PT80 getting hot and starting to give off burning smell - plz help

[Pushtone]

So it's still getting hot?

And what is it thats getting hot again? I forget.


Not sure what the neovibe has to do with it. And I don't see the non-polar cap head spaz is talking about.

Your board photos look the same as the instruction pdf and mine as far as the caps go.

Perhaps you should modify your board to comply with the "non-charge pump" layout also available at GGG.
Eliminate the charge pump and see if it works then.

Dave

[stumper1]

Re-read the pdf on the neovibe. Might I suggest that you re-read it with the sole intent of COMPREHENDING what you're reading this time? Simple deduction indicates that the extra resistor values are provided as revisional options, for tayloring the circuit to your particular taste.

If you want to fix the volume drop and use true bypass, change resistor R9 to 3.6K and resistor R8 to 910 ohms.
This increases the gain of the initial preamp to make up for some of the losses.

I don't see a battery in your pics... are you using an external powersupply. Are you SURE that its output is DC and not AC?
Why are you using nonpolar capacitors in the charge pump circuit?
Something is not right with your readings on the MAX1044. Pin 3 should be zero volts... it's supposed to be at ground level.
Have you verified the polarity of your power input?


When in doubt.... RTFM!!!

[znowman]

can anyone confirm what that neovibe guy said about needing polarised caps with the max1044, (i assumed polarity wasnt an issue, due to no mention on the layout), and as far as the battery goes, ive just ommitted the live wire from the dc jack to the battery and ommitted the negative wire from battery to ring, as i only use a wart

just wanted to confirm these details before i start ripping wires off the board and doing it again...

cheers

[stumper1]

I can't read the values or voltage rating on the caps you are using - but they are polarized and appear to be oriented correctly.

- I have no idea what the NeoVibe guy was talking about.............  anywho...

What kind of wall wart are you using?

[znowman]

i think Head Spaz ("neovibe guy") was on about the 1uF caps, i believe you can get polarised 1uF's (the previous GGG layout drawing had the polarities shown)

simple deduction indicates

that Head Spaz didnt follow his own advice by reading/COMPREHENDING what i'd written 

for power supply im using a regulated 9v wart, polarity is also correct- ive just tried the wart with my rodent, and all is fine

Perhaps you should modify your board to comply with the "non-charge pump" layout also available at GGG.
Eliminate the charge pump and see if it works then.

i did think of doing that, but the problem is, ive already built a PT80 (without charge pump), but my friend who im building this for has one of those specific stompbox power supplies, which runs 5x 9v supplies (i think), so it needs to work with 9v

i suppose i'll try rewiring (as Papa_lazerous suggested) and if that doesnt work, i'll bypass the charge pump part, to see if thats causing the problems

thanks again for all the help...

[head_spaz]

OK... I deserve it. Go ahead and laugh it up.
And when you're done.... go fix your PCB.

[znowman]

OK... I deserve it. Go ahead and laugh it up.

i hope you werent offended by what i said, i am in no position to laugh at anothers writings, due to some of the rediculous things ive posted on boards in the past (usually when tired/drunk etc...)

i know it looks like i dismissed what you said, but it made me check how my power wiring was done (without a battery), and that the power supply was working correctly, it also made me ask about polarised caps

so i am honestly grateful for your input, it was just how you worded it really.

anyway i will look at what you have suggested in that pic tomorrow - need sleep now...

[znowman]

hmmm, should i unsolder and remove the 100uF cap from where the jumper connects, are you thinking one/both of the caps are suspicious ?     i can replace them if needs be

[head_spaz]

are you thinking one/both of the caps are suspicious ?

No.
Your PCB, the layout itself is in error.

[GREEN FUZ]

It`s true that your PCB seems to differ from the one pictured on the GGG website; specifically in the area that head spaz has pointed out.

[head_spaz]

Don't ya just hate when that happens?

[Papa_lazerous]

who made the PCB then?

[znowman]

god only knows how you have managed to spot that Head Spaz, i would never have got it in a million years.

i etched the board myself but other than thickening the tracks up a bit in illustrator...  damn, must have happened at that stage (i etched two at the same time, so i will check the other to confirm it)

anyway, i will correct the error tomorrow and see what happens - i'll keep my fingers crossed (and i'll let you know)

[head_spaz]

I caught the error because the MAX1044 - pin three - should have measured zero volts, as I pointed out in a previous posting. Your ground was missing. What else could it be?
Testing has a purpose, but often test results are misinterpreted. Good thing it wasn't heart surgery eh?

[znowman]

YES !  that has done the trick, everything is working fine and sounds great, i really dont know how to thank you people, and Head Spaz get a large cookie

it was completely my fault, as the other board i etched has the same problem, not sure what the hell i was thinking about, when i did it 

Good thing it wasn't heart surgery eh?

my way of removing healthy parts while leaving the problem would probably make me a good NHS surgeon  (only joking)

anyway, thanks again for all the advice and help you've given me - i really do appreciate it, and ive learnt a few valuable lessons from all this.