Wiring diagram in the amplifier romantic at 101. Complete alteration of the amplifier Radio engineering U101. Checking the health of the output transistors
Amplifier radio u 101 - so I decided to try to write an article about reworking the amplifier. Well, I'll probably start with its history, namely why I decided to completely redo it. Firstly, everything is old and does not correspond to the present. And secondly, he worked very hard, before he got into my hands, and accordingly broke down more than once.
6 times they repaired the final stage, repaired the tone block 2 times, with the input selector there was something incomprehensible, and besides, they burned the indicator once, connecting it incorrectly, but they put another one from another amplifier, but I also managed to burn it when myself was picking his mustache. In general, to say there, they passed on to me this VCL. I decided to end these glitches by redoing it completely.
Before the rework, it looked like this:
End amplifier
I wanted to insert something more interesting there, not some 7294 there, but something more serious. Googling for a week, I found what I needed.
The parameters are:
- THD: ~ 0.005% (measured) sim'd: 0.002%
- Power into 8ohm: 60 watts
- Power into 4ohm: 100 watts
- Gain: 32dB (~ 1: 40) full output at 0.7v input (0.5v rms)
- Feedback: 57dB
- Phase margin:\u003e 90 °
- Supply voltage: +/- 36v
- Biasing: 55ma, 12.1mv across a single 0.22 ohm
- Frequency response: 3.2hz to 145khz (-1db) using 4.7uf input cap
Phaseshift at 10khz:<3°
Isn't the beautiful characteristics true? Without hesitation, I collected 1 channel, and there I finished 2. The sound quality is remarkable!
A huge disadvantage is that there was no printed circuit board in lay format for it, and I don't know how to use it in other programs, so I had to overlay a drawing and transfer the board to light. Now other people who want to build this amplifier can replicate it without any problem. See the application for the board.
And the main thing is that the power is about 100W for a load of 4 Ohms with a power supply of + -33V. This is what you need! Although I was going to redo it, I decided to leave the transformer the same. When straightened to a constant, there was a suitable voltage. Another plus, 2 such amplifiers can work on a native radiator from the u101, without overloading, it's checked! The heating of the radiator at full power output did not exceed 70 degrees for an hour, but I like listening to music very loudly
A small guide to assembling and configuring the power amplifier.
Vintage amplifier radio u 101 contains the following components at the cascade output: transistors output pair 2SC5200 / 2SA1943. But in the original circuit there were MJL3281A / MJL1302A, and MJE15030 / MJE15031 were replaced by 2SA1837 / 2SC4793. BC transistors are sold everywhere, there is nothing to replace them with, they are common. I replaced BD135 with BD139, it works the same. But with the MPSA18 there may be problems, if you do not find them, then you can easily replace them with the BC550, but when soldered into the board, it must be turned 180 degrees, because it has a MIRROR PORT, unlike the MPSA18.
The VR1 trimmer resistor can be a vertical type 3296 multiturn, or you can also use a regular single-turn one, I would advise taking 3296, it is easier to adjust the amplifier, when you turn on the amplifier for the first time, this resistor should have a MAXIMUM resistance.
Resistors R24 R25 0.22 Ohm 5W cement. Resistors R22 R23 1.2 Ohm 1W. Resistor R26 4.7ohm for 1-2W. Resistor R27 10 Ohm 2W, a coil of 10 turns with 0.8mm wire is wound over it. All other resistors are 0.25W.
Capacitors ... It's better not to put bullshit here. Electrolytic capacitors for power supply must be taken with a voltage margin, I have 50V when powered by + -33V.
Capacitor C3 470μF from 16V. The capacitor at the input of the C1 amplifier needs a film capacitor, from 4.7μF to 63v, you can polypropylene yellow, put it vertically, it is ideal. It is very desirable to use a film, but if you do not find it, then we turn on the opposite 2 capacitors of 10 μF per volt with 50 minuses, and solder the extreme pluses into the board, and it is advisable to add a film capacitor parallel to the prefabricated capacitor, at least 1 μF.
C15 47nF 63V film cap, in the power supply C9 C11 C16 C17 it is also desirable to put a film.
The rest of the capacitors are ceramic, preferably NPO, but if you don't find it, then you can stick in Chinese brown ones, but I would look for a better one.
Fuses from 2.5A.
In principle, that's all, you can go to collect the legendary amplifier radio u 101.
Transistors must be installed on the radiator through insulating gaskets, and under no circumstances should they be short-circuited!
