Death of a Sunking

[MattL]

I was wondering...I had been building lots of pedals, but last November I got the building parts guitar habit going, and I guess I don't have time for both obsessions at a time! Anyway, a Sunking I made (double sided, V.3, I believe) that had worked fine just kicked the bucket. Wouldn't matter that much, but I had sold it to a friend, and when I tried to figure out what was wrong, I failed miserably. Normally I'd expect the problem to have been in the switch or the outboard wiring, as I haven't heard much about components just suddenly stopping working. But the switch was okay, and the solder was all reflowed. The ins and outs, board and jacks, were checked. Grounding, and potential for anything grounding out inside was checked. I changed out the Opamps...all good. Anybody else ever have this happen? My problems have been more not getting them to work to begin with, but never having one fail that had previously worked. But I've built around 85 successfully, and in all honesty, I'm stumped! Any ideas would be greatly appreciated.
Thanks!

[ch1naski]

Diode? 1n4742 in particular?
And is the charge pump still putting out correct voltage?
Just ideas, from other people's problems I've read about......

Sent from my Nexus 7 using Tapatalk 4

[juansolo]

Check for ground at the other side of the zener. If it's there, swap it out. I've had one pop before when it had something it didn't like from the PSU.

[MattL]

Diode? 1n4742 in particular?
And is the charge pump still putting out correct voltage?
Just ideas, from other people's problems I've read about......

Sent from my Nexus 7 using Tapatalk 4

Thanks for the answer, I don't think there's a charge pump in there though...

[MattL]

Check for ground at the other side of the zener. If it's there, swap it out. I've had one pop before when it had something it didn't like from the PSU.

Thanks, I'll try changing that!

[rullywowr]

Diode? 1n4742 in particular?
And is the charge pump still putting out correct voltage?
Just ideas, from other people's problems I've read about......

Sent from my Nexus 7 using Tapatalk 4

Thanks for the answer, I don't think there's a charge pump in there though...

All good information.  There most definitely is a charge pump in the Sunking, it is IC3.  If a incorrect (edit: reverse) voltage is applied to the pedal, the zener is supposed to protect the charge pump (IC3) by blowing.  Depending on the charge pump, I have heard that many of them do not like getting more than 12v.  Check/replace the zener first.  After that, check the positive side of D5 or the positive side of C21 to see if you are getting 18v.  If not, the pump may need to be replaced.  Let us know how you make out!

[oldhousescott]

I also suggest replacing the zener. I wouldn't say it's designed to blow, just that it will usually do so if the power supply polarity is backwards, or if it's subjected to a higher voltage than the zener rating. My recommendation would be to put a 1N5817 in series with the power supply voltage. It'll drop a half volt off the V+, but you probably won't miss it, and it will protect against a reverse polarity connection.

[MattL]

I did try replacing IC3, as well as the other IC's, but didn't help. I'm now going to try replacing the zener, but I'm wondering how to check if the charge pump is putting out correct voltage? As you can see troubleshooting is a big weakness for me, because I see the "how" of building, but not the "why". Any recommendations on literature would be greatly appreciated!

[ch1naski]

Google the data sheet for the charge pump IC. Find which pin puts out your 18 volts, and check that it is putting that out with your meter.

You may be able to tell which pin to test by looking at the schematic, I don't have it handy to look at it.

[RobA]

The output voltage of the charge pump can be measured at pins 8 and 4 of IC2 (I have the version 3 schematic if that makes a difference). You can't really measure the boosted voltage from the charge pump itself since it comes from the capacitors and diodes.

As a note, the zener voltage regulator on this has an issue (although from what I can find it does look like it follows the original design). When the voltage goes over the zener limit, the current rise is essentially asymptotic. It's going to be limited by the power source but this still isn't good and it could cause problems. The design needs a current limiting resistor at the power input. The value for the resistor can be determined from current needs of the pedal.

A quick web search turned up this page with a calculator http://www.reuk.co.uk/Zener-Diode-Voltage-Regulator.htm. I've seen others before that give more info. Anyway, you could put a small value resistor at the power input to protect the zener (and power source).

Edit: I should note that this is only going to be an issue if you plug in a power source greater than the zener voltage. If you know that you won't do that, it isn't a problem.

[MattL]

So is the design flawed? I know it's not made anymore, and a lot of these answers seem to be work arounds to getting it to work as it originally should have...

I have replaced diode 3 to no effect. Also, when hooked up to my test rig, with effect engaged, I don't hear anything that I'm supposed to, like guitar, but I notice the gain control can be heard to increase or decrease hiss, which makes me quess that the output is working. I have another of these boards that I'm going to make, but it seems that there are common problems with this, particularly based around charge pumps etc. Any suggestions as to how to avoid this in the future, or is it just the design? Thanks

[RobA]

So is the design flawed? I know it's not made anymore, and a lot of these answers seem to be work arounds to getting it to work as it originally should have...

