I messed up! Not getting 5.333V range

[game-tech-us]

This is my first xox, I ordered the express kit from Willzyx and the rest from mouser and digikey.
Anyway, i'm not new to electronics so i'm sure the other parts are correct and my soldering skills are excellent, the ft232 was easy.
What I did do was a total newb mistake and put one of the 2200uF caps in backwards! I still can't believe I did that!
I caught it before it exploded in my face, the domed top was a dead give away.
I've triple checked all resistor and trim pot values and all 8 diodes were pulled and checked out of circuit, all good.
But I still can't get the 5.25 to 5.75 volt range. I've stopped there, there are no other components in the board, except the ft232.
I do get 5.01vdc from the 7805. 5.98vdc from the 7806. Lm336z5 1.881v on pin 1 and pin 2 range of 4.56 to 4.82.
My psu is 9vac 1.3A, shows 10.9vac with no load.
Is the lm336z5 toast?

edit: Of course I also replaced the 2200uF cap! Forgot to mention that...

[mmm]

While the LM336 could be at fault here I would like you to measure the voltage from pin 4 to pin 8 for IC23 (or for the solder pads if IC23 isn't yet installed).

[game-tech-us]

While the LM336 could be at fault here I would like you to measure the voltage from pin 4 to pin 8 for IC23 (or for the solder pads if IC23 isn't yet installed).

With pos lead on pad 4, it started out at ~23mV but wil not stay put, its still moving, after ~1 minute its at -310mV and still going.

[mmm]

Hmmmm. Can you measure between ground (or pin 4 of IC 23) and either side of R1? (Make sure that it's a DC measurement.)

[game-tech-us]

Hmmmm. Can you measure between ground (or pin 4 of IC 23) and either side of R1? (Make sure that it's a DC measurement.)

Disregard previous post, I was measuring 1-5 not 4-8, I also switched out of auto range and got it on V, it shows 2mV on 4-8 of ic23 unless I touch stuff like the top of c2 then it goes to 15mV, weird.
R1 is not populated either, pad nearest c2 shows 28V, other shows 0.

[mmm]

Ok, then let's follow with either side of R2 and R3.

[game-tech-us]

Ok, then let's follow with either side of R2 and R3.

R2 leg closest to c5 28.3 other 25.3
R3 leg closest to r2 25.3 other 4.5 to 4.75 depending on tm6

[mmm]

Ok.

Could you also measure the voltage between the various components in the reference section:

between D44 and D45
between D45 and R5
between R5 and TM6
between TM6 and R4
between R4 and D46
between D46 and D47

For two different boards I've checked I also found that the input for IC23 is not at 5.33v (it's more like 5.20v) but the output at J4 sits at the normal value. But 4.82v is probably too low.

[game-tech-us]

I assume you mean voltage to ground at the junction of these pairs of components? If so:

between D44 and D45 .55V
between D45 and R5 1.1V
between R5 and TM6 1.87V
between TM6 and R4 2.46V
between R4 and D46 4.22V
between D46 and D47 4.76V

[mmm]

The relations of the values look ok so we can assume that those components are fine.

Doublecheck again the value of R3. If it is correct then IC22 is probably faulty.

[ScunnerDarkly]

I'm on my first build and I had exactly the same problem. I was using the build guide on ladyada.net and got stuck at the stage where it shows a voltage reading of between 5.27v and 5.76v being taken from IC23 pad 5, before IC23 etc is fitted. I couldn't get anywhere near, the best I could muster was 4.92v and thought the worst. Spent some time changing components over from another kit but still no joy, and everything was where it should be and the right way around.

Then I looked at some other guides and they showed the desired 5.333v reading being taken from J4 after IC23 and its surrounding components had been fitted, so I figured I'd tried everything else so I took a leap of faith and went for it.

End result, after finishing the complete PSU section the output range is now from 5.25v to 5.75v (ish) measured at J4, with the 5.333v easily achievable.

Worked for me so if anybody else is stuck at this stage it's worth a go

Cheers, Darkly

[mmm]

Then I looked at some other guides and they showed the desired 5.333v reading being taken from J4 after IC23 and its surrounding components had been fitted, so I figured I'd tried everything else so I took a leap of faith and went for it.

End result, after finishing the complete PSU section the output range is now from 5.25v to 5.75v (ish) measured at J4, with the 5.333v easily achievable.

As was suggested by aminoacid in the xoxmods forum this may have something to do with the impedance of the multimeter. So yes; by all means it is a good idea to see if things work with IC23 installed in such a situation.

[game-tech-us]

I swapped in a new 366z5, got a higher range but still only 4.7 to 4.99.
Put in all the rest of the parts and only get 5.31v and 11.8v at J4 with TM6 maxed.

[mmm]

Since you are still getting different readings between input and output of the buffer and the output of the buffer is "almost there" I personally would for the moment continue building the xoxbox and then test the voltage again under full load (with the populated mainboard connected). The different values probably hint at the aforementioned multimeter impedance problem. Do you have a different multimeter that you could use to doublecheck?

[game-tech-us]

Cheapy DMM and HP oscilloscope confirm low readings.