Soundtank FET Switching "sticking" ,very erratic..replaced switch.. CULPRIT??

[analog kid]

I have a problem with a DL5 Soundtank where the on/off is extremely erratic. stomping it harder and presicely seemed to make it switch more consistantly so I attributed it to the cheapo little switch going bad. When I got a new one and popped it in there to my surprise the situation remained the same! It will switch if you press it enough times  but extemely erratic!
I know most of these stomps are not much to write home about but the Super Chorus and Dig Delay to my ears are alright and kind of fun little boxes. And at least I'd like the option of selling it If I ever want!
SO.. aside from the mechanical of the switching itself (replaced), what else in the FET circuitry is likely to go bad and/or cause this 'sticking' problem??
If anyone has experience with this I really appreciate it!!

[George Giblet]

It's *highly likely* it's the little push button. 

The circuit goes switch -> small series resistor -> 1n Cap

Replace the cap with 10n to 47n cap.  That will keep it going for some time.

[analog kid]

You say likely to be the switch? I replaced it with a brand new one. Still does same thing! You can step/press on it 10 times sometimes before it actuates! Then other times if you step hard and direct it will switch everytime
This isn't a Flip Flop FET switcher? I thought it was but I don't see the same setup as the boss crkts and I"m not that exp with these.
you say that's all there is to the switching(switch, res., cap) And that replacing the cap "will keep it going".  Well by that are you saying that cap failing could cause this behavior? That's really what I'm trying to figure out here, what's the culprit?  I didn't expect it to be anything OTHER than the switch at first. and unless I got a bad new one from Steve then It obviously wasn't the mechanical

[George Giblet]

Ah now I see you had "(replaced)".

My solution is aimed at the Flip/Flop types.    Over time the push button switch bounces more and the filtering provided my the 1n cap isn't enough to cope with it.   Increasing the cap as I suggested will usually fix it because it decreases the bounce time.  You can of course replace the switch.   The supplied 1n cap doesn't fail the value change just makes the circuit less critical regarding switch bounce.

Now I don't have a schematic for the DL 5 but I know some of those Ibanez effects with the "big chips" don't use the flip-flop circuit.  The push button switch connects to the one of the big chips.   Typically something like a 1MEG pull-up and a 1nF cap directly across the switch.  I saw one which had a power-on reset circuit using a transistor+resistor+caps, the transistor connects across the switch and also to the big chip.

The (possibly) bad news is in those cases there is very little between the switch and the big chip so if the switching is failing, and the switch is OK, then it could be the big chip.  However, before the doom and gloom sets in I suggest tracing out the circuit around the switch at least you will be able to make a better judgement.   Also,  don't rule out that one of the jacks, the power connector, or the power supply is dodgy.  If those are loose the power could be going on and off and that will make the unit behave erratically.

I can only point your nose in a few directions, unfortunately I don't know a recipe solution for that one.

[George Giblet]

If you go here and download the mods pdf

http://filters.muziq.be/model/ibanez/soundtank/dl5?PHPSESSID=50a5056af1cbc879c0ea91b8aac707b3

there is a section which talks about the intermittent switching.  The suggestion is to change the cap to 5nF.  So possibly the cap trick works on that one.

I don't know what is wrong with you new switch, possible nothing, it's just the design of that circuit is dodgy.

[analog kid]

ah! Sorry I didn't read your replies until just now. Thanks very much, this is exactly what I had been looking for referring to the link. I haven't tried the cap tweak but I DO believe it not to be the switch (cause I've never got a flakey component from steve before, not that it couldn't happen from any parts house) and that it IS a prob in the circuit switching itself..]BUT I have a pile of these soundtanks , which some of which actually are worth while IMO, but have been wondering about finding simple mods for some of them(aside from just Input cap and hifi changeouts) and never have found any ~
Are there such pdf's on this site for many other of the '5' series??

