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DIY Stompboxes => Building your own stompbox => Topic started by: Benoitcarp on November 28, 2019, 05:47:47 AM

Title: MXR Blue Box fourth transistor Q4 name?
Post by: Benoitcarp on November 28, 2019, 05:47:47 AM
Hi,
I have here a broken MXR blue bow with green pcb. Trasistor  (or regulator?) Q4 is broken and I can't seen what is written on it. Could anybody help me? This part doesn't show on classic blue box schematics...

Thank you fellars!
Title: Re: MXR Blue Box fourth transistor Q4 name?
Post by: Mark Hammer on November 28, 2019, 10:14:18 AM
As far as I know, there are only 3 transistors in the circuit.
(http://files.effectsdatabase.com/gear/pics/mxr_bluebox_002.jpg)
Is it possible someone decided to add a 4th one for some sort of buffering purpose?
Title: Re: MXR Blue Box fourth transistor Q4 name?
Post by: antonis on November 29, 2019, 06:09:48 AM
Maybe it's some kind of Blue Fool version..
https://shop.pedalparts.co.uk/Blue_Fool_MXR_Blue_Box/p847124_12489300.aspx (https://shop.pedalparts.co.uk/Blue_Fool_MXR_Blue_Box/p847124_12489300.aspx)

(https://i.imgur.com/mmIguSq.jpg)
Title: Re: MXR Blue Box fourth transistor Q4 name?
Post by: Mark Hammer on November 29, 2019, 07:45:00 AM
If it IS that particular circuit, then the 4th transistor s apparently assigned to an added booster stage, in which case it can likely be any old NPN, assuming it conforms to the pinout.
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