Testing a Battery Snap

MustangMartigan · January 19, 2018, 02:54:10 PM

Is there a way to use a Multi-Meter to test if a battery snap is working?

I'm having an issue with a Crybaby GCB-95 (rev. F) not outputting a signal when engaged; it works fine when disengaged. I tried removing the circuit board to test the switch for continuity, but I don't have the right socket wrench for the job. If it's not the switch, I have a gut feeling that it's the battery snap.. and with no socket wrench to get to where the snap connects to the board, probing that actual female connectors on the snap is all I have access to. If this is a possible test, where do I set the MM's rotary knob, and which port do I connect the red and black probes?

Thanks,
-Adam

vigilante397 · January 19, 2018, 03:29:51 PM

Can you get to the board itself? If so, attach a battery then check for voltage on the board where you would expect it (collectors of the transistors would be a good place to start), and if you do then the battery snap is fine.

How small are your DMM probes? Mine will fit into the backside of the connector between the PCB and offboard components, so I can test for continuity between the battery snap connectors and the red and black leads on the left of the connector.

Hope this helps

EBK · January 19, 2018, 03:50:51 PM

You could measure current through the connector by connecting half of the snap to a battery terminal and connecting your meter's test leads to the remaining snap connector and battery terminal. If there is an open circuit, no current will flow. If you need help with meter settings, post a pic of your meter.

But first, try a new battery in the pedal.

vigilante397 · January 19, 2018, 04:41:40 PM

Quote from: EBK on January 19, 2018, 03:50:51 PM
You could measure current through the connector by connecting half of the snap to a battery terminal and connecting your meter's test leads to the remaining snap connector and battery terminal. If there is an open circuit, no current will flow.

Ooh, I like that one too. Good call

MustangMartigan · January 19, 2018, 07:32:42 PM

Quote from: EBK on January 19, 2018, 03:50:51 PM
You could measure current through the connector by connecting half of the snap to a battery terminal and connecting your meter's test leads to the remaining snap connector and battery terminal. If there is an open circuit, no current will flow. If you need help with meter settings, post a pic of your meter.

But first, try a new battery in the pedal.

First think I did was try a fresh battery, as well as one from a working pedal. And I don't have a 9V power supply.

Does it matter if I connect the big or little battery terminal? Thanks

EBK · January 19, 2018, 09:06:54 PM

Quote from: MustangMartigan on January 19, 2018, 07:32:42 PM
Does it matter if I connect the big or little battery terminal? Thanks

No, you can pick either one. The current will be the same.
I can't see the labels on your meter too well from that pic, but it looks like you have a 20mA range setting in that green region. That's an ok place to start. You'll either get 0, a number, or an out of range indication.

MustangMartigan · January 20, 2018, 08:01:13 AM

Quote from: EBK on January 19, 2018, 09:06:54 PM
No, you can pick either one. The current will be the same.
I can't see the labels on your meter too well from that pic, but it looks like you have a 20mA range setting in that green region. That's an ok place to start. You'll either get 0, a number, or an out of range indication.

Yep. That's the 9V (25mA) setting. I'm hoping I would have figured that one out when I took a look at it. So I set the rotary dial to that setting, plugged the black probe into the COM port and the red into the V(omega)mA port.

I tried the test in every possible way, connecting to just the small terminal and just the big terminal, etc. Every test registered a 0 on the MM. My 9V tested -23.9, so I'm guessing that the zero reading means that my battery snap is the problem, yes?

Since I don't have the socket wrench to remove the circuit board and attach the new snap wires properly, I'm just gonna cut the old one off and splice on a new snap. I'm pretty confident, by it's loose behavior, that the problem isn't with the solders on the circuit board, but the snap itself.

I bought this wah used from this dummy that cut a section out of the back panel for easier access to the battery. I'm guessing that this brilliant mod is the reason for the snap failing. I gotta remember to secure the battery and cover that opening better. I've just been using a piece of duct tape over it, that sticks to the battery. Apparently that's not enough protection.

