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Silent Sunking, no LED, no bypass

Started by whitebread47, May 19, 2012, 11:10:26 PM

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whitebread47

I got my hands on an old fabbed Sunking ver.3 a couple of days ago.  I populated and wired it all up and....nothing.

A helpful anecdote:  I went to test it at about 3 in the morning in an area that has terrible lighting, so I accidentally plugged in the cord from the wall that was supposed to go into my DC Brick into the DC jack of the Sunking.  As expected, it did not work when I used the correct cable.  Having made this mistake (yes, it's true  :-[) before on a Klone, I immediately looked at the diodes for observable damage.  None of the diodes seem blown visually.  I substituted the stock diodes as follows:  BAT41's in D1 & D2, D3 is a 1N4739A, and D4 & D5 are 1N4001's.

I also switched out the 2 TL072's and put a new TC1044SCPA in, but to no avail.  I remember when I had my Klone (Sagittarian Charger board) fixed a year or so ago from the same problem, all that needed replacing was the 9.1v Zener and I think the 1044.  I have not replaced the 1N4739 yet, as it doesn't appear damaged like the one I had before.

I've triple-checked my wiring and all checks out.  Also, I'm getting continuity in all the jacks (DC included)  All my solder joints appear to be secure enough (will take close up pics in a moment).  There is also continuity from the DC jack to the positive LED lead. 

As for the "box it before you rock it" thing, I have no testing rig right now, so I do what I call a partial boxing just to ensure grounding.  I basically just connect the footswitch and in and out jacks to the enclosure and ensure that nothing is shorting when I test it, so this isn't necessarily a "boxed" circuit that's been pulled apart.

I'm getting no bypass at all.  I used a 2PDT switch (first tie with those) and 2 of the lugs lifted a tad from their positions.  Of course, I impatiently proceeded after that red flag, so I'm not sure how to check and see if that is working correctly.  Would a ruined switch prevent both sound and no bypass, leaving voltages normal?

I also used my DMM to check voltages.  This particular area is where some assistance is needed.  I have my DMM set on 20VDC and am getting a reading of 0.34 from ground to the DC jack.  I don't know what these decimals equate to or what calculation to perform to test against proper voltage.  ???  I also tested the Opamps, which read as follows: 

IC1 -
1 = 0.16   8 = 0.34 (same as DC jack reading)
2 = 0.16   7 = 0.11
3 = 0.08   6 = 0.15
4 = 0       5 = 0.16
IC2 -
1 = 0.16   8 = climbs anywhere from 0.07 to 0.34 and then drops rapidly.
2 = 0.16   7 = 0.16
3 = 0.16   6 = 0.15
4 = 0.16   5 = 0.16
IC3 (1044)
1 = 0.34   8 = 0.34
2 = 0.01   7 = 0.02
3 = 0       6 = 0
4 = 0.03   5 = 0.17

I'm going to take some pictures once I post this and follow up with those. 

Thanks in advance for any help or advice.  I'm really trying to learn here, so dropping some knowledge on me is truly appreciated!

Pictures (pardon if this is overkill, but I wanted to be thorough):





Blake

"I don't think people are looking for the meaning of life as much as they are looking for the experience of being alive." - Joseph Campbell

madbean

The cord that goes to your DC Brick--what are the specs on that? Is is DC or AC, voltage rating etc?

Try removing all the ICs and measure what voltage you get on either pin1 or 8 sockets on IC3. Getting 9v to the board?

If you remove the wire from the PCB to the DC Jack, are you getting 9v to the DC Jack?


whitebread47

#2
The input cord for the DC Brick is AC.  Dunlop's site says it is "18 watt, 18VDC @ 1,000mA regulated."  Says it can utilize anywhere from 100 to 240 volts.

Once these pictures have uploaded (will be in OP) I will check those IC3 socket voltages and the DC jack, thanks.

EDIT:  PIcs added.  With all IC's removed, IC3 socket pins 1 & 8 read at 0.34, same as with them in.
Blake

"I don't think people are looking for the meaning of life as much as they are looking for the experience of being alive." - Joseph Campbell

whitebread47

I disconnected the +9v wire from the board, and the DC jack is still reading around 9v (8.95 or so).
Blake

"I don't think people are looking for the meaning of life as much as they are looking for the experience of being alive." - Joseph Campbell

whitebread47

While inspecting and referring to the schematic (trying to learn how to read them, now seems as good a time as any) I noticed I had soldered 1uf box caps where 100n were needed.  Nothing has changed in terms of my voltage readings, though.

What kind of readings should I be getting in a working circuit on these IC's?  The readings are the same whether the chips are in the sockets or not.  Continuity tests are indicating that my solder joints are sound.  What could cause an absence of usable voltage?

I feel like Sherlock Holmes investigating the case of the missing signal.
Blake

"I don't think people are looking for the meaning of life as much as they are looking for the experience of being alive." - Joseph Campbell

madbean

I would pull out D3 and check to see if you can get 9v to IC3.

whitebread47

Quote from: madbean on May 20, 2012, 02:42:17 AM
I would pull out D3 and check to see if you can get 9v to IC3.


I actually just switched D3 out for a 1N4742 and it works!  As soon as I got it soldered in I got better voltage readings from the IC's and the LED lit up.

Man, what a great pedal.  My first thought was to replace it, but I guess I wanted to do it the hard way.  Thanks for the help!
Blake

"I don't think people are looking for the meaning of life as much as they are looking for the experience of being alive." - Joseph Campbell