DIY turntable repair

In the distant 90th year, during the liquidation of one very old household store, a large amount of stale goods was pulled out of the back rooms and basement. Arranged a sale. The "Impulse-201 stereo" turntable attracted attention with its bright red body. The price of this lot was discouraging - 25 rubles - a fifth of what the manufacturer estimated it. The contents of the body were a direct-drive EPU, with a microlift and a hitchhiking, with a device for fine-tuning the rotation of the records being played (a stroboscope was used) and with a shearing force compensator (anti-skating).

How can you pass by such goodness? There was also a teaspoon of ointment. An honest saleswoman (they disappeared in the process of business evolution) said that this device has an unrecoverable defect, which she does not know specifically. This information did not bother - I bought it, brought it home. At first I did not find any defect, everything was spinning, the sound was reproduced, however, only on headphones, because it was not a turntable (according to the correct electrophone), but only a "turntable" - EPU (electro-playing device). After some time, it migrated to storage in the garage, because indeed one channel played much quieter than the other, which became immediately noticeable after connecting it to an external sound amplifier.

• Power supply from an alternating current with a frequency of 50 Hz and a voltage of 220 V ± 10%.
• The rotation frequencies of the records are 33 1/3 and 45 rpm.
• Rotation speed adjustment range ± 2. 5%.
• Knock coefficient is not worse than 0.15%.
• The range of reproducible frequencies is 31.5. 16000 Hz.
• The unevenness of the frequency response is no more than 10 dB.
• Frequency response mismatch of the pickup is no more than 2 dB.
• The pick-up clamping force is not more than 20 mN.
• The relative noise level with a weighting filter is not worse than -55 dB.
• The level of the electric background is -53 dB.
• Separation between stereo channels at frequencies:
• 315 Hz - not less than 15 dB
• 1000 Hz - not less than 20 dB
• 5000 Hz - not less than 15 dB
• 10,000 Hz - not less than 6 dB.
• Power consumption no more than 15 W.
• Overall dimensions 375х300х120 mm.
• Weight without packaging 5 kg.

Video (click to play).

But a month ago, I was "loaded" with a "Sanyo TP6100" turntable, I intended to operate it, of course, after completing it with a correcting amplifier and appropriate improvements. So naturally, an appropriate sparring was needed initially - a partner and the "Impulse" was brought out into the Light of God. Substantively, I did not look for the reason for the different volume of the channels; I started with the power supply. Measurement of current consumption showed that under standard load, the voltage sags to 9 volts, and should be 10 - 12 V.

It is clear that 12V is better. At the same time, the step-down transformer was heated and the KT801B transistor was very hot. Which is natural, because the manufacturer himself wrote in the technical specifications about the permissible power of 15 W, and installed a 10 W transformer. The KT801B transistor can have a static current transfer coefficient from 30 to 150, in fact it turned out to be 50, which is clearly not enough in this circuit solution. I put the transformer at 15 W (which it was), I did not find the transistor better - I installed a passive radiator on my own, without checking the old ones, installed other, tested electrolytes, instead of 2000 μF x 25 V - 4700 μF x 25 V, others at par. I loaded the updated power supply unit - now, even with a current output of 500 mA, the voltage did not fall below 10 V.And the real need for current at the EPU is as follows: control board - 40 mA, electric motor - 150 mA, correcting amplifier - 80 mA. Total 270 mA, I admit a maximum of 300. The transformer no longer heats up, but the transistor continues, although to a lesser extent.

The equalizing amplifier is enclosed in a shielding metal case. For ESP class 2, this, as well as many other things, is already chic. Were replaced not only electrolytic, but also ceramic "flag" capacitors. Sockets are installed under the K553UD1A microcircuits. It will be curious to listen and it is possible to detect a difference in the sound when changing them. There are a dozen of them in stock.

On the control board, in addition to replacing electrolytes and "flags", a variable resistor was repaired. Instead of the specified nominal value of 33 kOhm, in fact, it turned out to be 24 kOhm (that is, the adjustment of the rotation speed was difficult). I opened the lid and with a file reduced the width of the resistive layer, as a result of which the resistance increased to the required value, while I note that in the process of adjusting the speed of rotation of the disk, it was found that a resistor for a higher resistance, for example, 47 kOhm, would be appropriate here.

The EPU was assembled and turned on - it played, but one channel was still quieter than the other. Then I got into the tonearm and there, at last, the "weak link" was discovered - single pin connections, which were bad even for the 2nd class. Replacing the GZM-105 pickup with the GZM-005, I simply took and soldered these connections, the latter may be the way it should be done, even at the factory. The sound of both channels has become not only equally strong, but also subjectively better quality.

For possible experiments, I placed an “exit” in the corner in front of the correcting amplifier. Now it is possible to remove the sound signal directly from the sound head, for example, try some other corrector. Also send a sound signal from another turntable - compare the work of the correcting amplifiers. So, having connected the Sanyo TP6100 turntable to this corrector, which does not have a correcting amplifier in its case, I found that it does not function, or rather does not reproduce sound. Having built something similar to a microscope, I discovered the absence of the diamond tip of the needle in the stylus of the cartridge, there was only one pin in place, on which the diamond should be located and which was originally mistaken for it. For visual viewing, at least 10x magnification is required here.

