sammich - voltage check fail

[kaleaf]

hello,

I am doing the final voltage check before I install IC's. I am reading 0v from the ground to all the power spots (blue/purple dots on instructions). I checked for crossed connections with the beep mode and everything seems as it should be there so I think I must have fried something. Not sure where to go from here. Maybe you guys can help me narrow it down. I can get some readings from ground to rectifier. I am using a 9v ac 1a , also tried other 9v ac's and a 12v (not sure if it regulated).

I can post my readings from rectifier but not sure what supply to use.

---update---

with jbp header on the right set I can read 5v from J2

hope this narrows it down I have been thinking it might be the big blue cap because before I put it in one of the legs felt kinda loose does that sound like it could be it

more info

--with jumpers in 6581 mode

12v dc power

5v reads 5.01

9v reads 8.92

12v reads 12.73

9v ac in 6581 mode reads 1.2-2v on 5v,9v,12v spots

-- with jumpers in 6582 i get nothing

Edited May 16, 2010 by kaleaf

[Wilba]

Your 9V AC tests sort of show that it's not strong enough to supply 10.5V after it's rectified by the bridge rectifier, and with less than that going into the 7809 voltage regulator, you don't get 9V DC, which means you also don't get 5V DC.

The 12V DC supply is better. At least with jumper in 6581 mode, that looks OK.

The big blue cap is used to smooth AC into DC. If you supply with 12V DC, it's not that critical and is probably not the cause of your problem.

Just to confirm, when you say "--with jumpers in 6581 mode" and "-- with jumpers in 6582 i get nothing" do you mean you set both JBP and JP headers, or only JP?

Don't use JBP unless you are using a regulated DC tip-positive power supply.

Still, I can assume you've set JP to "6582" and left JBP open... that should work just as well as JP set to "6581" i.e. you should still be getting 9V and 5V. So perhaps there's some kind of short. But it really doesn't make sense at all to me... all JP does is connect the SIDs and the audio buffers to either the 9V supply or the 12V (input) supply. If there was a short to ground on the middle (common) pin of JP, then it would also be shorting when the jumper is set to "6581", shorting your input supply and you wouldn't be getting 9V and 5V output. Hmm...

Stick with the 12V DC supply. Do voltage tests with NO shunt in JP or JBP. Test voltages. Repeat with JP set to "6582", no shunt in JBP. Post results. I'll scratch my beard some more. I might have to grow back my beard, which will take a while, sorry. :whistle:

[Wilba]

OK I have a theory...

If the "6581" pins of JP are shorted together, then when the shunt is in "6581" position, it's redundant and stuff works. Then when the shunt is in "6582" position, it's now shorting between the input power (eg. 12ish V) and the 9V supply. Well, actually this is shorting between the input and output of the 7809 voltage regulator. Bad. I would not be surprised if that causes weird stuff to happen.

Check if the "6581" pins of JP are connected. You probably might have caught this when I said "Do voltage tests with NO shunt in JP or JBP" if you extended this to testing the voltages at the SID modules. With no shunt in JP, there should not be any 12V or 9V power supplied to the SID modules (i.e. top right corner pin of the SID socket).

[kaleaf]

I ment when in 6581 mode on JP mode with JBP's on I get power. When I am testing the only way I get power is with the right JBP on when I take it off the board is dead.

-testing

no shunts - no voltage

right side JBP shunt installed - can read voltage with any other combo of shunts or with other shunts removed

any other combo of shunt without right JBP - no voltage

-power supply

tip positive symbol

12v (symbol for dc) 1a

i do not know how to tell if its regulated I thought dc means regulated but I might be wrong

[Wilba]

Shunts in JBP bypass the bridge rectifier. If you are using AC power supply, then you need the bridge rectifer. If you are usingDC power supply that is tip positive, then you can use JBP shunts, however it should STILL work without JBP shunts. You should always use TWO or ZERO shunts in JBP.

Did you install the bridge rectifier correctly? The flat side should match the outline on the PCB. The "+" should be at the bottom left corner, closest to the big blue capacitor.

Perhaps there is a bad solder joint with the bridge rectifier pins. Maybe it only works with the JBP bypass because the bridge rectifier isn't connected properly.

[kaleaf]

when testing the voltage off top right sid pin

no shunts - no power

JBP shunts on, no JP shunt - 0.29v

JBP shunts on, JP in 6581 mode - 12.55v

JBP shunts on, JP in 6582 mode - 8.92v

JBP shunts off, JP off - 0.14v

JBP shunts off, JP in 6581 mode- 0.62-1v

JBP shunts off, JP in 6582 mode - 0v

no cross connects on JP or JPB

going to clean up soldering on rectifier

[kaleaf]

So I touched up my soldering on the rectifier and the 2 caps under it. When I tested I was no longer getting any reading at all. I switched back to the 9v ac.

I think it might be working now!!

J2 now shows power without JBP shunts and with jp in the right mode, yay

With the 12v dc I get no readings though, maybe I blew the supply, I noticed at one point the rectifier got really hot and I herd a slight click maybe from the cap, maybe from the power supply. It still seems a little weird going to test this supply.

any reason dc power would stop working on the board?

Wilba I really apprediate the help, I understand how hard it can be to troubleshoot remotely, im a network admin, will report back later after I check out this supply.

Edited May 16, 2010 by kaleaf

[kaleaf]

I think I had a short between big blue cap and the small yellow one next to it.

Here is my voltage results

5 volt connections (J2) --- 5.01v

9v connections --- 8.92v

(J20 and sid pin top right)

12v line --- 13.39v

(from backlight header)

is that 12volt line at 13.3v going to be a problem?

---edit i read the f'n manual

(btw I blew my 12v dc supply somehow maybe it wasnt regulated)

Edited May 16, 2010 by kaleaf

[kaleaf]

Got it to power on and show ready. Could not query device. Saw I was getting f0 f0 f0 before the id message and research said that might mean a bad cap. Is that the big blue cap?

[Wilba]

The shorts between C5 and C6 probably weren't the problem... they are already connected in parallel.

Most likely the rectifier was the problem, and why shunts in JBP would make things work, and a 9V AC wasn't working, as without a rectifier, you don't turn AC into DC.

If you blew your 12V supply, it wasn't because it was unregulated. Regulated just means there's a voltage regulator inside it. Well, I suppose with a regulated supply, a short circuit will cause oversupply of current and the regulator will shut down. With an unregulated supply, it probably just melts the transformer wires. I don't know, I'm just guessing.

Your voltages look OK now... that 9V AC will work for now, but might have trouble later when you're supplying SIDs, they'll each draw 100mA max. on the 5V supply, plus 40mA max. on the 9V supply. But you said it's 1A so it should work. 13.3V DC at no load is pretty decent, just be aware the voltage might drop.

So... I'm assuming you mean you get an upload request but it has a few extra F0 to start. I guess that means it's possible there's a voltage stability issue... it's a bit slow to get stable 5V (or just a bit noisy), so the PIC resets a few times on bootup. Replacing C5 (the big blue 2200uF cap) might be a good start. I'll post you a replacement if you can't get one yourself or can't wait :wink: just let me know.

[kaleaf]

yo, i replaced the 2200uf i also bought a bridge rectifier... i started a new thread because I did not think the problems were related