[analog kid]

( I looked , and it seems that the DL5 is the only of the soundtanks that have mods listed there, of the ones I own at least. but that's some pretty cool stuff for it though! Maybe this "5" series delay isn't quite the crap effect that alot of the 5's are?
Anyhow I did replace C4 with a 4700pf cap , up from 1000pf and it seems to make no change . actually this thing's erratic switching seems to have gotten much worse the more I use it! I can push it like 10 times before it will On/Off. 
Maybe I will try another switch just in case.  I picked up 2 from Steve awhile back.
IF NOT 'A FIX - You mentioned this being a different switching system than FET flipflop , using an IC instead. IF SO and all else fails to fix the prob then Is it likely that the IC has went bad?? I haven't heard of IC controlled switching before .  You called it "the Big chip"..... There's a BIG.. M50195P chip slightly on top of the switch , is that the one ??   If not there is another IC closer to the Switch and to the left. An NEC D4164C.  I guess I may have to trace and see which if either of these have pins that connect to the switch. But I'd like to know for sure so that maybe I will pick one up with my next Mouser or Jameco order.
Thanks again friend! You've been very helpful. I just would love to get this thing switching

[George Giblet]

It took me a while to work out what effect it was.  The one with the "big chip" is the DFL from,
http://www.8bitsindgenug.net/mn0bit.htm

Note that this unit has JFET switch which is driven from the big chip.

The M50195P datasheet is available from,

http://www.datasheetarchive.com/semiconductors/download.php?Datasheet=1230724

I cannot see any built-in switching.  It's just a typical digital delay chip which runs off an external ram chip (the NEC D4164C).

I strongly recommend tracing a small part of the switch circuit - if I had to guess I'd say it was a flip-flop + JFET thing.

Have you tried pressing on the button itself instead of the footswitch?  Perhaps the problem is mechanical.

[Paul Perry (Frostwave)]

Why not temporarily bypass the switch with a pair of wires, so you can see clearly what happens when you touch the wires together? Then you will now once and for all whether it is a switch problem.
It sounds more like a logic problem, maybe a partial short by gunk on the board.

[Stompin Tom]

rehouse and true bypass?

I imagine you actually want to fix the pedal and leave it in its current enclosure, but I recently rehoused my DL5 (in addition to the switch going bad, and the cap changing trick not working, the crappy pots were getting really scratchy and one of the jacks started to stick).  Plus there's potentially more room for mods in a new enclosure.  I used a box from effects connection:

http://effectsconnection.com/oscommerce/product_info.php?cPath=21&products_id=56

but I had to sand down(!) the top and bottom of the board to get it to fit lengthwise and it's really crammed in there because of the true bypass switch...  I'd try to find a slightly bigger box or at least a deeper one.  My unit also developed a high pitched whine even while bypassed...  I'd suggest leaving the buffering/fet switching in the circuit (leaving it on all the time) instead of completely removing it from the circuit (like i did).  I suspect this would eliminate the high pitched whine problem (because if I use a buffered pedal before my rehoused dl5 there's no more whine). 

In anycase, I like the dl5 sounds, too.  It'll probably sound even better once I get all the mods done...               

[TheBigMan]

Given that the switches are momentary, and that the usual problem with Soundtanks is that they toggle whilst you have your foot on the switch but don't latch, it's reasonable to assume that the problem is not the switch but a poorly designed flip-flop.

I haven't done the cap change myself but I know a guy who has on a TS5 and it worked for him.

[analog kid]

Have you tried pressing on the button itself instead of the footswitch?  Perhaps the problem is mechanical.

Yes that is the way I check it always. It doesn't work any better directly on the switch. Actually you can get a better PRESS to ACTUATE ratio (I guess that's what you could call it?) when Working it with the pedal mech. because it sems you can really push it harder and get it to actuate, at least more frequently. don't know if that means anything and i realize that it kind of makes it sound like it's not electronic related if this is true.

