PYE Compressor/Limiter Thread *boards shipping* BOM up!

[maxwall]

I'll have to read thru that cascaded pi filter a few times.......
Makes sense now , however , can this filter only be achieved with an inductor , is there a more modern alternative or is this a design limitation in the way this filter circuit operates ?

 

[Ilya]

Also , very painful to find 150uf 50v

I'm not sure about this particular design, but nowhere in the original PYE such high voltages are found. I suppose anything in the 25-35V range should be fine.

As for the SMT adapter, this is probably the only way to go given that a lot of through-hole components are obsolete now.

 

[ruffrecords]

I'll have to read thru that cascaded pi filter a few times.......
Makes sense now , however , can this filter only be achieved with an inductor , is there a more modern alternative or is this a design limitation in the way this filter circuit operates ?

It is the most cost effective answer even today. There is probably one in every cellphone.

Cheers

Ian

 

[Quantum J Audio]

Would be nice to have a toroid or pot core inductor specified for the osc board as a alternative to the TLC555 chip to keep the design as close to original. Ex: wire # , core part number description (ferrite or permalloy) and wire turns starting point are unknown leaving TLC555 chip the only option , the cost on the chip is reasonable though. Should'nt be to hard to experiment with toroid cores and windings to get close. The one pictured ( T3 80uh ) is a small one for the oscillator board. Not sure if 80uh is accurate though. Time to gather some cores and wire for some experiments. It looks as if its a easy wind at around 3-4 turns.

If you are using the self wound oscillator check this post. https://groupdiy.com/threads/pye-compressor-limiter-thread-boards-shipping-bom-up.43351/post-1062245

 

[maxwall]

If you are using the self wound oscillator check this post. https://groupdiy.com/threads/pye-compressor-limiter-thread-boards-shipping-bom-up.43351/post-1062245

How far did you get with the oscillator board inductor and did you still use a low hfe 2N4124 transistor successfully ? Also , regarding the inductor based osc plug in board , the base leg of 2N4124 is very close to the negative side (cathode) of D15 1N4148 diode , which looks to be a sensitive area on the pcb for a accidental solder bridge - as you indicated, not sure.





This oscillator inductor appears to have two windings on a single toroid core , this can be seen on the schematic (below) showing footprint 1 thru 4. T3 Pins 1-2 (coil 1) and T3 Pins 3-4 (coil 2). The T3 3-4 coils appear to have ~ 3 windings, while T3 1-2 coil appears to have ~5 windings. Question now, are both windings at 80uh, doubt it. My guess , Pins 1-2 have to be higher uh, while pin 3-4 are lower uh value. If I had to guess, the windings at T3 pin 1 & 2 are probably at 80uf and the other at a lower uf value. DCR on these coils looks to be very low 1-5 ohms or even less. The key to this inductor is finding the correct ( small ) toriod core ( red colored or T60-2 ? ) and also the wire gauge used. Finding the correct inductances will take some trial and error ( inductance calculator, LCR Meter, frequency measuring device , scope, dmm ) to get to a stable oscillator at 250khz freq. Incidentally, as a starting point , the wire gauge for T3, for both windings, looks similar in size to the leads on a 1/4w resistor - pictured below.

Q : What is the purpose of coil 3 & 4 on the emitter of VT12/TR12 , tame potential unfavorable trasnsitor behavior ?




Note : VT12/TR12 BSY95a/2N4124 ( Collector ) pin3 , Toroid pin1 - 250khz freq test point , this is taken off the A/C PI 3141 oscillator sub board ( trace side pictured above ) using the T3 inductor, assuming this is also the same test point for other oscillator board running the TLC555 8 pin timer chip. MR2 IS44 or 1N4148 diode in parallel seams to help block any spiked energy from coil T3 pins 1 & 2.





Just tryin to get more info flowing on this project, as it is pretty slim already. Depending on the approach you take , inductors over chips, I don't think this is a easy project for most part. Nevertheless, I like taking the approach that gets me as close to the real circuit as possible.