[time-nuts] TB DAC, was Re: Embarrassing stuff...

[David Hooke]

Azelio,

I was lucky, it was just the opamp, so the TB is happily driving the 
MV89 again. Back to three cornered hat testing!

The DAC is no more than PWM, so I'm guessing the reference (5V, not as I 
thought 4V) and DAC output are sampled by the CPU to get the PWM output 
close to what's required.

One interesting thing: the Trimble oscillator is now dead (ignoring 
EFC). I had tried it after the MV89 failure, and it apparently didn't 
like more than +/-5V.

Cheers.

> and maybe that the DAC's output feeds an OPAMP first, if so then
> replacing the OPAMP should fix the problem...
>
> On Thu, May 16, 2013 at 12:10 PM, David Hooke <dhooke-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org> wrote:
>>
>> OK.
>>
>> This MV89 is mounted on a PCB with SMA connectors for the EFC, REF and
>> 10MHz. I connected the EFC from the TB to the REF out of the oscillator, not
>> for very long, and things haven't been quite right since then.
>>
>> I should not play in the workshop after drinking wine with dinner!
>>
>> It'll be interesting to see how Trimble designed the DAC. There doesn't seem
>> to be much more than a 4V reference, a quad opamp and a bunch of RCs. I
>> guess that as long as it's monotonic, accuracy is not overly important.
>>
>> Cheers.
>>
>> david
>>
>>> Fess up David. Tell the story.
>>>
>>> LOL,
>>> Tom
>>> ----- Original Message ----- From: "Burt I. Weiner"
>>> <biwa-fOdFMYwuEsI-XMD5yJDbdMReXY1tMh2IBg at public.gmane.org>
>>> To: <time-nuts-JSkTLETqlTM-XMD5yJDbdMReXY1tMh2IBg at public.gmane.org>
>>> Sent: Wednesday, May 15, 2013 11:54 AM
>>> Subject: [time-nuts] Embarrassing stuff...
>>>
>>>
>>> David,
>>>
>>> I'm sure it's nothing compared to what I did many years ago to my
>>> Singer FM-10C Synthesizer.  You tell us your story and I'll tell you
>>> mine.  You're among friends.  Every time my life flashes before my
>>> eyes it's mostly embarrassing stuff.
>>>
>>> Burt, K6OQK
>>>
>>>> From: David Hooke <dhooke-Re5JQEeQqe8AvxtiuMwx3w-XMD5yJDbdMReXY1tMh2IBg at public.gmane.org>
>>>>
>>>> Subject: Re: [time-nuts] three cornered comparison tools
>>>>
>>>> Hi All,
>>>>
>>>> I've managed to blow up the DAC output on my TBOLT; it now has about
>>>> 0.5V 42kHz ripple on it. I think I know how I did this, but it's too
>>>> embarrassing to share in public.
>>>
>>> Burt I. Weiner Associates
>>> Broadcast Technical Services
>>> Glendale, California  U.S.A.
>>> biwa-fOdFMYwuEsI-XMD5yJDbdMReXY1tMh2IBg at public.gmane.org
>>> www.biwa.cc
>>> K6OQK
>>>
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>>
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