My sammichSID has been broken for quite some time now, and I really want to get it back working. I don’t have a lot of experience in tracking down what’s the problem, so I thought I’d ask around.
It was working fine until I decided that I wanted to use the low power Optrex STEP LCD instead of the stock high power LCD. (Jason had previously sent me one, because of some issues during the build, but I never used it).
After I set everything up, made sure all the jumpers were correct, it didn’t show anything on screen, but the audio was still working and I also still had the LED animation. I asked around, and it was probably the PIC that needed to be replaced. After I replaced the PIC with a fresh pre-burned one and connected it with MIOS, I uploaded the latest software, aaand nothing. No LEDs and no sound. I misplaced the previous PIC so I don’t know if it’s the MIOS not uploading correctly. It says it uploaded correctly. But nothing happens when I reboot. I occasionally see a really short flash of leds lighting up when I switch it on.
The only thing I found out later was that I had the polarity on the power supply the wrong way around (I had it set to center negative), which apparently works fine with a high powered LCD and 8580 chips, but might be wrong when using a low powered one? Could that be a good assumption? Could that also lead to finding out what part I might have blown?
Okay this took a while, I had to replace my multimeter.
I measured the voltages in the sockets as shown in the build guide. They all give 5V as they’re supposed to, so that seems ok. Are there more points I could measure based on the base-pcb? I had a look, but I don’t know what I’m looking for. I can only find the ground points, and I can recognize the 5V points because I know they are there based on the build guide.
Alright, thanks a lot. I think it responds to MIOS studio just fine, at least it connected and I could upload and it told me everything went well. Except no reboot etc.
Always what i do in such cases - back to this point when something been working. Replace LCD with this old one to check that in this configuration everything is still working. Reason could be contrast pot.
True. That’s the first thing I tried, and it didn’t work; which led me to believe I fried the PIC. but the other thing is that all the LED’s stopped blinking on start up as well. The screen still gets powered, I can see it lighting up. But it seems there’s no control.
I still have to check those voltages with the PIC installed, but should I remove all IC’s and measure everything? I didn’t actually remove the smaller ones before, or the memory sticks, just the big PIC and the SID’s.
Only PIC and LCD should tell you they working. So remove all other ICs. Once i had problems with fried 595 shift registers - they were big short for entire circuit. Another reason could be crappy sockets and its possible because you said that PIC is responding for MIOS other thing - bent legs.
Cheers
P.S. I would also suspect bad connections via connectors MAIN PCB vs CS PCB. Bad soldering points are also possible. No blinking/disco leds may be just because differences in software or wrong software/incomplete.
Okay so I removed all the ICs except for the banksticks, and inserted the PIC. I switched it on and tried to measure voltages, but there was nothing. Not even 12V on the power switch itself. scratch that, this was just a bad connection from the power supply I was using; I was using a different one and the head of the plug was too big which caused intermittency.
When I remove the PIC I measure the correct voltages again.
Also, when I insert all the ICs except for the SID I get the correct voltages. So that’s probably nothing.
I tried connecting with MIOS without the LCD and SIDs but it’s not working anymore..
Okay I could get new 595 chips then. Is that a good next step? I believe all the voltages measure correct, the pins aren’t bent and the sockets and solder points are all fine. Could there be something else I should check?
Should I try and reburn the PICs? The guy that burnt them for me offered to do it, he told me that might be the problem.
Did I mention the fact that I soldered two wires to the bottom of the board in order to give the Optrex LCD the current? Could this have been the error? I’ve included pics of the mod here:
Hm, why was that display mod necessary? No backlight otherwise? Don´t know the sammiches, but this looks strange to me Could you remove the wires for a test?
The header for the Optrex is different from the standard Display. They are both 16 pins, but the pins for power are at the bottom instead of at the top. And the header is shifted 1 down in comparison to the normal LCD. At least that’s what I got out of it. It’s really a longshot though. those pins are unconnected on the PCB otherwise.
I’ll give it a try, unless someone can confirm this is ok.
Hmmm, as long as you install the Optrex display so, that Pin 1/2 are plugged into the pins connected with your wires, all should be well (Shuriken: the whole display pin connection is moved by one step) - did not know that Optrex speciality pinout! No need to remove the second ground wire, but no harm uninstalling it, as it is connected to ground already (see the PCB in your last dropbox upload).
Could the second wire I added be the cause of my problems? I’m going to remove it anyway, but it’s just the grounds, right?
No, it’s not ground. It could very well be you killed T1 with the extra wire.But since i don’t have the schematic of the new revision i am not sure. But since T1 is responsible for the current flow to the backlight, it’s a likely suspect.
I would remove the extra wire and my guess is you need to replace T1 (BC337). But you could check first.
First at all. Do you have any backlight? Measure these 2 pins where you soldered wires. Im not sure where there is connected transistor but probably to B-. So there should be ground potential when transistor is short and you can remove this transistor and solder there maybe 300R resistor. Second pin you have connected wire to B+ should be 5V and measure that. All measurements make to ground: B- to gnd = short; B+ to gnd = 5V. Or something like that. Thats what you have to be sure to get LCD baclight. Any reasons are: pins swapped, broken LCD led, your connected wires are shorted to gnd. Measure and if there no 5V then try to find where is the closest point you can find it. Maybe as Shuriken said: you fried T1 (im not familiar with proper row order they numbered). You can even remove entire CS and put legs from any LED inside these pins you soldered some wires (lower than 1, 2 and 15, 16). Maybe add here 300R resistor in series with your led. Now you should know that you have backlight voltage and there is enough current to light it up. You may also try the same with yours LCDs. In optrex connect 5V to pins 1 and 2, to this older 15 and 16. Cell phone chargers often use lower than 5V and it will ok for your test - thats in case you not have any power supply. Otherwise you may use sammichSID power supply but add in series with your LCD led something about 1k. I dont know you have there any resistor already soldered.
Please check your blue wire is that shorted to the ground. Looks your problems started before mod. So we have to try something different. Try maybe that sammich is responding for midi - i mean that you can play any sounds.
Could you remove the wires for a test?
