LabGruppen Line-Xtension Service Manual
Line Extension
Circuit description and schematics for
C 20:8X
C 10:8X
C 10:4X
C 5:4X
Some of the schematics included here are not complete, or up to date. They should be used for educational
purposes only.
INDEX
INDEX ....................................................................................................................................... 2
SP20F – Circuit description ....................................................................................................... 4
Functional overview............................................................................................................... 4
Block diagram ........................................................................................................................ 4
Soft Start................................................................................................................................. 5
Stand-by (Auxiliary) supply................................................................................................... 5
Mains Detector ....................................................................................................................... 5
PowerGood_AUX .................................................................................................................. 6
PowerOn................................................................................................................................. 6
PFC......................................................................................................................................... 6
Resonant converter................................................................................................................. 6
PowerGood_2kW ................................................................................................................... 7
Service tips ............................................................................................................................. 8
SP20F Schematics .................................................................................................................. 9
AICO4b – Circuit description .................................................................................................. 13
Power supplies and power up/down..................................................................................... 13
Stand-by supply................................................................................................................ 13
Start-up ............................................................................................................................. 13
Local supplies................................................................................................................... 13
FanControl........................................................................................................................ 14
Control Ports ........................................................................................................................ 14
GPI ................................................................................................................................... 14
GPO.................................................................................................................................. 14
NomadLink....................................................................................................................... 14
Controller operation ............................................................................................................. 15
Controller ......................................................................................................................... 15
Analogue measurements .................................................................................................. 15
Digital measurements....................................................................................................... 16
FanControl........................................................................................................................ 16
Signal flow ........................................................................................................................... 16
Input circuitry................................................................................................................... 16
Analogue control and monitor.......................................................................................... 16
Limiters ................................................................................................................................ 17
Clip limiter ....................................................................................................................... 17
Current Limiter................................................................................................................. 17
Average Current Limiter .................................................................................................. 17
Protections............................................................................................................................ 18
Turn off channels ............................................................................................................. 18
Low Impedance ................................................................................................................ 18
Short circuit ...................................................................................................................... 18
VHF.................................................................................................................................. 18
DC-Protection................................................................................................................... 18
Temp Protection ............................................................................................................... 19
DIP-switches ........................................................................................................................ 19
Service tips ........................................................................................................................... 20
AICO4b Schematics (Partly)................................................................................................ 21
SPSMR – Circuit description ................................................................................................... 29
SPSMR - schematics ............................................................................................................ 29
Front Panel ............................................................................................................................... 30
A10D – Circuit description ...................................................................................................... 32
Power supplies and power up/down..................................................................................... 32
Supplies ............................................................................................................................ 32
Power up........................................................................................................................... 32
Signal Flow .......................................................................................................................... 33
Enable/Disable of a channel................................................................................................. 34
Protections............................................................................................................................ 34
VHF.................................................................................................................................. 35
DC-Protection................................................................................................................... 35
Temp Protection ............................................................................................................... 35
Crowbar............................................................................................................................ 35
Limiters ................................................................................................................................ 35
Clip limiter ....................................................................................................................... 35
Service Tips.......................................................................................................................... 37
A10D Schematics (Partly).................................................................................................... 38
SP20F – Circuit description
Functional overview
The power supply SP20F is used in the C-Series line extension amplifiers. It incorporates:
• Universal voltage input, 90-265 VAC
• Power Factor Correction (PFC)
• Soft start
• Fast mains unplugged detector
• A highly efficient isolated resonant converter for the high power outputs.
• A standby supply also used for lower voltages.
Block diagram
Soft Start
[PFC] When the mains cord is plugged into the wall, the following will happen:
The rectified mains will through D5 start to charge the capacitor bank C22-C25. The soft start
circuitry will make the capacitor tank charge slowly with low inrush current. R33 is used as a
current sense resistor and Q7 and Q4 is used to slow down this event. The voltage over the
capacitor tank will rise slowly, and after about 1-2 seconds it will have completed it’s inrush
cycle and R33 is bypassed via Q5, thus shorting the entire soft start circuitry. The node that in
the schematics is named 400V, will be Vin * 1,41 (for 220v Mains it will be ~311V, for 110v
Mains it will be ~155v). The circuitry will remain in this state until the external “Power On”
is activated from the input board (PWR_ON_CTRL).
Stand-by (Auxiliary) supply
When the capacitor tank has reached about 80VDC the standby supply will try to start.
