Brunetti Taxi Drive  [traced]

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Brunetti Taxi Drive  [traced]

Postby lars-musik » 25 Jan 2018, 18:39

I finally did it. My first "real" trace. Still, three cap values are missing but I am going to get them sooner or later.
Would you kindly look over the schematic for some obvious beginner's mistake?

TD_Top01.jpg


TD_BOT01_illu.jpg


TD_Top01_illu.jpg


TD.jpg
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Re: Brunetti Taxi Drive

Postby brejna » 25 Jan 2018, 19:51

I've been waiting for this! :)
C2 is missing it is probably cap in pF..
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Re: Brunetti Taxi Drive

Postby lars-musik » 27 Jan 2018, 22:57

After some desoldering here is my final version with all the values.

Could somebody who actually knows some electronics check the schematic on plausibility? Especially the JFET section with the two 1M resistors look unfamiliar to me. Can this be right?
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Re: Brunetti Taxi Drive

Postby alexradium » 28 Jan 2018, 09:48

lars-musik wrote:After some desoldering here is my final version with all the values.

Could somebody who actually knows some electronics check the schematic on plausibility? Especially the JFET section with the two 1M resistors look unfamiliar to me. Can this be right?
C2 should be parallel to the diodes not in series with drive pot,source resistor of the fet could probably be 1k.
In general i see couple things missing,if you post hi res pics of both sides i could tell more.
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Re: Brunetti Taxi Drive

Postby alexradium » 28 Jan 2018, 11:14

yes C2 is parallel to diodes and source resistor is 470 ohm.
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Re: Brunetti Taxi Drive

Postby alexradium » 28 Jan 2018, 11:20

fet output missing c5
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Re: Brunetti Taxi Drive

Postby alexradium » 28 Jan 2018, 11:30

the transistor buffer needs a bias reference
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Re: Brunetti Taxi Drive

Postby lars-musik » 28 Jan 2018, 11:42

Thanks for chiming in!

alexradium wrote:
lars-musik wrote:After some desoldering here is my final version with all the values.

....if you post hi res pics of both sides i could tell more.


Have you seen the pictures in the first post? When you click on them (twice), they are full resolution!
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Re: Brunetti Taxi Drive

Postby alexradium » 28 Jan 2018, 15:46

apart from the 220p cap and 470 ohm source resistor,the rest should be fine,there is some confusion from the numbering of components,recheck that.
Diode missing?
can you desolder it?

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Re: Brunetti Taxi Drive

Postby lars-musik » 29 Jan 2018, 11:14

alexradium wrote:.... and 470 ohm ....


You're right. It is 470 Ohm

alexradium wrote:apart from the 220p cap


Right again!
alexradium wrote:,there is some confusion from the numbering of components,recheck that.


What exactly is confusing you?

alexradium wrote:Diode missing?
can you desolder it?


Yes, there are two diodes not installed that have deisgnators on the silkscreen (D2 and DNC in the last schematic): DNC is jumpered (in the clipping section of the opamp's feedback loop) and D2 is not connected (whatever a diode on the JFET source could be supposed for). I took both of them out of the new schematic.

I measured the forward voltage of the "BA" diode and it measures at 1.15 (the two 1N4148 unsurprisingly measure at .74 and .8V).

So when I find the time I'll try to built a 1590a version to verify it. Unfortunately I am no breadboard guy.

Thanks again, alexradium!

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Re: Brunetti Taxi Drive

Postby alexradium » 29 Jan 2018, 14:32

diode could be ba157/159 which is right,it has a Vf over 1v.
From what i can see from pics,C5 is on the output of the fet,in place of C13,which in reality is the 47nF on top thats related to the gain stage,near the switch.

Another important thing is the voltage on the drain of J201 fet,and on the buffer transistor
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Re: Brunetti Taxi Drive

Postby lars-musik » 29 Jan 2018, 15:34

Hi alexradium,

check your message box please!

And here are the voltages of the two trannies:

PSU: 9.06V
J201: Drain voltage 3.89V


BC337:
Emitter: 1.5V
Base: 2.0V

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Re: Brunetti Taxi Drive

Postby alexradium » 29 Jan 2018, 16:46

ok,i thought you did your own schematic following the actual board numbering,that's why numbers are different.
I can call it verified. :applause:
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