Need Help Troubleshooting Maestro Boomerang BG-2

[joegagan]

i told gus that i suspect some weird mechanical reason that some pots exhibit this behavior while others don't. shaft stress causing wiper to lift (static?), something slightly off in the actual carbon trace at far end or   ?

anyway, the 330 is probably enough to keep whatever it is from from going full ground just enough to solve the noise.

john, i think your explanation is off. it isn't just raising the overall resistance that solves the problem.

[John Lyons]

whoops, yeah 25.3K...math skills right there boy! 
BUT, the pot is still traveling the same amount and to the same places on it's wafer...

Hmmm. So I guess it's the fact that it's being held from ground
by a small amount that does it... I don't understand what's going on there.
So that resistance is what's helping right Joe? (330 from ground).
Not the total resistance but that 330 buffer zone.

[joegagan]

you got it  bushka!

( just turned you russian for no good reason)

[Paul Marossy]

Hmmm. So I guess it's the fact that it's being held from ground
by a small amount that does it... I don't understand what's going on there.
So that resistance is what's helping right Joe? (330 from ground).
Not the total resistance but that 330 buffer zone.

I don't quite understand it, either. Maybe it helps by limiting the current that can go thru the pot when it's at the extreme end of the treble? It still seems to me like that there is DC floating around in the circuit somewhere.

Someone emailed me the other day about a "Boomer 2" they had that is operating on a 1.5V battery, and they included a few pictures. I wonder if these things were originally designed to operate on a 1.5V battery. I can't tell if it's been modified or if it came from the factory that way. Anyway, if this is the case, when you elevate the voltage to 9V, maybe weird stuff starts happening? In the BG-2s that have a schematic on the bottom plate, the battery number is always obliterated with permanent marker and the battery holder looks like something that was designed to hold a 1.5V "C" battery. Curious...

[John Lyons]

I think Gus is our only hope here.  (no joke)

[joegagan]

no, that was a '226" battery. 9 volts. somewhat common in cameras in the 60s from what i have heard.

[joegagan]

[joegagan]

ha! i just noticed i stuck it in backwards when i shot that photo

[Paul Marossy]

no, that was a '226" battery. 9 volts. somewhat common in cameras in the 60s from what i have heard.

Oh, I see. Well, this person has one that is functioning on a 1.5V C battery and he says it's fine. Looking at it closer, it looks like someone has messed with it and it didn't come from the factory that way. So forget what I said earlier. But I wonder why all the schematics inside the pedal have that battery information crossed out. Maybe that type of battery was being phased out when the pedal was out on the market for a few years? It looks like they are still available, though.

[joegagan]

aha. look at the inductor date codes on the two photos above.

ours is 6719, 19th week of 67.
your photo shows 6741 or 47.

the tacked on resistors on the board are consistent with quite a few i've seen that were  BG1 boards modded at the factory to make them BG2s.

r mintz does not know who produced the BG1s, or where the white inductors came from.

i have seen these  bg1 boards used on BG2s with el rad inductors, also later boards with the white inductors, who knows, parts  just got used as they were around back then apparently.

the 'crossed out' line you refer to is a factory mod that canceled out the  '226' batt designation that was printed on the schematic printing. looks like a regular width magic marker to me. that is also very consistent in many pedals, hence my belief that  this magic marker mod was a factory thing.

[Paul Marossy]

aha. look at the inductor date codes on the two photos above.

ours is 6719, 19th week of 67.
your photo shows 6741 or 47.

the tacked on resistors on the board are consistent with quite a few i've seen that were  BG1 boards modded at the factory to make them BG2s.

r mintz does not know who produced the BG1s, or where the white inductors came from.

i have seen these  bg1 boards used on BG2s with el rad inductors, also later boards with the white inductors, who knows, parts  just got used as they were around back then apparently.

the 'crossed out' line you refer to is a factory mod that canceled out the  '226' batt designation that was printed on the schematic printing. looks like a regular width magic marker to me. that is also very consistent in many pedals, hence my belief that  this magic marker mod was a factory thing.

Huh, interesting. That explains a few things. So that guy who emailed me is probably just operating his on the wrong battery then. Odd, because he says it sounds fine. But I don't see how that's possible. 

[joegagan]

unless he has a sneaky tech who installed a teeny tiny step up transformer in the 1.5v batt, not sure why he thinks this works.

[Paul Marossy]

unless he has a sneaky tech who installed a teeny tiny step up transformer in the 1.5v batt, not sure why he thinks this works.

No such thing in the picture I posted above...

[Govmnt_Lacky]

Huh, interesting. That explains a few things. So that guy who emailed me is probably just operating his on the wrong battery then. Odd, because he says it sounds fine. But I don't see how that's possible. 

Not surprised in the least. If I had a nickel for every time I saw a layout, design, etc. that says "Verified" or "Works GREAT!" only to build it and find out that the wiring was backwards, pots were wrong taper, resistor values were typo'd..... I would be rich 

I have found that people are LAZY and are much more willing to type "It works" than to type out what they had to do to MAKE IT WORK!

My 2 

[joegagan]

 rechargeable, around 14 bucks. now people don't have to alter their original boomers.
• Type: LiMnO2 (replacement for original Carbon-Zinc)
• Voltage: 9V
• Amperage: 220mAh
• Terminals: Large Snap Contacts

[Paul Marossy]

Or you can do this: http://www.diystompboxes.com/smfforum/index.php?topic=48519.0

I still haven't used up these batteries, and I made them in 2006. I haven't used the wah pedals that much, either, but they are still going in any case. 

[joegagan]

cool, paul i never saw that thread i guess. i can't get those 123 batts for cheap, i have a flashlight that takes em and they are expensive when i look.

[Paul Marossy]

Yes, they are kinda expensive. They were batteries from my old home security system. In a circuit like a wah pedal, they last a very very long time. 

[Gus]

Measure the voltage drop across the wha pot at two positions without the added 330 ohm jumper it if it was added for the measurement.  Measure voltage at the outside lugs not the wiper

Wiper at bass end voltage at outer lugs

Wiper at treble end voltage at outer lugs

If the cap at the wiper to base is leaking the current/voltage will change at the different wiper positions, that is why the two readings are needed.

This will help find out if the caps are leaking without removing them from circuit.

Ohms law

Voltage / wha pot resistance = leakage currents

[Paul Marossy]

Measure the voltage drop across the wha pot at two positions without the added 330 ohm jumper it if it was added for the measurement.  Measure voltage at the outside lugs not the wiper

Wiper at bass end voltage at outer lugs

Wiper at treble end voltage at outer lugs

If the cap at the wiper to base is leaking the current/voltage will change at the different wiper positions, that is why the two readings are needed.

This will help find out if the caps are leaking without removing them from circuit.

Ohms law

Voltage / wha pot resistance = leakage currents

That's an easy way to do it. I'll have to give this a try!