EPU electronics b1 01 printed circuit boards.
Preamble:
In 11th grade, I took all the discarded junk from the music school. Of the entire assortment, I was not given only one turntable, as it turned out later it was the first version of the Elektronika B1-01 turntable with a tonearm as close as possible to sme3009. Three years later, when I again returned to vinyl as a source of music, a wild anger took me that I did not take it away first of all, but left it at the end, and perhaps I would have had it for a long time.
In 2006 I bought myself a beshechka from a local huckster in a terrible state. The bottom of the shaft was loose and all the grease was leaking out, the bead was stretched, there was no anti-skating weight, the hull was falling apart.
The first thing when I brought it home, I assembled the turntable body. The bottom was made by someone new from foil PCB, but I immediately took it off and put it aside.
I don't remember where I got Pasik from, he scored on anti-skating. In general, there were a lot of all sorts of minor improvements, but globally I did not deal with the guard. The eternal problem of the behi is the crumbling body, or rather the wooden corners to which the legs are screwed. Under the weight, the hull was constantly falling through. A month ago, finally getting angry with his beshka, he disassembled the body into four planks and began to assemble it.
First of all, I ripped off the remnants of the old glue and sanded everything. After that I glued the boards together. Then I cut out a new bottom from 12mm plywood, to which I glued the body. I don't remember just what happened first, glued a sheet of plywood and cut out holes in the bottom, or vice versa, cut out the holes, and then glued the bottom. In general, in the end, the bottom turned out in the form of a cross, so that you can screw on the chassis and adjust the cups with springs.
After gluing, glued the trees in the corners. With them, the main problem was what to press. If someone repeats, I advise you to buy two clamps to press tightly.
When I finished all the sizing work, I removed the old paint along the contour of the bottom (black) with a sandpaper and at the same time aligned the new bottom and the contour of the old hull around the perimeter.
The most difficult stage was to level the sanded part with a putty. I used wood putty, leveled it with small and wide spatulas, and also a tricky device from the corner for windows. The usual corner, which is screwed onto wooden windows, cut off only one part and turned the inner fillet into a right angle. Thus, the long part led along the bottom, and the narrow part at an angle of 90 degrees leveled the putty around the perimeter of the guardhouse.
The final stage was painting with black acrylic. Before painting, try on unnecessary plywood, I had to dilute it heavily with water so that the paint lay evenly.
The result is a reinforced case, where all the weight falls not on the corners, but a new 12 mm plywood bottom. The legs were used from the sonata guard, because one of the native legs has fallen into disrepair, but I would prefer to keep the original legs.
After installing the chassis, one of the fixing screws of the transformer began to rest against the bottom, so I removed the trans and decided to make the power supply external.
Now I am reworking the electronic part of the guardhouse. As already said, the power supply is taken overboard (trans, rectifier, conduits), for the first time I will leave the stroboscope at 220V, and later I'm going to convert it to LED. At first I wanted to throw out the solenoid of the tonearm, but decided to leave it, let it be. It works only when the tonearm is raised and should not give interference. I am not going to alter the control circuit of the solenoid and the engine turn-on relay, I just want to put the power regulator of the relays from the main board on a separate board, where the power will come from the external power supply, and be routed to the rest of the turntable units, plus additionally plug in a couple of 2000 μF capacitors.
But that's enough for today. When I do the electronic part, I'll post a report. Then I will deal directly with the arm, the table and everything else.
Modernization of EPU ELECTRONICS B1-01
Over the past quarter of a century, the design of the Electronica B1-01 EPU, which was considered a high-quality signal source, has in many ways, of course, become outdated, especially in comparison with modern equipment. However, according to the author of the article, by means of some modernization of the EPU, it is possible not only to significantly expand its dynamic range, but also to increase the noise immunity of the device. This will undoubtedly improve the reproduction of the low sound levels often found in classical music recordings.
