MidiDAC not working

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collinspr
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MidiDAC not working

Post by collinspr » Mon May 02, 2016 4:44 am

Looking for some help here. I've had great fun building nine Oakley modules over the last few months. I have to say that the PCBs are great quality as is the documentation. All the modules have worked first time with the exception of the MidiDAC.

Basically, the only sign of life is the two LEDs lighting permanently.

I have done all the obvious checks (component values, orientations, solder joints, shorts) numerous times now.

Supply voltages are all present and correct.

I was expecting to see some action occurring on the PIC ports but, on checking with a scope, these are all static. MCLR goes high on power up, as expected.

I have tried monitoring OSC1/OSC2 with the scope and there appears to be nothing happening here (also monitored via buffer in case scope loading upset the clock). Have replaced XTAL and C25/26 - still no joy.

Eventually replaced the PIC with a new part from Tony in case I Had damaged the original part at some point but this has made no difference.

Any ideas appreciated,

Paul

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Synthbuilder
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Post by Synthbuilder » Mon May 02, 2016 7:51 am

I'm not in the office today so I don't have access to the schematic unfortunately. However, the first thing to check is that the PIC does have +5V on its Vcc pin - measure on the IC body directly and not on the IC socket. With the power off and using a resistance meter check that all the pins connected to 0V are actually doing so.

If still no go, then pull out the 4104 chip and power up again and see if this fires up the clock pulses from the PIC. If you don't see anything then suspect a shorted PIC pin somewhere. The problem could be underneath the PIC's IC socket - if you have a turned pin socket you can check all the pins around the base of the socket without removing it. A magnifying glass is useful here. You can also remove the PIC and use a meter to check the resistances between adjacent pins.

Tony

collinspr
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Location: Plymouth, UK

Post by collinspr » Mon May 02, 2016 8:58 am

Hi Tony,

Thanks for the quick response.

I have checked all the PIC pins for shorts (visually and with a meter) and it's all clean.

I have measured 5V on the pins of the device itself (between pin 5 and pin 14) and it's all good.

I've removed the 4104 and see no difference.

I've built a separate 4MHz oscillator which I've fed into CLKIN/OSC1 (having removed the XTAL and associated caps) - this should be OK according to the PIC data sheet (assuming the PIC osc has been configured to LP, XT or HS mode, which I think it should be to use an external xtal). I can see with the scope that this is providing a good clock but there is still no action on any of the PIC port pins.

I'm running out of ideas.

Paul

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Post by Synthbuilder » Tue May 03, 2016 2:35 am

Hi Paul,

It's the PICs. It's not your fault. Sorry.

I have just checked some more PICs from my current batch and they are all failing in my midiDAC module. They pass the software test on the PIC programmer but are not working in the module.

I will sort this out today and get a new PIC for you in the post. I'll get your additional PIC order reimbursed too.

Tony

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Post by Synthbuilder » Tue May 03, 2016 3:12 am

Just an update on this:

Paul I will get you a new working PIC sent in the post today for you. I have refunded the 11GBP you paid for your second PIC. You may dispose of the two PICs you have as you see fit. I am very sorry for all the hassle you have been through.

For others reading this: I have checked my order book and no one else has been affected by this issue. I have isolated the problem and all PICs from previous batches should be working as intended.

Tony

collinspr
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Joined: Sat Apr 23, 2016 9:26 pm
Location: Plymouth, UK

Post by collinspr » Tue May 03, 2016 6:57 am

Hi Tony,

No problem and thank you, that is a weight off my mind.

Look forward to getting the midiDAC up and running,

Paul

collinspr
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Location: Plymouth, UK

Post by collinspr » Wed May 04, 2016 3:11 pm

So new PIC arrived in the post today.

Inserted into MidiDAC, powered up and Hey Presto! MidiDAC is now working.

Thanks Tony for the quick diagnosis and turnaround of the new PIC.

Now to have a bit of fun ...... :banana:

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Post by Synthbuilder » Thu May 05, 2016 1:47 am

Thanks for the update Paul. I'm very glad it all works now.

Tony

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