Inexpensive amplifier for s30 speakers with your own hands. Ultimate remake of Radiotehnika S30. Correcting deformation of protective nets

Using visual examples, I will show how to repair “old and remote” acoustic speakers Radiotehnika S-30 with a small car power amplifier Weconic EQB-105, which is equipped with an output power indicator and a 7-band graphic equalizer. I will share interesting ideas for restoring dynamic heads, a circuit diagram of the UMZCH on the HA13001 and useful information on repairs.

Note: if you are only interested in repairing S-30 speakers, use the content navigation!

Instead of an introduction

While going through old/non-working electronics in my closet, I came across a small, but no longer working Weconic EQB-105 car power amplifier. Before I assembled my homemade UMZCH Phoenix P-400, this little guy rocked all my speaker systems and pleased me with a pretty good sound. Later, this amplifier burned out because it was supplied with a slightly too high supply voltage and driven to full power.

There were still non-working Radiotehnika S-30 acoustic speakers, I thought: “if they were repaired and combined with an amplifier, they would make excellent acoustics for a home TV”!

I didn’t want to buy a set of TV speakers for $150+, but here I had the opportunity to put together a budget Hi-FI audio system by investing a little of my time and quite a bit of money.

So, I'll start my story with the amplifier...

Weconic EQB-105 power amplifier review

This is what this amplifier looked like, although I got it without the side ears, which are used to attach the amplifier to the internal chassis of the car.

Rice. 1. Appearance of the Weconic EQB-105 power amplifier with a 7-band equalizer.

The amplifier manufacturer is WECONIC Professional Carhifi, a company owned by Inter-Union Techno GmbH, 76829 Landau (inter-union.de). She was engaged in the manufacture of various automotive audio equipment: acoustic systems (AS), power amplifiers, equalizers.

The Weconic brand has already become a thing of the past, leaving behind a set of various audio devices, one of which fell into my hands.

Amplifier characteristics:

• 4 outputs for connecting speaker systems;
• 2 signal inputs;
• Output power indicator of 5 multi-colored LEDs;
• Graphic equalizer for 7 bands;
• Balance regulator between each pair of speakers;
• Power supply - 12-14V.

I remember the first time I saw the inscription on the amplifier “100 Watt Live Sound” - I just couldn’t wait to connect it to my Amphiton 100AC-022, then I realized that this value was exaggerated. It was assumed that the amplifier produces 4x25W, but in reality you can get about 17W per channel provided there is good power supply.

Amplifier repair

The power amplifier is made using a bridge circuit using two HA13001 microcircuits. The preamplifier is assembled on four op-amps, which are contained in one BA10324 chip, the equalizer filters are assembled on 14 transistors, and the output power indicator is on the LB1403 chip.

Having completely disassembled the amplifier, I realized that there was a little more work to be done than expected.

Rice. 2. Weconic EQB-105 amplifier disassembled, only electronics (picture clickable).

What you have to do:

1. Replace the HA13001 chip;
2. Replace burnt out backlight bulbs;
3. Clear everything of debris.

Although the amplifier had 4 outputs, it actually has 2 power amplification channels, and the power distribution between the four channels is done using a dual ceramic variable resistor. The handle of this resistor is combined with a switch that allows you to connect the signal source through the amplifier (pressed, the amplifier is on), or directly to the speakers (pressed).

One of the HA13001 chips in the amplifier burned out. As it turned out, this is a rather rare microcircuit from Hitachi Semiconductor.

Rice. 3. Chip Hitachi HA13001 (Japan).

Searches for this microcircuit in online stores did not yield results; a trip to radio outlets on the market was also unsuccessful. One of the old-time radio amateurs at the bazaar told me that Hitachi ULF microcircuits were very difficult to counterfeit, so they were valued.

In one of the local electronic components stores, I still managed to find two HA13001 microcircuits, although one had a broken leg - I took both at a discount! Then I found microcircuits HA13001 on AliExpress.

