Mystery PCB

GringoAudio · 9th December 2011, 01:17 PM

Hi,
I bought a bunch of PCBs a few years ago with more enthusiasm than actual time to work on them. As a result I have at least one completely mysterious PCB. It was from a group buy likely and it has no identifying markings. One side has traces, one side is almost all ground plane. It is stereo and has one small transistor per channel it looks like. Perhaps a Buffer?? Can you guys help me identify this PCB and provided some stuffing instructions?

I also have a legit P3A PCB I bought from a buddy and have no assembly/stuffing instructions. So if anyone can help me there too. ...and I have some Aleph-X boards I know I have somewhere that I will never use ... someone can have these for postage only if I can find them.

Thanks.

madtecchy · 9th December 2011, 01:38 PM

Hi Gringo.

I dont know what it is but im taking a guess it is not stereo.

Best regards Ian

siliconray · 9th December 2011, 01:44 PM

I also vote its not a stereo

GringoAudio · 06:58 PM

It has four signal connections (2-in and 2-out I am guessing) very close together and despite the irregular layout has two very possibly symmetrical circuits starting with a small signal transistor for each channel. There is a spot for two or four big caps in the middle. One was loaded and not soldered in but I cannot remember the value. I can look when I get home.

Enzo · 10th December 2011, 12:52 AM

I have no idea, but there are possibilities other than "stereo."

For example a couple LEDs on one end shining on a couple phototransistors on the other makes a dual photo-interruptor. SOmething like that is used in limit sensing in equipment or even steering wheels on arcade games.

On the other hand, extensive ground plane like that might suggest low signal levels, such as antenna booster or some sort of preamp thingie.

How about this: the two red circled three-holes hold three-leg voltage regulators. A dual polarity power supply board. That would explain why the top one has the line from the filter cap feeding the center pin while the lower one had the feed to the end pin.

Just a thought.

GringoAudio · 10th December 2011, 05:25 PM

Thanks guys. About 6-8 years and two big concussions between the purchase of this and other PCB boards and I just cannot remember anything about it/them!

mickeymoose · 10th December 2011, 09:33 PM

The 2 big holes on the East (plus the one smaller one next) more than likely are for a DC socket
About the concussions: Stop beating yourself on the head with unmarked pc boards! E

GringoAudio · 10th December 2011, 10:23 PM

A power supply with two regulators makes sense. I will pursue analyzing it from that angle.

As for the concussions... downhill mountain biking is something I have to give up. At 53 I am finally admitting that it is a younger man's game. Thanks.

It would still be nice if someone recognized this exact PCB though!

jitter · 06:40 AM

It seems to me that the designer used square holes in the layout to indicate pin one of the component, a common practice. With that in mind, look at the holes for the four caps in the middle of the pcb and then turn over the pcb to the side with the ground plane. Two of the caps have pin one connected to the plane, the other two do not.
This implies a symmetrical power supply.

Looking at the left of the pcb, I can't help but think this is based around the LM317 and LM337, both of which have adj on pin one, but input and output are swapped. This also seems to be the case in the layout. The adjust pins connect to two of the connectors, perhaps for off-pcb potmeters.

But I might be totally wrong, I have no clue what the three pin part right in the middle on the left is for that connects to both assumed-to-be-regulators...

paulb · 11th December 2011, 03:28 PM

Good guess jitter. The IC is an LT1010, used in an ill-fated attempt to have a supply splitter as part of the design (for use with single-polarity DC wallwarts). However, I found it to be really expensive so can't see it to be of much use.
As it is the board is for use with an AC wallwart or transformer. I made a few copies for general use and gave one to Greg a few years back.
Hey Greg, I can give you the user guide for the P3A as well if you like.

9th December 2011, 01:44 PM	#3
siliconray diyAudio Member Join Date: Sep 2011	I also vote its not a stereo __________________ www.siliconray.com High Quality Audio Enclosures, Amp Kits, Amplifiers, PCB Fab Services Chat with me

11th December 2011, 06:28 AM	#9
jitter diyAudio Member Join Date: Aug 2004 Location: Eindhoven, The Netherlands	It seems to me that the designer used square holes in the layout to indicate pin one of the component, a common practice. With that in mind, look at the holes for the four caps in the middle of the pcb and then turn over the pcb to the side with the ground plane. Two of the caps have pin one connected to the plane, the other two do not. This implies a symmetrical power supply. Looking at the left of the pcb, I can't help but think this is based around the LM317 and LM337, both of which have adj on pin one, but input and output are swapped. This also seems to be the case in the layout. The adjust pins connect to two of the connectors, perhaps for off-pcb potmeters. But I might be totally wrong, I have no clue what the three pin part right in the middle on the left is for that connects to both assumed-to-be-regulators... Last edited by jitter; 11th December 2011 at 06:40 AM.

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9th December 2011, 01:38 PM	#2
madtecchy diyAudio Member Join Date: Dec 2010 Location: wigan	Hi Gringo. I dont know what it is but im taking a guess it is not stereo. Best regards Ian

10th December 2011, 12:52 AM	#5
Enzo diyAudio Member Join Date: Sep 2004 Location: Lansing, Michigan	I have no idea, but there are possibilities other than "stereo." For example a couple LEDs on one end shining on a couple phototransistors on the other makes a dual photo-interruptor. SOmething like that is used in limit sensing in equipment or even steering wheels on arcade games. On the other hand, extensive ground plane like that might suggest low signal levels, such as antenna booster or some sort of preamp thingie. How about this: the two red circled three-holes hold three-leg voltage regulators. A dual polarity power supply board. That would explain why the top one has the line from the filter cap feeding the center pin while the lower one had the feed to the end pin. Just a thought.

10th December 2011, 05:25 PM	#6
GringoAudio diyAudio Member Join Date: Oct 2007	Thanks guys. About 6-8 years and two big concussions between the purchase of this and other PCB boards and I just cannot remember anything about it/them!

10th December 2011, 09:33 PM	#7
mickeymoose diyAudio Member Join Date: Nov 2008	The 2 big holes on the East (plus the one smaller one next) more than likely are for a DC socket About the concussions: Stop beating yourself on the head with unmarked pc boards! E

10th December 2011, 10:23 PM	#8
GringoAudio diyAudio Member Join Date: Oct 2007	A power supply with two regulators makes sense. I will pursue analyzing it from that angle. As for the concussions... downhill mountain biking is something I have to give up. At 53 I am finally admitting that it is a younger man's game. Thanks. It would still be nice if someone recognized this exact PCB though!