[time-nuts] 5370A vs 5370B

[Bob Camp]

Hi

That was my thought.

I've seen pictures of a number of 5370's reading their internal oven "off". I suspect is only going to take a few weeks of reading to find the magic pot.

Bob


On Mar 9, 2010, at 8:57 PM, John Miles wrote:

> It should be good to go right away, if working properly.
> 
> If it were measuring an independent 10 MHz source at 99.998xxx MHz I would
> suspect the thermal fuse in the 10811.. but if it's measuring its own
> reference, I'm not immediately sure what would be up with that.  It would be
> time to start going through the manual at that point.
> 
> -- john, KE5FX
> 
>> -----Original Message-----
>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
>> Behalf Of paul swed
>> Sent: Tuesday, March 09, 2010 5:50 PM
>> To: Discussion of precise time and frequency measurement
>> Subject: Re: [time-nuts] 5370A vs 5370B
>> 
>> 
>> I think it has to warm up for about 30 minutes
>> Seem to recall interpolators maybe not just seems like that
>> 
>> On Tue, Mar 9, 2010 at 8:37 PM, Bob Camp <lists at rtty.us> wrote:
>> 
>>> Hi
>>> 
>>> Ok, the trigger level pots are bent but functional. The one
>> that was stuck
>>> works after a bit of readjustment of the knob.
>>> 
>>> All three inputs (ext arm,  and the two channels) blink when I
>> put the 10
>>> MHz into them. The two with the working pots behave as expected
>> as the pot
>>> is turned (trigger in the middle, no trigger on both ends).
>>> 
>>> For what ever reason it seems to think that the period of it's 10 MHz
>>> standard is 99.5 ns. In frequency mode it thinks the standard
>> is at 9.998xxx
>>> MHz. Obviously it's a little confused ....
>>> 
>>> Sounds like it's worth working on, unless the 99.5 ns thing
>> indicates some
>>> sort of massive failure.
>>> 
>>> Bob
>>> 
>>> 
>>> On Mar 9, 2010, at 7:03 PM, Mark Sims wrote:
>>> 
>>>> 
>>>> I've had the "pleasure" of fixing way too many 5370A and 5370B front
>>> panels.  It's been a while so these musings may be clouded...
>> also beware
>>> of the two or three different front panel designs.  Also there
>> are "hybrid"
>>> 5370A's out there with 5370B front ends.
>>>> 
>>>> There are 4 pots on the front panel:  the 470K display update rate,  a
>>> 10K or 200 ohm arming level (200 ohm on 5370B and later
>> 5370A's),  and two
>>> 5K trigger level.  All are linear taper,  all have switches,
>> all are small
>>> pots with (1/4"? bushings).   Finding pots with proper switches
>> ain't easy.
>>>> 
>>>> I have never had to do the trigger level pots.  They have metal shafts
>>> and seldom break.  Their switches are what you would expect
>> (closed when the
>>> pot is turned clockwise).  In the far CCW direction the switch
>> is open and
>>> selects the 0V trigger level.
>>>> 
>>>> The other two pots are an exceedingly crappy hp design.  They have
>>> fragile plastic shafts and really poor quality switches.  The
>> switches need
>>> to be closed when the switch is counterclockwise. HP's pots have both
>>> normally open and normally closed contacts.   Frankly these
>> pots are seldom
>>> used and you can use a switchless pot and just hardwire those pads.
>>>> 
>>>> The display rate pots is particularly useless.  You can just
>> hardwire it
>>> to max.
>>>> 
>>>> The biggest bugaboo in buying a 5370 is the state of the HP
>> custom input
>>> amplifier chips.  They can be damaged by overloading the input.
>>  Blow one
>>> and you are screwed.  Buy a 5370 with a blown input amp and you
>> are screwed.
>>>  The 5370A and 5370B used different chips.  The 5345A counter
>> is a source
>>> of input amp chips.
>>>> 
>>>> It would be VERY nice if some clever person built  drop in replacement
>>> "chips" built of modern SMD parts on a DIP header.  Those input
>> amp chips
>>> are socketed.  They are little more than a comparator.
>>>> 
>>>> Quick check of the 5370A inputs is to set the unit to
>> "SEParate" inputs
>>> and connect the back panel 10 MHz ref signal to each of the inputs.  The
>>> signal level LED should flash.  A steady LED means that input
>> is toast (or
>>> the input PCB slide switches are full of navel lint and need cleaning).
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