question about transistors(Guyatone WR2 woes)

[mr.death]

My Guyatone WR2 took a turn for the worse when I used an AC adapter instead of a DC adapter. It no longer works so I took it to a local amp repair guy and he replaced a bunch of components. It works now but its character is not what it use to be. I got in touch with the repair guy and he said I may need to replace the k30A Y7J transistors(3 in total). I dont have any more money to throw at this pedal in terms of labour costs so I plan on swapping out the 3 transistors myself. Im having a hard time finding the exact same components that were in the pedal.

My question is are all K30A transistors the same? In the pedal as it is I have K30A Y7J transistors. Can I use others or do they have to be the exact same ones. Thanks for your time. Rick

[Mark Hammer]

All three are used for switching purposes, so you're not really depending on their sonic characteristics; one should be just as good as another. 

You can likely substitute a J113 (what DOD uses for the identical function), although you may have some difficulty in finding them.  I imagine other folks here will recommend other FETs suitable for switching.

On the other hand, if the unit engages and bypasses, just like it always has, then there is likely nothing "wrong" with those JFETs, and the problem lies elsewhere.  One of the JFETs is used to engage/lift the filter output, another is used to engage/lift the unfiltered output (both of these go to a common output stage), and the third is used to essentially kill the envelope-follower/rectifier by dropping its gain down to 1x.

It's hard to see anything specific that might be damaged by the application of AC.  Was this a case of plugging in 9VAC instead of 9VDC?

[mr.death]

It's hard to see anything specific that might be damaged by the application of AC.  Was this a case of plugging in 9VAC instead of 9VDC?

Exactly what happened.

[mr.death]

[mr.death]

So these are the parts that were replaced.....

How it went down...I used an AC adapter instead of a DC adapter and fried the pedal. Stopped working and I could smell electronics burning but no smoke. I brought it to the local reapir guy and he checked all of the other components and they checked out as good except for the pieces pictured. Now the pedal works kind of. Its a dynamic wah so as you hit the strings hard the was opens up more. When I hit the strings hard now I lose most of the signal. Gets quiet in the filter sweep up high but gets louder as the sweep returns down low. It can be used with light picking but when I lay into the strings the signal degrades. The repair guy said the only things left to replace were the K30A transistors. Any ideas? Thanks again

[mr.death]

The repair guy said there was no diode to protect the unit from the wrong power supply. He did add one.

[mr.death]