16-Bit PSN-ADC-USB, Crystal and Scale Issues

[carlbe...@hotmail.co.uk]

Hello All.

I don't know if anyone can help, but I recently finished building the 16-Bit PSN-ADC-USB and I'm having some trouble adjusting the crystal and Scale.
 
Crystal: In the build_info it says to use a 74HC14 Hex Schmitt-trigger to measure the frequency, which i have done. When adjusting C27 (9-50pf ceramic trimmer) nothing happens, it just jumps from 7.98Mhz to 8.02Mhz regardless if i alter the pot or not. When measuring the frequency without the 74HC14, just measuring pin 14 i get the same.
 
Scale:  When the board is connected to my PC running WinSDR, looking at the ADC counts, providing 10v into pin 1 with the jumper shortened and adjusting Scale, again nothing happens. The ADC counts stay the same.
 
Could i have flashed the wrong Hex data? In the hexfiles i uploaded 'SdrBoot3014_Usb.hex' and using command prompt ran 'dsdr26_usb.hex', both where successful.

I have checked all my solder joints and everything looks good to me. When powering the board for the first time there was no smoke or heating of the IC's.

Also, when tapping the inputs with my finger i see small jumps/spikes on the graph on WinSDR and i have no issue adjusting the Offset.

Thank You.

[Larry Cochrane]

See comments below...

On 4/22/2026 1:34 PM, carlbe...@hotmail.co.uk wrote:
> Hello All.
>
> I don't know if anyone can help, but I recently finished building the 16-Bit PSN-ADC-USB and I'm having some trouble
> adjusting the crystal and Scale.
>

> _Crystal_: In the build_info it says to use a 74HC14 Hex Schmitt-trigger to measure the frequency, which i have done.

> When adjusting C27 (9-50pf ceramic trimmer) nothing happens, it just jumps from 7.98Mhz to 8.02Mhz regardless if i alter
> the pot or not. When measuring the frequency without the 74HC14, just measuring pin 14 i get the same.

You might be overloading the crystal. Adding a FET amplifier/buffer, with low input capacitance, instead of 74HC14
between the crystal and the frequency counter may stabilize things.

>
> _Scale_:  When the board is connected to my PC running WinSDR, looking at the ADC counts, providing 10v into pin 1 with

> the jumper shortened and adjusting Scale, again nothing happens. The ADC counts stay the same.

I ran into this problem now and then when I was producing the board. To fix the problem I would lower the 1 meg resistor
going to the scale pot to around 800k to 900k.

Regards,
Larry Cochrane
Redwood City, PSN

[Carl]

Hi  Larry,

Thank You for your reply.

I will give this ago, I just need to order a  FET amplifier. I'm going to use a MPF102 and will report back here if it worked or not.

On the seismicnet site it shows C52 (68uf) as unpopulated, is this correct?

Thanks Again for the help.

[Larry Cochrane]

Hi Carl,

> I will give this ago, I just need to order a FET amplifier. I'm going to use a MPF102 and will report back here if it
> worked or not.

When you make the measurement be sure to connect the amp/counter to the crystal output driver on the DspPic IC. The
effect of the extra capacitance is less if you use the crystal driver output not the crystal input pins.

>
> On the seismicnet site it shows C52 (68uf) as unpopulated, is this correct?

I'm leaving town for a few days so I don't have time to look this up. What page/document do you see this note on?

-Larry

[Carl]

C52. It was just in the picture (https://www.seismicnet.com/serialatod.html) and i dont see it in the BOM, so i assumed it was not populated.

[Carl]

I have tried different resistors (680k, 750k, 820k, and 910k) and non made any change. During each test i applied 10v into input 1 and had the jumper closed. Adjusting the Scale all the way in each direction made no change.

I also tried the MPF102 to measure the crystal and nothing, i still get the same thing. I removed the ceramic cap to see if it was damaged and it works perfectly. Also, as suggested by Google Gemini removed C28, it though that the capacitance may be to high. It did nothing. 

I'm stumped as what to do next. I don't think any of the IC's are damaged, as adjusting 'Offset' works and when i tap the inputs with my finger i see change on the graph on WinSDR. Also, when i apply 10v the graph shoots up and i get an alarm.

[Carl]

I have rebuilt the board as i thought there might be some broken traces.

And i have been going back an forth with Google Gemini. It thinks that there is an issue with my power, but i don't trust what it says.

Are you able to tell me what the voltages are for (U8)LTC1605 pin 1, 10 and (U7)DG508 pin 12.

Thank You.

[Larry Cochrane]

One thing you need to double check is that you have the right version of the LTC1605. Linear Tech makes 3 versions of
the chip. The LTC1605 has a +-10V input range, the LtC1605-1 has a 0 to 4v range and the -2 has a +-4v range. The board
and software was designed for the the LTC1605 part not the -1 or -2 parts.

