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 >>>> >> >> >> _______________________________________________ >> time-nuts mailing list >> time-nuts@febo.com >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> >> > 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 _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