A properly assembled amplifier turns on immediately and you can listen to it. The first turn-on is better done through a lamp inserted between 220v and the primary winding of the transformer, if you make a mistake somewhere, the lamp will glow, but the details will not burn out.
If you are fearless, you are confident in yourself and nothing is interfering with you, then well, good luck, turn it on without a lamp, if something is phoning, buzzing or on, turn it off immediately and look for errors. But all the same, it is better to collect without errors, to google carefully for each plug, because if you make a mistake, then a mistake can come out dearly.
Amplifier setup
Already collected? Wow! Congratulations. Now there is little to do.
It is necessary to set the quiescent current within 50-70mA. I put up 70mA.
For a successful setup, amplifier radio u 101 you need to warm it up, just turn it on and listen to music for about 30 minutes, the fact is that until we set it up, it works in mode B, so it will not heat up itself.
How's the sound? Excellent, of course. Now we need a multimeter. We set the millivolts to the measurement mode, and turn on the probes between the EMITTERS of the first and second transistors, and set the required quiescent current, slowly twisting the VR1 resistor. For 70mA it is 30.8mV (U \u003d I * R, U \u003d 70mA * (2 * 0.22 Ohm) \u003d 30.8mV).
That's all, congratulations! We do the same with the second channel.
Tone block
A slightly altered circuit:
We solder the variable resistors from the timbre block from the u101, bite off the additional leads, and solder them into the board, having previously inserted the mounting plate.
The operational amplifier here needs a "musical" one, recommended by NE5532, but you can look for analogs, for example, I used the RC4580IP, it was obtained from sound equipment.
All capacitors in the sound path are film capacitors! But in the power supply electrolytes at 470μF at 25V. Resistors in the power supply 1kOhm 0.5W. The rest of the resistors are 0.25W. Zener diodes were used by 1N4743, unfortunately there were no other less powerful ones.
It does not need configuration, it works right away.
Attention! The board has an SMD jumper, or a 0 ohm resistor on the track side. Don't forget to put it on!
The * .lay board is in the applications.
Power Supply
Here you yourself choose what you prefer. I preferred the 22000uF caps, but here it is desirable to parallelize several capacitors so that the total is about 20000uF, the total ESR of the capacitors will be less than that of the large one, therefore, it will be able to give more current at the peak. Soft start was not necessary here. I have diodes KD2997. Film capacitors 1-4.7μF at 63V.
See the appendices for the power supply board.
How to connect a transformer?
Pins 2 and 2 are connected to each other. Connect A 220 to pins 1 and 1.
Now ... Pins 7 and 7 are connected, and pins 8 and 8 will be connected to the indicator.
Protection block
Although you can leave my own, I still decided to replace it. Used ready-made from the amplifier Slap Mikruham, author Ilya S. (Nem0). Protects against overload and from a constant at the output, and from a constant from both plus and minus relative to the ground.
All resistors are 0.25W. The BD135 transistor can also be replaced with the BD139, it must be installed on a small radiator. Zener diodes for 12V and 13V, modular, obtained at 25V. Relay for 24V.
Capacitors C1 C2 C3 C4 25V. C5 for 50V.
The board is also in applications. One board already contains protection for two channels.
Indicator
Here I would have left my native indicator, but since I burned it with the wrong connection, the fact is that another indicator was put there, I did not find a circuit for it anywhere, presumably it was a radio designer.
All resistors are 0.25W. The outermost LEDs "100W" are red, the rest are green. It is set up as follows: we connect the radio equipment at 101 to the output of the amplifier and turn the trimmer, at maximum volume, to show the entire display scale, and at minimum volume, so that the "0.2W" LED winks.
We do the same with the second indicator. When you turn on the indicator for the first time, set the variable resistor to the middle position.
Mounting
Now we push everything into the case. I came up with such a fastener for the speaker terminals. So, I cut it out of PCB.
First of all, we will deal with the most important element of any system - its heart. The amplifier has, you guessed it, a power supply. We will finalize it following the advice of Nikolai Vasilyevich + add a few features of our own.
All wires are assembled inside with special ties. This is the first time I see such accuracy in Soviet technology. Although, most likely, I just did not come across such samples.
Unscrew the clamping screws
disconnect the loop powered from the preamplifier
display unit, while unfastening the tie
and terminal amplifiers, while also removing a couple of ties.
That's it, the easy path is over, now you have to pick up a soldering iron. We unsolder the power supply from the input board. Yeah kids, never solder on the couch.