"Electronics B1-01 at one time was the" first sign "among the EPU of the highest class. Thanks to successful design solutions and reliability in operation, it still serves thousands of record lovers. The long life of this device is largely due to the presence of an excellent tonearm in it: this successful a copy of the SME 30D9 tonearm, which is still rightly considered one of the best in the world. It significantly surpasses the popular nowadays, but expensive RB 300. It should also be remembered that a low-speed engine TSK-1 was developed specially for "Electronics B1-0 G" 278 rpm (for 33.3 speed) powered by a low frequency generator. The fundamental rumble frequency was reduced to 5 Hz. However, the vibration levels generated by the drive do not meet current regulations. True, by improving the mechanical decoupling, it is not difficult to reduce it.
Structurally, the EPU consists of two main units: a panel with a disk and a tonearm and a body with a metal chassis on which the engine and all electrical components are fixed. The engine is mounted under a permalloy screen on springs, which are tightened by screws that transmit vibration to the chassis.
When reworking the engine, it is necessary to remove and drill the mounting threaded holes in the chassis to 4.5 mm. The new suspension requires three M3 bolts 18 ... 20 mm long with nuts, three steel washers with an outer diameter of 6 ... 7 mm and six washers with a diameter of 9 mm made of soft rubber or polyurethane 4 mm thick. and even better - composited from layers of rubber and felt. It is best to stick the lower damping washers to the chassis prior to assembly to facilitate installation and ensure alignment. The motor assembly must not come into contact with the chassis or screen (check with an ohmmeter), and its housing is connected to ground with a separate wire. Light oils are used to lubricate engine bearings: watch, spindle, etc.
In three investigated copies of the EPU, it turned out that the nozzle on the axis of the drive motor is made very poorly - it has noticeable beats. In addition, the rib in the middle of the nozzle does not stabilize the position of the belt. Its random displacement is limited only by a special bracket, which is accompanied by acoustic noise. To give the surface of the barrel-shaped nozzle, it is sanded with medium-grain sandpaper glued to a hard surface, with the engine running and with minimal effort.
The decoupling of the chassis from the panel is also unsatisfactory. Three plastic cups are screwed into the chassis to support the panel springs. The springs are equipped with rubber cups at both ends, however they are tightened with screws with plastic nuts. As a result, vibrations of the motor and transformer are also transmitted through the screws to the panel. The nuts must be removed and the height of the panel can be adjusted by turning the glasses. In addition, the internal volume of the springs is stuffed with scraps of foam rubber or foamed polyethylene (it is used as a packaging material), which will reduce vibrations and transmission of vibrations along the coils. Felt washers are placed under the lower rubber cups.
It is also necessary to dampen the resonant vibrations of the panel. For this, its lower surface is covered with a layer of vibration-absorbing mastic or, in extreme cases, plasticine. Similarly, the drive and main discs are damped, with the obligatory smearing of the edges (skirts) with mastic. Using a medical stethoscope, pressing it against the upper side of the panel, you are convinced of the action of the measures taken. In the "muffled" EPU, the roar of the engine is not audible at all.
To reduce the sensitivity of the EPU to acoustic feedback (AOC), the bottom of the device, made of hardboard, is removed, and "legs" of four to five layers of thick soft rubber are glued to the corners of the body. For the same purpose, it is advisable to install the EPU on a massive base with a soft suspension (the so-called sub-chassis). In the modified EPU, the author even used two such sub-chassis with dampers (in order from bottom to top): a 40 mm thick polyurethane foam sheet. marble slab 20 mm thick. a sheet of porous rubber with a thickness of 5 mm, a plate of alloy D16Tv with a thickness of 10 mm, on which the standard spring "legs" of the EPU with rubber and felt gaskets rest. To improve the vibration damping of the plate itself, the rubber pad of the disc should be turned over and a central clamp should be used, which is easy to make from a non-magnetic material.
Adjustment of the tonearm in height and azimuth is carried out by reversing the sleeve at the base of the tonearm, which is fixed with two screws. But in the case of installing a higher-height cartridge, it is more convenient to use a different method: the arm for moving the tonearm, which is located between the cartridge and its holder, can also be fixed over the holder. For this purpose, the mounting holes for the Corvette-128 head are bored with an oval file.
