Keywords: 6p16, electronic pipe power discharge circuit
Video pipe 6p15 was a TV special tube in the 1970s, making video voltage amplifies. Later, the integrated circuit TV has spread, 6p15 tube has also exited the TV field, and the audio enthusiasts have less. The author believes that the tube TV at that time is high-tech, imagination, 6p15 (or 6p12, 6p13) of this type of pipe production process and quality, no general power tube, it is very close to EL84, 6P14 pipes very close And the same five poles. The author decided to make a push-pull power amplifier with a 6P15 cellular, which should be able to achieve better results. The production steps are as follows:
First, design according to the basic electrical performance parameters of the pipe
Since the anode voltage of 6P15 is 300V to 330V, the current is 30mA, the transconductance 14.7mA / V, the output power is 6P14, and the EL84 is close. If the tube is used to make a single-end, the output power is small, it is difficult to promote the speakers above two-degree, obviously not too suitable. Thus, the author is designed by a super linear push circuit, and 14W output power can be obtained, pushing the two-point speaker or 90 dB three-point speakers, can satisfy the living room or bedroom listening in 15 square meters. The author uses a concise three magnification, see Figure 1. The first stage voltage is enlarged with direct coupling, and the wider channel frequency is obtained, and the second stage is inverted.
The author also passes some technical measures, allowing 6P14, EL84, and 6P15 universal interchangements, future maintenance and indiscons are not restricted by tube.
Second, the device selection
Voltage amplification and inverted phase selection of ordinary 6N1, 6N3, 6N4 series double triodes (6N1 used by the author]. The 1/2 of the 6n1 double triode is large, and the other 1/2 drove-level screen is inverted. Push the end power tube 6p15. The resistance can be used as shown (not indicated by 1 / 2W), the coupling capacitance C1, C2 is selected from the oil immersion type of 0.2uF / 400V, or a metallized paper can be used. Power supply decoupling capacitor with oil immersed capacitance or metallized paper content, which is beneficial to the sound.
Third, push-pull pipe gate pressure
The gate negative pressure generally has two ways, and the species is the self-birld gate bias, and the second is a fixed gate bias. Each of these two ways has a thousand autumn, and the self-bias is hardly adjusted. Does not add the winding of the transformer, and the gate negative regulation of the power supply, but the trouble is transferred to the next step, making the selection or pairing difficulty. The differential gate bias is required to require the transformer to more than a set of 70V-100V windings, as a gate negative pressure adjustment power supply, supply the bias voltage of the tube. At the same screen pressure, the self-bias is equal to the screen pressure gain voltage, and the fixed bias is a bit like the positive and negative power supply of the OCL circuit, that is, the screen pressure gauge negative pressure. Obviously, the fixed bias can increase the supply voltage and increase the output power. When the tube is taken, it is not necessary to adjust the balance of the two tubes easily. In particular, the amplifier is not very powerful. To increase the output power, it is more reasonable to use a fixed gate negative pressure and the reason for the author.
Fourth, power supply requirements and processing
The power supply seems simple. In fact, it is not a simple link, which will directly affect the performance of the whole machine. The author determines the current of the secondary side high voltage winding in accordance with the total and 120mA of the screen current of 4 6p15 tubes.
Small and requires greater than 15% to meet the requirements of this circuit.
Filament power processing. In order to eliminate the acoustic sound, the intermediate tap of 6P15 filament power supply is grounded, and the power supply of 6N1 is not directly grounded. It uses the elevation potential method, and the method is to connect two resistance through high voltage power supply and ground wire (R17: 3D0KΩ, R18) = 68kΩ), perform a voltage dividing to obtain a voltage of about 70V, and then the communication sound can be eliminated at one end F1 of the 6N1 filament. It is also easy to ignore the wire power line of the AC power supply to generate magnetic field radiation and generate communication. In this regard, any wire with power supply must be built, the direction of the winner should be opposite to the transformer winding direction, which is an indispensable step of reducing communication.
V. Power transformers and output transformers
The power transformer power is 120W. Output transformer core cut
The area is 22mm × 40mm, the primary use φ0.14mm enameled wire by 900 + 900 + 900 + 900, the secondary φ0.83mm enameled wire around 120 (4Ω), 160 (8Ω), silicon steel sheet cross-inserted, no air gap .
Six, complete machine debugging
Before the power is not energized, the correctness of each solder joint should be checked, and there is a short circuit of the connection line. If there is no tube, it will not be inserted, and the power is measured to measure the screen pressure, filament voltage, and gate of each pin. Pressure, etc., then adjust 4 (W1, 妣, W3, W3, W4] potentiometer of the gate negative pressure to the intermediate position, then disconnect the power switch plug, output the eight speakers to avoid empty load Bad output transformer. Equipped measuring the voltage of each operating point, after basically normal, then adjust W1, W2, so that the resistance R14 and R15 are 0.25V, current 25mA, right channel adjustment W3 and W4, check every 15 minutes Second, adjust it once, I would like to listen to "Gong Wang Yue" "" Gong Wang Yue "after half an hour later, the sound is soft and sweet, and every note is very clear, very beautiful. Author: Wang Dingyong
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