Tonepad FSH-1 not working. voltages..etc... please help

[oldrocker]

Check this area of the circuit.  Make sure that Q5 and Q6 pins are correct.  Audio probe starting at the drain of Q6 and see where the signal stops.  Double and triple check everything in this area and I mean everything.  There is no quick fix for debugging you'll have to dig deep and trace the circuit using the audio probe to find the cause.   Good luck.

[gijimmbo]

here are my voltages from q5 and q6:

Q5  =

-7.4 (ish)
-.2
-7.4 (ish)



Q6  =

+9.63
-5.9 (ish)
-7.4 (ish)


this seems very strange when compared to gigimarga''s.  is this some clue??  i tried audio probe for a second, but have not explored fully the audio probe of this section of circuit. 

[oldrocker]

Double check the pinouts of those Jfets and solder issues too.  They need to be oriented right.  Do a google search for the jfet type and company brand.

[gijimmbo]

alright, here's some stuff i found online, but i can't really make heads or tails of this stuff.  i am still a noob at transistors in general and don't really understand much, except what is posted in the wiki page.  how can i tell which way they should be oriented according to this stuff?  additionaly, not sure about pinouts, ect.
thanks a bunch for helping.  i hope this stuff helps, cause i don't know the company brand, just the name of it.   

i searched for this in google:     bf245a


http://www.nxp.com/acrobat_download/datasheets/BF245A-B-C_2.pdf

http://www.datasheetcatalog.com/datasheets_pdf/B/F/2/4/BF245A.shtml

http://www.fairchildsemi.com/ds/BF%2FBF245A.pdf

[gigimarga]

If you used BF245A as i did you must only to flip all the 3 FETs, as you said before (thx a lot again...i gaved up to try to make mine working good)...

[fogwolf]

You do want to flip the BF245A (at least for the Fairchild - I'm assuming the pin out would be the same for every manufacturer but check the data sheet for your specific make just to be sure). Look at the pin out on page 1 of this data sheet (again, this is the Fairchild BF245A) - I'm referring to the large diagram at the top right of the page:

http://www.fairchildsemi.com/ds/BF/BF245A.pdf

This will show you which pin is which (Drain, Source and Gate - you can see they label pin 1 here for you then show you the pins are Gate, Source and Drain in that order starting with pin 1 - make sure to note the orientation of the part in this pin out diagram when connecting your Fet). If you then look at the parts layout on the Tonepad PDF, don't look at the shape of the transistor in the diagram, rather look for the "G" symbol that is next to one of the pins on one end of each transistor in the diagram. You will want to connect the gate pin from your transistor to this pad to orient the transistor correctly. In the case of the BF245A, this is backwards from the way the transistor *shape* is drawn on the parts layout diagram at Tonepad, which is strange, because they say they used the BF245A for the Fets. Regardless, they make it unambiguous by putting that "G" in each one - helps to clear it up and give you some flexibility for whatever Fet you decide to use (though you could always consult the schematic  as well to double check).

alright, here's some stuff i found online, but i can't really make heads or tails of this stuff.  i am still a noob at transistors in general and don't really understand much, except what is posted in the wiki page.  how can i tell which way they should be oriented according to this stuff?  additionaly, not sure about pinouts, ect.
thanks a bunch for helping.  i hope this stuff helps, cause i don't know the company brand, just the name of it.   

i searched for this in google:     bf245a


http://www.nxp.com/acrobat_download/datasheets/BF245A-B-C_2.pdf

http://www.datasheetcatalog.com/datasheets_pdf/B/F/2/4/BF245A.shtml

http://www.fairchildsemi.com/ds/BF%2FBF245A.pdf

[gijimmbo]

thank you very much fogwolf that was an awesome help!!  well i guess i have them on the board correctly, time to start checking solder joints and stuff.  and back to the audio probe.
thanks again for the info

[gijimmbo]

o.k. solder joints are fine, i've checked them a ton of times, rid them, etc. 
while conducting audio probe of this part of the circuit, i don't get any signal at all, just loud ticking that changes when i turn the speed pot.  i did like oldrocker said, and started probing at Q6 and Q5, no signal except that ticking.  probed all around the area, and nothing. 
what does this mean? 
thanks again for taking time to help!!!!