Why not temporarily bypass the switch with a pair of wires

That is a very good recommendation! Thanks Paul I will try it. Also based on this couldn't you run the two wires to a SPDT switch and try it out OR will the switching simply  cycle between on/off each time the wires are tapped against each other??

but I recently rehoused my DL5 (in addition to the switch

yeah although It is a nice sounding delay and seems to be more highly regarded than alot of the "5"s I really would rather just fix it and keep or sell it and I think I want to save any of my boxes that I'll use for a delay to build a PT into. THough I would be rather let down if the PT-80 ended up to not sound even as good AS the DL5!!  yeah John is a really great guy!! I deal with him for everything that I can and he does me FAR more than fair. highly recommended
Observation: This model definitely DOES look different than any of the other Tanks I've opened up. The others have SMD IC's and stuff and none of them have that really HUGE 50195P  chip which is like a 46pin or something (IF that 's the one you guys said controls the switching)  So maybe some of the "5"s use different sytles switching , OR just this one ? ? I don't recall seeing that big chip on the other 5 I have.
THANKS GUYS

[George Giblet]

Sounds like a cracked track or solder point, broken cap, perhaps even a dogdy power jack.  I mentioned before  "If those are loose the power could be going on and off and that will make the unit behave erratically".   

When you press on the board it mechanically disturbes something.

[Paul Perry (Frostwave)]

Why not temporarily bypass the switch with a pair of wires

I will try it. Also based on this couldn't you run the two wires to a SPDT switch and try it out OR will the switching simply  cycle between on/off each time the wires are tapped against each other??

If the flip flop is working (personally, I'm starting to think that might be where the problem is) then, tapping the wires should do the switching back and foward.

[analog kid]

sorry it took awhile to try the two wire switching method, it DID work better but still not a perfect on/off cycle, I probably wouldn't have thought to troubleshoot it this way at least for awhile so I'm glad someone suggested it
Anyway, it did switch much more consistant with the direct lead wired switching (tapped together) than with the mechanical in there. Although if 'touched' enough times or rapid enough it WOULD still take a few touches to switch. at least it seemed to.  So I guess I will clean and inspect the pcb real good around the switch pads etc... I can't imagine the orig. and one of the switches I bought would be bad but you never know they are cheesey little plastic things New or Old
  BTW IF it still does act erratic after all , what have we decided controls the switching here? the real BIG IC , a Tranny, or what ? I  mean that would be most likely to failing and cause the erratic behavior.  (or am I asking for too much here to expect someone to be able to just know that without looking)?
thanks

[runmikeyrun]

I am just adding this in case someone else reads it someday.  I have a soundtank PL5 and had the problem with unreliable switching.  Tried some contact cleaner inside the switch first, did not help.  Replaced C27 (1nf cap to ground right after R48, a 22 ohm) with a 47nf cap (473) and now it is reliable and switches fine. 

If you have a different soundtank the capacitor and resistor numbers will probably be different, that's ok.  See the pic of the schematic attached for the cap you're looking for (circled).  Like mentioned before it's switch->resistor in series->1nf cap to ground.

While I know these switches can be subject to wear, based on my experience and that of the people listed here I'm willing to bet most times it is this capacitor value needs changed, not the switch. 


Ham fisting my way through one build to the next since 2003. 

[mojek]

Hi everybody,

i know this topic is relatively old, but should share my experience with DL5 switching issue i solved after some hours today, and i think it's the same problem as mentioned here. DL5 i bought relatively cheap had problem to switch OFF since the very begining, sometimes it worked sometimes not. I've changed the switch and suddenly it stopped switching off at all I tried to change the 1nF cap to 5nF and back and checked nearly everything and it was everytime the same. I plugged the power in and it was OFF, the i switched it ON, but can't switch it OFF at all. The remedy was to heat through all the parts around the switch. I my case, i presume, it was the small capacitor C6 between connected to not-grouded switch leg. But if you are not sure, heat through all the capacitor and resitor connections around switch. IMO during switching is PCB pushed by pedal and it create cold joints around. This is the reason of most failures of effect pedals IMO.

BTW switching on this schematic http://www.freeinfosociety.com/electronics/schemview.php?id=2316 doesn't agree with my DL5 PCB, where C4 and C6 values are like interchanged.

Cheers
M.

[Rob Strand]

I tried to change the 1nF cap to 5nF and back and checked nearly everything and it was everytime the same. I p

You need at least 10nF maybe 47nF (as mentioned above).