Lab_Gruppen_fP6400_Service_Manual.pdf

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fP6400
Functional description for class TD amplifiers .................................................3
Functional description schematics ....................................................................5
Internal connections ..........................................................................................6
Component list ..................................................................................................7
Variant specific components .............................................................................7
Description for variant dependent components.................................................7
Sparepart list for fP6400 ...................................................................................8
A20TDH
Schematics for A20TDH...................................................................................2
Board placement for A20TDH..........................................................................3
Component list for A20TDH-32-2 - rev 02.......................................................4
A20TDL
Schematics for A20TDL ...................................................................................2
Board placement for A20TDL ..........................................................................3
Component list for A20TDL - rev 02A.............................................................4
Variant specific components .............................................................................7
Description for variant dependent components.................................................8
IN2GTD
Schematics for IN2GTD ...................................................................................2
Board placement for IN2GTD ..........................................................................3
Component list for IN2GTD - rev 02A.............................................................4
Variant specific components .............................................................................7
Description for variant dependent components.................................................8
LD92
Schematics for LD92 ........................................................................................2
Board placement for LD92................................................................................3
Component list for LD92 - rev 01.....................................................................4
Variant specific components .............................................................................5
Description for variant dependent components.................................................6
SP80CB
Schematics for SP80CB ....................................................................................2
Board placement for SP80CB ...........................................................................3
Component list for SP80CB-2x32-2 - rev 01A .................................................4
SP80FA / SP80FB
Functional description for switch mode powersupply SP80FA & SP80FB......2
Schematics for SP80FA & SP80FB ..................................................................4
Schematics for SP80FA, SP80FB & PIND.......................................................5
SP80FA .............................................................................................................6
Board placement for SP80FA - rev 04 ..............................................................6
Board placement for SP80FA - rev 06 ..............................................................7
Component list for SP80FA - rev 06.................................................................8
Variant specific components for 230V versions - rev 06 ..................................9
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Variant specific components for 115V versions - rev 06 ................................10
Description for variant dependent components...............................................11
SP80FB ...........................................................................................................12
Board placement for SP80FB & PIND ...........................................................12
Component list for PIND, SP80FB - rev 01A.................................................13
Variant specific components for 230V versions - rev 01A .............................15
Variant specific components for 115V versions - rev 01A .............................16
Description for variant dependent components...............................................17
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Theory of function
The input signal is connected to the balanced amplifier and gain switch U1, U201 on the IN2GTD-board. The signal is then
passing the gain control on the front panel, going to amplifier U2 (IN2GTD). The gain in this amplifier can be reduced by opto
resistor U5 to prevent clipping in the output amplifier. Limiter Q1, Q2 together with the phase linear lowpassfilter U3, U4 limits
the slewrate of the signal going to the output amplifier A20TDL, preventing intermodulation in this amplifier if signals of too
high frequencies are presented on the input terminal.
The output amplifier A20TDL works as an ordinary power amplifier with the difference that the collector voltage to the output
transistors is supplied from the switch mode amplifier A20TDH. The base voltage of the output transistors Q26-Q28, Q31-Q33
(A20TDL) is sensed by voltage divider R36-R38 and is then sent to the adjustable limiter U3, U4 on the IN2GTD-board, before
it reaches the input of the switch mode amplifier (A20TDH) . Limit level is set by the MLS switches S1 and S2. This limiter is
used to limit the maximum output voltage from the amplifier. These switches also change the sensitivity for the led bars on the
front panel.
The amplifier U1 (U2) on the A20TDH-board makes sure that the output signal on terminal CP4 (CP8) is a copy of the input
signal on terminal CP12, by giving correct control voltage to pulse width modulator U3. U3 compares this voltage with an
614kHz triangular wave giving a pulse width modulated output signal from Q1 (Q7) which is filtered by L1, C1 (L4, C10). The
gain from the base of the output transistors on the A20TDL-board to the output of the A20TDH-board is equal to one. VR1
(VR2) is used to add a DC-offset on the input of U1 (U2) giving +7,5V (CP4) -7,5V (CP8) relative output of the LF-amplifier
(CP6A), which is the same as collector-emitter voltage for the output transistors Q26-Q28 and Q31-Q33.
Repairing instructions
REQUIRED MEASUREMENT EQUIPMENT:
-Audio generator
-Dummy load, 16 ohm
-AC-voltmeter/THD-meter
-2 digital voltmeters
-Two channel oscilloscope for audio
1.
Without changing any fuses check the power supply +155V, -155V, +16V, -16V and +45V. If these aren't OK go to the
service manual for the power supply. (The +45V voltage is not regulated and can vary between 30 and 60V depending on
the load of the power supply.)
If all fuses are OK, follow the signal from input to output, and repair in normal way. The best way is to place the
amplifier on the front handles, loosen the rear panel, and mount it back on distances (delivered with this manual) to make
it possible to measure.
If there is a fault in the power amplifier stage do as follows:
3:1
3:2
3:3
3:4
3:5
3:6
3:7
Turn VR1, VR2 (A20TDH) and VR3 (SP80FB) counter clockwise.
Short-circuit R38 on A20TDL-board.
Disconnect cables from CP23 and CP24 (A20TDL) (Q26-Q28 and Q31-Q33 collectors).
Replace broken fuses. (only for the channel you repair)
Connect DC-voltmeter (200V) to the positive (negative) rail voltage.
Connect another DC-voltmeter (20V) to the cable disconnected from CP23 (CP24).
Turn VR3 (SP80FB) slowly clockwise, and watch the voltmeters. Rail voltage should increase rapidly, "collector
voltage" should read 0. After turning VR3 maximum 30°, rail voltage should be 155V.
2.
3.
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3:8
3:9
3:10
3:11
3:12
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If the rail voltage is zero or very low, check Q1, D1A, D1B (Q7, D5A, D5B) (shorted) on the A20TDH-
board. If Q1 (Q7) is broken, also replace R3 (R16) and D2 (D6).
If the rail voltage is OK, turn VR1 (VR2) on the A20TDH-board slowly maximum clockwise. Voltage
measured on the disconnected collector cable should stop at about 7,5V.
If OK turn VR1 (VR2) (A20TDH) and TP3 (SP80FB) counter clockwise.
Repeat from 3:5 for the negative side.
Reconnect cable to CP23 (Q26-Q28 collector).
Connect dummy load 16 ohm to output, and connect an oscilloscope (10V/div) across the load.
Slowly turn VR3 (SP80FB) for 155V (-155V) rail voltage.
Slowly turn VR1 (VR2) (A20TDH) clockwise and look at the oscilloscope. There should be no DC on the
oscilloscope. If there is DC (>1V) repair the positive (negative) output section on the A20TDL-board.
Turn back VR1 (VR2) (A20TDH) and VR3 (SP80FB), and disconnect the cable from CP23 (Q26-Q28 collector).
Reconnect cable to CP24 (Q31-Q33 collector) and repeat from 3:11 for the negative side.
Reconnect cables to CP23 and CP24. Turn VR3 for 155V rail voltage. Turn VR1 clockwise, no DC on the
oscilloscope. Then slowly turn VR2 clockwise. There can be some oscillation with VR2 in middle position, but it
will stop at further turning.
Connect 1kHz sine wave to the input of the amplifier. Adjust gain until there is signal on the output. It should be a
7V PK sine wave with no distortion.
Disconnect short circuit from R38, and the amplifier will work.
3:16
3:17

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