I am now replacing a diff pair on a 240 for the third time. I matched them before installing at 427 both, and now one of them is reporting 388 and there is DC imbalance and hiss/noise on that channel. Two previous times that was what I found as well, including the originals.
As for the drivers - I used a MJE15030/MJE15031 pair to replace the original SJ2586 / SJ2585 pair which had a wide beta difference (44/173). It so happens that the MJE15030/MJE15031 betas are also very much apart and they were purchased brand new from Mouser (98/218).
I just ordered what I hope are matched pairs of KSA940/KSC2073 (or at least within 30%).
My question is - is it a reasonable assumption that beta mismatch on drivers can cause damage to the differential pair?
As for the drivers - I used a MJE15030/MJE15031 pair to replace the original SJ2586 / SJ2585 pair which had a wide beta difference (44/173). It so happens that the MJE15030/MJE15031 betas are also very much apart and they were purchased brand new from Mouser (98/218).
I just ordered what I hope are matched pairs of KSA940/KSC2073 (or at least within 30%).
My question is - is it a reasonable assumption that beta mismatch on drivers can cause damage to the differential pair?