Received one unit from a friend for fix on "no sound" issue. After replaced the open circuit current limiting resistors for the pre-amp power supply, now it works just fine.
Out of curiosity, as the amplification circuitry seems a bit 'complex', schematics are reproduced, as a reference for service or DIY build purpose.Only the input buffer and power amplifier section schematics are available.
Big thanks to @osexm, a forum member for his work on the Tempo 1 schematic as it lay a foundation for my reverse engineering work (both design almost identical). All I have to do is just 'double confirm' all the connection.
Some technical details for the Tempo 2:
-signal flow : input relays -> input buffer -> CS3310 -> CFA power amp -> output relay.
-the input buffer which is a diamond, look similar to HDAM-SA2, with different arrangement for the first stage CCS.
-fully DC-coupled from input till speaker output.
-extensive of BC550C/BC560C are used for the small signal section.
-lots of red Wima caps.
-Resistors are mostly 6-band E96 50ppm 1% tolerance, except for higher wattage application.
-standard issue LM317/LM337 are used for voltage regulator for input buffer and first stage of the CFA power amp.
-amplification+volume+dc offset detection circuit and control+other protection+display circuit are electrically isolated using optocouplers.
-dc offset, over temperature, rail fuse detection are available for protection and will display status (in case being activated) on the main VFD display( which is actually a CD player display!).
-speaker output relay does not offer turn-off delay(which actually not needed for Tempo 2, almost silence), but merely just cut-off the speaker in case protection kick-in.
Out of curiosity, as the amplification circuitry seems a bit 'complex', schematics are reproduced, as a reference for service or DIY build purpose.Only the input buffer and power amplifier section schematics are available.
Big thanks to @osexm, a forum member for his work on the Tempo 1 schematic as it lay a foundation for my reverse engineering work (both design almost identical). All I have to do is just 'double confirm' all the connection.
Some technical details for the Tempo 2:
-signal flow : input relays -> input buffer -> CS3310 -> CFA power amp -> output relay.
-the input buffer which is a diamond, look similar to HDAM-SA2, with different arrangement for the first stage CCS.
-fully DC-coupled from input till speaker output.
-extensive of BC550C/BC560C are used for the small signal section.
-lots of red Wima caps.
-Resistors are mostly 6-band E96 50ppm 1% tolerance, except for higher wattage application.
-standard issue LM317/LM337 are used for voltage regulator for input buffer and first stage of the CFA power amp.
-amplification+volume+dc offset detection circuit and control+other protection+display circuit are electrically isolated using optocouplers.
-dc offset, over temperature, rail fuse detection are available for protection and will display status (in case being activated) on the main VFD display( which is actually a CD player display!).
-speaker output relay does not offer turn-off delay(which actually not needed for Tempo 2, almost silence), but merely just cut-off the speaker in case protection kick-in.
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