I'll come back on with an update to let you guys know if the new snap fixed the problem. I really appreciate all the help.

duck_arse · January 20, 2018, 09:09:42 AM

I'm not sure you are doing this reading right. snap one lug of the battery into the snap, so you have a battery lug and a snap lug free. it doesn't really matter which lug you use. then complete the circuit from the battery to the snap with your meter, which is set to the current range mentioned. IF the circuit is continuous, there will be some reading, in milliamps.

I don't know wahs from sht, but if the battery is off switched by the in/out plugs, you'll need to have a plug inserted to do the current test. and if the unit has an external DC socket, you'll need to confirm that the changeover switch is continuous when there is no dc supply plug plugged in.

don't try and measure resistance with the battery connected, tho.

- oh, also, you should ask a moderator to move this thread to the 'building my stompbox' - erm - board, as this sub-board is for people testing things like image posting [and we've been told not to answer posts in here!].

MustangMartigan · January 20, 2018, 09:43:55 AM

Quote from: duck_arse on January 20, 2018, 09:09:42 AM
I'm not sure you are doing this reading right. snap one lug of the battery into the snap, so you have a battery lug and a snap lug free. it doesn't really matter which lug you use. then complete the circuit from the battery to the snap with your meter, which is set to the current range mentioned. IF the circuit is continuous, there will be some reading, in milliamps.

I don't know wahs from sht, but if the battery is off switched by the in/out plugs, you'll need to have a plug inserted to do the current test. and if the unit has an external DC socket, you'll need to confirm that the changeover switch is continuous when there is no dc supply plug plugged in.

Great point. Now I'm getting a reading of 0.1; it alternates between 0.0 and 0.1. Is this enough of a reading to throw out the bad battery snap theory and move onto something else? Like the switch..?

duck_arse · January 20, 2018, 10:01:36 AM

if you are getting "0.1" reading on the "25mA" meter setting, I'd say there was no current flowing. I think it would draw at least a milliamp.

disconnect the battery - on the batter snap, the castlellated lug [sp?] is positive, so put your meter probe (set to ohms, low range) on the other lug and probe the ground points on the circuit board. you should get a low value reading. then probe the other lug, follow the wiring to the dc jack (is there one?), then follow that to the pcb. you should get low ohms readings again. if/where you get an open or high reading, you've found or disproved the wiring theory.

MustangMartigan · January 20, 2018, 10:08:23 AM

Quote from: duck_arse on January 20, 2018, 10:01:36 AM
if you are getting "0.1" reading on the "25mA" meter setting, I'd say there was no current flowing. I think it would draw at least a milliamp.

disconnect the battery - on the batter snap, the castlellated lug [sp?] is positive, so put your meter probe (set to ohms, low range) on the other lug and probe the ground points on the circuit board. you should get a low value reading. then probe the other lug, follow the wiring to the dc jack (is there one?), then follow that to the pcb. you should get low ohms readings again. if/where you get an open or high reading, you've found or disproved the wiring theory.

Castellated lug? Huh? Would that be the bigger female connector on the snap? I can't get to the ground points of the snap wires. I need a socket wrench, that I don't have, to remove the board and flip it over. Check it out, here's all I have access to until I get that wrench.

EBK · January 20, 2018, 10:24:19 AM

There has been some "work" done to that wah pot area.... Do yhose parts still move like they should?

MustangMartigan · January 20, 2018, 10:33:03 AM

Quote from: EBK on January 20, 2018, 10:24:19 AM
There has been some "work" done to that wah pot area.... Do yhose parts still move like they should?

What type of work? Move around as in the action of the pedal? I never noticed anything off about it. It also says Rev C on the back panel and Rev G on the circuit board; I'm not sure of the reason for that f^ckery.

