N_Cook wrote:

I thought I'd messed up the USB lead of my HP 1020 laserjet , measuring
voltages etc, trying to learn about USB function. Turned out I must have
strained a USB A to B adaptor and nothing wrong with the printer. Is one
rule of thumb (for a suspect USB connection) that a maximum USB insertion
force of 250 gram is too low and above 450 gram is generally good ? ( I
later went around a number of leads /connectors, adaptors with the kitchen
scales).
Anyway inside the printer there were 6 unmarked 2 land SMD lumps marked on
the overlay as E1 to E6 , is E a designation for fuse?, all were 0 ohms
across.


'E' is often used to indicate a connection off the board. They are
probably there for automated testing in a 'Bed of Nails' (AKA: Pogo
Pins) test fixture during the manufacturing process. More and more
manufacturing is moving to this method where boards are handled by
machines from the time the blanks are loaded into a pick & place
machine, till they are ready to be installed in a product.


There were 2 unmarked green 2 land lumps on the USB lines marked VR
on the overlay, bidirectional transient suppressors ?
and 2 SMD contacting the USB lines marked CR, presumably rectifiers, but can
anyone identify with more certainty
4 land device marked topmark D132
found on topcode listings
D13 AZZ23C8V2 Diode SOT23 dual zener 8.2V 0.3W, 3 pin
related?

2 land device marked WU1
found
WU BZX284-B4V3 Phi I SOD110 0.4W zener 4.3V E24 ±2%, 2 pin
related ?

Generally do truncated 3 and 4 character topcodes have any relation to the
full code ?


No. They match the component's location on the schematics and B.O.M.


--
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