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Unable to make FV-1 work..
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cloudscapes



Joined: 26 Aug 2015
Posts: 7

PostPosted: Sat Sep 19, 2015 3:50 pm    Post subject: Unable to make FV-1 work.. Reply with quote

Hi all,

After prototyping an effect using the FV-1 devboard, I had designed a PCB layout based off of it, confident that as long as I stick to the rules, it'll work.

My PCBs have come in. Populated the first one, but the FV-1 seemed dead. Checked voltages, tested continuity, caps, everything, and when I was confident that I had indeed kept to the rules, populated a second test PCB this time with the bare minimum the FV-1 would need. The crystal, a few caps and resistors, and the EEPROM. I still get nothing.

Here's the kicker. I get no clock signal on the clock pins on either of my two test boards. If I probe the clock pins on my devboard, I do indeed get the 32KHz clock as expected. The other kicker, the clipping led is constantly on as soon as I power on, even though I keep the input pins floating. That doesn't make any sense.

This is my initial layout, the one I thought would work:
http://www.soniccrayonfx.com/private/pitch_shifter_pcb.jpg

And when that didn't work, I populated only this on a fresh board. Same PCB layout as above, but using only the following components. The minimum that would be needed:



This is exactly how it's hooked up for the official dev board. Decoupling caps as close to the chip as possible, ground fills, etc. I left the inputs/outputs floating as all I needed to confirm was that I could get the FV-1 running, by probing the clock pins. But I don't even have a clock signal. Both chips on both boards just seem dead, and I have no idea why. When I populate only these parts, it's isolated from the rest of the board, so no trouble would come from unpopulated parts of this test board.

I solder quickly and cleanly. I'm used to hand-soldering much finer pitch than this, SOIC is as easy as DIP for me. Not a single shorted pin.

What did I do wrong? I just don't see it!

Voltages are fine, and continuity tests show no shorts and pins are connected to where they're supposed to.

Both the chip and the crystal come from smallbear.
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frank



Joined: 19 Oct 2005
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PostPosted: Sat Sep 19, 2015 10:12 pm    Post subject: Reply with quote

Couple things to try:

Increase the cap on the crystal, some crystals need a larger value and some need a cap on both legs.

You are running in external EEPROM mode, are you sure the EEPROM was programmed correctly?

Try running internal programs and see if it is an issue with the EEPROM.
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cloudscapes



Joined: 26 Aug 2015
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PostPosted: Sun Sep 20, 2015 6:24 am    Post subject: Reply with quote

Hi, thanks for the reply! I tried a few things this morning:

- Increased crystal cap to 22pf to see. No change.

- Tried internal programs by pulling T0 to ground instead. No change.

- The EEPROM works. It's the same socketed chip I use on the devboard. I've been swapping it back to the devboard from time to time to check things and it still works fine.

- Removed crystal and tried driving X1 with a logic level 32.768khz sine clock with my function generator. As said I can do in the datasheet. When I do this, I get a clock return on X2, but the clip LED is still on even though I have no input. What's more is I get a kind of buzzing motorboating sound from the audio outputs. At least it's different!

I've mostly given up on these PCBs. I think the best thing for me to do right now is redesign a minimalist "stamp" PCB for the chip, so that I don't have to cut traces and mod this defective PCB to try and get it working. Though I can't say if it's both my FV-1 that were defective either. They both came in a non antistatic bag which I don't find super hot.

Discouraging. I went through my layout a dozen times since the middle of last week, trying to find a mistake I'd made. Couldn't find any. It's exactly how it is on the official devboard.
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cloudscapes



Joined: 26 Aug 2015
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PostPosted: Sun Sep 20, 2015 7:16 am    Post subject: Reply with quote

Designed this stamp this morning

I'll wait a day or so to make sure there aren't any mistakes, then I'll order.




Wondering if I should order new FV-1's from elsewhere.
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puretube



Joined: 25 Oct 2006
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PostPosted: Sun Sep 20, 2015 8:50 am    Post subject: Reply with quote

Hi, your MID-cap is quite large,
while your REFP-cap is rather small...
REFP-resistor is smaller than in the datasheet, too.

