Charge Pump Question (is my op amp torched?)

[HKimball]

So, I posted another thread in the general discussion, but as it turns out all of my problems were either misinterpretations of the schematic/layout or bad solder joints, so I fixed those.

My charge pump however is still not working right - It's the 3PRR which is a charge pump/true bypass thingy.

I'm seeing (with a 9.6v input) ~10.3v right now at the +18 pad. I'm seeing ~9.2-9.3v at the + pad of c3, and ~10.2v (sometimes 10.3v) at the + pad of C4

I used 5818 diodes (I think those are the ones - their part number/designation is one higher than the ones recommended in the build document), and the charge pump by itself worked fine. Thing is they do take out about .3v - and with R2 the I/C (LTR 1054) is seeing ~8.2v or so.

Pin 1 on the LTR shows 1.15v, Pin 2 shows 1.5v, pin 3 shows 0v, and pin 4 shows -.95v
Pin 5 shows -1.5v, pin 6 shows 2.6v, pin 7 shows 1.45v, and pin 8 (which I think is getting 8v from the supply)

Also it seems like a ~1v drop for a 10r resistor is a bit much so I'm going to check r2.

So, my suspicion is that my charge pump is torched, because if I'm looking at this correctly (and I may not be because I'm a huge newb) I should be seeing a combined 9v from the outputs of pin 2 and pin 4 from IC1. Is that right? Do I need to get a new IC?

Thanks in advance for the help and I may socket the IP next time I make one of these haha

[Matt]

Which IC are you using?  If you are using a 1054, don't connect pin 1

[RobA]

The 1n5818 should be fine there. Seeing a 1V drop across the 10Ω resistor indicates that you are drawing about 100mA which is pretty high. Unless you know that you should be drawing that much, I'd look for a short. If you should be drawing that much, the charge pump isn't going to do the job because the LT1054 can only source a max of about 80mA and it's the charge pump that can source the most current.

What do you have in place for the Zener at D2? That can draw a ton of current if you are over the zener voltage. You also need to make sure that you don't have the pads jumped on the IC since you are using the LT1054.

[HKimball]

First off, thank you for the replies! I do appreciate it.

Pads are not jumpered, or at least I've not soldered them at all

Zener is a 12v (originally I had planned on using this with a 12v supply for ~24v to the circuit)

I will check for a short and get back to you guys - FWIW the board put out ~18v off a 9v batter before I attached everything so a short is a very real possibility.

edit: Just measured and it looks like I'm drawing 114mA but I have no idea how much I should be drawing - for reference this is a fatpants build that I made on perfboard so w/e current draw requirements that has is what mine are.

[RobA]

Just to clarify, you've done a FatPants without a charge pump on the main board and are then powering it from a 3PRR? If so, that should work fine. The FatPants circuit itself should draw very little current.

If there is a short somewhere causing the current draw you are seeing, that would explain the voltage levels you are getting. When you try to draw to much current from the charge pumps, they dump their voltage output. So, I'd look for a short somewhere post the charge pump. Another possibility is that the Zener is toast. This could be causing a short at the Zener with a current draw that is limited only by the current your power supply can source. The voltage after the 3PRR could then be low because it's being starved for current. I'd guess the first scenario is more likely, but I'd check the Zener too. Actually, since you are using the LT1054 and it can take 15V, there isn't much reason to have the Zener in there unless you think there is a risk of applying more than 15V.  The J201 can take a ton of voltage so the max voltage limit is going to be set mainly by your electrolytic caps.

[HKimball]

Yes, when I was ready to order the fatpants circuit the boards here were sold out so I copied the schematic/layout on some perfboard and used the 3PRR to power it. The wiring is hideous, and there are solder globs everywhere, but it works.

A short post-charge pump is likely because of how messy everything is. I'll re-check the wiring as it goes from the charge pump to the board as that's the most likely culprit.

Thanks again for your help Rob (and Matt) - I kind of bit off as much as I could chew with this one.

[HKimball]

So, this is sort of a necro bump, but I've been busy and had a hard time getting around to messing with the fatpants.

I've got voltage to q2 now (may have said that already), but the charge pump is still a problem. I disconnected everything from the charge pump except the power supply and it still reads 10.6v with no current draw coming from the circuit.

At this point I think I'm just going to take out the 12v zener and solder in a jumper. If that doesn't work I'll just order another charge pump.

Besides the charge pump though the circuit seems to be working fine.

Thank all of you for your help - and I will report back with more findings as they occur. But I'll just edit this post so it doesn't get necro-bumped every time I get something working again.

[the3secondrule]

DONT jumper the zener. Just remove it and leave that spot empty

[HKimball]

Oh oh oh derp.

Okay well in that case new results inbound.

[HKimball]

Removed the Zener - voltage went up .15v from 10.6 to 10.75 - this is also with no load on the circuit so I'm thinking I might just order a whole new charge pump and parts. Once the 3pdt switch is mounted it's really hard to add/remove the other components.

As always thank you again for the help.