[time-nuts] Re: 5370A repair

[zfe]

>> On Jul 15, 2025, at 5:00 PM, Magnus Danielson via time-nuts <time-nuts at lists.febo.com> wrote:
>>
>> Hi,
>>> Service powersupply. Should be relatively trivial.
> I removed all the boards except the power supply controller and the 15V was now present. Unfortunately…
>
> I then reinserted boards one by one to find the one that’s pulling the 15V down: it’s the 10MHz detector board that sits next to the OCXO power supply board. All other boards are plugged in. 
>
> I would expect that with only this board removed, the CPU should be up and running and maybe displaying an error message? But that’s not the case: except for a 4 status LEDs, the display stays dark. 
>
> Does anyone know if that’s expected? 
>
> The 10 MHz detection board is not connected to the CPU bus, so the lack of it shouldn’t result in a bus hang. 
>
> Tom
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Assuming you are talking of the "A8Â  Reference Frequency Buffer
Assembly": The clocking of the CPU is generated from the 10MHz
Reference. So it is normal that without taht board the CPU is not working.