Re: Q122/222 Jfet J300 subs for 2215A scope ?


charlesterrebonne@...
 

Well since Im the OP ill update...

This week sorting parts I fell upon a 2n5458 (NOS) that looks close to J300 specs...lets recap & quickly clear up stuff...

*Scope arrived to me with prob with ch A (no signal / vert position control : little or no mov) ...ch B was fine.

*ch A (Q122) had a "J210" marked part...ch B (Q222) had a "J300" marked part. J210 looked bad in quick testing and actully I think its not bad now.

*I now think someone attempted to fix ch A with a "J210" that never worked there and left scope like that using only Ch B.

*After trying to sub Q122 with no success, simply moving Q222 Ch B that had a "J300" marked part got Ch A working...and Ch B now missing a Q222 fet...

*Trying 2n5458 @ Q222 didnt work today with *yes correct par orientation*...looks almost like "not a fet in the circuit" with 2n5458...3-4vdc on gate and 7vdc on zener cathode pin (drain) where 12v should be.

Seems that old scope will be a single channel from now on...well maybe a last try if I find NOS J300 part...I still think those were J300s were hand picked and became J2400 siliconix part no / tektronix 151-1124-00 (from Tek parts book)

and lastly..dont wanna send the thread in a different direction here, but after buying a ~$200US china lcd 1g/s scope a while back...I was impressed...and spending time on these old CRT scopes make less and less sense to me...

Thanks too all who commented...

Join TekScopes@groups.io to automatically receive all group messages.