Possible damaged chip?

Hardware questions and issues with the FV-1

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differo
Posts: 22
Joined: Fri Feb 26, 2010 8:01 pm

Possible damaged chip?

Post by differo »

I've built the circuit/board from the Scmatics on Tonepad site. I'm currently studying/debugging this circuit which is really hard because of the complexity of the chip.

I've might damaged the circuit. It never worked, I traced the signal to the pin one without problem. But I'm not getting anything on either output pins. Circuit is rather simple but yet a buger. I don't own oscilloscope which makes it hard to debug even more. I don't know if watch is ticking, and the biggest one: clip led is on all the time. I don't remember if it was lit from the begining, I've stared to this board now a several hours too long for a day.
If anyone have anything, advice, recognizes problem, well anything, I would appreciate it a lot.
I use lm317 on a separate perf board to get regulated 3.3 V.
djmalan
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Joined: Fri Mar 06, 2009 8:22 am

Post by djmalan »

I got the chips from sergio and ,built 40 pieces of boards with lm317 at 3,2 volts by using input polarity protection diode before lm317 and 4,7 ohm res.,till now I have same problem about 2 chips no output and clip led is on all the time and 1 chip was ringing with the last internal rev. program I solved the ringing by using only external memory,till now 2.5 chips vaste.. :(
frank
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Post by frank »

Hmmm, very odd. We do 100% testing so it is possible it is what we call 'infant mortality', chip passes test but fails a short time later in circuit. There is no test for that.

Couple things to check... do you have a 15pf cap on the X2 pin (pin 9)? Some designs omitted this and it is required for certain crystal manufacturers. The clip light being on is one of the indicators of the crystal not oscillating correctly. Power good and stable? If you can get your hands on a scope it would really help to debug.
Frank Thomson
Experimental Noize
differo
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Joined: Fri Feb 26, 2010 8:01 pm

Post by differo »

Sorry I forgot to mention, yes I have a 15pF cap there from osc to the ground, I do have lm317 power supply that does not change over time (the chip becomes somewhat warm but nothing extreme), its a plain 317 power supply (two resistors and two caps on a separate board). I measured all the voltages on all the pins and it seems to sorrespond to the pins in the sheet - I can not know the exact voltages to be anticipated but I don't have any voltages over 3.3V and no voltages on the grounded pins. I've checked for the shorts, none that I could notice. But I do have some DC voltage on the input pins (1 and 2) which is kind odd isn't it? like around 2V, somehow I want to belive that I should expect any dc voltages there..
Is there any chance to check the oscillator part without oscilloscope? I don't any one unfortunatelly..
If the clock is not supply none output can be generated? not even in the possition 5 for debug? (clean sound)
I would really like to know what I did wrong at least not to fry the next chip I order if it shows that this one is damaged.
differo
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Joined: Fri Feb 26, 2010 8:01 pm

Post by differo »

Ok, after many many hours of what-not trying and abusing the board, I got some sound of of it! But I hear some clicks and pops on everything but this is not constant sometimes it manages to work for 10 seconds and everything sounds nice (some noise present but nothing too much) reverb, pitch, flanger chorus, tremolo everything works and adjustable. And the damn:) led is not lit anymore. But after a while and sometimes directly after start it goes crazy, clicks pops, noise.. Really hard to do anything more on my own, I'm running out of the ideas. I tried different values on X2 cap, seems to be no difference between 10, 15 or more pF. Power supply: I tried some tricks to make it even more stable (it's constant on 3.3V during the tests even when the clicks start. Current is around 70mA but varying around that value +-10%. I tried to supply it with two batteries in series (1.5V) it works but no improvements on clicks and pops. The things is that these clicks also appear on the input stage (tested with audio probe) but on input they are quieter and much louder on the output.
Frank, as an expert, please tell me you have experienced something like this, or am I just a guy with no luck at all? :)
frank
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Post by frank »

OK, if the clicks are on the inputs then it is not the chip, it is something external to the chip. Check everything on the input audio path, power rails, etc. Basically find the source of the clicks.

Exactly what did you do to start getting sound? That may help determine the source of the problem.