Characteristics of HA13001:

• Output power, stereo - 2 x 5.5 W;
• Output power, bridge - 17.5 W;
• Supply voltage, min. - 8 V;
• Supply voltage, typ. - 13.2 V;
• Supply voltage, max. - 18 V;
• Quiescent current - 80mA;
• Reproducible frequency range - 20-20000Hz;
• Maximum output current - 4.5A;
• Gain - 50 dB.

Rice. 4. Schematic diagram of a two-channel and bridge power amplifier on the HA13001.

Replacing the microcircuit immediately produced results - both channels began to sing, but for some reason one of them played an order of magnitude quieter. I was already a little upset, but then Mr. “chance” came to the rescue.

Guests came into my room with a baby, who immediately became interested in what was playing and even glowing. Taking the baby away from the working amplifier, I lifted the board a little - both channels started playing smoothly for a second.

Apparently there is no contact somewhere: bad soldering, a torn conductor, a damaged part, a crack on the board? - the cause had to be found out and eliminated.

Having felt all the details and conductors, I did not hear any changes in the sound. Turning on the desk lamp and armed with a magnifying glass, I began a thorough inspection of the printed circuit board and electronic components for any visible defects. All the parts are intact, I only soldered some connections, but I still couldn’t find the location of the missing contact.

I really didn’t want to, but I still had to unsolder the board with the regulators and look for the reason on it. Getinaks printed circuit boards are very delicate - if the contact is slightly overheated with a soldering iron, any trace can easily fall off.

Rice. 5. Sealed equalizer board with regulators (picture clickable).

As expected, several tracks fell off - no problem, then we will replace them with heat-resistant conductors and everything will be OK.

I soldered the suspicious connections on the regulator board, and since the board was sealed off and there was easy access to the components, I decided to replace all the control panel backlight bulbs at the same time.

A quick measurement of the current consumed by one light bulb showed me a value of 34mA. And if all 4 light bulbs light up - approximately 140mA of current to nowhere, 12V*0.14A=1.68W!

Rice. 6. Measuring the current consumed by an incandescent lamp to illuminate the panel.

I decided to replace incandescent light bulbs with blue LEDs, which turned out to be very economical. I connected one LED through a 10 kOhm variable resistor to a +12V power source, turning the resistor knob I achieved a fairly bright glow at a current of only 4 mA. Having measured the resistance of the resistor in a fixed state, I got a value of 2.5 kOhm.

Result: 4x4mA=16mA (versus 140mA) + pleasant blue glow.))

As it turned out, it won’t be possible to simply install LEDs - their diameter is 5 mm versus the diameter of the light bulbs 3.5 mm. The solution here is simple - adjust the dimensions of the housing of each LED using a needle file.

Rice. 7. Adjusting the size of LEDs using a diamond file (clickable).

I soldered the LEDs in place of the incandescent lamps, and connected 2.5 kOhm quenching resistors in series to each LED with a surface-mounted mounting on the back side of the board, having previously cut the tracks so that each pair of LED + resistor was connected in parallel.

Rice. 8. Soldered LEDs with quenching resistors.

Rice. 9. LED glow test for the backlight panel.

The brightness of the glow is excellent; then all that remains is to solder an LED to illuminate the volume control area. We've sorted out the backlight, let's return to the problem with the skew in the volume of the channels.

Having soldered the board with tone controls to the main one and connected the amplifier to the power supply, I was convinced that the problem had not disappeared; now no deformation of the board or its bending affected the operation of the amplifier in a positive direction.

I unsoldered the front panel board back, decided to connect both boards with flexible conductors and then look for the cause of the problem in this form. This had to be done right away, but I hoped that the problem lay in the solder joints of both boards - as it turned out later - almost so, but not quite.

Rice. 10. Temporary connection of boards using flexible conductors.

After playing a little with these scarves, rotating them, squeezing them and feeling the details, the reason for the distortion in the sound of the channels was found. It was hidden in a cracked path near the hole-groove for inserting part of the main board.

It was not possible to notice this crack by visual inspection - it was hidden under a thin layer of rosin. I began to unsolder all the conductors connecting both boards one by one and analyze them. Having unsoldered one of the outer conductors, I noticed that this did not affect the operation of the amplifier in any way - strange. Having cleared the track to which this conductor was soldered of debris, I immediately noticed a defect - HURRAY!

