WAIT mod on an issue 3 board
Posted: Sun Oct 11, 2015 4:08 pm
Greetings,
Did anyone try the "WAIT mod" by Wilf Rigter (who apparently did it on an issue 1 board) on an issue 3 board ?
If yes, did you get a *stable* system afterwards and if yes to that second question, what PNP transistor did you use ?... I tried with a BC559B (i.e. a lower-noise-but-lower-max-Vce-BC557), and the result was catastrophic (totally unstable system with numerous random crashes). I think this is due to the bad switching qualities of the transistor (storage time >200ns, against 13ns for the ZTX313 it is coupled with). Had it been a NPN transistor, I had used a 2N2369A (same storage, rise and fall times as for the ZTX313), but I didn't find any PNP equivalent in my drawers and none either in my usual components suppliers' catalog: an ideal candidate would have been the 2N5771(20ns storage time), but it's impossible to find, nowadays...
I see that Wilf Rigter used a 2N2907A, but this transistor is just as bad a switching transistor as the BC55x (300ns switch off time, and probably a worst storage time), so I'm wondering it this mod is at all valid, at least on an issue 3 board...
Did anyone try the "WAIT mod" by Wilf Rigter (who apparently did it on an issue 1 board) on an issue 3 board ?
If yes, did you get a *stable* system afterwards and if yes to that second question, what PNP transistor did you use ?... I tried with a BC559B (i.e. a lower-noise-but-lower-max-Vce-BC557), and the result was catastrophic (totally unstable system with numerous random crashes). I think this is due to the bad switching qualities of the transistor (storage time >200ns, against 13ns for the ZTX313 it is coupled with). Had it been a NPN transistor, I had used a 2N2369A (same storage, rise and fall times as for the ZTX313), but I didn't find any PNP equivalent in my drawers and none either in my usual components suppliers' catalog: an ideal candidate would have been the 2N5771(20ns storage time), but it's impossible to find, nowadays...
I see that Wilf Rigter used a 2N2907A, but this transistor is just as bad a switching transistor as the BC55x (300ns switch off time, and probably a worst storage time), so I'm wondering it this mod is at all valid, at least on an issue 3 board...