By the way, I still haven't figured out where to find the equalizing amplifier for the turntable. It seems like a separate block is on the input board, but at the same time, some additional microcircuit is on the preamplifier. Okay, we'll figure it out along the way. We solder the zeros going to the output to the speakers and to the case. Soldering is hard, my 25 watt soldering iron does the trick.
Okay, of course, you can still unsolder from the transformer and the protection unit, but I'm too lazy, especially since the power supply has already received more than enough mobility for further manipulations with it. The girl moves to the table.
Well, let's start by soldering the capacitor into the network circuit to protect our baby from all sorts of unnecessary interference. This one from the old monitor is fine.
We proceed with the revision of the power supply itself. As Nikolai Vasilyevich wrote in his newer article, it is not at all necessary to transfer all power to 31 volts, it is enough to power the terminals to the maximum in order to get the maximum return, and put all other consumers on a 26-volt "diet". Among other things, this will help avoid many problems, in particular with overheating of the resistors in the display unit.
I will not breed zero as Nikolai Vasilyevich advises. Something seems to me that there will be much less tangible benefit than hemorrhoids with new wires. Moreover, the iron body should already protect against interference, if you believe what we were told in physics.
Let's start by swapping the 26 and 31 volt terminals from the transformer in order to supply more voltage to a more stabilized section. (Although, considering that 10,000 uF capacitors will be used, this benefit becomes slightly doubtful, because everything will be in chocolate anyway, but nevertheless)
We swap the wires on both 4 and 5 terminals of the transformer. Now, as it should be, more voltage flows through the wires of the larger section.
We cut out (anti) filter capacitors MBM. Never loved them.
Let's move on to replacing the main "barrels". It's a pity, but they have to be thrown away. It is unlikely that even a third of the declared capacity remained in them.
As it turned out, the process is much easier if you remove the plastic pad.
And now we gash our 10-mile-long monsters here. Jackcon, of course, is not the most expensive brand, but for our purposes - just right.
What we have in the end. The capacity has increased by 5 times, while the volume has decreased by 2. Progress, Epta!
And now - the promised trick. We solder parallel to each direction along a non-polar capacitor of the k73-17 type. Nikolai Vasilyevich does not have this, but according to many close to the topic, this increases the quality of the response at high frequencies. Yes, the power supply in the amplifier is a very important sound-shaping element! Have you thought? The world is not at all what catches the eye at first sight.
After the third turn on, it became clear that the diodes of the small rectifier were smoking. When measured, two of them were pierced. Who knows, maybe the first time something was turned on unsuccessfully, or 10 miles is too big a burden for them, but, in any case, there is no turning back. There are no diodes either, so tomorrow I'll run to the store.
But, we will not be stopped by this minor nuisance! Muahaha! We continue to test the larger rectifier.
At first the author was very surprised why the larger rectifier produces 66 volts instead of the expected 31. But then he guessed to look at the circuit and saw that it says -31 and +31, i.e. the total potential difference is 62 volts, which is the same as 66, only under load.
Well, hallelujah, brothers and sisters, the motor is almost ready to carry us into a bright future filled with divine sound. There are a couple of small but necessary details left, and we will move on to the most interesting part of our story. Amen.
At the dawn of my career as a receiver, Speedola 232 was considered the best amplifier, and Ishim was one step lower. Then came "VEF 216" - a small, wildly stylish, with a built-in power supply and excellent sound, it brightened up the gray days and sometimes the same gray weekends. Then "Wilma" appeared, a little later - columns for her. Life has become more fun: firstly, stereo, and secondly, the sound, as we say, can be "piled up", although I don't like loud music.
And suddenly, quite recently, I realized that her volume control margin was very small, so to speak, "quiet -\u003e normal -\u003e loud -\u003e I-start-to-compensate-according to Freud -\u003e no longer spinning" (2 x 4 W) ... I wanted something more powerful.
But we usually have how? We say “normal available amplifier” - we mean “Radio engineering U-101” (2 x 20 W), we say “Radio engineering U-101” - we mean “normal available amplifier”. Perhaps, the "duckling syndrome" also played an important role - I came across one such thing in the repair, what's inside, I know about.
In general, I found and bought.
Yes, the shed is still one, it takes up a lot of space on the table, mainly because of the depth.
The kit included only a DIN5 - DIN5 interconnect cable, so for the initial check, I also had to get the Wilma out. Played. Sound is normal, nothing out of the ordinary. I was even a little upset that I could not hear "airiness", "warmth" and "transparency". Still, the first class, it seems like it's time.