Rice. 11. The reason for the distortion in the sound of the amplifier channels is a crack in the track (clickable).

The cracked track was cleaned and soldered. To connect the contacts in places where the tracks disappeared, I decided to use a heat-resistant wire with fluoroplastic insulation - MGTF.

Rice. 12. We restore the tracks by connecting the contacts with heat-resistant MGTF wire.

After restoring the tracks and connecting the boards, all that remains is to remove all debris on the variable resistors, clean the case and controls from dust. To do this, I used a piece of cotton wool soaked in alcohol and wound around a cleaned match.

Rice. 13. Cleaning the amplifier case and components from dust and debris.

Rice. 14. Refurbished Weconic EQB-105 amplifier.

Acoustic speakers Radiotehnika S-30

I figured out the power amplifier, it’s time for the Radiotekhnika S-30 speaker systems. The speakers are old, but they sound very good if everything is put in order.

Technical characteristics of S-30:

• Rated electrical power - 10 W;
• Rated electrical power - 30 W;
• Nominal electrical resistance - 4 Ohms;
• Nominal sound pressure (in the frequency range 100 - 4000 Hz) - 1.2 Pa;
• Reproducible frequency range - 50-18000 Hz;
• Speaker system dimensions - 364x214x195 mm;
• The mass of the speaker is 6 kg.

The schematic diagram of the Radio Engineering S30 speakers is shown in the figure below.

Rice. 15. Schematic diagram of acoustic speakers Radiotehnika S-30.

We disassemble the speakers and inspect problem areas

In one of the speakers, the low-frequency (LF) speaker hardly plays anymore. Everything is covered in dust, the woofer grilles are deformed.

Rice. 16. Speakers Radiotehnika S-30 (condition before repair).

There is also a clearly noticeable defect in the bass reflexes of the speakers - the foam rubber has turned into a deformed and solid mass, in one of the speakers it completely blocked the bass reflex hole.

I removed the cover of the first speaker and measured the length of the bass reflex tube made from old foam rubber - 5 cm.

Rice. 17. The first speaker S-30 with the cover removed, we measure the length of the pipe of the partially preserved bass reflex.

Rice. 18. Second column S-30 with the cover removed, the foam rubber has turned into a solid mass.

In the second column there is an even more terrible sight. Part of the foam rubber has turned into a solid mass, part of it crumbles like powder, and another part has become a sticky mass that it is better not to touch with your fingers.

I cleaned off the remaining foam rubber using a screwdriver and knife. I unscrewed the screws from the protective grilles from the woofers, thereby freeing them for subsequent removal.

Rice. 19. Remove the protective mesh from the woofer of the Radiotehnika S-30 column.

Carefully, using a screwdriver, I removed the woofer, which was placed on a mixture resembling plasticine. When soldering conductors from the speaker, it is very important to remember their connection: two conductors connected to one point go to the minus of the speaker, one conductor to the plus.

In order not to get confused in the polarity of connecting the speaker after repair, the conductor going to the plus of the speaker can be wrapped with a piece of electrical tape or marked with a marker. In any case, you can refer to the circuit diagram of the speakers.

A bag of cotton wool was removed from the speaker, followed by a walk outside to blow out the remains of powdered foam rubber and other debris that had accumulated there over the entire life of the speaker.

Rice. 20. Removing the subwoofer from the Radio Engineering S30 column.

Rice. 21. Speakers 10GD-34-80 (4 Ohm) from Radiotehnika S-30 speakers.

Repair of flexible flagella leading to speaker diffusers

Having freed up space on my desktop and putting the speaker housings aside, I set about repairing the 10GD-34-80 speakers. A very common cause of speaker failure in Soviet-made speakers is a fracture of the flexible braided cords running from the contact block to the diffuser, which leads to loss of contact with the magnetic system coil.

Rice. 22. The reason for the inoperability of the 10GD-34-80 speaker is a flexible flagellum broken off from the diffuser (clickable picture).