On 5/7/2026 12:48 PM, Carl wrote:
> I have rebuilt the board as i thought there might be some broken traces.
> And i have been going back an forth with Google Gemini. It thinks that there is an issue with my power,

You should see a steady +5V and +- ~13 volts from the LM2574 switching regulators.

>but i don't trust what it says.

I'm not sure how AI will help you debug a board that it knows nothing about, but what do I know...

> Are you able to tell me what the voltages are for (U8)LTC1605 pin 1

Don't know. Because of the 200 and 33.2k ohm resistors it will be a somewhat lower then the input voltage.

>Pin 10

This is one of the digital output pins. It is not connected to the DspPic. The cpu only reads the lower 8 bits from the
ADC and toggles the BYTE pin to read the other 8 bits.

and (U7)DG508 pin 12.

This is channel 5 input. If you have nothing connected to channel 5 you should see 0 vdc.

-Larry

[Carl]

Hello, Thank You for your reply.

I rebuild the board and all my voltages are stable, I'm using a 15v power supply.

I still cannot adjust the Scale, nothing happens when i adjust the pot. I have attached a two screen shots of WinSDR showing what happens when i connect 10v and disconnect it. Maybe it helps.

I believe the LCT is the correct one, iv attached a photo hopefully you can see it. 

I gave Gemini the schematics, BOM and build info. So it new what the board was about. It did also mention the variants of the LTC device.

I have been trying the MPF102 but don't see any difference on my scope, i get the same readings. Perhaps i have it set up wrong? I connected my probe to 'Source' pin.

 

[Carl]

Finally successes.

I don't know why it worked but here is what i did. 

Apply 10v to pin 1 before plugging USB into the board, that's it.

I would normally have the board powered and plugged into my PC with WinSDR opened, then apply 10v.

But this time i did it before and now i can adjust the Scale.

Also, i can see and adjust the crystal. This was my error i had gate and source mixed up.

Thank You all for your help and sorry if i was a pain. 

[Larry Cochrane]

Hi Carl,

It looks like you did a good job at building the board. I'm also impressed that Gemini would recommend you check that
you have the right LCT part. From the picture it look like you have the correct ADC version.

Here is a test I suggest you try. Temporarily remove one end of the 200 ohm resistor, the one going to the LF411, from
the PCB. This will remove the LF411 op-amp and DB508 mux chip from the ADC input. Now ground the free end of the 200 ohm
resistor using a clip lead. Startup WinSDR and make sure you have it set to record one channel. You should see a
continuous straight line on the screen with the average ADC count around zero +- a few counts. If you get a straight
line near zero you should be able to use the offset pot to set to zero.

Let me know how this test goes. One more thing. Before the test delete the current winsdr.log file and start the test.
After the test post it here so we can take a look at it. Maybe something in it will help debug the problem.

-Larry

On 5/23/2026 9:34 AM, Carl wrote:
> Hello, Thank You for your reply.
>
> I rebuild the board and all my voltages are stable, I'm using a 15v power supply.
> I still cannot adjust the Scale, nothing happens when i adjust the pot. I have attached a two screen shots of WinSDR
> showing what happens when i connect 10v and disconnect it. Maybe it helps.
> I believe the LCT is the correct one, iv attached a photo hopefully you can see it.
> I gave Gemini the schematics, BOM and build info. So it new what the board was about. It did also mention the variants
> of the LTC device.
> I have been trying the MPF102 but don't see any difference on my scope, i get the same readings. Perhaps i have it set
> up wrong? I connected my probe to 'Source' pin.
>

> 20260523_171057.jpg
>
> 10v Connected.png 10v disconnected.png

[Ted Blank]

Carl, many years ago I spent many months trying to understand why my home built amplifier board wasn’t working. I was trying to get both + and -12 V out of two  6V batteries wired in series center tapped.   Of course you need four batteries in series for that.   It’s a lesson you never forget. 

Ted

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[Jonathan]

Carl,

Was this a blank board? The gerber files that Larry put on his GitHub for this board had the SOIC footprint of the ADC and I believe was serial only. I ordered some from JLC and have been meaning to build them along with SOIC ADCs. 

He changed it because only the SOIC package was available and the DIP was discontinued.

Jonathan

To view this discussion visit https://groups.google.com/d/msgid/psnlist/CAC8W%3Dt2%2B19GP-N2g_ZsPHuCeh9EszUy7PaAokNYQMe5pKKd4cA%40mail.gmail.com.

