Latching circuit doesn't seem to work right

hgmjr

Joined Jan 28, 2005
9,027
I see the flaw in my description. It is as you say. I had simply overlooked the 0.01uFd capacitor's effect on the control. How embarrassing is that?

I was also still operating under the false notion that the switch was normally closed.

Thanks for the sanity check.

Your explanation of the circuits operation should be a good troubleshooting road map for Andy.

hgmjr
 

Ron H

Joined Apr 14, 2005
7,061
I see the flaw in my description. It is as you say. I had simply overlooked the 0.01uFd capacitor's effect on the control. How embarrassing is that?

I was also still operating under the false notion that the switch was normally closed.

Thanks for the sanity check.

Your explanation of the circuits operation should be a good troubleshooting road map for Andy.

hgmjr
Please accept my apologies if I seemed rather blunt. I'm actually a nice guy. :)
 

hgmjr

Joined Jan 28, 2005
9,027
RonH,

I have no doubt that you are as you say "a nice guy".

No offense was taken. Your explanation was correct. I removed my earlier description to avoid the possibility of confusing Andy.

It is hard enough for a newcomer to understand an electronic circuit without the existence of a flawed description.

We both contributed meaningful inputs and hopefully to the benefit of the poster.

hgmjr
 

Thread Starter

Andy S.

Joined Mar 26, 2007
9
.............As I said, in the schematic, you are seeing artifacts of multiple copies that makes the switch look normally closed. The toggle action occurs when the switch closes. Nothing is supposed to happen when it opens.
Sorry about the condition of the schematic, you are correct that the switch is normally OPEN and the circuit change is only when the switch is closed.


I still don't see how the LED can be ON while the non-distorted path is enabled, and the stated FF symptoms also occur, unless something is wrong with one or more of the JFETs (or their biasing components) AND something is wrong with one or more of the FF parts.
BTW, I simulated the FF, and it works as I described. The simulation was to see if I could induce the described faults, but then it dawned on me that something else was wrong (as described above), or Andy is inadvertently not giving us an accurate description of the symptoms.
As for the symptoms, I tried to be as concises as possible. This device was given to me as described as "doesn't work, probably just needs a switch replaced." Yeh, right..........

The circuit I mention here is the actual distortion circuit, not the FF. And the Momentary open switch is pushed closed, the distortion works. When I release the switch (open), the distortion stops working, but the LED stays lit.
... I'll dbl check this, but to be honest, this morning I can't recall whether the distorted signal and ALL signal stops, or if the distorted signal reverts back to clean. In any case, the LED does stay on. I'll get back this evening to clarify this point. Sorry for any confusion.


Anyway, unfortunately it's been extremely busy with my fulltime job and family that I haven't had time to dig back into this. I hope to work on it tonight. After reading all this information, a lot of the stuff is coming back from my schooling days 20 + years ago. I am leaning towards something in the FF circuit isn't working correctly.

I cannot express my thanks for all the help I've gotten so far. This is an incredible site and I feel like I'm getting a refresher course in my electronics training from 1979!
 

Thread Starter

Andy S.

Joined Mar 26, 2007
9
Folks,

Just an update. Not sure exactly how this would affect the FF, but R45 in that part of the circuit, according to the schematics, should be 50k ohm. When I checked it, out of circuit, it was well over 1 MEG. I replaced that.

I also noticed that when I started going through and touching up what looked like possible cold solder joints, the unit started working without me holding down the switch whenever the soldering iron was touched tothe PCB trace.

The section in the middle of the page shows two clusters of pots. One of the wires on the cable, which was to ground, was not connecting. Retouching the solder joint there completed the circuit.

The unit is now functioning as designed. FF does work, LED comes on only when the switch is pushed and the FF is activated to turn on the distortion circuit. LED stays on until the switch is pushed again, FF turning off the Distortion circuit.

Great thanks to everyone. I am going to pull my electronics books on basic circuitry and start brushing up on the stuff I haven't used in decades. (wierd that I carried them around all these years after graduation, but I did.)



Thanks!

Andy
 

Ron H

Joined Apr 14, 2005
7,061
Congratulations, Andy!

Just a couple of notes -
There appears to be an R45 connected to R42 (100 ohms) which in turn connects to the switch. That particular R45 is supposed to be 1Meg. I wonder why there are duplicate reference designators?

The other note - Never touch a soldering iron to a circuit board when the board's power is on. You can easily short something out. The tips of most soldering irons are connected to earth ground. If your circuit board's common is also connected to ground... I think you can see where this is going.
 

Thread Starter

Andy S.

Joined Mar 26, 2007
9
.............
The other note - Never touch a soldering iron to a circuit board when the board's power is on. You can easily short something out. The tips of most soldering irons are connected to earth ground. If your circuit board's common is also connected to ground... I think you can see where this is going.

oh yes!!! One, letting the smoke out of the components!
The other, if it's AC powered, is letting the smoke out of the soldering iron holder!!!

Since this was a low dollar item and 9-volt battery powered, I wasn't too concerned. Also, it was a last resort type thing. I was getting a bit frustrated, partially reassembling the unit to test it, then unassembling it to work on it some more.

Again, thanks for the information and the assist. Would've taken me nearly forever to get it myself. The good part is this site has inspired me to dig out the books and also read the articles to refresh my formal training!!

Thanks!

Andy
 
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