When starting repairs, in addition to a soldering iron with a thin tip, you will need: wire cutters, a small screwdriver, tweezers and a thin scalpel. If you don’t have a scalpel, you can make a small homemade cutter from a metal saw blade by sharpening it on a sharpening machine.

Rice. 23. Necessary tools for repairing flexible flagella.

The flagella going to the diffuser were sealed off from the speaker contact blocks, and the insulating rubber tubes - cambrics - were also removed.

Rice. 24. Unsolder the flagella from the contact columns in the 10GD-34-80 speaker.

Rice. 25. Remove the end of the contact flagellum with the insulating tube.

Very carefully, slowly, I bent the two antennae to the sides, which press the flagellum of conductors to the diffuser. To do this, you can use a scalpel or a small screwdriver with a thin tip.

Rice. 26. Unbend the antennae that hold the electrically conductive flagellum on the speaker diffuser (clickable).

After this procedure, it is very important not to move the flagellum or tug on it, since it is no longer secured and a conductor from the coil of the speaker’s magnetic system is soldered to it.

Using a soldering iron with a thin tip, the flagellum was sealed off from the coil conductor. If a soldering iron with a thin tip is not available, then you can make a temporary thin tip by winding a thick (3-5 mm cross-section) copper conductor, cleared of enamel, onto a thick soldering iron tip, followed by sharpening the wound tip using a file.

Rice. 27. The damaged flexible conductor was removed from the speaker, the thread remained and the wire mesh was broken.

Having unsoldered all four flagella (for 2 speakers), I began to look for a donor for new flagella - flexible conductors going to the diffuser.

Cable conductors that connect telephone handsets to the base can be an excellent donor - they are twisted into a spiral and are very flexible, resistant to repeated bending. Finding such a conductor will not be difficult at the bazaar, or by visiting local telephone operators.

Rice. 28. A cable from a telephone handset is a donor for making flexible flagella.

Rice. 29. Structure of a flexible telephone cable (click on the picture to enlarge).

A telephone cable consists of three cores, each of which is a conductor in multi-colored insulation, which in turn consists of six cores, and each core is an electrically conductive foil wound on a fibrous base (thread).

The cable insulation was carefully cut along the entire required length, all three conductors were removed and cleaned of insulation. The length of the donor conductors required to repair two speakers is approximately 35 cm.

Rice. 30. Flexible conductors removed from the cable from the telephone handset.

At first I thought of simply twisting two or three sets of conductors into one, but a more sensible idea came to mind - weave all three sets of conductors into a braid!

Rice. 31. We braid a pigtail from flexible telephone conductors for repairing Radiotehnika S30 speakers (click on the picture to enlarge).

A few minutes of magic, with the help of dexterous fingers, and the braid of three sets of six conductors is ready!

Rice. 32. Finished braid of 18 flexible conductors (3 sets of 6 pieces).

The flagellum turned out to be a little thicker than the original one, and it is also much more flexible than the previous one, it will be an excellent replacement!

The length of the braided braid was divided into four even parts, each approximately 8 cm long (with a margin). The length of the original flagella is approximately 6-7 cm.

Rice. 33. We measure the length of the original flagella from the woofer from the Radiotehnika S30 column.

One of the ends of the cut pigtail was well tinned with lactic acid, thus all 18 conductors were soldered together.

If there is no lactic acid, then rosin will do; in this case, you may have to pre-clean the conductors before tinning.

Rice. 34. Tinned end of a pigtail (harness) made of flexible conductors from a telephone.

An extra piece of the harness (not tinned, on the left) was bitten off using wire cutters and placed between the tendrils on the speaker diffuser. For ease of installation, the speaker can be raised slightly by placing an unnecessary book or other object about 4-5 cm high under it.

Rice. 35. The flexible flagellum is attached to the diffuser using through metal tendrils (click to enlarge).

After the antennae were carefully bent, the speaker was slightly raised. Using a small piece of hard material on the back side of the antenna mount, I pressed well on the place where the harness was attached to securely fasten it between the antennae. After this, the tinned end of the flagellum was soldered to the terminal of the coil of the speaker’s magnetic system.