[John L. Males]

Jonathan,

I am jumping in as I believe an inquiry I made 16 January 2026 via
PSNList is the gerber files Carl used and pictured in recent
post by Carl.

I had inquired about the USB version of the PSN ADC Serial USB
version gerber as there appeared not to be gerber files for on
github files for <https://github.com/lcochrane24/PSN-ADC-SERIAL>.
There is a USB hex file, but no schematic nor gerber files for the
USB version on <https://github.com/lcochrane24/PSN-ADC-SERIAL> as
of this eMail for last github update of 17 March 2021 that is V4.0
2019 board. The LTC1605 of the
<https://github.com/lcochrane24/PSN-ADC-SERIAL> is surface mount as
you noted for the gerber files for serial only, but has the USB
firmware as well. Ergo my inquiry of 16 January
2026.

Larry replied to me 20 January 2026 via PSNList that included link
<https://www.seismicnet.com/software/DspSdrUsb.zip>. This is the
board I believe Carl had made from the gerbers of
<https://www.seismicnet.com/software/DspSdrUsb.zip>. The files of
<https://www.seismicnet.com/software/DspSdrUsb.zip> use the PDIP
version of LTC1605 and are for board Rev4.1 2011. The gerbers are
for 8 channel pin header compatiable with PreAmp
<https://github.com /lcochrane24/4-Channel-AmpFilter>and DB25.
There is no source for firmware of serial/USB is one source file
with define set to create serial or USB firmware.

The files on <https://github.com/lcochrane24/PSN-ADC-SERIAL>
include input for 8 channels pin header that is compatable for use
with PreAmp <https://github.com/lcochrane24/4-Channel-AmpFilter>
and input for 8 channels via DB25 that connect to host system via
serial DB9. These are for V4.0 2019 version of PSN-ADC-SERIAL.

There is no schematic for USB version yet has the USB hex file for
<https://github.com/lcochrane24/PSN-ADC-SERIAL>. Of course the
serial hex file is on
<https://github.com/lcochrane24/PSN-ADC-SERIAL> V4.0 2019 version.

There are no gerber files for the 8 input channel pin header nor
8 channel input DB25 USB versions nor schematic for the USB version
of <https://github.com/lcochrane24/PSN-ADC-SERIAL> V4.0 2019
version.

What the schematic differences and firmware source code differences
of V3.1, V4.0, and V4.1 boards is not known. The .sch files are in
EDA format that Larry no longer has software for to read to create
PDFs of schematics that is normal with closed source software
tools. I had this experience many times over years past which is
why I always use Open Source solutions were possible. I like to
hope there is some software present day that could at least read
the .sch files to create PDF of the schematics. Once have complete
set of schematics that would enable one to create EDA versions of
schematics and then PCB files using Open source EDA like KiCAD or
any other Open Source EDA. The reason for a goal of schematics and
PCB files in Open Source EDA is to enable long term use of not only
the great and robust digitizer hardware design, but the great
software API design that allows these boards to be use with Unix as
well as Windows for very long time despite OS changes most notable
for Windows. This also allows changes to be made as USB interface
standards evolve.


John L. Males
Toronto, Ontario
Canada

2026-05-25 05:58+0000 UTC eMail Start
2026-05-25 07:23+0000 UTC
2026-05-25 03:23-0400 EDT

*****Not GPG/PG Signed*****



On Date: Sun, 24 May 2026 22:17:47 -0400
From: Jonathan <emum...@gmail.com>
To: psn...@googlegroups.com
Subject: Re: [PsnList] 16-Bit PSN-ADC-USB, Crystal and Scale Issues

> >> <https://groups.google.com/d/msgid/psnlist/bd74e94a-24af-4745-812d-1a504484d1c1n%40googlegroups.com?utm_medium=email&utm_source=footer>
> >> .

> >>
> > --
> > You received this message because you are subscribed to the
> > Google Groups "Public Seismic Network Mailing List" group.
> > To unsubscribe from this group and stop receiving emails from
> > it, send an email to psnlist+u...@googlegroups.com.
> > To view this discussion visit

> > https://groups.google.com/d/msgid/psnlist/CAC8W%3Dt2%2B19GP-N2g_ZsPHuCeh9EszUy7PaAokNYQMe5pKKd4cA%40mail.gmail.com
> > <https://groups.google.com/d/msgid/psnlist/CAC8W%3Dt2%2B19GP-N2g_ZsPHuCeh9EszUy7PaAokNYQMe5pKKd4cA%40mail.gmail.com?utm_medium=email&utm_source=footer>
> > .

> >
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[PIMOHDAIMAOH]

I hope he can share the latest updated gerber files for us to try too

To view this discussion visit https://groups.google.com/d/msgid/psnlist/CAOY0kB1qXqF3udu_ZC8kxSC34PH8jHrQ9HiMj2-_eoK2H009nw%40mail.gmail.com.

