Barcus-Berry Standard Pre-Amp Model 1330-1  [schematic]

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
Manfred
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Post by Manfred »

Only thing valuable about this now is the dimensions which are ~13mm long and ~7mm diameter.
Inductors with ferrite core in the millihenry range are available in this size.
ihd-239901.pdf
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I'll be running a simulation over the next few days.

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Post by soulsonic »

I recently bought a 1330 that isn't working and I conveniently have to dissect and repair. But mine is a different version than this which uses an opamp. Wonder if any of the circuit is similar? There are several deliberately obscured components.

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Post by turbofeedus »

soulsonic wrote:I recently bought a 1330 that isn't working and I conveniently have to dissect and repair. But mine is a different version than this which uses an opamp. Wonder if any of the circuit is similar? There are several deliberately obscured components.
Yeah I've seen a couple schematics for Barcus-berry products, but none for this one (1330-1). Does yours have the inductor?

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Post by soulsonic »

turbofeedus wrote:
soulsonic wrote:I recently bought a 1330 that isn't working and I conveniently have to dissect and repair. But mine is a different version than this which uses an opamp. Wonder if any of the circuit is similar? There are several deliberately obscured components.
Yeah I've seen a couple schematics for Barcus-berry products, but none for this one (1330-1). Does yours have the inductor?
Judging from your board pic, mine appears to have TWO! Need to dig in and see what the mystery parts are...

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Post by soulsonic »

The schematic found HERE appears to match my unit. But, surprise, the values of the two inductors are "?" :lol:

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Post by turbofeedus »

soulsonic wrote:The schematic found HERE appears to match my unit. But, surprise, the values of the two inductors are "?" :lol:

Figures :roll:
Is it possible to measure the inductor in yours?

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Post by soulsonic »

turbofeedus wrote:Is it possible to measure the inductor in yours?
Quite possible... :lol: :lol: :lol:

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Post by turbofeedus »

soulsonic wrote:
turbofeedus wrote:Is it possible to measure the inductor in yours?
Quite possible... :lol: :lol: :lol:
Cool, hopefully yours is continuous, unlike mine :?

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Post by Manfred »

I ran a simulation but I cannot get expected results.
I have replaced the ITS30326 transistor with another JFET without knowing the data from this one, I could not find a datasheet anywhere.
Maybe a crazy idea, please measure the part with your RCL meter in the capacitance range, maybe it is a capacitor.

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Post by turbofeedus »

Manfred wrote:I ran a simulation but I cannot get expected results.
I have replaced the ITS30326 transistor with another JFET without knowing the data from this one, I could not find a datasheet anywhere.
Maybe a crazy idea, please measure the part with your RCL meter in the capacitance range, maybe it is a capacitor.
Measures around 20pf, surely that can't be it. Must be just some capacitance happening between the broken ends of the coil, or something residual in the meter.

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Post by Manfred »

Measures around 20pf, surely that can't be it. Must be just some capacitance happening between the broken ends of the coil, or something residual in the meter.
Thanks for the measurement now it is clear that it is an inductance.
The circuitry of the low pass filter of Soulsonic's device is different but if we know the values, we can deduce the bass filter range.
BarcusBerryStdPerOpAmpVersion.jpg

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Post by Axldeziak »

Any of this info help?
manual-pg1.jpg
manual-pg2.jpg

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Post by soulsonic »

Well, now that I'm looking closely at it, I can say that mine doesn't exactly match that schematic, though generally it's close...
should have it finished up later today.

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Post by soulsonic »

Well... my Atlas LCR40 says they're 1.5K resistors... :lol:

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Post by soulsonic »

And where the tone controls connect back to inverting input of the opamp, it's at the junction of the 1uF cap and the 10K to ground, making a parallel connection to that 10K; not connected directly to pin 2.
So do these being resistors make more sense now? Starting to make sense to me, especially the bass cut from it being fully counterclockwise, putting 1.5K to ground after that tiny output cap. :lol:

I have another meter around here somewhere that can read inductance directly without the LCR's brain trying to "guess" its an inductor. I'll try to dig that up and see if it gives any meaningful inductance reading.

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Post by Manfred »

soulsonic wrote:Well... my Atlas LCR40 says they're 1.5K resistors... :lol:
Have you measured the coils incircuit?
I have the LCR45 I think it is similar to the LCR40,
sometimes does not recognize the component type correctly incircuit.

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Post by soulsonic »

Manfred wrote:
soulsonic wrote:Well... my Atlas LCR40 says they're 1.5K resistors... :lol:
Have you measured the coils incircuit?
I have the LCR45 I think it is similar to the LCR40,
sometimes does not recognize the component type correctly incircuit.
They were desoldered out of circuit.

I tried the other meter, and it says they have a resistance of around 1.5K...and an inductance of over 4H! :lol:
My guess is they are maybe outside the range of what the LCR can guess? Anyway, it seems they are indeed inductors after all, and fairly high value. One measured around 4.5H, the other around 4.9H

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Post by soulsonic »

Found another big discrepancy with that other schematic. All the pots are 100K linear taper. That's measured with them desoldered from the board.
The values in that other schematic are something like what you read if they're still on the board, depending how the controls are set. :lol:

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Post by turbofeedus »

Manfred wrote:I ran a simulation but I cannot get expected results.
I have replaced the ITS30326 transistor with another JFET without knowing the data from this one, I could not find a datasheet anywhere.
Maybe a crazy idea, please measure the part with your RCL meter in the capacitance range, maybe it is a capacitor.
Like I said, I have that DCA55. Is there any info I can measure for you to help simulate?

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Post by turbofeedus »

Just found another 1330-1 on ebay and bought it, hopefully this one has a working inductor that I can measure.
I'd also like to measure the trimpot, hopefully it hasn't been messed with :hmmm:

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