Bold machines made with fu-29
Fu-29 is a double-beamed four-power electronic tube with a high resistance and a limit of 750 v, as well as a large screen extreme power consumption and screen extreme current, good linearity, low saturation and pressure reduction and high cross-guide。
The main difficulty in producing fu-29 is the high working voltage and the production of more specific output transformers. Of course, 600 vs are nothing for amateurs who have already done so boldly, such as 211, 845 and 805, but it is a challenge for inexperienced primary fever friends. The output transformer, which resisted 13. 75 k, could hardly be found on the market. The solution is to find a businessman who can provide tailor-made services, and to detoxify himself, but the problem of insulation deserves attention because of its high working voltage. The output transformer parameters of this machine. High-quality output transformers are the basic guarantee for the success of electronic tube power amplifiers。
This is a fairly “classical” form of circuit, which in its entirety highlights the characteristics of balance. The transformer b1 enters and reverses, with a sharp end to 6j4p for voltage amplification in the pentaple tube, power enhancement in the launch tube fu-29 and output resistance in transformer b2。
In all forms of reverses, transformers have excellent rectangular properties and simple circuits, with small waveforms and good symmetry. The early years of the electrode amplifiers, which are now constrained by such factors as frequency, sound, price, etc., are rarely applied in reverse form, but remain one of our preferred forms of circuits. In fact, in the audio range, the design of an ideal bandwidth transformer is completely unproblematic, and the different input transformers have different voice manifestations due to different design, materials, manufacturing processes, which precisely provides a method for proofing the sound. We use a pair of second-hand shredders of input transformers, with a resistance ratio of 1:1+1, which, of course, can be bypassed by a capable reader。
The 6j4p is a sharp cut-off tube that is commonly magnified by medium-frequency voltage and is rarely used in the audio field, but is quite well used here because of its high cross-guide and large screens, which are affordable and one of our favorite electronic tubes, the parameters of which are shown in table 2. R1 and r2 are 6j4p grids of extreme resistance and load resistance for input transformers, and decide to input resistance sizes. R3 and r4 are 6j4p cathode electrical resistance, which provides negative bias to the fence by using the pressure of the cathode currents on r3 and r4 and which also function as negative current feedback at this level because the cathodes are not connected. The curtain fence was obtained through the r9 pressure reduction c5 retreat. In order to obtain a larger screen, the curtain fence can be higher. Due to the strong negative current feedback at this level and the low resistance of the screens to r7 and r8, although the magnification of the quintoons is large, the in-house gain is not too high, at about 38db. For power tubes such as fu-29, the required boosting voltage is low, so the gain at this level is not only sufficient, but also substantial。
C1-c2 is a coupling of electro-voltage and power-magnification stages, which have a significant effect on the sound, and which, if possible, should use as much of the oil-impregnated oil as possible from home and abroad. Since fu-29 is a high-frequency power tube, special attention is paid to its stability in the audio band, where r16, r17 and r19 and r20 are installed on the screen. Negative pressure was added to the fu-29 fences through w1, r12 and r13, ensuring that fu-29 was at the normal work point. R10, r11 are two negative feedback resistances, which together with r3 and r4 form the loop negative feedback, which can stabilize circuits and reduce distortions. C3 and c4 act in high pressure isolation here to avoid the effect of very high screen pressure on the voltage magnification level work point。
6p1, r21, c8 and two ion-pressure tubes wf2p form a simple series of steady-pressure circuits for use by the fu-29 fence. In general, the five-power piping and beam-fired tubes perform well under the working conditions of a stable curtain fence, and their sound performance is smoothing out due to the distance between the curtain voltage and the screen working voltage of the fu-29, which generally uses a smooth-pressure pattern of the curtain and, more often, a high-power crystal smoother. Maybe that's why fu-29's "coward stone" is famous. We use here a steady voltage circuit consisting of an ion-pressure tube and an electronic tube to put pressure on the curtain fence, so we want to add a rhyme to this. While maintaining the control and speed sense of fu-29, increase the thickness and density of the medium frequency for the purpose of timidity, audibleness and abrasiveness. This is an amplification-level voltage magnification factor of about 60 times the equivalent of 35. 5 db. The total gain of the two tiers was approximately 73. 5 db, plus negative feedback from the ring, which resulted in 47. 5 db and a total negative feedback of 26 db. This translates the transformer gain to 6 db, two-stage magnification plus negative feedback totalling 47. 5 db, and the output transformer also has 32. 5 db gain, with an actual unit gain of 21 db。
The power component of the screen is also shown in the figure, where the very 600v high voltage is obtained directly from the 220v exchange market through the d1 and d2 double voltage and filtering of c12, c13 and c14, c15 and c16. Of these, the 300v voltage power scale magnification level and the fu-29 fence obtained after half-wave filtration of d2 and c13 were extremely useful. R22, r23 is a power-release barrier that provides an energy release route to filtering caps, after which both will release the remaining electrical energy from the caps, otherwise the caps will have a high voltage after the electrode cooling has ceased and will remain in place for a long time, to the detriment of safety and the life of the tubes。
This method of power supply saves a high-pressure high-power transformer, which not only reduces costs, but also receives very low internal resistance. There is no doubt that the power source energy without transformer resistance is abundant and reacts more quickly. High voltage is very small in static and large dynamics, and this is the best performance of the medium- and low-frequency segment of the machine. But without the power transformer isolation, safety becomes a problem, and a transistor-enable amplifier is inconceivable. The input of transformer b1 and output transformer b2 here completes the isolation, leaving the case unconnected with market power. It is worth noting that the site of the shell and the internal circuit are separate and cannot be linked together. Since b1 and b2 are here to complete both transmission and isolation, the quality of these transformers cannot be taken lightly。
There has been very little use of this method of electricity supply, mainly for safety reasons, but as long as there are two transformers before and after, the effect of isolation is exactly the same as that of a power transformer, which has been used for years and is very safe. The machine did not go that far on the wire, or set up an ordinary power transformer, b3。
A separate power transformer, b3, was provided by 6. 3 v for 3 sets of lights and 36 v for 1 set of fences. As the required power is small, a 60w small power transformer is sufficient. The 100-bit device w3, attached to the 6j4p light at voltage magnification level, has the effect of minimizing communication interference with the light. One end of the fuse for fu-29 is sufficient, and 12. 6 v can also be used for changing the slot light for fu-29. However, attention is drawn to the fact that the 6p1-connected wiring group is not available. Here, the 6p1 cathode level has reached 220v, and if the light is on the ground, the voltage between the cathode and the light is well above the 100v limit of 6p1 and can only be suspended. The exchange of 36v through the silicon bridge, c9, r21, and c10 filters, with a steady pressure of d3 in the steady pipe, was adjusted by w2 to provide fixed negative pressure to the fu-29 fence。
Fu-29 has a high tolerance of up to 150 vs, and in order to increase efficiency and output power, it is necessary to make the electronic tube work high-screened, low-screened. Here the screen pressure of fu-29 is ua = 600v, the maximum screen stream iamax = 60ma. From the ua-ia curve of fu-29 (figure 2), the pressure down between the ug=0v, ia=160ma at screen and cathode is about 40v, so the output power of the machine can be calculated at p=(600-40) x 0. 16/2=44. 8(w)
The actual output power of 40 w, which is calculated to be 90% of the efficiency of the output transformer, is already in the gold section for the electrode power amplifier, and the actual drive is not less than 100 w's transistor amplifier。
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