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SammichFM control surface not working

17 posts in this topic

Posted · Report post

Hi. I completed my sammichFM tonigh, or so I thoughtt. I uploaded the firmware, got the rhodes sound, everything appeared to be ok, but none of the controls work. Three LED's are lit (the top left 2, and on the bottom row second from the left). No response from any buttons or the encoder or any of the other LED's.

FWIW, to the best of my knowledge all the voltage and continuity tests came up fine.

Now, some background, or what I think the problem could be. When i was building the control board, some solder fell from the iron while tacking and got in the hole for pin 16 on IC2. Whilst removing said solder I accidently lifted the solder pad. Also before I noticed the solder in the hole, I pushed the socket in and broke of the end of the socket pin. So, here is where things get dicey.

First off, I did not get rid of the socket (so, so dumb). I just flipped it over, becuase it looked like pin 8 had no traces going to or from it and was unused (though I never checked any schematic). For the record, the chip is orientated correctly, I just followed the marker on the board and ignored the reverse socket.

Second, I follow the trace from pin 16 of IC2 and it appeared to just run to a resistor network RN4 I believe. So I soldered a jumper from pin 16 on the socket to the correct pin on the resistor network. I tested continuity, it checked out ok.

So, any idea's on what's up? Was it my butchery, or something else? Any help would be most graciously appreciated.

Thanks.

Matt

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Posted · Report post

Pin 8 would be the ground pin of the IC, which is connected to the ground plane (which is why you don't see any traces coming off of it). If that's not properly connected the CS won't work. Check continuity between ground and IC2:8 - if it's not connected, fix it. Then try again.

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Posted · Report post

I made a jumper wire going from pin 8 to ground, via 1 of the Vs pins on the unused J2 connections. I have continuity to ground from pin 8 now.

As far as IC2 pin 16, (the lifted pad) I made a jumper from pin 16 to the correct pin on RN4, and then I bridged pin 16 together with C2 (the pin on the 5v rail) and the jumper wire. I did it that way instead of using 2 wires because they are so close together. The pad on the top part of the board for pin 16 seems fine, I tested continuity with RN3 and C2.

I still have the exact same problem. I don't think it's a bad solder joint, I rechecked many times. Perhaps the software didn't load correctly? Something else entirely?

Any idea's would be most appreciated.

Thanks,

Matt

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Posted · Report post

At this point we have essentially no information other than "I might have borked something on the board". I seriously doubt it's the software, since it's playing the sound.

a) Did you upload the correct firmware (the sammichFM variant)?

b) Show some pics of the CS board, both top and bottom side. This let us take a look at what might be problems instead of asking for each individual part's placement ;)

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Posted · Report post

I thought for sure it would be a component placement issue in relation to the rework I had to do, thats why I focused on that.

My camera is not so good, also my photography skills are seriously lacking. Here is some pics, I did the best I could, if you want to take more pictures in certain area's in certain ways please let me know. Really, just tell me what area you want a pic of. Any shiny sections in the pics are from flux, I was rehitting solder joints.

post-5231-0-02452400-1323543171_thumb.jppost-5231-0-98065500-1323543107_thumb.jp

post-5231-0-51331800-1323543118_thumb.jp

post-5231-0-92296600-1323543128_thumb.jp

post-5231-0-25400100-1323543139_thumb.jp

post-5231-0-04160200-1323543150_thumb.jp

post-5231-0-72699500-1323543160_thumb.jp

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Posted · Report post

Forgot to mention in the last post that yes I did upload the correct firmware, the sammichFM version.

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Posted · Report post

Yes, the pictures are kinda... not really all that helpful ;)

Are the resistor networks correctly oriented? They should have a little white dot above one pin, that pin should be next to the dot on the PCB.

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Posted · Report post

Yes, the dot is in the correct place, I just checked again to be sure.

This is pretty devastating...

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Posted · Report post

I redid every single voltage test and all continuity test's, everything checks out fine. Also, rechecked all the polarized components. But still no reaction from any of the controls. How is that possible?

Does that mean a chip is bad or something? Can anyone suggest some different test's to try other than the voltage and continuity test's listed in the build guide?

Is there any significance to the fact that none of the controls work, instead of just certain controls?

I'm sort of ready to give up, I can't think of anything else to try.....

-Matt

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Posted · Report post

Have you checked, that the right shift register types are in the right ic slots? Maybe you have some output shift registers where some input shift registers belong or vice versa.

If that´s not it, grab a good camera and take full pcb coverage high-res shots of the front and back sides of the pcbs, so that they are not blurred.

The resolution of the pictures before was good, but they were blurred (get a tripod).

Greets,

Peter

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Posted · Report post

I checked that few times, no dice. I tried to reseat the chips in the sockets and ended up breaking a pin of 1 of the shift registers. I ordered another set (both types), perhaps they are the problem to begin with? It's a long shot, I know, but I can't think of anything else other than the PIC chip.

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Posted · Report post

It's possible you broke one of the ICs by feeding it 5V without a ground connection, so it might just be that.

My next suggestion would be to check the continuity of the J1 pins to the correspoding pins of the 74HC165s. You can use http://ucapps.de/mbhp/mbhp_dinx4.pdf as reference. Make sure the SC/RC/SI pins connect to the IC.

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Posted · Report post

Hiya,

Stop trying to fix things here there and everywhere and follow the advice given by nils....................he's a grumpy german (wack) but he is also very smart and will work through this with you.......if you listen to him.

Electronic problem solving needs a methodical step by step approach so that you can ring the changes.

(no offence to anyone intended.....................honest)

cheers

Paul

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Posted (edited) · Report post

I followed every bit of advice he's given me to the best of my ability, and I'm very appreciative for every bit of it. I don't think he's been grumpy with me, some of his comment actually made me giggle a bit.

I think I'm getting close to fixing it, I'm just waiting for new shift registers in the mail. Wilba cheered me up with a helpful email, I really appreciate people taking the time to give me help. Now I'm even getting philosophical advice, as opposed to technical, so I'm that much more equipped to face life's challenges. ; ).

Just kidding with you taxi man, btw

Edited by kid versus chemical

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Posted · Report post

Hehe, no I am not specifically grumpy with you, just in general ;-)

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Posted · Report post

Hiya,

@ kid versus chemical,

No worries mate,it's just that I could see you doing what I used to do and getting frustrated for ya :)

The number of times I have said 'oh f**k it' and started over again are unbelievable,all due to getting lost in the mayhem of unguided fault finding.

Quoting Nils "Hehe, no I am not specifically grumpy with you, just in general".............Nils speaks the truth....lol.

cheers

Paul

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Posted · Report post

I'm 99.999% sure the problem is solved. The trace connecting the shift register IC1 (pin 9 or 10, I forget which) to the serial input for the PIC was very slightly lifted by the solder pad. Made a jumper and got controls to respond,, I'm just waiting for a replacement shift register to replace the one with the broken pin, then I can test it 100%. Nice. Just thought I would share, for archive purposes.

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