[AUXILIARY] This converter is a self oscillating type and will change frequency depending
on its load. The high voltage (>80VDC) is fed through R76 & R77 and D13 will make sure
that the SOPS_STARTUP has a constant voltage of 12v. When the supply operates this
voltage will be supplied from the winding through D16, thus relieving the stress on R76 &
R77. This voltage will make Q10 conduct, thus making Q15 and Q12 to conduct. Now,
current flows through the primary winding, building up a magnetic flux. The current will
increase linearly with the time and so will the voltage over R62 & R78 current sense resistors.
When the voltage is enough it will trigger Q14 to conduct, thus making Q11 to discharge C85
and Q12 gate. This will stop the current in the primary winding, and the voltage polarity on
all transformer windings will reverse to discharge the magnetic flux. Mainly the transformer
discharges the flux to the secondary side, building up the voltage over the secondary
capacitors. During this time the voltage on pin 2 on the transformer will be positive, and
through C35 and R89 it will keep Q10 from conducting. When the flux in the transformer has
been discharged, the entire event will start all over again. D7 taps out a primary voltage
12V_Aux to be used on the primary side. Normally when IC5 optocoupler is not conducting
current, the transformer is charged with a high amount of energy, transferring all the energy
the transformer can handle. When the output reaches the desired voltages D49 will start to
conduct, driving current through the IC5 diode. This will alter the sensitivity on the current
sense circuitry, and make Q14 trigger on a lower primary current, thus transferring less
energy. This regulation will make the primary side not to put in more energy into the
transformer than we take out of it, thus keeping steady output voltages. When current flows in
the diode of IC5, Q13 will start to conduct current, thus making Pwr_AUX, that goes beyond
this page, to be -12v.
Mains Detector
[TOP] the Mains Detector is made up by IC1 and its surrounding components. When the
mains go above 80VAC (~113VDC) the voltage on IC1 pin 4 will go above 6,2v (D2) thus
making pin 2 discharge C7 rapidly. This will make pin 6 go below its reference thus making
its output high. This will slowly charge C8 through R3 and when it reaches 6,2v pin 14 will
go high, and the ENA will be high, thus bypassing the soft start and enabling the power
supply to turn on. During this time pin 13 will be close to 12v. If the mains cord is unplugged,
pin 13 will immediately go low, thus making the diode in IC2 conduct current, and disable
PWR_AUX to reach the PowerGood. To the input board this will signal a “PowerFail”
rapidly, thus making all circuitry turn off in a nice manner.
PowerGood_AUX
[TOP] When the standby supply has started and all auxiliary output voltages are stable Q1
will be pulled negative by the standby supply, as long as it’s not forced to ground by IC2.
This will make Q1 to be high impedance instead of shorted. The input board senses this and
uses this as a criterion for further startup.
Now we have reached this power supply state for standby. It will remain in this state until we
receive a “Power On” signal from the input board. This will only happen if the
PowerGood_AUX is high impedence.
PowerOn
[PFC]When the input board puts ~3,3v on the PWR_ON_CTRL node, the diode in IC4 will
conduct making the transistor in IC4 also conduct. If the ENA from the mains detector is high
this will make Q9 to conduct, which makes the 12V_ON to be 12v. If the ENA from the
mains detector is low, Q2 will conduct and prohibits Q9 from conducting.
PFC
The PFC is made up around IC3, which is the controller IC. The PFC controller is an advance
integrated circuitry and I will not go into detail about its regulator function. When it functions
as it should it should keep the capacitor tank (C22-C25) at 400VDC.
When the 12V_ON is close to 12v IC3 will have supply voltage and start to generate pulses to
Q3 via Q6 & Q8. When Q3 is conducting it will build up a magnetic flux in the coil L1. When
Q3 is not conducting, the coil L1 will discharge itself via D3 to the capacitor tank, making the
voltage over them be more than Vin*1,41. The main point of having a PFC is to make the
current in to the supply to be shaped as the voltage, thus making the supply look like a
resistive load on the mains. The controller ensures this by sensing the current by measuring
the voltage over R36 & R43. Since the current has to have the same shape as the voltage, the
IC3 also senses the voltage on the mains through R53. Several different regulators inside IC3
make the voltage and the current to have the same shape, sinusoidal on normal mains. The
controller senses the voltage on the capacitor tank through R42 & R38 and ensures it to be
400VDC.