The wiring in the tonearm remains the same, and the wire going to the corrector needs to be replaced. Unfortunately, there is no full-fledged alternative to good, but expensive audio cables. However, in an amateur environment, you can make good home-made cables from a thin MGTF wire, preferably past the stage of natural aging (up to ten years). Conductors for each channel of the suite are paired and enclosed in fluoroplastic tubes 5 mm in diameter. Screen braids are pulled over the tubes (they are connected to a common wire only from the side of the amplifier-corrector), and then ordinary PVC tubes are put on.
The EPU body is connected to the amplifier unit with a separate wire. It is more rational to connect it through an additional screening braid, which contains both cables with screens connected on one side. To reduce the level of high-frequency interference in some cases, ferrite rings also help, through which cables are passed - they perform the function of a common mode choke. It is worth noting that few firms produce special noise-immune cables abroad.
Techniques for reducing noise in the power supply of audio sources are often underestimated. Meanwhile, it is in them that the level of interference is most critical. So. the signal level from the magnetic pick-up head is 7 ... 12 mV, however, with a full dynamic range of the record signal of more than 60 dB, counting must be carried out in microvolts and even fractions of microvolts, and for some other sources even lower. High-frequency interference, having passed the amplification path up to the UMZCH inclusive, generates wheezing or, at best, harshness and squeaky in sound. This is especially noticeable when listening to recordings of a string group. Signal sources are often to blame for the "transistor sounding phenomenon"! A sure sign of the presence of such interference in the signal is an unexpected "rise" in high frequencies caused by an increase in the level of harmonic and combination frequencies. It is characteristic that the use of tube amplifiers, less prone to signal detection, is also not able to solve the problem, since the combination frequencies arise already in the preamplifiers. Therefore, the only correct solution for suppressing RF interference is to eliminate them in the power supplies themselves, in particular, using mains filters.
Line filters are known to consist of coils (chokes) and capacitors. In addition to their direct purpose, LC filters also perform a protective function, smoothing and limiting impulse noise in the network, the amplitude of which can reach 1.5 kV. However, not all industrial filters, including foreign ones, work satisfactorily as part of audio equipment.
As practice has shown, a high quality power supply should be equipped with a multi-stage filter with a higher order slope and a low cutoff frequency.
The figure shows a diagram of a remote power supply unit EPU "Elektronika B1-01" used by the author. In addition to the mains transformer, a rectifier bridge with filters is also placed outside the device - this also helps to reduce the level of interference. In order to further reduce them in the rectifier, it is possible to use pulse rectifier diodes, shunted by small capacitors.
In the rectifier filter, all oxide capacitors are of foreign production, which have good parameter stability and a long service life.
It is advisable to select blocking capacitors in pairs or equalize their capacities by connecting additional capacitors. Capacitors C1 and C2 - any high-voltage. С5- С8 - К73-9 or similar with a capacity of 0.1 ... 0.47 μF. Common mode choke windings (in foreign literature - longitudinal transformers) L1. 12 on ring magnetic cores made of M2000NM ferrite with an outer diameter of 45 ... 50 mm and a cross section of about 1 cmg are wound with pieces of network or thick mounting wire with fiber insulation, folded together. With a length of no 1.5 m, the number of turns can be in the range of 20-40. XS1 sockets. XS2 (wall outlets) are provided for powering other audio equipment. An MTZ toggle switch is used as SA2.
Installation is carried out with a sufficiently thick (cross-section of at least 0.35 mm2) wire. Since with an increase in the area of \u200b\u200bthe circuit, the noise immunity deteriorates, in especially critical cases, for example, with a close location of powerful radio transmitters, the power wires to the EPU should be twisted, and the common wire should be made in the form of a braid. Their length should be at least 1.5 m. In order to exclude a noticeable influence of interference from the transformer on the signal circuits of the EPU. Power is supplied directly to the generator board to the capacitors C9, C10, installed in place of the former C1, C2 (numbering of elements according to the EPU schematic diagram).
