So I thought I would start at square one. I can get +5V across JD9. So as a first test, I touched a resistor to +5V, touched the long leg of a spare LED to the resistor, and then the short leg to GND. The LED lights. So (I think) this confirms that my LEDs are short-leg=cathode like the MB-6582 CS construction guide indicates.
I then tapped into current from JD9’s counterpart on the CS. I routed current based on the above cathode description to the LED directly above JD9’s counterpart (i.e., ramp waveform). Doing this caused the LED to light.
Anyone have some thoughts on what I should check next? I’m getting power to the CS. FWIW all encoders work whereas no switches work.
Also, nothing lights up when running the contents of mb6582_led_matrix_test2.zip.
Updates: I had not soldered T2-T9 since they are listed as optional. However some searching reveals that Wilba says “They are not really optional”. <___base_url___>/index.php?/topic/13131-how-optional-are-these-bc547s-on-t2-t9-of-the-mb-6582/&do=embed
After soldering these, all buttons have effect on the LCD display save the following:
Matrix Col 7
Matrix – all rows
Sid Engine 2
Mode 2,3,4
Sid L/R
It’s possible I was not in the right menu for these buttons to have effects.
Also, all LEDs are still off. LED test app also did not light them. Nebula indicates failure to solder T2-T9 may blow a shift register IC. Would that be an explanation for no LEDs? If so, which parts would these be - couldn’t quite figure that one out.
First, the 5V connection to the CS is not used. It’s there for completeness. All the LEDs are powered from the LED matrix of the 74HC595s.
I don’t know how not soldering T2-T9 could cause a 74HC595 to blow, since nothing would be connected to the output pins of that 74HC595. The fact that some buttons work means that 74HC595 is not blown, since you wouldn’t get any buttons working if it was.
Some but not all buttons working means either something wrong with one or more input pins, or something wrong with one or more of the LED/matrix column “sinks” i.e. T2-T9, the 74HC595 above it, the connection to the CS PCB… OR something wrong on the PCB itself (broken track, short). In these cases I always suggest removing the LCD from the CS PCB and checking for shorts between the LCD and the pads it touches on CS (perhaps you forgot to insulate between them).
Check there are no shorts between adjacent pads that connect the base PCB to the CS PCB, or a short to ground.
Likewise, you can test if the LEDs are working by first disconnecting all the 74HC595 and then applying ground to JD8 pin and 5V (through 220 ohm resistor!) to JD7 and JD6 pins. If that works, the LEDs are not dead, if it doesn’t work, the problem is (probably) not on the base PCB side. You can also try putting 5V to a pin of U23 (to simulate sinking one column of the matrix) and then 5V to one pin of U22 or U21 (to simulate driving one row of the matrix)… that is with ICs removed.
Unfortunately while chasing down 2 minor problems I introduced more.
Sid 2 button did not work, and Matrix column 7 button did not work.
I traced connectivity of Matrix column 7 button to JD5 D6 on the main board. However, while doing this I saw some LEDs flash at a certain point -even though the power was disconnected-. Perhaps a capacitor discharged?
One pin on Sid 2 button was not soldered so that looked like the culprit.
I soldered Sid 2 button and all of the encoder tabs.
Now when powering on, LEDs on Matrix Rows 1, 2, 4, 5, & 8 do not even flash (they had before). Matrix Rows and Columns 1, 2, 4, 5, & 8 are not selectable (button).
There are also a number of other buttons and LEDs out.
After a nice round of cursing I checked for shorts. The Sid 2 button looks fine and there’s no way to tell if there is a short under the encoders, although from the looks of the schematic there is nothing in the vicinity of the encoder tabs to short to.
I tried permuting the 595s in U21-U23 - this did not change anything.
It’s not clear to me how I would test T2-T9.
The LCD has not yet been mounted so that can be ruled out.
<stumped>I will try looking at things again but I haven’t much of a clue since just about all of this was working before</stumped>
Remove all the 74HC165 just to rule them out as a cause.