[oldrocker]

[gijimmbo]

oh, sweet! thanks again man. 
i'm sure now that i have the transistors oriented the correct way.  however, now when i use an audio probe on that part of the circuit, i get no signal, except the ticking sound...which is comming through strong and clear. 
do you have an idea what this means??  i am getting signal on other parts of the board, but where does the signal from this part trace back to?? 
sorry if these are dumb noob questions.  i am trying to figure this out and learn from my mistakes. 
thanks again,
alex

[gigimarga]

Any good news? Do you make it working?

[gijimmbo]

no progress yet.  i gave up thinking it was a soldering/pcb/wiring issue. 
i'm sure i have all components properly oriented and the S/H part of circuit is still not working.  using an audio probe, all i get is this loud ticking that changes speed when i turn the pot. 
i don't know. i finally put in an order to small bear for new parts (local electronic store doesn't have the BF245As). 
i'm going to replace all the transistors (using sockets this time!!!!! ) and ics, cause the only other thing i can think of is that i probably fried them when i was resoldering them like 5 times.  i don't know how to tell if they are bad or not, but i can't think of anything else.
i will probably get working on it again in a few days once the new parts arrive.

[gijimmbo]

egad...great googly-moogly....

it's ALLLLLLLIIIIIIIIIIIVVVVVVVVVVVVVVVEEEEEEEEe.........

i got my order from small bear last night and today i put in the sockets for the transistors, and all new transistors.  i also replaced the two opamps.  now it is working great and i couldn't be happier.  thanks for all the help guys.  i really appreciate it.  i knew if i worked slow and methodically i would eventually solve it. 
theres nothing like kicking a circuits ass and saying "hahaha..i beat you"
now i will spend the day boxing it up, but i'm sick of making nice boxes, so probably just throw this crap together with nothing fancy. 
thanks again everyone!!!!

[gigimarga]

WOOOOOOOOOOW...

I'me very happy for you...mine it's working good too, but i still have problems with the ticking...i hope to resolve it very soon...

CONGRATULATIONS!!!

[liquids]

Gigimarga - FYI your voltages were very helpful!  I just breadboarded it, and was able to get it working with the assistance of your voltages. 

I can offer some more info I didn't find here...this applies only to the sample and hold side, as at this point I've ignored the envelope filter part altogether.

To add to the bucket, I would say that the voltages in a few other places are helpful as well.  I found that I got it working with the MPSA13 or other fairly high gain transistors, as well as 2N5088s and 2N5089.  I didn't try too hard, but notably the 2N2222 and other low gainers did not work for me.  But more important than this vs. that transistor mojo, the functionality of the said transistors as Q1 is also dependent on other variables, I believe, rather than just plug and play for 'best noise'....whatever that means.
It's frustrating to be turning two trimmers, hoping that at some point you'll hear it work. 
Knowing the voltages in other places helps.  So once I got it working, I did some sophomoric voltage probing on some of the transistors....  I found the S/H part is only going to work with a variable voltage in the proper range  on the collector and emitter of Q3.  Everything worked when I could get a variable voltage on the emitter of Q3 (per the tonepad schematic) that varied +/- 2v from ground or so, over time.  And FYI, if you aren't already getting a continually variable voltage at the chips in the appropriate pins, as documented by gigimarga, than the S/H side is certainly not going to work, so continue debugging until you get those variable.    

