[time-nuts] HP5370A A22 arming assembly circuit diagram error

[Dr Bruce Griffiths]

Dr Bruce Griffiths wrote:
> John Miles wrote:
>> In the 5370B manual (2940A prefix), it looks like they are running U7 
>> from
>> +5 on pin 3 and -5.2 on pin 12.  Probably a drafting error in the -A 
>> manual.
>>
>> -- john, KE5FX
>>
>>
>>  
>>> Dr Bruce Griffiths wrote:
>>>    
>>>> Correction to previous post. (typed U7 instead of U6 VVC connected too
>>>> ground OK for U7 as inputs are ECL levels. )
>>>>
>>>> The positive supply connection to A22:U7 (LM339 quad comparator) is
>>>> shown as ground in the circuit diagram.
>>>> This is surely incorrect as the inputs of U6B and U6C are connected to
>>>> TTL(+5V VCC) signals.
>>>>
>>>> Surely this is not the designers intention
>>>> The positive supply of A22:U6 should be +5V.
>>>>
>>>> Is there a manual change correcting this schematic error that I have
>>>> missed?
>>>>
>>>> If A22:U6 positive supply is indeed ground, the circuit may still work
>>>> but its reliability will be compromised by the relatively large
>>>>       
>>> currents
>>>    
>>>> flowing into A22:U6C&D input substrate diodes.
>>>>
>>>> Bruce
>>>>       
>>
>>
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>>   
> The 5370A A22 circuit diagram appears to be riddled with errors.
> U9 is shown as both as an MC10107 (triple exclusive OR/NOR gate) and 
> as a Line receiver/comparator.
> The signals on A22 J1 coming from A16 are all 5V TTL (74LS175 outputs) 
> with 500 ohm pullups to 5V.
> On A22 some of these inputs are shown connected in series with 82.5 
> ohm and pulled down to -5.2V with 1000 ohms.
> The junction of the 1000 ohm pulldowns and the 82.5 ohm resistors is 
> then (in some cases) shown connected to ECL gate inputs or even 
> emitter dotted to the output of an ECL gate (U1A). I've successfully 
> used resistive divider networks to interface between 5V TTL and ECL, 
> however the values shown in the schematic surely cannot be correct and 
> will produce incorrect (and possibly damaging) output levels for the 
> ECL gates.
>
> Bruce
>
The level translation function would actually work well if only the 82.5 
ohm resistors were actually 825 ohm resistors, maybe its just a simple 
error in erroneous placement of a decimal point??

Bruce