[PLUG-AV] Found failed part on the dead Numato

[Nick Bannon]

Heya, Harry! Sure, if you've got an order going in, grab 'em now.

(I haven't done an order yet, though I'm sure I can get a minimum shipping
order together, still happy to. Yes, PLUG has a credit card handy for
online orders, or can reimburse promptly.)

Thanks,
Nick.

On Sun, Feb 21, 2021 at 10:18:29PM +0800, Harry McNally wrote:
> Ah ha! I see a PLUG + POSH do on March 14. Do you think we can fix the
> Numoto by then ?
> 
> The stock detail on that part is:
> 
> "*197* available for 4 - 5 business days delivery"
> 
> which means it is coming out of the UK. So that should be enough time. I
> have some parts I may order shortly. If I do, I will give you a text or ring
> to see if you have odrdered some and, if not, add to my order. Or let me
> know if/when you have ordered. I realised PLUG may not have a CC which is
> the easiest way to place a guest order.
> 
> All the best
> Harry
> 
> On 11/2/21 11:18 am, Harry McNally wrote:
> > Hello Both
> > 
> > On 11/2/21 9:45 am, Nick Bannon wrote:
> > > Heya, Harry, Patrick!
> > > 
> > > On Wed, Feb 10, 2021 at 01:11:24PM +0800, Harry McNally wrote:
> > > > Hi Nick
> > > > See attached. U8 had failed in the 1.5 volt supply and was overcurrent for
> > > > the 1A plugpack. Plugpack shut itself down after 45mS then retried to start
> > > > after a second which is why the Numato LEDs were flashing. I think this may
> > > > have saved the board; fingers crossed.
> > > Fabulous! Was that all hardware diagnosis?
> > 
> > Yes. I used my low impedance meter to see where on the board the
> > resistance was lowest across the 12V supply and this led to that PSU
> > circuit and the TI switcher was the only possible cause. Once removed,
> > the impedance matched the good board (well .. "open circuit" from a low
> > impedance perspective).
> > 
> > >   and/or have you tried talking to the firmware on either board over USB?
> > 
> > You've got me. Many months ago I was shopping for a Xilinx JTAG
> > programmer clone and settled in a Open PCB to build up (hasn't arrived
> > even now) I did this assuming I had to bring up a bricked board (and to
> > test the FPGA spoke back to me etc).
> > 
> > Because of that expected entry point I didn't realise that there was
> > also USB access to JTAG. So I haven't tried this access to either the
> > good or the dead board yet.
> > 
> > > > This is U8:
> > > > https://www.ti.com/lit/ds/symlink/tps54625.pdf
> > > ooh, up to 6.5A output...?
> > It may not be used to deliver 6.5A although 1.5V supplies in FPGAs (like
> > PC CPUs) can be quite high currents.
> > > > I have removed it and that has cleared the 12V supply loading but I don't
> > > > want to power the circuit in case 1.5V is necessary to prevent failures
> > > > elsewhere.
> > > > 
> > > > I'll will add some of these parts to another order (or freight is $15).
> > > > Element14 have them:
> > > > https://au.element14.com/texas-instruments/tps54625pwp/ic-sync-step-down-650khz-htssop/dp/3007368?ost=tps54625
> > > > 
> > > Lovely - and don't be out of pocket, we're happy to pay.
> > > Thank you for your time so far.
> > 
> > I'm a bit away from another order so, if you like, jump on the element14
> > site and order say three pieces with a CC as a guest (no difference in
> > price). Sometimes element14 run specials for free delivery but I haven't
> > seen that offer code come through recently. So freight will be $14 or so
> > which doubles the price of three pieces unfortunately. I suggest three
> > in case some intermittent short exists on the 1.5V rail. I can't see any
> > now and the TI part should current limit and protect itself but not much
> > point in buying one then "*smoke* oh, we actually need another one now"
> > scenario.
> > 
> > > I'm hoping we can get together for an AV hack session very soon, I'm sure
> > > the new PLUG VP, Patrick, is up for it. We'd want to use a "working"
> > > Opsis board, and probably a cheap black-box hdmi2usb widget too - but
> > > debugging is really hard if every setup is a unique snowflake.
> > 
> > Ok. Well what about if you get parts and I repair the PCB and see if we
> > get the blue "loading" light (then off) like the good board. After that,
> > have a good look at USB programming etc at the following AV meetup ?
> > 
> > We can try the board access through USB and decide if we want to by an
> > off-the-ebay Xiling JTAG debugger clone (around $30US vs $200US for the
> > genuine Xilinx device).
> > 
> > > We'd rather start with replicating someone else's system than figure it
> > > all out for ourselves, or we just don't end up getting very far in a day:
> > > 
> > > - https://debconf-video-team.pages.debian.net/docs/hardware.html
> > > - https://debconf-video-team.pages.debian.net/docs/opsis.html
> > > 
> > > Every Second Sunday - including this Valentine's weekend coming -
> > > is an opportunity, but maybe we need something else to kickstart the
> > > process again.
> > Yes. I won't have the PCB ready by Sunday but happy to repair then
> > attend the next meetup.
> > > Had a lovely PLUG talk on Tuesday - but we were running around getting the
> > > basics working at the last minute, like any kind of audio out, as usual...
> > > https://meetings.ucc.asn.au/b/nic-4cd-3jg
> > Listening and viewing now ..
> > > > When I get them I need to use hot air to re-install (it has a heatsink tab
> > > > underneath the package). But probing around the circuit, I cant see anything
> > > > shorting the 1.5 volt supply rail so U8 alone may fix it.
> > > > 
> > > > Smalls steps but progress none the less :-)
> > > > 
> > > > All the best
> > > > Harry
> > > Thank you!
> > > Nick.
> > 
> > More than welcome Nick. It is a small contribution back to PLUG.
> > Apologies I put this aside waiting for the JTAG PCB.
> > 
> > All the best
> > Harry

-- 
   Nick Bannon   | "I made this letter longer than usual because
nick-sig at rcpt.to | I lack the time to make it shorter." - Pascal