Modernization of the Chinese speaker system F&D (SVEN) SPS-828


I want to share with you my experience in the modernization of the F&D speaker system (it is also distributed under the SVEN brand) of the SPS-828 model. I just want to apologize for the quality of the photo, I took pictures when such crafts were made - in the evening, by phone in a hurry.

I haven’t taken any photographs of the “virgin” type of speaker system myself, as I didn’t think about it during disassembly, so I borrowed them from various resources using Google Images so that you had an idea of ​​how the speakers looked before the intervention.

Let's start with the original look.

This is how the overall speaker looks: The

subwoofer is made of fiberboard about 1 cm thick, the speakers are completely made of plastic about 2 mm thick. All components of the speaker system are painted black.

The interface and control panel, which is located behind the subwoofer:

As you can see, access to the controls is very inconvenient, the controls and the power switch should have been brought to the front panel, or at least from the side, which at first I just wanted to do, but then changed my mind .

Disassembled interface panel:

The board itself holds onto the aluminum plate with two variable-adjuster nuts, one screw that is screwed into the plastic case of the RCA jacks and a bunch of glue. The aluminum plate, in turn, is screwed to the subwoofer itself with 10 screws.

The heart of this speaker system is located on the bottom of the subwoofer, after unscrewing 14 screws, we can observe the following picture:

The transformer is attached with two bolts and nuts that pass through the bottom, the board is screwed with four screws to two small bars, which in turn are glued to the bottom.

The heatsink cools the LM1875T chip, which is responsible for the subwoofer woofer, and the smaller heatsink houses two TDA2030 chips on which the left and right speaker channels are implemented.

Let's take a closer look at the transformer itself (my photos will go further): The

transformer has two secondary windings with a midpoint.
The characteristics of the winding that supplies the LM1875T op amp (subwoofer) 18V, 1.2A, the winding supplying the TDA2030 op amp (speakers) is satisfied with the lower voltage and current 13V, 1A.

I want to note that in a wooden, closed case, without active cooling, especially in the summer, the power transformer and radiators on which the operational amplifiers are installed heated very strongly, it was impossible to touch them with a finger and this is in idle mode, without any load, in general, it’s strange how the thermistor in the transformer didn’t work for so many hot summer days, unless it’s there, but oh well, let’s leave it to the conscience of the engineers, although what conscience is there, especially if you take into account the price of this product, I don’t remember exactly how much it cost, but I know that a little.

What I wanted most of all was to replace low-quality Chinese electrolytes of the incoming power circuits with higher-quality and capacious ones, but as we know - the larger the capacitance and voltage, the larger the size of the capacitor itself. Instead of four full-time 2x3300mkF 35V (sub) and 2x2200mkF 25V (speakers) of an unknown company Konmo, I wanted to put 2x4700mkF 35V by Samwha (sub) and 2x10000mkF 25V by Jamicon (speakers), but they simply did not fit into the subwoofer housing, the latter rested on the phases.

Then the idea came to me, to move the entire middle from the wooden active subwoofer, to the ATX case from a 400W computer power supply, immediately replacing some parts.

- For that matter, the first thing I did was replace two TDA2030 chips with a TDA2050, the latter have better frequency response characteristics.
-Then he undertook to replace all the small electrolytes on the board, for seven years of work day in day in this temperature regime, they just dried out and partially lost their properties.
- I also replaced the diodes in the bridges, instead of the same, small 1A 1000V, I put more, 3A 1000V for the LM1875T (subwoofer), and 3A 80V Schottky for the TDA2050 (speakers).

The part in which I took measurements, drilled, twisted, sawed ... I will skip, because there are still no photos of the whole process, and this is a boring task, at least for me: D

Okay, enough stories about replacement, let's see which of everything it happened.

Amplifier board:

Replaced all of the above details and of course thermal grease on microcircuits.

The amplifier is assembled without a top cover:

I am glad that all the components of the amplifier fit in the case from a computer power supply unit and even more - an EMI filter on the power connector.
The amplifier board was fixed on four racks, the transformer was installed on two gaskets from felt so that vibration was not transmitted and screwed it with two bolts to the case, the interface board was not modified, it was fixed on the same two nuts of the variable controllers and a screw.

I don’t like just one moment, the radiator that cools the TDA2050 microcircuit is closed by a board with connectors, it will interfere with air circulation, but no matter how I twist and rearrange everything, it didn’t work out differently.

Rear Panel Connectors:

At the bottom left, there are two terminals on the woofer of the subwoofer, above them are two RCA jacks of the input signal, the control on the left is responsible for the speaker volume, right for the volume of the subwoofer, two jacks for the mini-jack left / right channels, respectively.

Fully assembled:

Self-adhesive “legs” from the D-Link DES-3200F switch kit perfectly fit.

It's time to turn it on.

Honestly, the sound is simply excellent and very different from what it was before the modernization, in words not convey, but.
If you put your hand to the grate, then there was a noticeable heat from both the transformer and the radiators of the microcircuits. I can’t imagine how all this lived for so long in a wooden, unventilated building ?! Then I decided to put a 120mm blower fan.

Instead of an EMI filter, which essentially gives nothing and does not take anything, I screwed a 9V pulse power supply from the TP-Link WR340GD router to separately power the fan:

In the pulse power supply of the router, the transformer emitted a high-frequency squeak, I had to glue it with epoxy when the epoxy hardened, the squeak decreased but it didn’t disappear completely, it is practically inaudible, except that when the ear approaches the amplifier, it’s okay, a person gets used to everything.

And this is how the already fixed BP of the router in the amplifier looks like:

I did not want to power the fan from the amplifier board, judging by the characteristics / dimensions of the transformer, it is already rather weak and is not designed for this type of load. I connected the turntable through a resistor (I don’t remember the rating anymore, I don’t want to disassemble 80 ohms), instead of 9V, it turned out ~ 5.3V, this is quite enough to blow components.

The final form of the device: The

speakers themselves also modernized, they were like in the first photo, in small plastic cases, the sound was just disgusting, especially when you cut the bass.

Unfortunately, I did not take photos of the converted columns, in principle, there is nothing to look at, now they are hanging on the wall, I’ll take it off for cleaning, take a picture and supplement this note.

In general, two new speakers from the Soviet tape recorder Mayak were lying around:

With speakers 15-GDSH, 15W, 4 Ohms:

In a speaker casing, above a large speaker, I cut a hole under the standard, standard small speaker of this speaker (do not roll around it idle) and screwed it into four screws. The speakers in the column were connected in series with each other, it turned out 8 Ohms, judging by the datasheet, this is an ideal impedance for the TDA2050, a minimum of side harmonics. I really wanted to turn it on in parallel, it would be louder, but then the resistance would be 2.6 Ohms, which is not buzzing.

Judging by the date of the pictures, I did it on 09/21/2012, but only now my hands reached to write a note about this.
It took me about eight hours to do everything.
The modernization and the time spent on it paid off both in terms of sound quality and aesthetic pleasure from the work done.
I bought this speaker system back in 2005. along with my first computer, from that time I changed a lot of system units, monitors, UPSs on my desk, but this amplifier has stayed with me all this time and makes me still happy.

Thank you for your time reading.

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