The standard rectifier bridge should be removed or cut off by cutting the current-carrying paths. The common wire to the motor forms a closed loop and is therefore removed. The mains voltage to power the stroboscope is supplied through the EPU main switch and must be turned off during listening. A multi-pin computer connector with gold-plated contacts, in which 7-10 pin pairs are connected in parallel to each power wire, has proven itself very well as connector X3.
The measures taken, which were discussed, have significantly improved the old player. A very clean and accurate sound reproduction of the record has been achieved.
See other articles section.
Putting together "Electronics B1-01"(we are doing "tuning by Elenium" in parallel).
Introduction.
Well, that happened! I hold this device in my hands (in very good condition) and naturally we start with ...
complete disassembly. To be honest, all the "made in USSR" equipment was assembled without the participation of "ears and brains", for that with the full participation of "legs" and not hands.
The basic principle that I followed in the process of tuning the turntable remained unchanged: "Do not make drastic changes to the design, and nevertheless squeeze the full potential out of it."
And he is in it, believe me, very big. I will not reveal a big secret by telling you that "B1-01" is a copy (and the "younger" version, the less so) at one time the cult player thorens td125. There were three modifications of "Electronics" (its clones, and we do not consider such). The first modification was almost 100% "tracing paper" with thorens. (why almost - because the changes mainly affected only the transition to the metric system and bringing the mechanical units to the standard ones that fit into the Soviet GOST. Naturally, the engine control was "pulled" under the Soviet element base. The second - "optimized" the tonearm assembly (removed the possibility of changing distance from the center of the plate, made the sub-chassis one-piece, without a separate platform for the tonearm) and changed the electronics (element base, the introduction of hitchhiking and electronic microlift). The third is essentially a modification of the second. In it, the changes only affected the electronics (the element base and topology were changed). Here, in fact, initially I came across the third modification, along the way I got hold of the second (in a wretched state). The text will periodically overlap the revision of the "second" and "third" electronics. in the original - has lost all meaning.
And so - let's get started.
The first impression is always deceiving.
And here it was confirmed 100 percent! The worst enemy of any turntable is who? -
PHONENDOSCOPE!
We take this instrument and listen. As a result - what I heard:
1. Wherever you put it - we hear the hum of the transformer
2. Similarly and even stronger - we hear the hum of the engine
3. We also hear an eerie grinding in the center bearing
4. And we even hear the noise of the bearings in the arm shaft!
Begin.
Naturally - we disassemble everything that can be disassembled without a crowbar and a hammer. Tonearm, all mechanics. We unscrew the transformer from the chassis, etc. etc.
Center bearing.
The backlash immediately prompted me to make a new one. I decided to change the design of the assembly - the bronze bushing is one-piece, the shaft with a removable support penny (naturally hardened somewhere up to 15-20 units) is sealed. The disadvantage is the use of liquid oils ("transmission" class) and a long sediment "pancake" in the mine.
The pluses are obvious - the COMPLETE absence of beats.
Discs (small and large).
Facing in a lathe is a must. Because they are both small and large curves. We do not lose weight significantly for that we remove the vertical vibrations. What is good.
In one of the copies, an inner disc with a curved hole for the axle was caught! The axis stood as if at an angle to the vertical. Therefore, I consider turning this unit mandatory.
Tonearm.
We sort it out, clean it, grease it, collect it. If you wish, you can change the wiring - here we read the forums and study the isotherics :) I changed the standard wire to a litz wire (there is a photo of the coil in the gallery) simply because the wire was removed and the tonearm was disassembled. Yes, a couple of sushi sticks were driven into the arm :) This was done because all the pipes of the SME3009 arm that I held in my hands had wood. Therefore, without bothering too much, we take a couple of sticks (they bend very well and do not break), we process it with a knife, then we skin it and drive it along with the wire into the pipe. The native shell had to be thrown away (it turned out to be crooked or rather snub-nosed).
