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let's say first that i do not need to have a credit for my opinion, i am a retired sparkie and i voluteerd to fix an electronic device for a local "Youthgroup",as no diagram was present i checked the "net" and gambled on this site and paying some fee via PayPall, i was gladly surprised that the manual arrived as was stated, GOOD SHOW, and best wishes, John
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I had been looking for a Manual for my CS2150 for quite a while -- in fact I had just about given up. I saw this site and decided to download the Manual. When I Received it by Email I was really pleased with what I got, with the result that My Kenwood 'Scope is now 100% repaired and working well. As an AV Serviceman, you need a good 'scope, and thanks to this site, and the Service Manual, I have been able to repair it. The Manual was a copy of the Factory Original and the copy was very clear, especially in the area of the Circuit Schematics, where You really need to be sure of what You are looking at.
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Once again, excellent price and manual delivered in a timely manner and as advertised!
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Outstanding quality manual. This is the exact documentation I needed to service my AKAI GX-210D. This is a PERFECT COPY of the service manual for my machine. Outstanding service. Thank-you!
f1723 / FP7317 / L1702 / vf17 / FP17 8. Power Board Operation Therory
8.1 Line filter consists of C801, T801, C802, C803, C804, C837, C838. It eliminates high frequency interference to meet EMI�s requirement. 8.2 Rec & Filter Bridge diode D801 converts AC source into pulsed DC. This pulsed DC is smoothed and filtered by C805. R802 is an NTC ( negative thermal coefficient ) resistor, used to reduce inrush current to be within safe range. 8.3 Power transformer : T802 converts energy for square wave from power source C805 to secondary side to generate +12V and +22.5V. 8.4 Output : The square wave from T802 is rectified by D809, D810, then filtered by C817, C822 to generate +22.5V and +12V respectively. 8.5 Driver : Q803 drive T802 from PWM control of I801 for power converted. 8.6 FB : Negative feedback CKT consists of photo coupler I802 and adjustable regulator I803. It can maintain output voltages +22.5V and +12V at a stable level. 8.7 PWM : 8.7.1 8.7.2 Start : When power is turned on. C807 is charged a 15 volt and a starting current above 40uA to pin 7 of I801. I801 starts to oscillate and outputs a pulse train through pin 6 to drive Q803. OPP : When Q803 turns on, C805 supplies a linearly increasing triangle current through the primary inductance of T802 to the driver Q803, once the peak value of this current multiplied by R811 exceeds1 volt, pulse train will be turn off immediately to protect Q803, T802 from being burned out. 8.7.3 Regulation : If output voltage +22.5V goes up, the R terminal of I803 gets more bias, accordingly photo transistor and photo diode flows more current. The voltage of pin 2 goes up too, making the pulse width of pin 6 to become narrower. So the output voltage +22.5V will be pulled down to a stable value. 8.7.4 OVP : If +22.5V goes up too much, the induced voltage on pin 4 of T802 becomes large also. Suppose that it is over 18 volts, ZD801 conducts, pin 3 of I801 is pulled up over 1 volt. The pulse train at pin 6 goes down to zero, shutting Q803 off immediately. 8.7.5 SCP : If output terminal is short to ground, photo transistor does not conduct, hence Q806 does not conduct either. Then oscillation of I801 is stop, shutting Q803 off immediately.
HPD-K17AA Power Board Block Diagram
Line Filter
Rec. & Filter
Power Transformer
Outpur Rec. & Filter
PWM
Driver
FB
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