SammichSID - problems with voltage tests **FIXED**

[unikoi]

So, i got to a point in soldering, where i finished my base pcb and congratulated myself. then i started building up the control surface pcb, and thought that why wouldn't i do the voltage test for the base pcb now, because it was built! So, i put the jumpers on correct places, took my regulated 9v/12v 500mA universal adatper (with multiple connector tips), tried which one would be best (there were 2), switched the polarity to positive, plugged it in, pushed the power button, took my multimeter and started measuring, but nothing. Everywhere. Then i tried different connector tip, still nothing. The meter showed 0 V. One exception was that, it gave readings when i took it from 12V and GND, or 12V and any other for that matter. (007 on 2000m DCV) But, it will give that regardless if my psu is hooked or not. I haven't yet succesfully tested 5V on my Sammich. So, this being my first time to troubleshoot, i'm posting here to have suggestions about what should i do? Is there a short circuit somewhere, is there something fried, is it because of my soldering (tried to stay loyal to the "check twice, solder once" -motto,though), is it possibly something else? Did i forget something? I first thought that it was just the power socket, so i soldered it again, but nothing happened. Help is very much appreciated.

-Asko

[strophlex]

Try to meassure the voltage of the output of the wall wart (when not connected to the sammich) to make sure it outputs what you expect. Make sure the multimeter probes don't touch eachother. If your multimeter has connectivity tester, check that the dc rails 5V and 9V/12V are not connected to ground. If it doesn't you can use the resistance setting and messure the resistance between dc rails and ground. It should not be near zero ohms. That would be a first step.

[Wilba]

What he said.

Check your multimeter is working first. "2000m DCV" suggests you haven't set the multimeter to a good range, like 20 volts. 2000mV is just 2 volts, anything higher than that and the measurement is invalid, perhaps even showing "0" on the display.

Then start with testing the power supply is outputting anything, then measure what is labelled as "12V" on the voltage test diagram, it might be higher or lower than 12V but should be at least 10.5V to make the 9V regulator work well.

[unikoi]

Thank you for your quick reply and information!

Unfortunately i don't have a connectivity tester in this,but i'll go and see if friend of mine has one.I checked the power supply, and it's giving little over 12V (12,15V to be exact). Is that ok, or should i used it only on 9v? I also set the multimeter to 20, and checked the DC rails again, and this time i got readings! :o The other, which i assume is the 12V rail, was giving 11,78V, while the other, assuming that's the 5V rail, is giving only 0,31V, while the other probe is connected on GND. Should it be more than that, is the problem there, or should i just go find the connectivity meter and go with the instructions strophlex gave? Thanks again for info, guys, i again feel there's hope for me to get this work, haha.

-Asko

edit: i might add, that everything else was the same. No readings from what is labelled 12V on the diagram. Only readings i got was when i connected probes to dc rails and GND.

edit: it seems that it gives the same reading (around 11,7V) nearly everywhere on board, as long as i keep the other probe on 12V dc rail.

Edited March 24, 2010 by unikoi

[strophlex]

Thank you for your quick reply and information!

Unfortunately i don't have a connectivity tester in this,but i'll go and see if friend of mine has one.I checked the power supply, and it's giving little over 12V (12,15V to be exact). Is that ok, or should i used it only on 9v? I also set the multimeter to 20, and checked the DC rails again, and this time i got readings! :o The other, which i assume is the 12V rail, was giving 11,78V, while the other, assuming that's the 5V rail, is giving only 0,31V, while the other probe is connected on GND. Should it be more than that, is the problem there, or should i just go find the connectivity meter and go with the instructions strophlex gave? Thanks again for info, guys, i again feel there's hope for me to get this work, haha.

-Asko

edit: i might add, that everything else was the same. No readings from what is labelled 12V on the diagram. Only readings i got was when i connected probes to dc rails and GND.

edit: it seems that it gives the same reading (around 11,7V) nearly everywhere on board, as long as i keep the other probe on 12V dc rail.

Did you configure for 9V / SID 6582?

Everything except the 12V rail seems to be shorted to ground. Pick up that connectivity tester and make sure there is no connection between 9V, 5V and ground.

[Wilba]

My best guess at present is a short between 5V and ground somewhere... could be between 9V and ground (you didn't report if the 9V was good).

You should check nothing is shorting on the voltage regulator pins, perhaps the heatsink is touching the pins, or you used conductive thermal compound instead of the non-conductive (silicone) kind.

It's probably not a good idea to leave it on for very long while it's like this, it might blow the 7805.

[unikoi]

Did you configure for 9V / SID 6582?

Everything except the 12V rail seems to be shorted to ground. Pick up that connectivity tester and make sure there is no connection between 9V, 5V and ground.