I will give an excursion for those who are not at all in the subject, what is under the hood of the "101st". The closest thing to us is a pre-amplifier-timbre block and a board of a vacuum-luminescent indicator. The second row is a capacitor bank (6 x 2000u, 63 V), two diode bridges (small for small household needs (+/- 31 volts) and powerful (+/- 26 volts) to power the power amplifiers) and a transformer. The third row is an input-switch board, a protection board (you can see a relay over there) and terminal amplifiers. "Electrolytes" are full, so
Only who knew that I would guess and this my favorite phrase would still come out sideways.
Well, okay, now more about blocks.
Pre-amplifier. The suspect dog nearly fell off the chair when it saw it. I read it on the Internet - it turns out that there is such a change when the first K157UD2 in the tone block is deleted. If you do not listen to the records, then it is quite possible to do without it, there will be less distortion. Looks like the previous owner decided so.
The shielded phono stage should be on the switch board directly under the colored power supply harness. The past owner decided for sure that the time of vinyl had passed (as well as the time of devices on four legs - "Radiotekhnika" turned out to be lame, without a rear right). However, one of the simplest and most effective alterations of the "101st" is just to remove the phono stage, it sometimes starts to make wild noise and even receive radio. So who knows, maybe it’s for the better - I still don’t have a “turntable” and I don’t expect it.
Slightly to the right is the protection board. "Electrolytes" were replaced with 85-degree ones. At first glance, everything is fine here. But this is only a first glance.
Wildly outraged that all the boards are made of getinax ("Vilma" is a second grader entirely on PCB).
End amplifiers, or, as they are also called, "ends". A little dusty. Also with traces of replacement of containers.
Indicator board. There are two extra resistors on the foil side - I didn't take pictures.
In general, what can you say here: life has dragged a Latvian woman. Nothing, the white horse is on its way, right now we, princess, will save you.
I was surprised how the discreteness of the volume control was made: a ratchet. Those who are accustomed to "analog" regulators can remove the spring or squeeze and fix the "dog".
Tests after replacing almost all containers showed: popping columns. And when turned on, and when turned off. And also "first class"! Strange, where is the defense looking? Although what is this? It's nothing! Then something interesting began.
I turned on the amplifier and listened for ten minutes. Suddenly, 50 Hz appears in the right channel, louder and louder, they do not react to sound reduction. The indicator is dancing with the right channel, the amplitude of the waves is increasing. By ear, this is perceived as an idling motorcycle. I turn it off, scratch my turnips, go to regulate the quiescent currents of the “ends”.
I set it to 45 mA. In the left channel, don't understand what happened at all, the 200 mA multimeter was off scale.
I turn it on again. It works for about ten minutes, the right one starts to growl again. I pull off the input plug from the right "tip" - the hum and "motorcycle" go to the left. I pull the entrance from the left - almost immediately the indicator goes off scale, so much so that the S-30 shines overload (although I saw these LEDs in action). The multimeter shows that a "constant" is growing at the output (up to 13 volts), then the relyushka clicks like a bad one. I began to understand.
Well, the coolest alteration in this "Radiotekhnika" - attention! - the output wires of both ULFs are soldered to the output wires of the protection board. IN detour protection, Karl! The relyushka can click as much as you like, but if a "constant" comes, then it, without thinking twice, will go directly to the acoustics. Unsurprisingly, the overload indicators were on. After the status quo was restored, the protection began to correctly handle the "motorcycle", that is, not to let it in to the speakers when the indicators were already dancing almost under the "ceiling". "Motorcycle" also changed - I found myself a warm, I would even say, hot garage in the left ULF, and settled there, almost immediately after turning on, starting a fifty-Hz song.
At my leisure, I decided to pick out the "tip". Here, as with periodontitis - you can pull out a sick tooth, or you can treat it. Our dentist friend says that whenever possible, it is better to treat. Something familiar is closer to the body.
Time to look into the ULCH-50-8 saloon was not found right away, but as soon as he came, he broke chairs and tables for them, broke the dishes, challenged all three-legged cowboys in turn to a duel with a transistor tester. I didn’t like KT837N with h21 more than three hundred (50-150 according to the reference book and 60 for another one). I replaced it with KT818G, but it burned out from the power supply, even a fragment of some track was annihilated.
Yes, this "Radiotekhnika" is bored! Such a difficult thing breaks!
