Heathkit AR-14 - Page 65

Page 58
DIFFICULTY
Hum
Low
supply voltage at points
[]] and [!].
Supply voltage on transistors Ql 5
and Ql 6 near point A supply
voltage.
Supply voltage on transistors Q15
and Ql 6 very low or zero.
I
~H·&i=fW
POSSIBLE CAUSE
1. Reverse AC line cord in the outlet.
2. Defective shield on audio cable.
3. No ground wire between ground terminal on
Receiver and turntable base plate when using
Phono input.
4.
Intermittent ground in Receiver. Check for
loose hardware or poor solder connections.
5. Transistor Ql00 faulty.
1. Transistor Ql00 open. Before replacing
Ql00, check resistance reading from Test
Point E to chassis ground. (See Initial
Test, Page 44.)
2. Short in preamplifier circuit, QlO0.
1.
Check wiring and components in circuits of
transistors Q15 and Q16.
2.
Transistor Ql 5 or Ql 6 shorted. Measure
resistance between the Emitter and Collec-
tor leads on lowest range. Zero ohms re-
gardless of ohmmeter lead connection,
indicates a short.
1. Check wiring of transistors Q15 and Q16.
2.
Resistor Rl69 or Rl 70 open.
✓