On my 130, the variable oscillator won't oscillate.
On Thursday, February 17, 2022, 05:08:34 PM PST, Tom Lee <tomlee@...> wrote:
Hi Dave,
The docs at VintageTek are great. The gentleman who wrote the three-part
article did a remarkable job of documenting his restoration of his 130.
He even restored the manual (he did more than photoshop an existing
manual -- he rewrote it!). After you've read his docs, you'll understand
how that unit works at a deep level.
If the signal that drives the Schmitt looks good (both amplitude- and
dc-wise), the number of possible faults goes way down. A few component
checks/substitutions should get your unit functioning again. Then
perform a cal, and it should be as good as new.
Good luck hunting!
--Cheers
Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
On 2/17/2022 16:54, Jerome D Leach wrote:
Thank you Tom, will take a closer look at the resistors in that
circuit, and will then report back.
Dave (yeah, go by Dave, never much cared for Jerome)
On 2/16/22 23:21, Tom Lee wrote:
Hi Jerome,
That's a nice unit and definitely worth fixing.
V70 is a straightforward Schmitt trigger, and there's not a lot that
can go wrong. Measure voltages on the tube pins. Measure resistances
(R72 and R73 in particular). If they've drifted far upward (including
going open-circuit altogether), that would certainly kill the
Schmitt. You'll find something quite obvious from those measurements.
Good luck!
-- Cheers,
Tom