And just then a friend Andrey, a big troublemaker in the field of electronics, comes to look at all this (and the sluggish repair has been sluggish for a couple of weeks) and says that he would buy ready-made motherboards based on TDA2030A and install these problematic "ends" instead. What's the difference - 20 watts or 18, and the hassle is much less.
And I realized that he was right. All the same, the authenticity of Radiotekhnika is already under a big question, there is nothing to lose. Of course, this is a risky step. Fans of "honest Soviet transistors" will sniff at me for replacing "cool Holton" with "soulless microcircuits." Fans of microcircuits - for not TDA2050 or TDA7294. Tube sound fans will sniff anyway.
Well, what am I? I'm not rebuilding the amplifier anymore, I'm building the Chevy.
Ready-made scarves were found on the Internet, the question arose with food. TDA2030A can operate at voltages up to +/- 22 volts, and the native Chevy amplifiers consumed +/- 26 volts. Normal peoplewould probably rewind the transformer or find another. But it is long and expensive, it is not worth the candle, especially since I quarreled with this sheepskin specifically for its boorish behavior. But what if we bring the U-101 closer to the zero grade? Odyssey U-010, for example, has stabilizers for ULF. Only there is a mountain of transistors, and I will take the L7820 and L7920, and it will be +/- 20 volts. On the Internet, however, I did not find any mention of someone doing this, and is it legal at all, but oh well, I'll be the first, I'll figure it out myself, I'll try.
I gave the left ULF board to the stabilizers and shifted it to the place of the right channel, and fixed the TDA-shki where the left one was.
LEDs indicate power supply. I try to always make an indication of turning on - I have come across more than once when another homemade product does not work, even though you crack, and the problem is not in the transistors and not even in the reel, but in the unconnected plus.
And so, I am bringing in those seven and a half liters of electrolyte ... The defense thinks for a couple of seconds, click! .. Oh, "motorcycle", hello. So you, dog, it turns out, not only live in the ULF. It is necessary to pick the timbre block.
First of all, I replaced the wires from it to the TDA-shkam with shielded ones (the screen is hung on the "ground" only from the side of the tone block). Not that. I replaced the two remaining non-polar capacitors (if there are no non-polar ones, then you can connect two pieces with a "plus" to a "plus" of twice the capacity), one was nothing, one was dry. Not that either. I saw what was so special living in the preliminary. Two K157UD2, normal, problem-free microcircuits, how much rubbish has already been collected on them. Are they really problem-free? There is no one else to blame. I uprooted one of the left channel (1983, brown case) and replaced it with a fresher one (for this I had to remove the aluminum muzzle and the entire timbre block). I turn it on - and not hum! But it's too early to rejoice: the sound is disgusting, "sand" appears at high volume. I spit on integrated technologies, idolize Vilma's multi-transistor circuitry, and finally, I look at the piece of paper that came with the TDA-shkam. " If self-excitation of the amplifier is noticed, solder the 2k and 82p circuit between legs 2 and 4"(The datasheet also contains this). Well, I finished ...
*** Digression ***
A hare walks through the forest, sees: the fox is stuck between the trees. He went, did all sorts of bad things and moved on. Meet the wolf:
- Hare, are you so happy?
- So there the fox got stuck, well, I ... I threw a couple of sticks!
The wolf ran there and did the same. Satisfied returns, and a bear meets him:
- Wolf, why is your face already shining?
- Yes, the fox got stuck there, so I threw a couple of sticks ...
The bear thinks “Come on, and I'll go. I went, returns to the wolf, all already glows with happiness. Wolf:
- Well, did you throw a couple of sticks?
- Not at all! There were no sticks ... So I showered her with cones!
So I still showered "Radiotekhnika" with cones: not a grain of sand remained. She plays loudly, notably, the LEDs in acoustics can even blink - “Vilma” is only chucking its teeth with envy. But she also found a job - it serves as a preamplifier, because the only 3.5-mm cable - DIN5, is not wired correctly, "101st". Alone she plays quietly from this cord, but cleaner - "Wilma" brings its second-class noise.
An important point: radiator temperature... The stabilizers are cold even under a good load, the TDAs get hot, but you can quite hold your hand on them. The hottest corner of the heatsink is the one closest to the input board. But even there, the temperature is very, very far from any exciting.
And now, it seems, everything is fine, you can sit, listen to music, watch movies ... Stop, b-p-ponsky tape recorder! I worked for an hour and a half or two, and suddenly a pink noise appears in the right channel. Well, to hell, it would seem, with him, so he is growing! Then in character it becomes like a tide at sea. Then some wild modulation starts.
