My VS Open Road has developed static problems

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Hanky-
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Post by Hanky- »

I have had a similar problem develop on their garagetone Tremolo pedal. This time its the open road pedal(clone of nobels odr1).

Both pedals are supposed to disconnect the battery when the input jack is unplugged.

Both of them start to generate lot of hiss and some sputtering/pops/static when I power them with a powersupply and the input cable is unplugged. With the input jacked plugged in the white noise decreases but the sputtering is still there. The noise is little less when using a battery but that might be due to the battery being not full/fresh. On the open road the noise isnt present in bypass mode, in the tremolo it is present in bypass mode too.

When powered by psu & the input cable is unplugged the pedals dont shut themselves off, the LED stays on and the noise goes up. At this point if I touch the positive terminal of the battery clip I can hear a high pitched squeal on the open road. Is that supposed to happen?

The open road is a buffered pedal, it shouldnt let any signal pass when unpowered but I can still get a faint signal to pass, how is that even possible? Residual charge stored in the filter caps causing the signal to pass maybe?

I wasn't sure where to post this. The pcb is smd on both pedals, my primary concern now is the open road pedal. If I can figure out a solution for it then I could apply it to the tremolo since both share the same buffer scheme I think anyway.

Tried the usual tests, new cables, different psu, different guitars, nothing helped.

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mauman
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Post by mauman »

There are usually two switches that control the battery and external power connections. One is the Ring contact of the input jack, which connects the battery's negative contact to the jack's Shield lead (and therefore the pedal's ground) when a guitar cable is plugged in. If that's wired wrong or something's amiss, removing the guitar cable from the input jack won't disconnect the internal battery.

The other switch is inside the DC jack. The internal battery's positive terminal is wired thru that, and plugging a power supply into the DC jack should disconnect the internal battery so you're not using both at once. If that's faulty, you'll need to replace the DC jack, it's not usually possible to repair their guts.

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Hanky-
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Post by Hanky- »

Visual Sound uses the Millenium Bypass 2 Plus using the mosfet transistors IC. http://www.geofex.com/Article_Folders/M ... l2plus.htm

I tried replacing the sockets (dc or 1/4" input) but it didnt solve the problem.

My guess is the bypass section is causing the issue. There too many smd components in the pcb of the open road viewtopic.php?t=18101

If I could isolate the buffer components and wire the circuit straight without the bypass portion then I'd be able to tell if the problem is not part of the switching/buffer components.

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Hanky-
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Post by Hanky- »

Ive been tracing the circuit somewhat. It doesnt have the millenium bypass in there, its something else. Anyways, still hunting for the gremlins in there.

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Post by Hanky- »

I found the problem. Its a pnp transistor that is found near the dc power entry section, looks like its used for switching between battery and adapter supply.

Now I cant read what is printed on it because the markings are damaged or nearly invisible due to the brown glue that was used on the wires near the pcb.

What would i need to replace it with? As in I found a few online but they are general purpose as well as high voltage application ones.

Im guessing the ideal one would be in the 4V to 20V tolerance range or do I need to look at the current ratings as well?

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mauman
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Post by mauman »

If it's switching 9V and passing the pedal's entire current, then I'd probably look for one that tolerates at least 20V and handles twice the pedal's current draw (an ODR-1 should take 20-30 mA or so).

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Post by Hanky- »

Thanks mauman.

I can get a BC807 and MMBT3906 locally online, looks like generic chinese import ones.

Specs on these are in the screenshots ive attached. Switching freq is higher on the MMBT3906, i suppose its faster. I think either should be able to handle the job :hmmm:
Screenshot_20220927-234934.jpg
Screenshot_20220927-235103.jpg

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Post by mauman »

Hanky- wrote: 27 Sep 2022, 18:31 I can get a BC807 and MMBT3906 locally online, looks like generic chinese import ones.... I think either should be able to handle the job
Yep, either one should work fine.

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