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Bill.b

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Joined: 25/06/2011
Location: Australia
Posts: 226

Posted: 11:44am 25 Aug 2012

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[quote]
Apart from checking the power supply as Geoff suggests, I'd also check where you are running your 0V or earth lines. Group the video earths to the one line and back to the 0V line and the same for the audio circuitry, try not to daisy chain the earth/0V lines from audio to video to 0V.

Rob [/quote]

I am using the standard Altronics maximite with NO audio
connected, NO external periferals only the Keyboard
Monitor and 9v powersupply.

Bill

In the interests of the environment, this post has been constructed entirely from recycled electrons.

aargee
Senior Member

Joined: 21/08/2008
Location: Australia
Posts: 255

Posted: 02:08pm 25 Aug 2012

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Oh, OK, ignore that

I didn't read the first line of your original post...

- Rob.

Edited by aargee 2012-08-27

For crying out loud, all I wanted to do was flash this blasted LED.

paceman
Guru

Joined: 07/10/2011
Location: Australia
Posts: 1329

Posted: 03:02am 26 Aug 2012

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I'm running an original Altronics 'Mite with the audio output wired to a socket on the case and a couple of other minor mods. Tonight I've got a 4x4 keypad (single analogue input), Freetronics 3231 RTC module and Nokia5110 all hooked up to the I/O socket. I've just loaded MMBasic V4 (monochrome) and tried out Geoff's demo "Music" program (which has three MOD files to test) and the whole thing's playing and displaying beautifully - no jitter at all.

The VGA monitor is a Samsung 2043BW. The 9v power supply is pretty robust though - it's a benchtop Manson EP-613 unit good for several amps so Geoff's comments about looking at your power supply is probably the place to start.

Greg

ajkw
Senior Member

Joined: 29/06/2011
Location: Australia
Posts: 290

Posted: 10:15pm 01 Sep 2012

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Jitter cause found!!!!

After taking the freezer spray to each and every component one at a time I eventually found the component that when cold stops the jitter.

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The PIC32.

I have gone on to try freezing the circuit board on each side of the PIC to see if it is a dry/poor solder joint but nothing short of a spray to the middle of the chip will do.

Perhaps this will still come back to the Vcap cap but I would have thought that freezing it (C5 or C12) would have induced some change. Anyone??

Anthony.

Edited by ajkw 2012-09-03

trippyben

Regular Member

Joined: 26/06/2011
Location: Australia
Posts: 91

Posted: 11:25pm 01 Sep 2012

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If your using a Through hole Vcap it might be less than great. Try a surface mount Vcap as close as possible to the PIC.

Other then that, I did see a MM on here somewhere with a heatsink on the PIC. That might be the go.

donmck

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Joined: 09/06/2011
Location: Australia
Posts: 1313

Posted: 11:46pm 01 Sep 2012

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trippyben said If your using a Through hole Vcap it might be less than great. Try a surface mount Vcap as close as possible to the PIC.

Other then that, I did see a MM on here somewhere with a heatsink on the PIC. That might be the go.

That was to do with a larger current drawn between versions, and what appeared to be a marginal PIC32.

Geoff explained that the versions (I think it was from 2.7 to 3.2) was drawing more current. Perhaps V4 is a bit further up the current load figure.

If the PIC32 needs a heat sink, then it sounds like a heat sensitive PIC again, if no one else is experiencing similar problems.

Don...

https://www.dontronics.com

ajkw
Senior Member

Joined: 29/06/2011
Location: Australia
Posts: 290

Posted: 12:23am 02 Sep 2012

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Heatsink wont freeze the PIC, room temp is enough for it to jitter.

I am going to buy some optional caps for C5 tomorrow and try them, other than that it would appear to be the PIC.

Anthony.

From Geoff's Website.
C5 must be a low ESR Tantalum capacitor and the PIC32 is very sensitive to its characteristics. If you suspect C5 try replacing it with a higher value and/or a higher working voltage (both of these will improve the ESR). Also try another brand.

Some readers have had success by wiring another Tantalum capacitor (22 or 47�F) from pin 56 (Vcap) of the PIC32 to the 3.3V supply. It is not certain why this would work but it is worth a try.

paceman
Guru

Joined: 07/10/2011
Location: Australia
Posts: 1329

Posted: 06:51pm 02 Sep 2012

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ajkw said Heatsink wont freeze the PIC, room temp is enough for it to jitter.
I am going to buy some optional caps for C5 tomorrow and try them, other than that it would appear to be the PIC.
Anthony.[/Quote]

Hi Anthony,
If the new capacitor(s) doesn't work then a heatsink might still work because it's the chip core temp that's important, not ambient levels. A heatsink (with good heat conducting compound, e.g. silver paste, and good contact) gets the heat off the chip faster and so lowers core temp. How you maintain the contact could be tricky!

If none of these work I'd say you're faced with replacing the chip (or automating your spray gun

). That'd be a good test of your surface mount soldering skills

but then Geoff says it's pretty easy and his site has a good description of how to do it. Mind you I take no responsibility and I guess he'd feel the same way!

GregEdited by paceman 2012-09-04

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