Diagnostic Testing and Troubleshooting (2620A/2625A)
Power Supply Troubleshooting
5
5-9
U9-7 and T2-2
5V/DIV
0V
20V
2
µ
S/DIV
Normal Load
s33f.eps
Figure 5-2. 5-Volt Switching Supply
If no square wave is present at A1U9-7, the oscillator can be checked by looking at the
signal at A1U9-3. The oscilloscope should be ac-coupled for this measurement. This
waveform should be a sawtooth signal with an amplitude of 0.6V p-p and a period of
approximately 14 us. Failure of the oscillator is usually caused by a defective capacitor
A1C21 or defective A1U9.
The output current of the 5-volt switching supply can be determined by measuring the
voltage across the current limit current sense resistors (A1R29, A1R30 and A1R31). The
current shunt is approximately 0.167 ohms. With line voltage at 120V ac and the
instrument not actively measuring, typical voltages across the current sense resistors are
as follows:
•
2620A Instrument without options: 28 mV
•
2620A Instrument with IEEE-488 Option: 50 mV
•
2625A Instrument: 28 mV
5-9. Inverter
Use an oscilloscope to troubleshoot the inverter supply. The outputs of the inverter
supply are -5V dc, -30V dc, and 5.4V ac outguard, and +5.3V dc, -5.4V dc, and +5.6V dc
inguard. Refer to Figure 5-3. The signal at the drains of the two inverter switch FETs
(A1Q7 and A1Q8) should be a 10V peak square wave with a period of approximately 18
us. The gate signal is a 5.1V peak square wave with rounded leading and trailing edges.
The leading edge has a small positive rounded pulse with an amplitude of 1.8V peak and
a pulse width of about 0.3
µ
s. The signal at A1U22-5 and A1U22-6 is a symmetrical
square wave with an amplitude of 5.1V peak and a period of about 18
µ
s. The negative-
going trailing edge of both square waves is slower than the rising edge and has a small
bump at about 1.5 volts. The signal at A1U22-3 (TP14) is a symmetrical square wave
with a period of about 9
µ
s.
Summary of Contents for 2620A
Page 4: ......
Page 18: ...HYDRA Service Manual 1 2...
Page 48: ...HYDRA Service Manual 1 32...
Page 140: ...HYDRA Service Manual 3 16...
Page 234: ...HYDRA Service Manual 5A 34...
Page 236: ...HYDRA Service Manual 6 2...
Page 254: ...HYDRA Service Manual 6 20 2620A 1601 s63f eps Figure 6 3 2620A 2625A A1 Main PCA...
Page 258: ...HYDRA Service Manual 6 24 2635A 1601 s64f eps Figure 6 4 2635A A1 Main PCA...
Page 260: ...HYDRA Service Manual 6 26 2620A 4002 CKT 1 CKT 2 s65f eps Figure 6 5 A2 Display PCA...
Page 272: ...HYDRA Service Manual 6 38...
Page 274: ...HYDRA Service Manual 7 2...
Page 282: ...HYDRA Service Manual 7 10...
Page 284: ...HYDRA Service Manual 8 2...
Page 285: ...Schematic Diagrams 8 8 3 Figure 8 1 A1 Main PCA 2620A 2625A 2620A 1601 s88f eps...
Page 288: ...Schematic Diagrams 8 8 6 Figure 8 1 A1 Main PCA 2620A 2625A cont 2620A 1001 3 of 4 s73f eps...
Page 292: ...Schematic Diagrams 8 8 10 2635A 1001 2 of 5 Figure 8 2 A1 Main PCA 2635A cont s76f eps...
Page 293: ...Schematic Diagrams 8 8 11 2635A 1001 3 of 5 Figure 8 2 A1 Main PCA 2635A cont s77f eps...
Page 296: ...Schematic Diagrams 8 8 14 2620A 4002 CKT 1 CKT 2 Figure 8 3 A2 Display PCA s90f eps...
Page 300: ...Schematic Diagrams 8 8 18 2620A 1003 2 of 3 Figure 8 4 A3 A D Converter PCA cont s82c eps...
Page 301: ...Schematic Diagrams 8 8 19 2620A 1003 3 of 3 Figure 8 4 A3 A D Converter PCA cont s83c eps...
Page 302: ...Schematic Diagrams 8 8 20 2620A 1604 Figure 8 5 A4 Analog Input PCA s92f eps...
Page 304: ...Schematic Diagrams 8 8 22 2620A 1605 Figure 8 6 A5 IEEE 488 Interface PCA 2620A Only s93f eps...
Page 306: ...Schematic Diagrams 8 8 24 2625A 1606 Figure 8 7 A6 Memory PCA 2625A s94f eps...
Page 310: ...Schematic Diagrams 8 8 28...