Resonant converter
[Resonance] the resonance converter is a self oscillating circuitry. But unlike the previous
described standby supply, this converter will oscillate on the resonance frequency of the
capacitors C50, C51, C52 and the coil L7. The converter is made up by IC13 and it
surrounding components. When the 12V_ON is close to 12v IC13 will have supply voltage
through D26 and R92. It will then start to generate pulses to Q18 and Q19. I will not go
deeper into the primary side. There are 3 taps on the secondary side of the transformer,
+105v, -105v and a 13,5v that is referenced to the -105v. To keep the voltages steady D20
will control the current through IC6 and make sure that there are 210VDC between the -105v
and +105v.
PowerGood_2kW
[Resonance] When the +105v has reached ~80v the IC7 pin 3 will go above the (-) input thus
making it’s output pin 1 be high impedance. When the 13,5v reaches ~11v Q28 and Q27 will
make Q26 conduct current, thus enabling the -105v reach the PwrGood comparators in IC7.
When the -105v reaches about -80v, pin 6 on IC7 will go below its reference and the output
pin 7 will be high impedance. When both pin 1 & 7 on IC7 is high impedance Q34 will
conduct current, thus making Q35 gate negative making it to be high impedance. Thus the
PowerGood_2kW is released. This is sensed by the input board and when Q35 is not
conducting, this is interpreted as the resonance converter is up and running and the input
board can start all its functions. If the PowerGood_2kW is not released, the input board will
remain in standby.
Service tips
- If the +/-105v (and the 13,5v) is very low although the switches Q18 and Q19 is
switching, you probably have short on the outputs. Please disconnect all outside
circuitry (by removing all amplifier fuses) to see if it starts up. When the outside short
has been found, continue repair there.
- The PowerGood signal controls the power state on the input boards, and the power
state on the entire device. So start by checking these. They should be above 2v to
signal good. If they are below, they signal fail.
- If the resistors R62 and R78 in the auxiliary supply have opened, the entire primary
will end up in an “in-between” state instead of switching between on and off. If the
auxiliary supply is not switching, check these before going into deeper fault localizing.
SP20F Schematics
AICO4b – Circuit description
Power supplies and power up/down.
Stand-by supply
The power supply in the unit has a standby supply which is always on when the mains cord is
plugged in. Once this converter has enough supply to generate good output power it will
generate a “PowerGood_Aux”, which will go high. Before this it can only be powered
through NomadLink.
[NLIPs] When a Voltage is present on NomadLink it will go through D407 and if the standby
supply is off it will go through Q410. When the standby supply is on, it’s PowerGood will,
through Q422, turn off Q410 and feed +12v from the standby supply through D408 to the
same node. The existence of Nomadlink power is sensed through R475 and R472, and when
this is high it will activate the Com-Led by pulling the ComCt high. This will turn on Q416
and turn off Q411, thus leading the current through the Nomadlink diode which is connected
between Com+ and Com-.
Q412 & Q414 forms a current limited +5v regulator. This is biased from R481. When the
voltage over R482 exceeds 0,6v the regulator will lower its output voltage until the current
remains constant. This +5vP supplies everything that needs to be on in standby, most
important the controller U407. [UPcB] The controller uses a lower voltage to operate, and this
is made through Q409 that will make the voltage be 3,0 – 3,6 V. [LVPsB1] In standby all
other voltages is turned off by Q401 and Q408.
Start-up
There are 3 different ways to turn on this amplifier; by NomadLink command, by GPI (only
when Nomadlink is disabled by dip switch) or on the front switches. The Controller will scan
the front switches for On/Off & Remote. Manual – on or off will directly generate and
internal request to turn on (or off) the PSU. When in Remote the same request will come from
either Nomadlink or GPI (depending on the switches). This internal request will be generated
to the PSU When “PowerGood_Aux” is high. This means that if the standby supply is not on,
then the controller will not start the amp.
When the standby supply is on and a Power On is requested the Controller will pull PwrOnCt
high and the power supply should start shortly after. When the supply has reached sufficient
output voltage it will release the PwrGood105V.
Local supplies
When PwrGood105V is high, the controller will wait about 0,6s before doing anything, and if
all is ok, it will then go over into operate-mode.
[LVPsB1] When PwrGood105V goes high, Q406 & Q402 will turn on and turn on Q408 and
Q401. U403 will regulate the voltage between -18 - +18 to be 35,5v – 35,9v (if they are not,
adjust VR401 until they are). Since this voltage from the supply is floating, U401 sets its
reference to ground to be exactly at 50% of this voltage. U401 will push and pull Q405 &
Q403 until AG is equal to the voltage division R408 and R410. This makes the +/- 18v.
U406 is a +5v regulator which will generate a local +5v (this is not the same as +5vP standby
voltage!).
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