Run the LED matrix test.
See which LEDs are working and which are not.
It might be easier for you to post a picture of the panel rather than describe it in text. Easier for me too.
This might show if a whole column of LEDs is out or a whole row.
Also try the LED testing process I described in the last post.
You can refer to the LED matrix diagram (see Control Surface Wiring in the wiki doco) to know which row/column combinations don’t have a LED connected. (Note also the mistake: BTW I just noticed my CS DOUT wiring PDF is wrong… “LFO Sin†and “LFO Tri†are swapped and “Syncâ€, “CCâ€, “Editâ€, “Play†are in the wrong order (should be “Playâ€, “Editâ€, “CCâ€, “Syncâ€) )
“Likewise, you can test if the LEDs are working by first disconnecting all the 74HC595 and then applying ground to JD8 pin and 5V (through 220 ohm resistor!) to JD7 and JD6 pins. If that works, the LEDs are not dead, if it doesn’t work, the problem is (probably) not on the base PCB side..â€
This test succeeds in lighting all LEDs. I seem to have HPF, BPF, and LPF filter in the reverse order of the schematic (verified twice) but a.) that’s the least of my worries, and b.) the filter selections worked fine before.
Apparently I am not having a good weekend as I replaced two of the 595s in the wrong orientations, dimming the LCD and causing the 595s to get very hot very fast. These will obviously need to be replaced.
Anyway, here is the picture after running the LED test hex file. Surprisingly there are some LEDs on after putting the 595s back in the right orientaiton. What’s become clear to me is that all of the opening and closing has put a lot of strain on the cabling. One portion of JD9’s cable has become separated. Moving the CS causes some LEDs to turn on and off, again consistent with certain bad connections (JD-D4 & D7; JD6 D1). I can’t visually see these bad connections except for the cabling one I mentioned so I don’t know if there’s stress fractures inside the PCB or what.
(I had about 48 hrs where the little guy was working near flawlessly and now it’s a mess – huge sigh…)
Get some solder wick (copper braid stuff) and mop up any excess solder on the joints of both ends of the cable.
Test every adjacent pair of joints on both ends for shorts (well… testing both ends is redundant).
Then test continuity between the nearest component on the base PCB (i.e. resistor or transistor lead that connects directly to the JD* pads) and the matching pad on the CS PCB. Preferably go one step further and test something past that CS PCB pad (like an LED pin).
Get some solder wick (copper braid stuff) and mop up any excess solder on the joints of both ends of the cable.
Test every adjacent pair of joints on both ends for shorts (well… testing both ends is redundant).
Then test continuity between the nearest component on the base PCB (i.e. resistor or transistor lead that connects directly to the JD* pads) and the matching pad on the CS PCB. Preferably go one step further and test something past that CS PCB pad (like an LED pin).
I didn’t describe things very well but a large number of the metal wires inside the cabling have sheared off due to metal fatigue (opening and closing the case has been bending them and they sheared off at the pads). So as a first step I was thinking these all need to be re-attached.
I have at least 2 options I can think of: a.) desolder base pads, restrip wires, and then do a proper solder of wires to base, or b.) do a quick solder of currently broken wires, test everything for continuity as described, and then hot glue gun the wires so they cannot move/shear.
Option A is preferable in a vacuum - however, I have already desoldered the base pads once for something else and they are in kind of rough shape already. I’m not very knowledgeable about how many desolderings a set of pads can take but if they can take a lot, Option A sounds viable. Also I have enough cable to make restripping viable as I misread the instructions and have 2 inches of cable instead of 42-43 mm.
Option B sounds like the crap way but again if the pads go, then I’m even farther in the hole.
Thoughts?
Thanks for your help, Wilba. This is my first big DIY project … and my first non-minor project problem, so I really appreciate the tips.
Without seeing how bad they are now, I’d have to recommend desoldering them all and starting from scratch.
