got back from a 10 mile hike with an old college and good friend. #

First thing tomorrow I have to go and drink coffee with my 80 year old next door neighbour, as she puts it 'To check she hasn't died in her sleep'. It is being so positive that keeps her going.

Then I have to clean the house as it is our annual band reunion (the first proper band I was in, late 60s, early 70s). We meet at my place, go out for lunch then back here to see what songs we cannot remember from 40 years ago, laughing all the while.

Anyway back to this pickup problem. I have zero knowledge of pickup loading so try 47k if you have one, or anything you have. Whatever you put in will drop the already low output slightly so may not be usable even if it does overcome the loading issue.

A better option may be to look out for a cheap MM clone pickup. I bought one from the far east about (3 years ago) and it cost me less than $15 including carriage.

Anyway it is time to turn in as my brain is ceasing to function
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