She's a crazy fool. If you let it cool down for ten minutes, the noise goes away, but then it comes back again. Soldered some little things, straightened the wires (it turned out that the input of the right ULF went exactly above its output, and this is a prerequisite for creating a positive feedback and turning the amplifier into a generator), even replaced the TDA-shka (suddenly a defective one). Sat down to test.
It looks nice and convincing (at night the indicator even dazzles), but again an hour and a half or two passes, and the "sea" begins. Shorted the output of the right channel from the preliminary to the ground - the noise disappeared. And then I wondered for the second time - what's wrong with the timbre block? Another K157UD2, - whispered amateur radio luck, it is not known where it was staggering before.
"Chevy" cooled down a little, when you turn on the noise was gone. He began to drive a screwdriver over the microcircuit ... Gotcha, animal: here you have noise, hum, and 50 Hz for tea. Change immediately! Oh, are they over, or what? Exactly. I had to disassemble homemade dial gaugesbut it was worth it. An hour, two, three, six - and not making noise! At last!
So believe these "udks".
The limp problem was solved surprisingly simply: in the local radio store, suitable legs were found (foreground).
They are called “legs for quick installation”. Indeed, it takes longer to poke a hole in the bottom than to fix a leg.
The preamplifier annoys me the most. Either I do not understand anything in circuitry, or something else, but included in the tone block +/- 31 volts after the resistors R47 and R48 (1.5 kΩ) turns into +/- 15 volts (blue dots). Where from, Karl? In my Chevy from the factory, 1.2 kOhm was soldered, and after that came +/- 22 volts. I replaced them with 1.5 kOhm, and even one-watt ones. It became +/- 19 volts. Still far from the scheme.
Therefore, another solution spied on by Odyssey is 15-volt zener diodes (1N4744A) for power supply. Was it really so difficult to do it back at the plant, at the design stage?
The input selector, which is so fond of finding fault on the forums, turned out to be a very useful thing. It is already difficult to imagine the situation when more than one input cable is connected to the U-101 (unless the lucky one has a complete set of Radiotekhnika 101 Stereo: tape recorder, tuner, turntable), so you can use it differently, as a function mute(temporarily mute the sound). By switching to another input, you can attenuate the incoming signal to a barely audible rustle, without even touching the volume control (the switch uses K190KT2P, field-effect transistor chips, which, no matter how close, but just pass the signal a little - this is not a relay).
But they can play such songs with "Vilma". And so the hand reaches out to turn up the volume.
Maybe a little later I will replace the TDA2030A with the TDA2050. It is impossible to go "fast enough".
P. S. Listened to "Chevy" for a day and a half, then made minor repairs to "Wilma" and put it on the electric run. And the sound, but the sound! The 157s hiss (in the ULF there are four of them per channel plus one in the recording-playback amplifier), there is no volume level "yes-I-have-serious-problems-in-Freud", the bass is too hammering, then they are sharply lacking ... It turns out that you get used to good things very quickly.
P. P. S. I smiled for a very long time when I saw this correlation on the ad site:
Modification of the amplifier "Radio Engineering U-101"
So, let's begin!
1.
Source of power.
Power supply diagrams may vary slightly!
To get decent power output you need to have a decent power supply. We will use a gift from the transformer manufacturers: the entire secondary winding is made with one thick wire (0.8mm in my opinion). Therefore, it is quite possible to switch the power supply of a powerful rectifierVD 5 ... VD 8 from contacts 4 - 4 * to 3 - 3 *, which will increase the voltage from +/- 26V to +/- 31V. In this case, the low-current rectifierVD 1 ... VD 4 becomes unnecessary and is removed along with the wires, and its storage capacitors C2 and C7 are connected in parallel with the corresponding capacitors of the powerful rectifier. But all connections with pins 5,6 and 9,10 should be preserved.
Then witchcraft begins.
1. Determine the geometric mean between the ground terminals of the capacitors C2, C3, C4 and C7, C8, C9 on the filter capacitor board, clean and tin it. We assign this point to the main common point of the entire amplifier.
2. From it we start up 2 thick wires on the minuses of the output connectors.
3. From it we start up common wires to the UM and UP.
4. From it we start up 2 wires to contacts 6 and 6 * of the transformer, removing the jumper between them. At the same time, we remove the connection between the rectifier board and the case.
5. We organize the connection of the common wire with the case at the input connectors of the amplifier.
6. And check - that there are no other contacts of the common wire with the body anywhere else.
And finally, we connect a 0.047x630V capacitor in parallel with the primary winding of the transformer to suppress impulse noise from the mains. 