Since I use pretty thick 0.1" spacing ribbon cable, both the wires and the insulation are pretty stiff, the wires can take a 90 degree bend and the way I solder them means there’s little to no movement of the wires, so they don’t break, and that’s after many openings of the MB-6582 prototype.
It’s hard to see how you did yours from that low res photo, but if you plan to resolder the cables, try to do the same thing - put a bend in the wires, don’t make big solder blobs over the bends, just very lightly solder the pads from the “wire bend” side (maybe 3 per cable), flip it over and do proper solder joints from the “wire end” side.
I am back at work on my MB6582 and in the course of desoldering, two pads came off. I recovered the pads. Although I doubt it, I was wondering if they are reattachable. They are on the bottom of the base board, i.e., in the above photo they are visible at right (specifically JD6 D01 and JD7 D03). The pads on the other side of the board are ok.
I saw on another post that it is possible to attach wires in the event that pads come off. I wasn’t sure how can I attach wires if the pads are off.
I don’t think they’re reattachable. If a pad is broken, you would attach a wire to the lead or wire in the hole, and then connect the other end to another pad which would be connected to the broken pad by a track. In this context, with a pad on the other side still good, perhaps you can solder the new wire at the same time as soldering the remaining good pad - i.e. poke it through if the wire and “part” are on opposite sides.
OK - thanks. For the next person, there is electrically conductive epoxy at Mouser (below) that is good for repairing traces (and pads presumably). I may just clean up the pads and pad locations with isopropyl and reglue them. $25 is a bit rich but nothing’s too good for my midibox
I forgot to mention another option… the lead or wire that’s supposed to be soldered to a missing pad can instead be soldered to a track that connects to the missing pad. Just scrape the solder mask off the track.
However, for JD6 and JD7, it doesn’t matter what the pad is like on the bottom, it’s only connected on the top layer to the resistors.
First some updates that might be of interest to others. I was successful in re-attaching the pads with silver epoxy glue as described in a previous post. So if you have this problem, you might consider this as an avenue. Also, I used Chip-Quik for some desoldering. I was able to desolder at 2.25 on the temperature dial on a small Weller iron as opposed to the usual 3. Might be of interest to others if you have a tough desolder as I did (my CS board’s connections are rather torched after several desolderings).
And now for the question - I am again reattaching the stiff gray cabling from the CS to the base. Currently it’s just on the CS. Cable 6 (looking from the top side of the CS) is shorted across all pads except 4. I’ve visually inspected and there are no obvious bridges. The guide indicates there should be no shorts/connections. My question is: would this possibly be due to some of the current values of the encoders, switches, etc.? Following the traces indicates that most (all?) of the traces go to various encoders. Or do I have some massive fault in the board due to all the soldering/desoldering?
So I have everything connected again but no encoders work (i.e., LCD shows no effect of encoders).
I’ve established that rotating several “guinea pig” encoders is detectable on the Base in that the rotation alternately shorts/unshorts adjacent pins. So would this indicate that my U16 etc IC’s are blown? There was a time when all encoders worked and the only thing that has really changed is the cabling.
Also, Column 7 of the matrix does not respond to its button press and Sid 2 Select LEDs is either out or dead. Will poke around some more to see if I can nail this down some more. I had a problem with these two previously (see above) but it appeared at the time to be a cabling issue.
Sid Engine 2 LED is not dead - I was able to accidentally light it with the power disconnected (!) by touching its lead while touching J8 D6. The switch corresponding to Sid Engine 2 is also connected to J8 D6 and J5 D2 as its supposed to be. (Perhaps a transistor or capacitor is discharging?)
I did not poke around for Column 7 as the usual inspections for shorts etc. did not turn anything up. Also Column 7 LEDs light up during the boot sequence so they are ok. It seems to be either the switch or the IC.
I checked for shorts. The Sid 2 button looks fine and there’s no way to tell if there is a short under the encoders, although from the looks of the schematic there is nothing in the vicinity of the encoder tabs to short to.
