Q-Tron power supply
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Posted: 14 February 2019 12:35 PM

[size=5]I have a late 90’s Q-Tron in the stamped steel chassis that came with a 24 VDC, 100mA power supply. Can I use a power supply that delivers 27 VDC instead? Is the Zener diode in the regulating section robust enough to handle that?[/size]

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Posted: 14 February 2019 01:42 PM | Link to this reply (#1)

What is the polarity of your adapter? Negative or positive tip? The 24V Qtron adapter is positive tip. If you use the wrong polarity, the best outcome is that it won’t work. The worst outcome is that you end up with an attractive door stop.

In which country do you live?

You can get the 24V 100mA USA adapter for $13.10 here:

https://shop.ehx.com/item/us24dc-100/guitar-effects-pedals-power-supplies-americas/

The 24V 100mA UK adapter here for $14.80 (USD) here:

https://shop.ehx.com/item/uk24dc-100/guitar-effects-pedals-power-supplies-uk/

The 24 100mA European adapter here for $14.80 (USD) here:

https://shop.ehx.com/item/eu24dc-100/guitar-effects-pedals-power-supplies-europe/

That’s not too much really for a properly matched adapter. My experience has been that sometimes even if the voltage and amperage are close enough, the polarity might be wrong, or the plug size might be off by just enough so that it works intermittently as things get bumped around, or it’s not properly shielded so that it creates excessive hum. This isn’t a digital circuit, but just FYI. With digital circuits, it’s even more important to use original matched adapters because of other differences in the way power adapters deliver power.

Edited: 14 February 2019 01:50 PM by gvelasco
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Posted: 14 February 2019 02:04 PM | Link to this reply (#2)

Thanks for the response. It’s a positive tip and I have several OEM 24 VDC wall warts (120 VAC for use in US).

The reason I am inquiring about the 27 VDC is because I have three unused isolated 9 VDC power plugs in my Furman SPB-8 pedalboard. Connected in series with a custom cable they will produce 27 volts and I can eliminate having to deal with the wall wart altogether. I am just concerned if the Zener diode in the Q-Tron can handle a constant over-voltage. Sometimes older things are over engineered, then again sometimes not!

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