Core problems

[jwillans]

Hi,

I have just built my first core using a smash tv kit.  I've checked and double checked and all the components seem to be correctly inserted and well soldered.  However I am not getting any voltages on the ICs when I apply the standard tests.

J1 is connected to a unregulated 500ma AC Adapter which is set to 7.5V.  This is spitting out DC, but I understand from the documentation that this does not matter that DC power is being fed into the rectifier..

When I check voltage on J1, it is a little odd since it is 11.86 even though it is set to 7.5V on the variable notch on the PSU.  Could this be a problem?

I've tried measuring the voltage at the regulator and I get nothing!

Help,

James

[jwillans]

Some images to help me diagnose:

Many thanks for any help offered,

James

[lylehaze]

It's normal for unregulated power supplies to output a higher voltage when not loaded.

Try this please:

set your meter to DC VOLTS

connect the black lead to the tab of the 7805 regulator

carefully touch the red lead to the first pin of the 7805, tell me the voltage.

carefully touch the red lead to the last leg of the 7805. again, tell me the voltage.

finally, is the metal tab of the 7805 hot?

watch your fingers.

LyleHaze

[dj3nk]

[quote name=lylehaze link=topic=9134.msg64922#msg64922

watch your fingers.

[lylehaze]

Hey, at least I was nice enough to warn him!

;D

LyleHaze

[jwillans]

Hi LyleHaze,

I'm not sure which is pin 1 and 3, but  I get -0.52V  on the one closest to the midi sockets (back) and 2.68V on the one closest to the front.  It does not get hot, or even warm and there were no sparks!

Following another thread with similar problems, I've also tested the rectifier + to - gives 10.62V ~ to ~ gives 11.83V (almost the same as the input on J1).

Something isn't right!!

James

Edited: clarified regulator voltages.

[lylehaze]

Interesting..

OK, when reading across the rectifier, you show 10.62 from + to -.. That looks good.

BUT!!

the - of the rectifier should be connected to the tab of the 7805, (also the middle pin) and the + of the rectifier should be connected to pin 1 of the 7805 (the pin furthest from the MIDI sockets).

Yes, there's a capacitor in between, but unless you got that in backwards, it shouldn't be a problem. and even if you did.. well, there's a connection problem here.

Make sure that the rectifier has the + in the correct place.

The 4 pins of the rectifier:

one is marked +, and should go across 2 caps and to the bottom pin of the 7805.

one is marked - , and should go to the middle pin of the 7805

2 are marked ~, and should each go to one pin of j1.

Let us know how it goes.

LyleHaze

[dj3nk]

@lyle: dont we all have to learn sometime by our own ;) I like midibox brandings ^^ (if they arent mines surely)

You just need to check the  ~  marked pins. The others will be right automaticaly. But what already lyle said... dont forget the big caps polarity .

greetz

[jwillans]

Hi Lylehaze,

I appreciate all your help, I think I am making progress.

I have just remeasured the voltages on the 7805, but using the middle pin rather than tab and I get:

pin 1 - middle = 10.52V

pin 3 - middle = 5.02V

So that looks fine.  I now get values on the IC sockets, but each of the tests reads 7.4V where it should read 5V.

James

[lylehaze]

I have never seen a 7805 with an isolated tab.

Weird! but the voltages sound good, at the 7805, at least.

I have something that will keep me busy, I'll be back in an hour or two.

Family comes first.

LyleHaze

[jwillans]

I resoldered the 7805 and all is now well with the test voltages 5.01, can now move to the next stage of plugging it into midi.

Many thanks Lylehaze.

James

[lylehaze]

Party on, Dude!

LyleHaze

[jwillans]

Thanks!  I've now moved from one problem to the next, I'm not sure whether I should start a new thread for this elsewhere - please let me know if so.

I've connected the core to the PC but I get no input requests from it, the bootstrap loader has been burnt on the PIC by smashtv so should be there.

I have verified that the midi card and cable work by connecting another midi device, this displays output in the MIOS window, so all is well here.

I have started working my way through the newbie troubleshooting section.  All my voltages are correct according to the following diagram:

http://www.ucapps.de/howtodebug/mbhp_core_extract_measuring_vdd.gif

I'm curious to know whether the "when nothing is sent voltage" (on pin 25 of the PIC) should change when message is sent via midi out?  If so, could my constant 5V be an indicator that requests are not being sent from the PIC? 

I'd like to check that the bootstrap has for sure being burnt, but didn't understand what "use the verify function of IC-Prog/P18" referred to in the troubleshooting guide?

Many thanks,

James

[lylehaze]

Hi, I'm back, for a few minutes anyway.

re:Pin25. Your meter is probably not fast enough to see brief transmissions on pin 25. Good thought though.

Got a spare LED? 220 Ohm resistor? 5 pin DIN plug?

I wonder if a MIDI activity monitor could be that easy?

I'll have to try that one day.

re: "Verify of ICProg" That would be if you burned your own PIC. Since you didn't, you'll have to trust that Smash got it right. I'd call that a pretty safe bet.

If all your voltages are good, and the crystal and it's caps are good, and the MIDI OUT circuit is good ( two reisitors?) there's not much else I think.

As long as you didn't plug the PIC in backwards..  ::)

Gotta go, I'll check in later

LyleHaze

[Jidis]

Got a spare LED? 220 Ohm resistor? 5 pin DIN plug?

I wonder if a MIDI activity monitor could be that easy?

Not 100% certain, but I seem to remember Thorsten's activity lights using a brief delay timer or something in the software. If so, maybe the "on time" of MIDI activity alone isn't long enough to produce any adequate "visuals". :'(

I'd guess someone in here could probably figure a passive component or two you could toss in to get it happening though. ;)

George

<edit> Plus, I guess it stays high too, so you'd have to flip that somehow to keep it from just staying "on". ???

[jwillans]

Thanks for your continued help.  I have made some progress, I decided to check my soldering, and resolder any joints in doubt.  Now when I reconnect to the PC I get a single message:

00000008477756 ms | Sysex message: F0 00 00 7E 40 00 01 F7

when the power is connected to the core, then nothing!!  If I disconnect and reconnect core power then I get a further message, what might be this symptomatic of?

James

[lylehaze]

I believe that is symptomatic of a working core.

But I might be mistaken. ;)

Confirmed: You have MIOS already installed!

See:

http://www.ucapps.de/mios_bootstrap_newbies.html

for more details.

Not long ago, PICs were shipped with a bootloader, and you loaded MIOS, then loaded your application.

recently, Smash started shipping with MIOS installed.

I think "Bootload only" would keep repeating the upload request, but MIOS may only issue it once.

I would try loading your application with MIOS studio. You may be ready to rock.

re: MIDI activity monitor:

I soldered up a DIN plug, 220 Ohm resistor, and a spare LED, and it provides a pretty good indicator.

Yes, if you are only getting a few messages, it only flickers faintly, but definetly good enough to see. More MIDI traffic results in brighter flickering.

See Attached pictures

The "Flat Side" of the LED is on the resistor side in this pic.

Cool toy for testing, about as cheap as it could be.

Good luck with your MIDIBox, let us know how it goes!

LyleHaze

[jwillans]

Hi Lylehaze,

I tried uploading the application and all indications seem to be that it uploaded okay.  I've not yet built any of the core modules, so I cannot test whether the application is behaving as expected.

Your midi activity monitor looks a useful debug tool although I didn't have the components to hand to build it.

Many thanks for all your help with this, I really appreciate your support.

James