After removing VT 6 and VT 7, installing a jumper, replacing R 10 with a diode D 7 and short-circuiting R 15, the D 7-VT 5-R 11 circuit turns into a diode stabilizer for a current source on VT 8, already on which the swinging transistor VT 10 works To reduce nonlinear distortion, the swinging transistor VT 10 must be high-voltage, powerful and with a high gain. just meets these requirements, so we replace the original transistor with a more suitable one. The classical scheme. The idyll is broken only by the resistor R 42. It is soldered from the print side into the notch of the printed conductor near the collector VT 2. The introduction of this resistor increases the stability of the entire PA and allows you to get rid of compensating capacitors C4, C5, C9, C10, as well as resistors R 20 , R 21. Side effects R 42 introductions will appear when listening.
For normal work electrolytic capacitor it needs a charging potential of 0.6V, but it is not on the C3 plate. Therefore, there must be a non-polar capacitor, limiting the bandwidth around 5 Hz. Hence, the nominal value is 22mk NP.
The setting is normal: connect an ammeter to the power supply gap and set the no-load current to about 40 mA. Then reestablish contact and launch.
colorthe removed components are highlighted.The numbering corresponds to the standard schemese.
3. Preamplifier .Djvu 60 kb
Chip The DA 1 is inserted into the preamplifier solely for matching with the piezoceramic pickup. I think that now this is no longer relevant, but it adds noise, and therefore we boldly discard the DA 1 microcircuit along with all the strapping and throw a jumper using the vacated holes on the printed circuit board.
Newly introduced or changed components and jumpers are highlighted in red, and colorthe removed components are highlighted. The numbering corresponds to the standard scheme.
This figure shows the DA1 chip and the components that should be removed along with it on the U5 ULF-P board.
Next, we more accurately adjust the loudness circuits to the volume control. Then we expand the bandwidth of the DA 2.1 and DA 3.1 amplifiers in both HF and LF and adjust the timbre block parameters. To return the supply voltage of the DA 2 and DA 3 microcircuits to the permissible channel, it is necessary to correct R 47 and R 48.
The preamplifier contains trimming resistors R 24 and R 26 to adjust the gain of the entire amplifier. Setting conditions: at the input - 0.5V 1kHz; volume control - to the maximum; at the output - 14V without load, set with resistors R 24 and R 26.
Rednew or changed components and jumpers are highlighted in color, and blue colorthe removed components are highlighted. The numbering corresponds to the standard scheme.
This diagram shows a diagram of the refinement of the ULF-P, the DA1 microcircuit is not shown.
5. Corrector UPZ-15.
Today, all known moving magnet pickups operate with a correction capacitance of 470pF. Accordingly, the capacity of capacitors C1 and C2 is changed to 470pF. 6. Entrance fee.
To expand the bandwidth down from 20 to 7 Hz, you can increase the capacity of the capacitors C4, C5, C14, C15 to 0.33μm. This is at the end of the work as the cheeks are inflated.
This treatise was drawn up on 03.06.09..
/ nivaga /
or by mail, address is attached.
The amplifier "Radio Engineering U-101-stereo" is designed for high-quality amplification of audio frequency signals both from the devices included in the complex and from external sources of sound programs. The amplifier has an electronic switch of inputs, electronic indicators of the output power level separated by channels, a protection device for output stages in case of a short circuit in the load; the loudspeakers are also protected from possible contact with a constant voltage component in the event of amplifier malfunctions, as well as protection of the output stage transistors from overheating.
Main technical characteristics of the amplifier Radio engineering U-101-stereo
- Rated output power, W: 2x20
- Nominal frequency range, Hz: 20...20 000
- Rated input voltage, mV, input:
pickup: 2
others: 200 - Harmonic coefficient in the nominal frequency range,%, no more: 0.3
- Signal to background ratio, dB: 60
- Signal-to-noise ratio (weighted), dB, at an output power of 50 mW: 83
- Output voltage for connecting headphones (R H \u003d 16 Ohm), V: 0,9
- Power consumption, W: 80
- Dimensions, mm: 430X330X80
- Weight, kg: 10
Diagram of electronic switches for the inputs of the amplifier Radio Engineering U-101
Fig. 2.
The electronic switches of the amplifier inputs are made on microcircuits DA1-DA3 (Fig. 2), controlled by constant voltage coming from the input selector - the switch SA1. Such a circuit solution simplified installation, eliminated cod when switching inputs, and reduced pickups on input circuits. The microcircuits are located directly next to the input connectors, and the switch is located on the front panel of the amplifier.
