The structure of this circuit I believe we are no strangers, in 1994 by Mr. Nelson Pass issued. Back in 1970, Pass has published numerous articles about Mr. A class amplifier production, from the earliest A-20, A-40, to the recent post-stage single-ended MOSFET amplifier, has a unique personal style, Mr. Pass : simple circuit structure, a small number of parts, will be able to building a good amplifier. DZ's Passion A-15 to the line of course, Mr. Pass is the original design blueprint. Of course not still COPY, we still made some small changes, so the circuit looks easier to install and adjust the system, but also take into account when planning the beauty of PCB.
In the MOSFET after a single-ended Class A preamplifier, the most important part was the highest price in the two main MOSFET: IRFP140 / 9140. Only expensive, but the general electrical materials is not very easy to find the line. Furthermore, this stage is a single-ended OTL circuit architecture, the output will need to string on a large capacitor, thousands of the capacity of non-uF aluminum electrolytic capacitors can not find. So it took some effort, come on capacitor agents, imports of a number of LOW ESR electrolytic capacitors. PCB's planning, but also a lot of friends like DIY biggest problem: the complicated process of PCB washing, washing out of something is also not necessarily make their own satisfaction, and no solder mask printing protection.
After all the difficulties, we still will be quite a different type of expansion of this structure out of local planning. And collected together parts, so that we can try this yourself Taiwan Class A amplifier characteristics. Remind friends in the machine first, so that the expansion of a machine part, though small, in the time be sure to install the system step by step, every step of cool to do the work, otherwise it is very easy to burn them because of carelessness, not cheaper components.
SETP1
Part number of parts within the package a lot, when you receive the parts package, please calm slowly counted in accordance with parts list. Occur if lack of parts, please contact your service department as soon as possible and send you a replacement issues.
STEP2
Please 1/2W resistor in accordance with the label installed on the PCB, equipment, when you paste the resistance level PCB re-welding. Many types of resistance, if you do not worry, I'm scared that blurred the wrong equipment, can be installed before the first resistance test with a voltmeter, and then installed correctly. 20V resistance Bahrain loaded the ZD, the location you installed in accordance with the polarity mark, do not install the wrong way. 2K finally installed the VR.
STEP3
This step is fitted with C5, C6, and Q3. Capacitance in the assembly, when the principle is to closely aligns the PCB. MPSA92 in the welding time, not on the solder iron on too long, so as not to heat the bad crystal. Can be the middle of the pin welding, adjust the angle fixed, and then soldering the other two pins.
STEP4
Next fit the terminal: 4Pin at the AC IN terminal is the first combination of first 2Pin terminal only after put something to weld. Input and output at the terminal also be installed. Terminal to be installed, this time it installed two 0.5 ohm 2W resistors, resistor packs should not be posted when the level PCB, resistors and terminal make about the same height, so let resistance to heat, but also to prevent the resistance in case of burning, heat PCB will be burned charred. Bahrain resistance can Chock put something after.
STEP5
The remaining parts are larger capacitance. Gradually installed in accordance with height order: first load of metal blue Philips 10uF film capacitor, the output again is 2200uF/50V interconnect capacitance, and finally four 10000uF/50V the filter capacitor. Were all close to the PCB installed.
STEP6
No rectification by the bridge rectifier loaded!! Practice here in the first bridge rectifier welding wire before the wire connected to the PCB, in the packing when the bridge rectifier to chassis lock to facilitate heat dissipation. Because the bridge rectifier high temperature at work, if weld directly on the PCB, the associated parts of the surrounding area will be such a high temperature, especially in aluminum electrolytic capacitors, life is likely to reduce the many. Soldering the wires to the PCB, one by one, when, do to their brains awake, do not get wrong.
STEP7
In the PCB and heat sink combination before, several preparatory work: the first fitted with 10mm of the pillars, please note that the strength and direction of the lock, do not hard-lock the thread lock is broken. If the lock is not a good time to add a little oil slowly, please try again. Placed on the insulating film, put away the MOSFET, IRFP140 / 9140 to note the position. Screw hole is about 13mm from the edge of the one, and if installed wrong, can not be combined with the PCB. Screws are also included on the first, like, do not lock.
STEP8
MOSFET pins to bending 90 degrees upward, careful not to be too rude!! The PCB solder joints aligned MOSFET pins, one by one installed, wait a minute implementation of the welding operation. Tighten all screws first turn, the PCB and fixed with the MOSFET, MOSFET began welding the pin. Because it is double-sided through-hole design, welding techniques, if the time is not good, solder has been sliding down, careful not to solder into the solder ball short of the plot.
STEP9
After the whole class has almost completed this module. At power before then carefully check to have access to the wrong line, or install the wrong parts. If all OK, to be installed on the transformer test. The power terminal block, there are two AC IN, to use the old T270 to demonstrate, the two received a set of red AC IN, the other group received two yellow lines on the AC IN OK.
STEP10
Power before about the VR to the central location. All preparations were made to connect the transformer power, no smoke ... ... MOSFET start heating ... ... almost a success!! Recruited multimeter, cut to the DCV file, the amount of MOSFET's drain to take a very (D) and GND voltage . VR to adjust the voltage 16.5V or so, until heat, then observation and adjustment time.
This, you can make your Passion A-15 look good warm-up. Heat sink temperature is high, about 60 to 70 degrees, the heat sink does not touch too long, otherwise the hand will be burnt. Tested several prototype machines, have a continuous power more than a week, or can normal work. If you do not worry, it was suggested to install cooling fans, especially the packing, the chassis will be almost air convection conditions, plus useful thermal efficiency of the fan. On the fan noise, in fact, 24V fan can only add 12 ~ 18V power supply like (or use 220Vac fan, only with 110Vac power), reduce the fan speed, so that sufficient cooling air flow, there will not be the sound of the fan blades wind shear noise.
A class is the need to expand the production of machine a little more patience and care, in the installed process, the need to do step by step slowly, otherwise it is very easy to burn accidents, some of parts. Also to be noted that the output signal is reversed, so the speaker wire should be "+" received a Passion of the GND, "-" received a Passion of the OUT. I wish you installed successfully, I hope you are satisfied with the sound.