SD-SH111 (serv.man11). Description of circuit for 1-bit unit - Sharp Audio Service Manual (repair manual)

sd-sh111 (serv.man11) service manual
Model
SD-SH111 (serv.man11)
Pages
1 Few pages! See other manuals at the bottom of the first or last page.
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7.78 KB
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PDF
Document
Service Manual
Brand
Device
Audio / System / Description of circuit for 1-bit unit
File
sd-sh111-sm11.pdf
Date

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SD-SH111
– 30 –
DESCRIPTION OF CIRCUIT FOR 1-BIT UNIT
(SEE THE WIRING DIAGRAMS ON PAGES 82 AND 83.)
Input
Signals over certain level input from BIA106 are sliced into waveforms by RA173 (RA174), DA126, and DA127 (DA128, DA129).
The slice levels depend on the output of the unit.
In case of 25 W output setting, the level is set to gain distortion of approx. 10 % during output.
The level on the positive side is determined by RA175, RA177 and RA179 and that on the negative side by RA176, RA178, and
RA180, respectively.
After DC cut by CA108, the signals are input to AD conversion IC.
        modulation 1-bit conversion
The signals input to the AD conversion IC are converted into 1-bit signals for differential output.
For detailed technical description of 1-bit signal conversion, refer the technical manual for SM-SX100 already published.
Dead time and level shift
When the 1-bit signals are output from the AD conversion IC, the leading edge of the waveform is delayed for 20 to 25 nsec by
DA103 (DA102, DA101, and DA100), RA115 (RA114, RA113, and RA112), and CA155 (CA154, CA153, and CA152), compared
with the trailing edge.
As mentioned below, this operation is for reducing switching circuit loss in the final stage.
The signals are input to the buffer IC (AND gate IC) for the waveform format and are output.
Then the DC level is shifted by CA115 (CA114, CA113, and CA112), DA107 (DA106, DA105, and DA104) and RA120 (RA119,
RA118, and RA117). This is because the buffer IC operates between ground and + 5 V, while the next stage IC, gate driver (ICA101
to ICA 104), operates between the negative power source and + 9 V.
The shift quantity is output with amplitude of 5 V, based on the voltage raised by DA108 and DA109 from the bottom by approx.
2 V.
Low-pass filter circuit
1-bit signals switched at output IC are converted into analog signals via the low-pass filter consisting of LA100 (LA102, LA104,
and LA106) and CA142 (CA143, CA150, and CA151).
Property of the low-pass filter is flat up to 20 kHz and then is attenuated by approx. 3 dB at around 40 kHz.
Dynamic feedback circuit
1-bit signals switched at output IC of output stage are amplified between the positive and negative power sources.
With resistance divided, 1-bit signals are fed back to AD conversion IC, via NF resistance 75 kohms.
P-P voltage, which becomes approx. 5V, is determined by the regulation property of the transformer depending on the output level.
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Here you can read online and download Sharp SD-SH111 (serv.man11) Service Manual in PDF. SD-SH111 (serv.man11) service manual will guide through the process and help you recover, restore, fix, disassemble and repair Sharp SD-SH111 (serv.man11) System. Information contained in service manuals typically includes schematics / circuit diagrams, wiring diagrams, block diagrams, printed wiring boards, exploded views, parts list, disassembly / assembly, pcb.