Yes, all my jumpers are horizontally alligned, first one is on the 5V backlight voltage, other 2 are on JMI and JMO, and the SID-jumper is on JP horizontally as well. I checked up dc rails' connection with GND but didn't find anything. Then i checked the connection between the 5V rail and the third joint from dc-socket. There's a connection. If it's the dc-socket's ground leg the others being 12V/9V and 5V, then there's a short with that, although i don't see any solder-connections or anything else. I'll try to resolder that one, and see how it goes. Thank you for the reply.

[unikoi]

My best guess at present is a short between 5V and ground somewhere... could be between 9V and ground (you didn't report if the 9V was good).

You should check nothing is shorting on the voltage regulator pins, perhaps the heatsink is touching the pins, or you used conductive thermal compound instead of the non-conductive (silicone) kind.

It's probably not a good idea to leave it on for very long while it's like this, it might blow the 7805.

Oh yes, sorry about that. I did check that as well i powered it on, and took a reading from 12V rail to the 12V labeled places on the diagran, with 20 on my multimeter. It gave 0,33V. So, is there something wrong with my voltage regulators? I used non-conductive thermal compound, and check the pins as well. There's no connection between them, or the heatsink (or at least it didn't beep). Thank you for the advices.

Edit: Ok, fixed on issue. now the reading of one probe on 12V rail and the other on other 12V place/9V place is little over 11V. Does that mean the regulators work and the problem is elsewhere? i tried soldering dc-socket again, but didn't help. I suppose the two pins have to be connected. Any suggestions how do i start looking for the possible 5V and GND shortage?

Edited March 24, 2010 by unikoi

[Wilba]

Oh yes, sorry about that. I did check that as well i powered it on, and took a reading from 12V rail to the 12V labeled places on the diagran, with 20 on my multimeter. It gave 0,33V. So, is there something wrong with my voltage regulators? I used non-conductive thermal compound, and check the pins as well. There's no connection between them, or the heatsink (or at least it didn't beep). Thank you for the advices.

Edit: Ok, fixed on issue. now the reading of one probe on 12V rail and the other on other 12V place/9V place is little over 11V. Does that mean the regulators work and the problem is elsewhere? i tried soldering dc-socket again, but didn't help. I suppose the two pins have to be connected. Any suggestions how do i start looking for the possible 5V and GND shortage?

You need to test voltages with the black (common) probe on ground, and the red probe on what you're testing.

Please repeat the voltage tests, and report what the voltage is for the 9V pins, and ALSO what the voltage is going into the 7805 (the left pin of the 7805)... this will be less than 9V because it passes through two diodes. If there's no voltage (or insufficient voltage) going into the 7805 then it won't output 5V.

Still assuming that the 7805 should be working, then the problem is still (perhaps) a short between 5V and ground, so check solder joints wherever there are 5V and ground pins in close proximity. There are a lot of these under the 24LC512 ICs (aka. the "Banksticks").

[legolars]

Hijacking thread:

Iv just about assembled my base pcb and decided to make the 5v - gnd test.

and it reads about 5k if i put the multimeter one way and about 10k if i put i the other.

is this normal?

iv double and tripple checked my solderings and i cant find any bad ones.

i havnt soldered the voltage regulators yet.

if i put it at 9v - gnd, there is no leakage.

thanks

[Wilba]

MY guess is the capacitors. Perhaps the electrolytics which are polarized show different voltages. Do you have any ICs installed? They also will have an effect I think.

It's probably nothing to worry about. 5K is not a short. 5 Ohms is a short.

[legolars]

MY guess is the capacitors. Perhaps the electrolytics which are polarized show different voltages. Do you have any ICs installed? They also will have an effect I think.

It's probably nothing to worry about. 5K is not a short. 5 Ohms is a short.

allright! thank you!

im checking with another multimeter now and it shows 9.15 k both ways.

i dont have any ic:s installed.

i guess it could be the caps loading up.

the electrolytes are all the right way.

well. thanks for your help!

now i can get back to building!

peace!

[unikoi]

All right, sorry for me to took a while, to come here again.(had a break from building sammich and also forgot my password, haha.) Anyway, with your help I checked the base PCB for shorts between 5v and GND, there was none. But, I then checked the regulator leg for 12V, and turns out that it was only 0,5V. So I started looking the problem between the power switch and the regulator (i checked the power switch, and it was all right). Reason for my problems was the rectifier, AND occasionally power switch, some really bad solder joints in them. I soldered them again, and everything worked like a charm. One problem i had with the preset-upload as well, was that it strangely cut the uploading process in the middle, saying midi-connection lost. i think it was the 5th or 6th time when it got through, and the reason it did that for me, was because of a PSU-tip too loose. changed to a smaller one and works good so far.No random resets. So, thank you for your help, because of it i'm an owner of a working sammichSID!:)

[Wilba]

Good to hear it's all fixed now!