Power Supply Tips - IBM 1410 Manual

Forcing Signals
A solid +S signal can be forced by wiring the required pin to
ground.
Caution: Because some emitter followers are returned to a
minus voltage through a very low impedance, care must be used
in grounding emitter followers. However, if a -8 level is de-
sired, place a 4700-ohm resistor in series with the jumper cir-
cuit to provide a proper load. Check to see that the pin is held
sufficiently negative.
Voltage Jumpers
Exercise care when working around the wiring
Hidt·
of any chassis
to prevent dislodging any voltage jumpers. Tht•st· can be easily
dislodged because they have clip-on terminals.
Shorted DE Logic Blocks
When a shorted DE Block is encountered, always "heck the pre-
ceding card. If the short was caused by a down level, the pre-
ceding circuit may be damaged.
Core Storage
When X, Y, inhibit, etc. , lines are suspected of being open, they
may be tested with an ohmmeter, but machine power must first
be turned off. Also, if a burnt core is suspected and the core
location is visible, the lines through or around the core will be a
light copper color near the core itself. The rest of the line will
be reddish copper due to the insulating material.
Insuiating Pins
Do not overlook the value of insulating pins when troubleshooting.
Inputs to "+AND" switc!ies can be forced all tbe time by using a
card extender and pulling the desired wire loose. This method
can enable scoping of some circuits, in a st.a.tic ::;tatc
1
which are
normally active only when some infrequently oeeurr ing input is
available.
POWER SUPPLY TIPS
If trouble is in an individual power supply ,note the following:
There is a 90% chance it is the SMS card (low or no adjust-
ment of output voltage). )
If voltage is high with no adjustment, then one of the series
regulator transistors is shorted (or SMS card is bad).
With power supply :removed you may wire 110 vac into TB 1
pins 1
&
2. Output may not reach full value but should be
close and adjustable. (Remove over-voltage device).
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