[time-nuts] 5370B stop trigger not working

Christopher E. Brown cbrown at woods.net
Mon Dec 21 15:44:38 EST 2015


You might want to re-scope the start and stop channel outputs where they cross A4 and
verify against the front panel labels.

The signal line crossing A4 that lines up with frontpanel start is start and the one that
lines up with stop is stop.


I mention this because the A3 board is a carry over from another unit and the start/stop
labeling on the board itself is reversed from the 5370B front panel labels and the parts
list follows the board labeling.  So, if you read front panel and lookup P/N in list you
get the wrong one.


The safe thing is to follow back from the output crossing A4 that is failing and
physically pull the hybrid and read the P/N on the mounting frame.  It should be a metal
can in a screw together frame, the part is socketed.


Once the A3 is out, do not remove the screws in frame, they just clamp the frame to part.
 Whole thing is held in by the collar on the pot shaft.


For a 5370B

5088-7061 (start channel hybrid)
5088-7062 (stop channel hybrid)

the manual lists it reversed, and they are actually different parts (not just diff
mounting frames) with crossed up triggers.


7061 (actual start manual lists as stop) is the one that usually fails and is almost
impossible to find.  Took me several years (and the help of another nut with a parts unit)
to get a working one.  7062 is much easier to find.


On 12/13/2015 11:26 AM, Jim Palfreyman wrote:
> Oops yes! I looked up the wrong item. I meant A3U1 which is 5088-7061
> 
> Jim
> 
> 
> On Sunday, 13 December 2015, Cok <Electronico at jpkoning.nl> wrote:
> 
>> According to the partlist A4U1 and A4U2 seems to be TL072CP opamps.
>>
>>>
>>> jim77742 at gmail.com said:
>>>
>>>> I have gone through the troubleshooting process from the manual and it
>>>> seems
>>>> to point to A4U2 (Schmidt trigger) being faulty.
>>>>
>>> I'd put a scope on it to check.
>>>
>>> Before I dive into this, does anyone have any advice? Most important being
>>>> the Schmidt trigger - where do I get one?
>>>>
>>> You need more info - the manufacturer's part number or something like
>>> that.
>>>
>>>
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