I got this thing for $20. I'm not a big fan of the GCB-95's, but this one doesn't sound half bad, esp for the price. I mean, it's no Tycobrahe Parapedal or Boomerang BG-1, but I don't have a grand to shell out for a pedal. I did once have a Boomer BG-2 that sounded beautiful. It's wah pot broke tho, and it was before that guy (damn, I forget his name) started producing a replacement pot for the bizarre one the Boomerang's use.

EBK · January 20, 2018, 10:45:51 AM

Just the broken tension clutch, which looks like it has been repaired with paper and hot glue. Just asking because I saw it. If it is bot a problem, then don't mess with it.

So, this pedal did work fine for you before, and at some point during your ownership, it quit working?

duck_arse · January 20, 2018, 10:52:24 AM

turn the batter snap over, and you have access to the + and - test points. the spring finger contacts of the in/out jack sockets closest to the outside will/should be continuous with ground, or the snap - test point. there is two metal contacts I can see on the DC socket, one of them will be the centre pin, the other should be the barrel. centre pin should be connecting w/ (-) and the barrel should be connecting w/ the + on the snap.

castlellated - like a castle, like the top of a turret or tower. yes, ok, the female one.

MustangMartigan · January 20, 2018, 10:55:33 AM

I just said screw it and spliced on a new snap; it's not the problem. The pedal still won't engage into wah mode; just silence.

MustangMartigan · January 20, 2018, 04:04:12 PM

Quote from: duck_arse on January 20, 2018, 10:52:24 AM
turn the batter snap over, and you have access to the + and - test points. the spring finger contacts of the in/out jack sockets closest to the outside will/should be continuous with ground, or the snap - test point. there is two metal contacts I can see on the DC socket, one of them will be the centre pin, the other should be the barrel. centre pin should be connecting w/ (-) and the barrel should be connecting w/ the + on the snap.

castlellated - like a castle, like the top of a turret or tower. yes, ok, the female one.

That went right over my head. I'm a musician with a multimeter, not a tech. Is this test a moot point now that I've spliced in a new battery snap and got the same results, no wah when the switch is engaged?

MustangMartigan · January 20, 2018, 04:12:56 PM

Quote from: EBK on January 20, 2018, 10:45:51 AM
Just the broken tension clutch, which looks like it has been repaired with paper and hot glue. Just asking because I saw it. If it is bot a problem, then don't mess with it.

So, this pedal did work fine for you before, and at some point during your ownership, it quit working?

I'm have no idea a tension clutch is, but I'm looking at the insides of the pedal now and don't see any paper.

And yes, the pedal worked perfectly since I bought it used about a year ago. It just randomly stopped working the other day. It didn't fall or get physically mistreated prior to it breaking down. Just sat in it's normal spot. It didn't even crap out while I was playing. It worked one day, then didn't work the next.

EBK · January 20, 2018, 04:18:01 PM

Quote from: MustangMartigan on January 20, 2018, 04:12:56 PM
I'm have no idea a tension clutch is, but I'm looking at the insides of the pedal now and don't see any paper.

Tension clutch looks like this, when intact:

Like I said, no need to worry about this.

MustangMartigan · January 20, 2018, 08:33:50 PM

Quote from: EBK on January 20, 2018, 04:18:01 PM
Tension clutch looks like this, when intact:

Like I said, no need to worry about this.

Right. By it's appearance, that's what I assumed you were talking about. That piece is definitely a hard plastic and looks just like the one in your photo.

So now that the defective battery snap therory has been disproven, the next most plausible culprit is the switch, yes? It either just needs a good cleaning or to be replaced. Is there anything I can do to clean it without having to disassemble it? After a close inspection, I couldn't find a small opening, similar to a pot, where I can point and spray some F5. Did I miss something, or is there no way around taking the thing apart? Also, is there some kind,of multimeter test that would confirm the switch being cooked?

Thabks.

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Testing a Battery Snap