BC Rich booster circuit  [schematic]

Pickups, wiring schemes, switch techniques and onboard active electronics for guitars and basses
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theehman
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Post by theehman »

Anybody have a schematic for the booster circuit found in 80s BC Rich guitars and basses or maybe someone has a BC Rich that can post some pics? Need to build one to replace the missing circuit in my 80s Fernandes Eagle copy.
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Post by blackbunny »

Here's a trace I made in 1979 of a '76 or '77 Mockingbird preamp & vari-tone. It uses an easy to find 2N5088 NPN low noise small signal transistor, and cheap greencaps.

The inductor in the vari-tone was cylindrical and dipped in black resin, and had 1000 stamped on it. I assumed it was 1000mH (= 1 Henry) but I had no way of measuring it at the time.
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BC Rich Mockingbird 1979 trace.jpg

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Post by bamboone »

I own a few golden era BC Rich guitars, but like you I need to build clones of the BCR pcbs for a gutted japanese BCR copy. I am currently on the fence about etching my own pcbs, or ordering some up. Are any group members expert in Eagle layout? I've looked into JLCPCB, but it seems like they'd need Gerber files, and I as of yet have not begun to start learning Eagle. Here are some pics:
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Last edited by bamboone on 29 Dec 2023, 00:22, edited 1 time in total.

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theehman
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Post by theehman »

What's the pcb dimensions? I could design the pcb and order some if you want to split the cost.
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Post by twotees »

Hello Blackbunny, Thanks for the schematic on the BC Rich pre amp. Just one thing, could you please elaborate a little more on how the power supply is connected to the circuit, like where does the +9V sit, where is Ground and where is -9V if it happens to be dual rail supply? Thanks

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Post by theehman »

Just noticed the ruler in the pics. Duh me! I'll work on these tomorrow.
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Post by bamboone »

theehman wrote: 29 Dec 2023, 00:05 What's the pcb dimensions? I could design the pcb and order some if you want to split the cost.
Yes, please. I would like to have extras also, because it does not seem that I'll stop tinkering anytime soon!

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Post by bamboone »

twotees wrote: 29 Dec 2023, 00:58 Hello Blackbunny, Thanks for the schematic on the BC Rich pre amp. Just one thing, could you please elaborate a little more on how the power supply is connected to the circuit, like where does the +9V sit, where is Ground and where is -9V if it happens to be dual rail supply? Thanks
The circuits are positive ground. The positive lead of the battery is connected to the ring connection of the tip/ring/sleeve output jack. Bich guitars and basses have two preamps, and each has it's own 9V battery. You can also find how the preamp board are wired in all BCR harnesses here: https://www.nealmoserguitars.com/store/ ... g+Diagrams
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Post by andregarcia57 »

bamboone wrote: 29 Dec 2023, 05:46
theehman wrote: 29 Dec 2023, 00:05 What's the pcb dimensions? I could design the pcb and order some if you want to split the cost.
Yes, please. I would like to have extras also, because it does not seem that I'll stop tinkering anytime soon!

Can boost be used separately?

https://oshpark.com/projects/1saR5sot/view_design
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Post by bamboone »

andregarcia57 wrote: 29 Dec 2023, 18:00
bamboone wrote: 29 Dec 2023, 05:46
theehman wrote: 29 Dec 2023, 00:05 What's the pcb dimensions? I could design the pcb and order some if you want to split the cost.
Yes, please. I would like to have extras also, because it does not seem that I'll stop tinkering anytime soon!

Can boost be used separately?

https://oshpark.com/projects/1saR5sot/view_design
Yes, the boost can be used separately. Bich guitars have 2 independent boosts (which can even be used simultaneously in series). In fact, although the BCR3 pcb has the capacitors for the varitone, the active part of that board is separate. The varitone is a passive selectable frequency notch filter, and it is not in effect when the rotary switch is turned full ccw.

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Post by bamboone »

andregarcia57, that is a beautiful BCR2 pcb: two-sided, through-hole plated, solder-masked on both sides, and silkscreened with component layout! WAY nicer that the original! Did you also do BCR3?

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Post by bamboone »

Oops, I made a boo-boo! The 1K resistors should be 10K.

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Post by theehman »

Can you recheck the varitone cap values on the BCR3? I sent you an email about it but maybe you didn't get it.
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Post by andregarcia57 »

bamboone wrote: 30 Dec 2023, 19:12 andregarcia57, that is a beautiful BCR2 pcb: two-sided, through-hole plated, solder-masked on both sides, and silkscreened with component layout! WAY nicer that the original! Did you also do BCR3?

https://oshpark.com/shared_projects/XGPtylDo
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Post by bamboone »

theehman wrote: 03 Jan 2024, 15:50 Can you recheck the varitone cap values on the BCR3? I sent you an email about it but maybe you didn't get it.
Yep. Big to little: .1uF, .05uF (in parallel for .15uF), .04uF, .04uF (in parallel for .08uF), .04uF, .02uF, .005uF

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Post by bamboone »

theehman wrote: 13 Mar 2020, 18:14 Anybody have a schematic for the booster circuit found in 80s BC Rich guitars and basses or maybe someone has a BC Rich that can post some pics? Need to build one to replace the missing circuit in my 80s Fernandes Eagle copy.
Btw, I also have a couple Fernandes BC Rich copy basses. I had already swapped out the guts of the Mockingbird one for genuine BCR stuff. The stock Fernandes harness you see here. Fernandes used negative ground (instead of pos like BCR), and although the varitone caps are soldered directly to the rotary switch, in circuit it is wired passively off the tone pot, just like BCR. The varitone caps are .15uF, .068uF, .039uF, .022uF, and .01uF (don't forget, this was in a bass). I do not yet have a value for the hand-wound inductor, because neither of my Fluke meters had inductance. For that matter, I have been so far unable to source the BCR type inductor, and I don't yet have any real idea of its value. I've ordered an LCR meter, so maybe I'll have those numbers in about a week. As for the Fernandes PCB: red is V+, black is gnd, white is input, green is output. I have another BCR harness to put in my Fernandes Warlock bass, so I'll take some pics of its stock harness to compare...
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Post by bamboone »

theehman wrote: 03 Jan 2024, 15:50 Can you recheck the varitone cap values on the BCR3? I sent you an email about it but maybe you didn't get it.
I think I inadvertently led you astray! The BCR3 board pics I previously posted (with scale) are from a BCR bass! It is the one that I'll be putting in the Fernandes Warlock bass. Here are pictures of the guitar BCR3 board (this is the one I was telling you the values of the caps).
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Post by bamboone »

andregarcia57 wrote: 03 Jan 2024, 17:47
bamboone wrote: 30 Dec 2023, 19:12 andregarcia57, that is a beautiful BCR2 pcb: two-sided, through-hole plated, solder-masked on both sides, and silkscreened with component layout! WAY nicer that the original! Did you also do BCR3?

https://oshpark.com/shared_projects/XGPtylDo
Magnificent! The 1K resistor on this board (and the other one) should be 10K (my bad: sorry!). Also the resistor you have marked 200 ohms is actually 220 ohms. Other than that, stupendous!

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Post by theehman »

Great pics of the Fernandes circuit! What's the size of the PCB and the values of the 2 smaller caps?
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