I have replaced diode 3 to no effect. Also, when hooked up to my test rig, with effect engaged, I don't hear anything that I'm supposed to, like guitar, but I notice the gain control can be heard to increase or decrease hiss, which makes me quess that the output is working. I have another of these boards that I'm going to make, but it seems that there are common problems with this, particularly based around charge pumps etc. Any suggestions as to how to avoid this in the future, or is it just the design? Thanks

No, I wouldn't say the design is flawed. If all the parts are right and the input voltage is right, then it should be fine.  It's just that with the addition of 1 extra resistor, it could have been made better. This pedal is basically OK with the 12V zener in there and a 9V power supply.

Charge pumps in general are fine and do the job of getting higher voltage and negative rails from 9V single supplies well. There are some issues with charge pumps and using the right one in the right way is important.

Also, you don't know yet what is causing your problem, it could be entirely unrelated to the charge pump and the zener. They just seem like good places to look first because of how the pedal died over time. It could be something like a cap gone bad or a cold solder joint that's become an issue too.

Did you get the voltage readings from the two op amps?

[MattL]

So is the design flawed? I know it's not made anymore, and a lot of these answers seem to be work arounds to getting it to work as it originally should have...

I have replaced diode 3 to no effect. Also, when hooked up to my test rig, with effect engaged, I don't hear anything that I'm supposed to, like guitar, but I notice the gain control can be heard to increase or decrease hiss, which makes me quess that the output is working. I have another of these boards that I'm going to make, but it seems that there are common problems with this, particularly based around charge pumps etc. Any suggestions as to how to avoid this in the future, or is it just the design? Thanks

No, I wouldn't say the design is flawed. If all the parts are right and the input voltage is right, then it should be fine.  It's just that with the addition of 1 extra resistor, it could have been made better. This pedal is basically OK with the 12V zener in there and a 9V power supply.

Charge pumps in general are fine and do the job of getting higher voltage and negative rails from 9V single supplies well. There are some issues with charge pumps and using the right one in the right way is important.

Also, you don't know yet what is causing your problem, it could be entirely unrelated to the charge pump and the zener. They just seem like good places to look first because of how the pedal died over time. It could be something like a cap gone bad or a cold solder joint that's become an issue too.

Did you get the voltage readings from the two op amps?

Hi, I have reflowed solder, I have changed out the opamps (I assume you mean the 72's, but I've changed them all) I have changed the zener also. I don't understand where to add the resistor, but since I've got another of these boards that I'm about to get started on I'd love to know, as well as how to check the voltage on the opamps!

[MattL]

So is the design flawed? I know it's not made anymore, and a lot of these answers seem to be work arounds to getting it to work as it originally should have...

I have replaced diode 3 to no effect. Also, when hooked up to my test rig, with effect engaged, I don't hear anything that I'm supposed to, like guitar, but I notice the gain control can be heard to increase or decrease hiss, which makes me quess that the output is working. I have another of these boards that I'm going to make, but it seems that there are common problems with this, particularly based around charge pumps etc. Any suggestions as to how to avoid this in the future, or is it just the design? Thanks

No, I wouldn't say the design is flawed. If all the parts are right and the input voltage is right, then it should be fine.  It's just that with the addition of 1 extra resistor, it could have been made better. This pedal is basically OK with the 12V zener in there and a 9V power supply.

Charge pumps in general are fine and do the job of getting higher voltage and negative rails from 9V single supplies well. There are some issues with charge pumps and using the right one in the right way is important.

Also, you don't know yet what is causing your problem, it could be entirely unrelated to the charge pump and the zener. They just seem like good places to look first because of how the pedal died over time. It could be something like a cap gone bad or a cold solder joint that's become an issue too.

Did you get the voltage readings from the two op amps?

Hi, I have reflowed solder, I have changed out the opamps (I assume you mean the 72's, but I've changed them all) I have changed the zener also. I don't understand where to add the resistor, but since I've got another of these boards that I'm about to get started on I'd love to know, as well as how to check the voltage on the opamps!

Oh, sorry, I see you've already included info about the opamp voltage.

[MattL]

Diode? 1n4742 in particular?
And is the charge pump still putting out correct voltage?
Just ideas, from other people's problems I've read about......

Sent from my Nexus 7 using Tapatalk 4

Thanks for the answer, I don't think there's a charge pump in there though...

All good information.  There most definitely is a charge pump in the Sunking, it is IC3.  If a incorrect (edit: reverse) voltage is applied to the pedal, the zener is supposed to protect the charge pump (IC3) by blowing.  Depending on the charge pump, I have heard that many of them do not like getting more than 12v.  Check/replace the zener first.  After that, check the positive side of D5 or the positive side of C21 to see if you are getting 18v.  If not, the pump may need to be replaced.  Let us know how you make out!

Can I check these voltages on board, or do they need to be removed?