Dunno if that matters, but...
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frank



Joined: 19 Oct 2005
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PostPosted: Sun Sep 20, 2015 8:51 am    Post subject: Reply with quote

Well, I would try a new FV-1. A few will fail quickly after being put in circuit, called infant mortality.
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cloudscapes



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PostPosted: Sun Sep 20, 2015 8:59 am    Post subject: Reply with quote

puretube wrote:
Hi, your MID-cap is quite large,
while your REFP-cap is rather small...
REFP-resistor is smaller than in the datasheet, too.

Dunno if that matters, but...


The MID cap is the same as the one on my devboard, as is the REFP cap. And since the devboard works fine, I don't see how they would be a problem.

http://www.spinsemi.com/Products/appnotes/spn1001-dev/SPN1001-DEVB_sch.pdf

I tried a 1uf cap for both, just in case, no difference.
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cloudscapes



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PostPosted: Sun Sep 20, 2015 9:04 am    Post subject: Reply with quote

frank wrote:
Well, I would try a new FV-1. A few will fail quickly after being put in circuit, called infant mortality.


I'm out of FV-1's anyway, so yeah I need to order a couple more. The ones I just got are dated 2011, don't know how they were stored, etc.

Can they hypothetically be ordered in small (2-4) quantities from experimentalnoize?
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frank



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PostPosted: Sun Sep 20, 2015 9:14 am    Post subject: Reply with quote

Sure, I'll sell small quantities. I generally use small box flat rate priority mail for shipping ($5.25 domestic) when it is just a few, have to add tax if in California. Email sales at xnoize . com (note "z" in xnoize) and they'll get an invoice to you. We take PayPal so do not email any credit card info, in fact our server will delete any email with a credit card number in it so we never see it.
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cloudscapes



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PostPosted: Sun Sep 20, 2015 12:10 pm    Post subject: Reply with quote

Will do, thanks.

It's a bit frustrating when you debug and aren't any closer to knowing where the error lies. Still don't know if my board is wrong or if by some bad luck got two bad chips. Or both!

Guess I'll find out with the new board in a few weeks, simplest board possible, and some new chips from a good source.
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frank



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PostPosted: Sun Sep 20, 2015 1:35 pm    Post subject: Reply with quote

Hmmm, 2 bad parts is strange. Post a schematic of the board.
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cloudscapes



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PostPosted: Sun Sep 20, 2015 2:01 pm    Post subject: Reply with quote

frank wrote:
Hmmm, 2 bad parts is strange. Post a schematic of the board.


The one in my original post is that, if I leave most parts unpopulated as I did with my second try on this batch of boards. With the decoupling caps next to their pins, of course.

The only thing omitted is the power supply. Linear 3.3v regulator, exactly the same part I use with my 32bit microcontrollers. And those things are sensitive, they don't like dirty power, so I trust it.
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frank



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PostPosted: Sun Sep 20, 2015 3:53 pm    Post subject: Reply with quote

There is a lot missing from the schematic in the top post. I mean a total and complete schematic showing everything (input conditioning, power, etc.).
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puretube



Joined: 25 Oct 2006
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PostPosted: Sun Sep 20, 2015 9:56 pm    Post subject: Reply with quote

cloudscapes wrote:
puretube wrote:
Hi, your MID-cap is quite large,
while your REFP-cap is rather small...
REFP-resistor is smaller than in the datasheet, too.

Dunno if that matters, but...


The MID cap is the same as the one on my devboard, as is the REFP cap. And since the devboard works fine, I don't see how they would be a problem.

http://www.spinsemi.com/Products/appnotes/spn1001-dev/SPN1001-DEVB_sch.pdf

I tried a 1uf cap for both, just in case, no difference.


OK, sorry - I compared the chip-datasheet,
thinking about a possible power-on-hiccup...
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knutolai



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PostPosted: Fri Feb 03, 2017 7:09 am    Post subject: Reply with quote

I know this is an old thread, but I seem to have a similar problem. Constant light on the CLIP LED, no audio output (in both internal and external mode), tried different crystals and different crystal cap sizes. Chips bought from Profusion (EU).

Was the issue ever resolved?
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