Hi Guys,
I am working on a Tek Telequipment D34 small portable analog scopes. There is a JFET, TR302 in the CRT circuit that is a Tek Part 151-1076-01 or a 151-1076-00 aka WN537B N Channel JFET
I can't find any data on this part or a replacement for it. I have tried 2N5457's and 2N5459's and they work well but only for a few hours. Being in an HV circuit it's hard to quantify what is going on other than perhaps breakdown. It seems that JFETS, especially higher voltage ones are rare these days.
I was thinking about putting some 20V or so zeners from the Gate to Source and from the Drain to source to protect the 2N5457 parts but am unsure of how that would affect the normal circuit operation of the current source circuit.
I have included a schematic of the HV Section showing the TR302 and a circuit description and a picture of a working one from the web.
So if anyone happens to have any of these parts I would appreciate getting one or two. The scope was made by Telequipment in England a subsidiary of Tek and overall is one of Telequipment's better efforts as it has a really sharp Tek ceramic bell tube and regulated power supplies (something the earlier Telequipment scopes were not known for).
Thanks for your time!
Sam
W3OHM