Engine.
In fact, it is not collapsible (assembled on rivets), if the shaft rotates freely and without extraneous sounds, then we do not touch it. The only thing is the pulley. We carefully examine it for beats. If everything is in order, then we do not touch it. On the "second" electronics, I got a "fried" engine. Therefore, we disassemble it (we drill out the rivets and rewind the windings, marking the "start" and "end". The winding data of the windings are as follows:
wire - pev-0.8 (approximately by eye)
turns - 644 (shouldn't have been mistaken)
resistance - 10-11 ohms.
Next, I measured the inductance of the coils and aligned them.
We assemble the engine back, if any, then on rivets - if not - on screws.
Sub-chassis.
Examine the sub-chassis (plate) carefully. I had a curve! Blocks at the edges of the slab down to 3-5 mm! I had to equalize. Automotive putty - priming - painting. Result - see the photo in the gallery.
Next is the body. As a rule - into the firebox. The fact is that the body of the "electoronic" is made of 8mm thick veneered plywood. For reference, the total weight of the player is about 20 kg. This plywood bends and crumbles very strongly when the player is moved. And time leaves its mark on him (deformation). Therefore, it is recommended to immediately make a new case with a wall thickness of about 10-15 mm. Plywood or solid wood - to your taste. It is up to you to paint or leave it as it is.
Damping.
The first thing we damp is a transformer
We take porous rubber and cut four spacers: one pair between the U-shaped transformer sub-chassis and the turntable chassis, the second between the transformer sub-chassis and the transformer itself. The result is that the trance should be attached to the turntable through the rubber and never touch the chassis and sub-chassis with its body. Pay attention to the buzzing of the trance (some instances are buzzing strongly by themselves (poor impregnation)) If, after the measures taken, the buzz is the same as before, change the trance. Preferably torriodal. If there is an opportunity and money, I recommend doing it right away (any imported torus with good impregnation or even filling will plug the native Soviet "TS" into the belt), but vibration damping is still necessary. Alternatively, move the transformer outside the enclosure.
Engine - throw out the springs. Cut a ring out of porous rubber or foam rubber and screw the engine to the chassis through this ring. Since the engine is covered with a permalloy screen, it is also necessary to control this moment (mechanical and vibration isolation).
Sub-chassis.
Everything is simple here - we paste over it from the inside with "vibroplast" or a similar material (based on bituminous mastic). We put new foam rubber in the springs.
To be continued....
Vinyl to play the Highest group of complexity "Electronics B1-01" from the musical complex of the same name.
In addition to the turntable, the complex "Electronics B1-01" included an amplifier and acoustics (by the way, 16 ohms!), But more on that later. I (scorpic) will not reveal a big secret by telling you that "B1-01" is a copy (and the "younger" version is, the less so) the cult Thorens td125 player in its time. I will also not tell you about how the Georgian craftsmen methodically "hacked" Thorens, it has been written about this without me.
In total, there were three modifications of "Electronics" (its clones, and there were such, we do not consider). The first modification was almost 100% blueprint from Thorens. (why almost - because the changes mainly affected only the transition to the metric system and bringing the mechanical units to the standard ones that fit into the Soviet GOST. Naturally, the engine control was "pulled" under the Soviet element base. The second - "optimized" the tonearm assembly (removed the possibility of changing distance from the center of the plate, made the sub-chassis one-piece, without a separate platform for the tonearm) and changed the electronics (element base, the introduction of hitchhiking and electronic microlift). The third is essentially a modification of the second. In it, the changes only affected the electronics (the element base and topology were changed). Here, actually, I came across a turntable of the third modification.
I bought it as not working, no belt and no signs of life. My copy was released in July 1980, and it has survived very well (I'm talking about cosmetics).
To begin with, I had to open the factory seals to inspect the insides.
It became visually clear that nothing had burned out ... Actually in the photo - the insides of Electronics B1-01.
The electric motor is 1980, as evidenced by the signature on the body thereof.
