Just confirmed this is a 453 pre A version.
Found D940 was open and when I looked at the two versions of this circuit there is considerable differences.
D940 is the biggest diode I've ever seen so I guess a 1n911 is not going to do the job. I haven't had a chance to look at the BOM but if any one knows the commercial P/N would be appreciated. Also stray thought what blew the diode? Everything else in the grid bias ckt seems to be alive and well. Any thoughts?
Thanks for your help been a great learning experience for me.