Voltage probing at 'CV' or the collector of Q3 when everything is connected properly should result in your DMM reading a variable voltage that stays negative, and varies centered around -7.5v or about .5v  above your -8v voltage (adjust for batteries and power supply). Without connecting the collector of Q3 to the 22k resistors that then feed the 13600 pins 1 and 16 (I just wanted to see and it's easy to check on the breadboard), the voltages at the said collector will be very different.  They will vary just above ground around .5V.  This may be of assistance in make sure that connection is being made.

The Q1 transistor swaps certainly change the range of the variable voltage on Q3 emitter.  Changing transistors and FETs means potentially needing to re-setting the trimmers until the voltages read the right range for the sound you want.  This takes the pressure off hoping for the perfect silicon a bit and puts it on the trimmers and your DMM...and swapping parts, so long as two trimmers could 'compensate' enough to get Q3's emitter back to varying between just slightly above and below ground (as mentioned above), than things would work.  The 'correct' sound is subjective and may indeed be influenced by the transistor and trimmers in other subtle ways, but basically, if all the variables there can align, it definitely functions, which is a better starting point for tweaking the sound.  I'm not sure that the 13600 can 'hear' anything but the range of voltages it's being fed on pin 1 and 16 when it comes down to it...

Tweaking the trimmers is a matter of taste at the point you have it making a S/H type sound. Some combinations forced the trimmers into the extremities of their ranges, or beyond their ability to compensate, hence being unable to get the right voltage ranges it seems...  The 10K trim is definitely the 'macro' trim for getting the voltage on Q3 emitter in the right range, while the 100k is the fine tuning of the voltage range.  I tried different value trimmers, 25k for example, and it did work, though I'm not sure it made it less sensitive--maybe a bit.

Also, I didn't get too deep into it, but I found that Q6 is picky. I don't have the original FETs mentioned for in my stash and I wanted to try it now, so I used what I had. In my experience, Q5 seemed to worked fairly well with about anything I tried in there--J201s and MPF102s. 

On the other hand, for Q6, my experience was that MPF102s and 2N5458s and 2N5485s worked easily and consistently, and I had limited to no success with J201s and 2N5457s in this spot.  That probably just means Q6 has a lot more bearing on the voltage range than Q5 does.  That doesn't mean they 'wont work,' but note that combination of variables means one change throws everything off and needs compensation.  The rest is taste!

[gigimarga]

Gigimarga - FYI your voltages were very helpful!  I just breadboarded it, and was able to get it working with the assistance of your voltages. 
...................

Hi liquids!

Your made me very happy because i can help someone here!

[chromesphere]

Sorry to dig up this old thread.

I too was getting quiet output on S&H mode.  The wah mode was fine, but the up down switch and the S&H both produced a low output with no audible effect.

Thought it might be worth while confirming, Liquids is correct.  Unless you have a varying voltage on Q3, (volts, mine was about 3.5-6 volts) S&H will not work.  I used the recommended on jfets on Tonepad.  I dont know, maybe i got lemons, but they didnt work.  No amount of turning the trimpots would make that Q3 volt fluctuate.  I then changed Q1 to a 2N5088 and the Jfets to J201's.  Straight away it was working, i didnt even have to adjust the trims at all!

Thanks for going to the trouble of supplying this description Liquids.  You put me on the right track!

CS

[liquids]

So glad that after all this time, one person was helped by my verbose write ups!

[chromesphere]

Yeah thanks liquids, it was a great help.  As soon as i knew what i was looking for, it made the pedal so much easier to get going.

Unfortunately, i think i've fried my max1044.  I was poking around the board with an LED + res, trying to find an LFO, an up/down switch LED & mode switch leds (which i found 2 of the 3).  I could smell something toasty.  Touched the max1044, burnt my finger on it, red hot.   Didnt take much to break it!

I'll order the TC1044 this time, apparently its harder to bust.  Bugger!  Had it sounding amazing!  Oh well, minor set back...

CS

[liquids]

I find the LT1054 much easier to work with, and more importantly, cheaper.