Also an exact schematic of what you built will help. Photo may also help.
Frank Thomson
Experimental Noize
differo
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Joined: Fri Feb 26, 2010 8:01 pm

Post by differo »

Hey Frank, thanks for propmt answer! I used the tonepad schematics Fraverb the one that is current on the website http://tonepad.com/project.asp?id=68 the changes I did is that I added the cap 15pF to the ground on X2 and reversed fets as they are shown opposite as they should. The circuit is rather simple so I'm starring blind to it now.. The thing is, if I disconnect the resistor 1K towards the chip, I don't get any clicks there with audio probe and strumming guitar. As soon as I connect it back this starts. I tried connecting both inputs together and separate, no significant difference. I cut the lead to the voltage reg IC in the tonepad layout and added separate power supply done with lm317 on a perfboard. I just connected this supply where layout IC should provide +3.3V. Any ideas?
differo
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Joined: Fri Feb 26, 2010 8:01 pm

Post by differo »

Also, the fet buffers are socketed in a female headers cut to size three, when I swap them to other ones nothing happens, don't know if socketing can cause this.. its something happening between the input hole where guitar signal comes in (NO clicks there!) and pin 1 on fv-1...
frank
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Post by frank »

What are you using to generate the voltage into the LM317?
Frank Thomson
Experimental Noize
differo
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Post by differo »

I have a 15V wall adapter that goes to 7809 regulator (with some filter caps etc..) which usually doesn't have noise on my other builds. This is then fed to the board and to the lm317 circuitry.
frank
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Post by frank »

Hmmmm, I assume you are using the output of the 7809 for the 9V to the board so it appears to be in the input section since if no clicks go in the input of the chip no clicks come out so not being generated by the chip.

Not having a scope makes this more difficult (would like to see that 9V rail looks like), do you have another low gain pedal that you could use it's input section to drive the circuit? Basically disconnect the 1K resistor from the FET and tie it to another pedals input buffer, I'm trying to drive the FV-1 using a different buffer for the guitar. Remember to tie the grounds together as well.
Frank Thomson
Experimental Noize
djmalan
Posts: 36
Joined: Fri Mar 06, 2009 8:22 am

Post by djmalan »

Hi,today I got some new experience about my broken chips(they re not broken but...)
1-I tried 15p cap.,result is ;no change.
2-With 2 1.5volt cells,result;no change.
3-Started the chip ,with pin13 (T0) with internal memory(logic0 ,to the ground) ,chip worked with internal program ,then seperated it from the ground(for external program),it worked. So I'll add a private code in microcontroller only for these two chips for opening. :D

I have no scope ,but I feel as these 2 are saturating too much or locks with pin13 when starting with logic1,because when it starts I get some hiss noise ,than after 1 second it goes with a noise like 'PLOPS'.

Finally ,this is my way to use them for now ,but I forgot to measure the amps crossing inside the chips when I see them working ,cause my happiness (normally from the others I got 50,55 ma)...

And when I use with higher voltages (9-15) I put always 150-220 ohm/2W resistor before the Lm317 (good for 317 ,so I dont need cooling).
djmalan
Posts: 36
Joined: Fri Mar 06, 2009 8:22 am

Post by djmalan »

Publishing a service datasheet is a good idea includes everything or so close to everything about the chip... :D
differo
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Joined: Fri Feb 26, 2010 8:01 pm

Post by differo »

djmalan could you explain more about what kind of noise pops you get? how long does it last? and what exactly are you doing to get rid of it?
frank, I'm really determined to fix this (or at least find out what the problem is) so I got my self a simple scope today:) its pretty simple called nano from seeedstudio but maybe it will work to get some idea what works and what not. I could at least see that clock is ticking but its unclear for me at which freq because I dont know yet how to read values :(
Do you have any guidelines what to try to observe with the scope in order to get some information? possibly if you can explain how and what to look for, it was ages ago when I used oscilloscope back in school and it was completely different than this one.
thanks
djmalan
Posts: 36
Joined: Fri Mar 06, 2009 8:22 am

Post by djmalan »

It just sounds 'PLOP' or PLOP sounds :D
than finish.Than alittle bit deep sound like dc as saturated too much.
But I have no heat on chip.Inspite of shorting the inputs to the ground (not the pins of the chip directly ,theboard inputs are grounded)output voltage is sometimes 2v for the one channel,the other is app.1 volt I think this shouldnt be more than the half of the supply voltage.(1.65 should be maximum).
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