HybrisBehemoth

Sammich FM

9 posts in this topic

Posted (edited)

I'm a total noob building a sammichFM. Finished all the soldering. All voltage tests OK, except that pin 13 socket on IC3 socket of the control PCB (74HC595) is not connected to ground as it is supposed to be referring to the build guide. I re-soldered the joint, but still no difference. 

Should I simply run a jumper wire on the back of the PCB or am I missing something? Any other tests I should run or components I should look at?  

Edited by HybrisBehemoth

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Pin 13 is /OE, so active-low output enable. It must have a connection to 0V/ground for the outputs to function. If there are other points already connected to 0V (i.e. it is not an interconnection or dry solder joint problem and somehow the plating is damaged ), then the right idea is to run a jumper wire. 

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This is weird cause it's a ground plane on the bottom side! You can also scratch the silkscreen a bit, stretch the solder a little and connect to ground plane.

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Thank you for the help. I ended up soldering a jumper wire to ground.

 

After passing the voltage checks as in the build manual, I installed the ICs (except banksticks) and turned on the power.

Pause... no smoke or smell of burning components. So far, so good.

 

At first the LEDs wouldn't light up. But after some wiggling of the MIDI-cables they came on.

After installing MIOS Studio 2.4.6 and setting MIDI in and out the upload requests keep ticking-in all the time that the sammichFM is connected. After pressing "Query" I do get the correct message that the unit is up & running. I upload the midibox_fm_v1_4i, which seems to be working;

upload of 25088 bytes completed after 16.55s (1.48 kb/s)

But the unit isn't rebooting after that as its supposed to. The screen is on but still just showing the row of rectangles. And the LEDs are all off. If I press "query" I get the message that "Bootloader is up & running!". The requests "f0 00 00 7e 40 00 01 f7" keep ticking-in in the top left window. If I connect audio out its giving of some low random static noise.

 

Suggestions are welcome. Thanks in advance for any help.

 

 

MIOS Studio 23.07.18.png

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Possibly your MIDI interface is not passing the data properly. Do you have anything else to try, especially on the whitelist?

The optocoupler is installed?

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Thank you for the input and sorry for being a total noob and not reading the MIDI troubleshooting before posting. :blush:

Got the software up and running now and I get sound out of the sammichFM. Its just really low and with a lot of static noise. Is this a power supply issue or are there other possible explanations?

Also: on the main PCB there are headers "JPB" in the top right corner. What are those for?

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Difficult to say without any photos (showing soldering quality etc.). Are you using stereo jacks for audio?

JPB looks like an alternative power connector. Did you fit the jumpers left of MS1?

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The jumpers by MS1 are in place. The jacks are stereo.

Here are some pictures. This is my first synth-build so I'm sure there is a lot to be said about soldering quality. ;)

Sammich FM 01.JPG

Sammich FM 02.JPG

Sammich FM 03.JPG

Sammich FM 04.JPG

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Generally quite good soldering but look for example at the resistor joints below the sandwich icon (fourth picture). Some could be cold, i.e. the fillet does not bond to the PTH properly.

If the voltages check out, I'd also suggest to install the bankstick ICs and load the default presets. I don't know how the storage works without, plus there may be some inputs left floating. 

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