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Author Topic: Pignose 7-100 (2013) schematic and PCB layout  (Read 15639 times)

drgrateful

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Pignose 7-100 (2013) schematic and PCB layout
« on: July 19, 2014, 11:10:48 AM »
I built a web site with the schematic, pcb layout, components list, offboard wiring and Eagle files for a 2013 Pignose 7-100 amp:

https://sites.google.com/site/pignose7100

An Eagle library for the Pignose 7-100 transformers is also included.

The only unknowns, for me, are the values for the driver and input transformers. Does anybody know where suitable replacements can be found (e.g., Mouser parts)?

J M Fahey

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Re: Pignose 7-100 (2013) schematic and PCB layout
« Reply #1 on: July 20, 2014, 06:07:06 AM »
THANKS for posting  :dbtu:

A couple comments on your page:

1) *Please*  label schematic (Lissovoy's or any other)  with parts designations (R1 ... C1 ... etc.)  as your reference to C1 , R2 , etc. is meaningless for us.
It´s you who has the actual PCB  :trouble     ;)

2) just guessing ;) , if you refer to the first cap labelled 10  , yes, a 100pF one there is reasonable as RF filter. So far so good. :)

3) I see an unidentified resistor with the M12 value.
Should mean 0.12M = 120K
If you have a 220K one there, fine, it means they increased bias a bit for the first transistor.
Real world products often have small changes to adapt to different batches or parts or simply they think it sounds/works better this way.

4)
Quote
the marking for C8 is "104" (thus describing a 100nF ceramic capacitor), the actual capacitor soldered to my board is marked "224", and thus it is a 220pF ceramic capacitor.
You mean 220nF = 0.22uF  .

5) those transformers *used* to be easily available in the "big"  catalog sales Companies ..... in the early 70's  :( .
Anyone remember Lafayette Radio?   :(
http://en.wikipedia.org/wiki/Lafayette_Radio_Electronics

Then they became obsolete and could be found for peanuts in large "pick 5 for 1 $"  surplus/obsolete parts in Electronics shops.
The kind you actually drive to and walk in .
Yes, there was such a kind ... long ago.

Nowadays they are most certainly OEM custom wound.

Won´t ask you to sacrifice yours  :o  but only certain way to find out is disassemble them, count wire turns, measure wire diameters with a caliper, measure EI laminations dimensions, thickness, stack width, etc. and clone them.

6) by the way the legend says that the first Pignose was just that, a preassembled Lafayette Radio "transistor amp" module, go figure.

It certainly looks like one ;)

Mouser? ... they won´t know what you are talking about  :(

drgrateful

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Re: Pignose 7-100 (2013) schematic and PCB layout
« Reply #2 on: July 22, 2014, 03:53:23 AM »
Thank you for your detailed comments!  :tu:

*Please*  label schematic (Lissovoy's or any other)  with parts designations (R1 ... C1 ... etc.)
OK, I added labels to the Lissovoy schematics. Now that schematic is labeled consistently with the other ones on the web site. I labeled components and also the pads for offboard wiring.

You mean 220nF = 0.22uF  .
Ooops: OK, corrected.

5) those transformers *used* to be easily available in the "big"  catalog sales Companies ..... in the early 70's  :( .
Anyone remember Lafayette Radio?   :(
http://en.wikipedia.org/wiki/Lafayette_Radio_Electronics

Then they became obsolete and could be found for peanuts in large "pick 5 for 1 $"  surplus/obsolete parts in Electronics shops.
The kind you actually drive to and walk in .
Yes, there was such a kind ... long ago.

Nowadays they are most certainly OEM custom wound.
I can't believe there are no online sources where transformers of this kind can still be found... I think the best approach here would be to experiment with different transformers that *might* be suitable (however, I need suggestions on what might be suitable).

legend says that the first Pignose was just that, a preassembled Lafayette Radio "transistor amp" module, go figure.
There are many old transistor radios on ebay. They are not expensive, so this might be a way to go. However, again, I would need suggestions on which old transistor radios might contain transformers I could experiment with. I added to the web site http://sites.google.com/site/pignose7100 pictures that maybe can help give suggestions.

Roly

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Re: Pignose 7-100 (2013) schematic and PCB layout
« Reply #3 on: July 22, 2014, 01:48:10 PM »
After I came on this thread the other night my curiosity got tweeked, I love an "intractable" problem - "you can't do that" has always been a red flag to me,  :trouble  so I went for a screen-shop.

My premise with the Lamington is that you can wish for whatever transformer you like, but if you aren't going to wind it yourself (and in a past life I did) then you have to start with what is.

For reasons that escape me, the tiny trannies used for this style of two transformer amplifier in small transistor radios in the 60's are still available for several suppliers.  Maybe somebody has a container load left over, but while they are for the right type of amp they are for a much lower power, maybe a watt at most, so what else?

Well I found some interesting looking 600 ohm to 150+150 ohm telecommunications transformers, and cheep cheep.  A bit short on turns ratio but lots of meat in the core.

When in doubt - cheat.  So I'm looking in the only reference that I have (Transistor Circuit Design, TI, 1963) that covers this circuit topology in any detail.

A couple of wild guesses are that it will be about 2k5 to 2x 150 ohms for the driver, and 1k2 collector-to-collector to 8 ohms for the output.
If you say theory and practice don't agree you haven't applied enough theory.

J M Fahey

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Re: Pignose 7-100 (2013) schematic and PCB layout
« Reply #4 on: July 22, 2014, 06:32:59 PM »
Problem is that typical "transistor radio" trasformer sets , are from 150mW to 250 mW, because that´s enough and higher power would needlessly drain batteries quick.
These were made by the millions and if any surplus is available will be certainly this kind.

A "table radio" might have a 500mW to 1W one but I doubt any of these survived.

"Small PA"  amp type, say 2 to 5W tops, were as rare as hen´s teeth way back then and unobtainable from, say, early 80´s on.

So you probably will be able to build a 200/300mW 9V battery powered amp but I very much doubt you will be able to buy transformers for a 2W to 5W one.