Benedetto B-6 rebuild.

[Brock Little]

I sold a pickup to a guy a couple of weeks ago, and it didn't survive shipping, arriving with a dead coil. I refunded the amount, and he was happy enough to send it back to me, so I could autopsy it. The guy was a lot more understanding than I would have been, in the same situation. Cheers, Sam!

The Benedetto B-6 is a fully sealed pickup, so I feel lucky to have been able to save the coils. Sorry, I didn't get a wire gauge measurement. The pickup had a few issues with connections: one hookup wire was just touching the coil wire, and one of the hookup wires was hanging by a thread at the bend. The solder for the earth wire to the shielding didn't hold, but shielding contact shouldn't have been a problem.

I've attached some pics with a few dimensions, for those who are interested. If there's any numbers you'd like, just let me know, and I'll see what I can learn before reassembly (sorry, no gauss meter). Coils measured 6.1kΩ each.

A couple of things that stood out were the bevels on the bass side of the poles (1.3mm at the end), the magnet was polished only on one side (function or quality control?), and the epoxy on the top was really thick (about 5mm). Benedetto doesn't seem to specify options for left or right handed pickups, so the bevels could be an issue for some.

I switched the wiring to 4 + ground instead of the original 3 wire, and made a new case for it out of some spare acrylic. I'm of two minds whether to fully polish the case, or leave it with the brushed finish. Also whether or not to seal it in epoxy again.

B

[Brock Little]

Moar pics.

[S a m]

Outstanding work there, Brock. You have the patience of a monk!

I suspect that the thick epoxy "cap" on this pickup is a sonic choice -- Duncan and Benedetto want to make sure that players leave physical space between the coils and strings in order to achieve the manufacturers' desired tonality.

It's a great-sounding pickup: Dark but not muddy, with perfect balance between the wound G and unwound B. I'm really glad to have it.

I'm sorry that our deal didn't work out. Thank you for making what would often be an awkward situation into something easy, and thanks again for what looks like hours of work chipping away at that broken B6 for the benefit of everyone who is viewing.

[Brock Little]

The man himself! Thanks, Sam. Not so much 'hours of patience' as a dremel with a rotary burr and a couple of small chisels. The wax potting helps the epoxy come away in most places. Welcome to the forum

B

[jack briggs]

Interesting to see such wide pole pieces. I imagine the inductance is really high. Did you measure that by chance?


cheers,

[big_teee]

I just read this on google.
I also wonder what the pole material is?

B-6 (6-string)
Magnet * Alnico V Bar
Cable * 4-Conductor shielded. Allows multiple wiring options.
DC resistance * 12.10 K Ohms
Inductance * 7.10 H
Resonant Frequency *
Series - 4.29 KHz
Split - 7.93 KHz
Body Measurements * 2.74 x 1.49 x .70"
Centers of Mounting Legs - 3.062"

[Brock Little]

Interesting to see such wide pole pieces. I imagine the inductance is really high. Did you measure that by chance?


cheers,

I don't have anything to measure Henries, except for me... It is quite a dark pickup as standard, but I'll see how it goes after being stripped.

B

[Brock Little]

I just read this on google.
I also wonder what the pole material is?
"

Looks to be steel poles. Can't tell if the tiniest spots are rust, or just left over muck. I doubt they're stainless. The baseplate/ring looks to be nickel, and not just plated.

B

[jack briggs]

I just read this on google.
I also wonder what the pole material is?

B-6 (6-string)
Magnet * Alnico V Bar
Cable * 4-Conductor shielded. Allows multiple wiring options.
DC resistance * 12.10 K Ohms
Inductance * 7.10 H
Resonant Frequency *
Series - 4.29 KHz
Split - 7.93 KHz
Body Measurements * 2.74 x 1.49 x .70"
Centers of Mounting Legs - 3.062"

yeah - that's about what I'd think. 7.1H is pretty high for a HB, even with 12.1K res.
thanks for that, Terry!

cheers,

[salvarsan]

That's outstanding work, Brock, and we're glad to have you here.

How'd you make the acrylic cover?

-drh

[edit] -- I've chipped epoxy from a circuit board or two. A heat gun or hair dryer softens it, makes it easier to work with.

[madzub]

so it's almost completely wrapped in copper foil? I guess that would have an effect like a nickel silver cover, some eddy currents to tame the highs, as jazz players appreciate.

[salvarsan]

The B-6, in my estimation ...

Brock documented the B-6 so well that I estimated the coil specs.

From the images the bobbin core dimensions are
length,height, thickness = 57.0, 6.35, 4.64 mm

[correction] bobbin height shown at 7.7mm suggests a 6.35mm/0.25" core height

The bobbin core spec is
2.24" length, 0.183" width, 0.25 height, 0.7" flange.

Nearest English unit dimensions for the bobbin core are:
2-1/4" length, 3/16" width, 1/4" height.

A single coil DCR is 6050 ohms (thanks, Terry).

Using the increasingly irrelevant Coil Estimator and
assuming a very tight wind,
either a very tight 7900 winds #42 or 6500 winds #43 are plausible.

The higher inductance suggests the higher winds estimate (7900, #42).

Since this is an estimate, pay close attention to my signature below.

-drh

[Brock Little]

Hi Salvarsan. The cover was made from 2.75mm acrylic sheet. Just cut the top roughly to size, then cut a strip to the total circumference. I heated the side strip with a small blow torch for the bends, and glued the ends with CA glue. Sand the top edge flat, and round out the 'hourglassing' at the corners. Rough up the glueing surfaces with 320 grit paper, and glue the cap on. Then it's just a matter of sanding the top back to size, and deciding on the finish. I thought of doing black sides and a cow bone top, but I ran out of bone. I get some nice effects by oxidising bone.

I sealed it in epoxy again, and a temporary wire hookup at the pickup end, until I can get some quick connectors. It sounds very marginally brighter without all the top shielding - kind of like going from mellow to warm. I was quite surprised that it didn't sound at all muddy on the low strings, even under high gain in the neck position. The SD 59 didn't perform this well under these conditions.

B

[S a m]

Brock, man, I'm just knocked out by your pickup mounting "un-rings."

What a brilliant idea! Stolen already and thank you very much!

SAM

[Jason Rodgers]

Interesting to see such wide pole pieces. I imagine the inductance is really high. Did you measure that by chance?


cheers,

Right, those are some serious chunks of steel in the cores. Makes me feel less silly about the fat steel blades I used in my first pickups (which I think ended up in the 5H range). Dark, but the lower windings probably help avoid the muddiness that should be expected. That was my problem: I wound em too hot.