The joint can be slightly filled with rosin or a small amount of glue, for example the Globus brand, can be applied to it.

The second end of the harness was threaded through the hole in the contact block, after which a sufficient length was selected and the excess end was bitten off using wire cutters.

The length of the flagellum and its fastening should be such that it bends freely and without tension when the diffuser moves in different directions, but does not touch the diffuser itself. When selecting the length of the harness, you can move the diffuser a little in different directions and see that everything is in the best possible shape.

An insulating tube was put on the remaining end of the flagellum and it was soldered to the block, having previously laid the tube in a special cutout in the speaker housing.

Rice. 36. A flexible homemade harness is soldered to the diffuser and speaker block of Radiotehnika S-30.

One of these tubes, when removed, literally crumbled from old age, so I replaced it with heat shrink of the same length, taking a obviously slightly larger diameter and, using a heated soldering iron, pulled it together on a bundle to the desired condition.

Rice. 37. We use heat shrink instead of a damaged insulating tube when repairing a speaker.

The mounting points for the antennae on the diffuser, on the opposite side, were secured using fusible silicone; glue could also be used.

Rice. 38. We fix the attachment points of the holders for the electrically conductive harness.

In this way, all the flexible harnesses in each of the speakers were replaced.

Replacing tubes for bass reflexes

To replace bass reflex tubes made of foam rubber, you can choose a variety of materials. If you need harder bass, then you can use PVC tubes, and if the bass needs to be soft, then we use fiber material.

I used a strip of artificial synthetic fiber, which turned out to be quite dense and from it it is quite possible to roll up a tube for a bass reflex.

Rice. 39. A skein of artificial synthetic fiber.

When disassembling the acoustic speakers, the approximate length of the bass reflex tube was measured - 5 cm, so I cut a strip of exactly this height. The length of the strip was approximately 40cm.

Rice. 40. Cut a strip of material to make a bass reflex tube.

Then this strip was twisted around the bass reflex protrusion on the speaker cover so as to form a tube. The places where the strip begins and ends were fixed with fusible silicone.

Rice. 41. We wind a synthetic pipe for the bass reflex and fix the ends of the strip with silicone.

To ensure that the front cover fits tightly to the wooden box of the speaker, two round gaskets were cut out of the same synthetic material in the place where the hole was made for the bass reflex. Essentially, we got two donuts, each with an outer diameter of 85mm and an inner hole of 35mm.

Rice. 42. Rings for tightly pressing the tube to the body and column cover.

The rings at several opposite points were impregnated with fusible silicone and glued together, then with the same silicone they were glued to the previously prepared tube. For reliability, the tube was additionally wrapped with nylon thread.

Rice. 43. Finished bass reflex tube for Radiotehnika S-30 loudspeakers.

As a result, two such bass reflex tubes for speakers were manufactured.

Correcting deformation of protective nets

The protective grilles of both woofers are slightly dented in the middle. It is very difficult to simply align them with your fingers - correcting a deflection in one place of the mesh will result in deformation in another.

Rice. 44. Deformed meshes from Radiotehnika S-30 woofers.

As a basis for leveling, you can use some small solid spherical object or the round protrusion of an old wooden chair.

I took a simple wine rind, installed it vertically, put a mesh on it and, resting my palms on it, easily aligned all the deformed places on the mesh.

Rice. 45. Restored grids for Radiotehnika S-30 woofers.

Putting the speakers back together

Before putting the speakers back together, I’ll describe what else can be done during the repair:

• disable the overload indication circuit if it is not needed;
• replace all conductors in the speakers with thicker ones made of copper, with a cross-section of 1 mm or more;
• Cover the inside of the body with soft material.

As for me, the conductors in my speakers are of sufficient thickness, the display circuit does not interfere, and gluing the body inside will take a lot of extra time.

Before installing the woofers, it was necessary to remove the old plasticine, which had become very hard and was no longer suitable for a tight fit of the dynamic head. I quickly and carefully performed this “medical procedure” using a scalpel.)

