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help to diagnose simple fault please
help to diagnose simple fault please
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Old 19th April 2018, 12:23 AM   #11
Pauld35 is offline Pauld35  New Zealand
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Join Date: Sep 2014
its working again, i had the heater on last night when it was failing, today is alot colder when i took the readings and it seems to be working fine, unusual.

Last edited by Pauld35; 19th April 2018 at 12:34 AM. Reason: info
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Old 19th April 2018, 02:55 AM   #12
turk 182 is offline turk 182  Canada
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make sure it's not a bad connection that is affected by temperature.

one thing that seems odd/ weird about that schematic that i may be not understanding correctly is where is the supply switching? shouldn't the battery B+ be switched via the input jack to prevent battery drain? no battery clip in the drawing nor is there a dc jack which to the best of my recall is a feature on most Dunlop wahs?

or is this meant to run off a supply?

Last edited by turk 182; 19th April 2018 at 03:02 AM.
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Old 19th April 2018, 03:28 AM   #13
JMFahey is offline JMFahey  Argentina
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Location: Buenos Aires - Argentina
Battery positive is always connected and negative is connected to ground through the input (or output) jack ring connection, when plugging a cable there; itīs the typical pedal supply switching system, so common that nobody bothers to draw it in detail, it is a given.

And thatīs not the Factory schematic but an amateur builderīs one.
Design/make/service musical stuff in Buenos Aires, Argentina, since 1969.
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Old 19th April 2018, 06:46 AM   #14
Mooly is offline Mooly  United Kingdom
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help to diagnose simple fault please
I agree that those voltages are good.

The best thing you can do is just use the device and see if the problem recurs. If it does then leave it running in the faulty state and re-measure the same voltages.
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Old 19th April 2018, 08:03 PM   #15
Gnobuddy is offline Gnobuddy  Canada
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Originally Posted by Pauld35 View Post
it would only work briefly...when i disconnected the 9v battery or the 9vdc adapter power supply.
Perhaps there is a bad (cracked) solder joint or PCB trace, or a broken wire, either in the battery connector, or the soldering to the power jack.

Failure of soldered joints and wires in these areas is relatively frequent, because both these areas experience repeated mechanical stress as batteries are plugged in or unplugged, and the external power plug is inserted and removed.

The fact that the circuit did work on a 5V power supply may turn out to be a red herring - does it always work reliably on the 5V power supply, even if you wiggle the power plug and/or battery connector?

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