Re: Is my Tek 468 beyond repair?


John
 

On Sat, Oct 17, 2020 at 05:46 AM, <robeughaas@gmail.com> wrote:


I see the IPROM's are still on the way to you. I've started a survey of the 13
468's in the Museum's boneyard and of the first seven, found two with shorted
+5 Storage Supplies, as evidenced by blown F4007 and F4009, 5-amp picofuses at
the back of the trigger board. I've dismantled one and found a shorted CR169,
the catch diode in the supply. I'll go through the remainder tomorrow, and I
suspect I'll find more with shorted supplies. Of the six I've been able to
test ROM's on, I have found all the ROM's were good. I suspect that the power
supply problem is causing the failure that is thought to be ROM rot.
That's an interesting observation. Some time ago I came across a 465 that had an intermittent shorting -8V supply due to a faulty smoothing can but so far in the 468 all supplies are good and as it turns out, the ROMs are good as well. The problem turned out to be a non-running CPU. I don't know much about the history MOSTEK EEPROMs but can't help wondering how long these are likely to last although I am glad to have backup spares "just in case" courtesy of a helpful contributor on here. Still it is a testament to Teks' engineering that they can be brought back to life and still work 40 years later.... For sure the 468 is an interesting example of a vintage scope with early storage computing.

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