[John L. Males]

PIMOHDAIMAOH,

I hope since you last posted you have seen my posting that was
about 12 hours after I received you expressing via PSNList sharing
the gerber files Carl used.

I am not sure I would class the board Carl used as "newer"
schematic or "newer" PCB design. I know the board Carl used has
higher revision number. Larry would know the "differences" between
the board revisions are schematic or board beyond one difference is
a 4.x PSN ADC Serial 16 bit board using SMD LTC1605 SSOP. The PDIP
LTC1605 was discontinued from being manufactured related to LTC
"Obsolescence of N28 PDIP package" April 2015 affecting parts that
LTC1605 was one of the affected parts impacted by unable find
alternate manufacturing solution to ageing equipment.



Information Delay of PSNList eMail
==================================

You sent your posting to PSNList about 45 minutes before I started
to compose my last PSNList posting. I have no idea why it took so
long for your last PSNList post to reach my eMail server. My guess
is along the way some delay in sending the eMail of your post from
PSNList outside of Google. The time stamps along way within Google
servers looked just fine then very very long, hours delay in hop on
west coast -0700 time zone that resulted in the over 12 hour delay
of your eMail via PSNList arrived to my eMail. I do not know if
the hours delay was Google trying to send to next hop point
outside Google or Google server sent to first hop point outside
Google after Google was unable to contact the next hop point(s)
outside Google. Hence the about 10 hour delay after I sent my last
posting to PSNList to receiving your PSNList posting made about 45+
minutes before I started my last PSNList posting.

Others on PSNList may or may not of had this hours or less long
delay as the route to their mail servers would not be same server
hop path as needed to send to my mail server.

John L. Males
Toronto, Ontario
Canada

2026-05-26 04:44+0000 UTC eMail Start
2026-05-26 05:41+0000 UTC
2026-05-26 01:41-0400 EDT

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On Date: Mon, 25 May 2026 13:08:10 +0800
From: PIMOHDAIMAOH <pimohd...@gmail.com>

To: psn...@googlegroups.com
Subject: Re: [PsnList] 16-Bit PSN-ADC-USB, Crystal and Scale Issues

> >>> <https://groups.google.com/d/msgid/psnlist/bd74e94a-24af-4745-812d-1a504484d1c1n%40googlegroups.com?utm_medium=email&utm_source=footer>
> >>> .

> >>>
> >> --
> >> You received this message because you are subscribed to the
> >> Google Groups "Public Seismic Network Mailing List" group.
> >> To unsubscribe from this group and stop receiving emails from
> >> it, send an email to psnlist+u...@googlegroups.com.
> >> To view this discussion visit

> >> https://groups.google.com/d/msgid/psnlist/CAC8W%3Dt2%2B19GP-N2g_ZsPHuCeh9EszUy7PaAokNYQMe5pKKd4cA%40mail.gmail.com
> >> <https://groups.google.com/d/msgid/psnlist/CAC8W%3Dt2%2B19GP-N2g_ZsPHuCeh9EszUy7PaAokNYQMe5pKKd4cA%40mail.gmail.com?utm_medium=email&utm_source=footer>
> >> .

> >>
> > --
> > You received this message because you are subscribed to the
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> > To unsubscribe from this group and stop receiving emails from
> > it, send an email to psnlist+u...@googlegroups.com.
> > To view this discussion visit

> > https://groups.google.com/d/msgid/psnlist/CAOY0kB1qXqF3udu_ZC8kxSC34PH8jHrQ9HiMj2-_eoK2H009nw%40mail.gmail.com
> > <https://groups.google.com/d/msgid/psnlist/CAOY0kB1qXqF3udu_ZC8kxSC34PH8jHrQ9HiMj2-_eoK2H009nw%40mail.gmail.com?utm_medium=email&utm_source=footer>
> > .

> >
>
> --
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[Carl]

I downloaded the Gerber files from here, I could not find the USB version on the Seismicnet site 

but found this google group where I found a conversation by John L. Males where Larry had posted the link to the files.

 
I don't know if you read the earlier post but I found that I can adjust the scale only if I apply 10v before connecting the board to my PC, 

if I connect the board to my PC then apply 10v adjusting scale does nothing in the program. 

Also, I am able to adjust the crystal to 7.99Mhz, some some reason it wont go above that.

I did the test with the 200ohm resistor. The first image shows me adjusting the Offset to 0 and the second image shows WinSDR after a reset. 

I also deleted the winsdr.log. The last image show the InputAvg where I'm able to get it to 32767 as advised in the build info.

The images can be made bigger if you open them in a new tab.