Rice. 46. ​​We remove old unusable plasticine from the S-30 body.

I was lucky to find a piece of plasticine in the school trash, so I didn’t have to buy anything. Small pieces were twisted from it, which were placed around the perimeter of the hole for the woofer and carefully evenly rubbed along the groove of the wooden case.

Rice. 47. Apply plasticine evenly along the groove near the round hole for the speaker.

Rice. 48. The platform for installing the speaker is ready.

Everything is ready to install the woofers in their places. I turned on the soldering iron, and while it was heating up I decided to do some cosmetic cleaning of the front panels of the speakers.

To clean, you can use a cotton swab soaked in alcohol, or simply take a damp antibacterial wipe with a neutral odor. At the same time, I cleaned the speaker grids from dust and dirt, as well as the rubber surrounds of the low-frequency heads.

Rice. 49. Cleaning the front panel of Radiotehnika S-30 speakers.

I soldered and screwed the low-frequency speaker together with the protective mesh, and placed a synthetic tube over the bass reflex protrusion.

To install the LED, the manufacturer provided everything so that its terminals were pressed with a foam rubber tube, and in my case that’s what happened - I didn’t have to glue anything.

Rice. 50. Reinstalling the LED to indicate AC overload.

Everything is ready, you can screw on the covers and try the sound of the restored Radiotehnika S-30 speakers!

Rice. 51. The speakers have been restored, all that remains is to screw on the covers.

Connecting speakers and power amplifier

To power the Weconic EQB-105 power amplifier, a small switching power supply (PS) from some computer peripheral was found. At the output, the power supply produces 12V at a current of up to 3A, which is quite enough to power this amplifier and produce about 2x15W at the output.

To connect the power supply to the amplifier, I found an old high-frequency coaxial connector, the kind used in old Ethernet computer networks based on coaxial cables. What I found, I applied.)

Rice. 52. Power supply for the amplifier.

I connected a holder with a 4A fuse to the gap in the positive power supply conductor of the amplifier, just in case.)

Rice. 53. Amplifier power connector with fuse.

I thought about putting heat shrink on the part of the connector that goes to the amplifier, but there was no suitable diameter in stock, so I simply insulated it and tied everything together using nylon thread - it turned out quite neatly and reliably.

Rice. 54. We isolate the connection of the conductors and the connector using a thread.

Since the amplifier has four independent (not pressed to ground) conductors for supplying a signal to each of the channels, I decided to do this: I connected one conductor from each input together and connected it to the power supply negative.

As a signal cable, I found a piece of shielded cable from some device with a USB connection, about 1.5 m long. The cable contains 4 cores in a dense screen with a binding of conductors.

I connected the two wires of the cable to each other and connected them together with the screen to the ground (minus) of the amplifier. The remaining two free wires in the cable were used as signal wires for the right and left amplification channels.

Rice. 55. Connecting the amplifier inputs to the signal cable.

The "Mini-Jack 3.5" connector was removed from non-working headphones. Soldering it to the signal cable was not difficult; the common conductor connected to the screen was covered with heat shrink. The connector at the junction was tightly and under tension wrapped with thread.

Rice. 56. Connecting the Mini-Jack 3.5 connector.

To connect the speaker to the amplifier I used a two-core audio cable. I cleaned the ends of the cable that will go to the speaker terminals by about 15mm and completely tinned them, and left the ends that will go to connect to the amplifier longer - about 40mm and tinned them only at the end so that the conductors do not unravel.

Rice. 57. Preparing conductors for connecting speakers to an amplifier.

The result of the work carried out can be seen and listened to in the short video below:

Composition playing in the demo: John Petrucci - Glasgow Kiss.

In conclusion

I and my family really liked the result of the work. The amplifier with speakers Radiotehnika S-30 is quite enough to watch a movie/concert with high-quality and detailed sound, listen to music, amuse your child with a cartoon with various sound effects, play toys on a laptop or Raspberry Pi, which is connected to the TV. In general, the budget Hi-Fi turned out to be quite successful!

Have a good and clear sound!