The switch SA2 "Copier" is also connected to the commutation board. It is intended for operative switching of tape recorders (without additional manipulations with connecting cables) when re-recording phonograms. The switching is purely mechanical, which allows, in the absence of the need for monitoring listening, to carry out these works without connecting the amplifier to the network.
Diagram of the terminal amplifiers "Radio Engineering U-101-stereo"
Fig. 3.
The unified ULCh-50-8 modules are used as the terminal amplifiers of the Radio Engineering U-101-stereo. The input stage of the module (Fig. 3) is a differential on transistors VT2, VT4 with a current source (VT1, VT3) in the emitter circuit. The next stage on transistors VT5-VT10 is also differential, with a dynamic load in the form of a current mirror (VT5, VT8), which provides a symmetrical swing of the output stage. High linearity of amplification of large signals by this part of the module is provided by the increased (compared to the output stage) supply voltage.
The output stage (VT13-VT20) is symmetrical, on composite emitter followers with parallel connection transistors in the last stage. Temperature stabilization of the cascade operating mode is provided by a device based on a VT9 transistor.
Amplifier protection scheme Radio Engineering U-101
Fig. 4.
The amplifier overload protection device is assembled on transistors VT11, VT12 and diodes VD3-VD6. In the event of a short circuit of the load, it limits the output current to 2 A. As already mentioned, the "Radio Engineering U 101 stereo" also provides for protection of the loudspeakers against direct voltage in the event of an amplifier failure and protection of the output stage transistors from overheating. The AF voltage is supplied to the loudspeakers through the contacts of the relay K1 (Fig. 4). If the amplifier is in good working order, it works in 3 ... 5 s after turning on the power, which eliminates clicks caused by transients in the amplifier. The loudspeaker connection delay time is determined by the parameters of the R10C3 circuit. With the appearance of a constant component (more than 2 V of any polarity), transistors VT1, VT2 form a voltage that goes to the base of the transistor VT3 and closes it. As a result, the coil of relay K1 is de-energized, and its contacts disconnect the speakers from the amplifier.
The same device is used to automatically turn off the loudspeakers when the headphone plug is inserted into the XS17 connector equipped with the SA3 switch, and the power transistors overheat.
The thermal relay is assembled on a DA1 microcircuit. The functions of the thermistor are performed by the VT transistor connected to one of the arms of the R12R13R16R17 bridge. The bridge is powered by a stabilized voltage through resistors R14, R15.In the initial state, the bridge is unbalanced by the appropriate choice of high-precision resistors in such a way that the voltage at pin 5 (relative to pin 4) of the DA1 microcircuit is 50 ± 5 mV, and at its pin 10 there is no. When the transistor VT (it is located on the heat sink of the output stage transistors) heats up to 86 ... 90 °, the bridge is balanced, and the voltage at the output of the microcircuit rises abruptly to the supply voltage (+ 26V). As a result, the VT4 transistor switch opens, and the protection system disconnects the loudspeakers from the terminal amplifiers.
Scheme of an electronic indicator of the output power level of the amplifier Radio Engineering U-101
Fig. 5.
A schematic diagram of an electronic indicator of the output power level with information output to a vacuum cathodoluminescent two-color display is shown in Fig. 5. When the output power is less than the nominal (-20 ... 0 dB), the green ruler glows, and when overloaded (0 ... + 5) dB - red. The operation of the HL1 display is controlled by the DDK chip, which provides analog-positional conversion of the output signal of each amplifier channel into the corresponding code. The threshold voltages of the switching elements of the microcircuit are stabilized by the current generator on the VT2 transistor. The inverter on the transistor VT1 together with the elements of the DDI microcircuit forms a generator of paraphase impulses that are fed to the display grids in time with the connection of the inputs of this microcircuit to the outputs of the DA1.1, DA1.2 op-amp. The pulse frequency is chosen equal to 150 Hz, it is determined by the ratings of the elements R11, C6. The processing of information from both channels by one analog-to-position converter ensures perfect consistency of display characteristics. The DA1 microcircuit amplifies the signals coming from the rectifiers on the VD1, VD2 diodes through the integrating circuits R1C1R4, R2C2R5 (the integration time of the indicator is about 30, the reverse stroke is 500 ms). Parametric stabilizers (VD4, VD5) provide stable indicator readings with significant changes in supply voltages.