Upon completion of all actions, I have this internal view of the EPU. And I was not too lazy to make an additional headphone output on the front panel of the case - a tremendous convenience. Having read about the dependence of sound even on the brand of electrolytic capacitors, in an incomprehensible way, I caught a less pleasant sound after replacing the electrolytes in the part of the power supply unit giving a bipolar voltage for the amplifier-corrector and replaced them with the previous ones, which turned out to be in good order in all respects.

Finally, according to the recommendations of advanced music lovers, I set the turntable strictly horizontally in terms of level. There are several licensed records of the company "Melodia" available, for this EPU it is not even bad, the release of the past years, somehow I will definitely move away from the everyday fuss and plunge headlong into the world of analog sound.

At the present time, for a radio amateur, a little more than a beginner, this EPU can easily become a kind of radio designer who will give the first understanding and the opportunity to get acquainted with analog sound. Tuning deeper than the one discussed in this article is desirable. Then it will be appropriate for the EPU to collect something on the radio tubes. Then change the body, for example, make it from a solid "piece" of wood. And then no one would even think of the "second-class" origin of your Hi-Fi equipment.

Recently I met an interesting person of 67 years old.The man is very fond of vinyl music and he has many different turntables - from Arctura-006 to Fine ARTS TD-903 from Grundig. However, all the players work poorly, or do not work at all, because they are only slightly younger than this person himself. And he carries me all these turntables for repair and hopes that I will give them a second youth. I try as best I can, because he is a good person, and I myself am interested. In the course of the repair, of course, you have to climb a lot on "these" Internet sites and read, at times, surprising and unexpected things.

So, for example, on one forum there is a very serious discussion about the benefits of making a player's disc heavier, one that is iron and on which the disc itself is directly placed. Type, to reduce the instability of the rotational speed. One expert writes about his experiments like this:

“I put on the disc of my turntable, for weighting, a disc from a prefab dumbbell, weighing 1 kg. The disc was spinning as if nothing had happened, nothing had changed in the world. Then I put another such disc and the player could not start itself. But I helped him with my hands and he started spinning again. I don’t know how this affected the sound quality, because the height of all these discs became such that the tonearm could not be lifted onto the record! Then I decided to just continue the experiment and put in another 3 kg disc (the kilogram ones were all over). I unrolled it again with my hands and it all spun and spun for some time quite well and, I think, very stable because of the large inertial moment. But then there was a smell of burning and smoke came from the player, damn it - the engine burned out. Based on the experiment done, we can conclude that, probably, the maximum weight of the disc is somewhere between two and five kilograms. I will buy a new engine, who has it? I want to determine the maximum possible weight of the disc with a higher accuracy. "

So, my friend brought in a 1985 Arctur-006 turntable for repair, whose disk suddenly stopped spinning. He said he removed the disk for troubleshooting and. did not find either the engine itself, not even any belt-rollers! The man was very puzzled by this state of affairs, because he lived for 67 years in this world and saw everything, but this is what. I asked if the engine could have burned to the ground, that is, completely without a trace? I expressed my doubts about this and we began to understand. They removed the disc and, indeed, did not find even traces of any engine.

This is understandable to me, because here is just an original low-speed engine, where the rotor is the player's disc itself with a glued-on magnetic tape. However, before explaining this fact to a person, I decided to draw his attention first to a large number of dead cockroaches in the voids of the body under the disk. I said that this is a unique turntable with an experimental biological engine, very economical and not harmful to the environment. And the driving force is just cockroaches, specially trained in the biological laboratory of the Polish company "Unitra". When the power is turned on, a current discharge is supplied to the cockroaches, they get angry, swear and start spinning the disk out of frustration - but where can they go ?! But nothing lasts forever under the moon, not even cockroaches. So they all died, and now there was no one to turn the disk.

Then, of course, he took pity on the man, stopped telling tales and repaired the player for him. Several years have passed since then, and "Arctur-006" is still playing. But I presume in advance his next quick death and train a new batch of cockroaches for now :-))

Even in this Arcturus, my imagination was struck by a preamplifier-equalizer, which looked like this:

The board seems to be clearly small for such capacitors. Although I may not be an ardent audiophile at all and do not understand what a beautiful, transparent, detailed sound is given by precisely such capacitors.Some will say that even such conductors are perhaps too small for a particularly high-quality and natural sound! Moreover, if you still load the disc with "pancakes" from the bar by 25 kilograms? Surely, you get a truly divine sound! But how many specially trained cockroaches are needed? The author is Andrey Baryshev.

We really need a master to repair Electronics 017C. I phoned the services - they call them a relic and do not take it. The problem is that when turned on, everything works, but there is no sound. Help, good people! The stepmother does not have a weak record library and to lose the wiretapping of her rarities is a great grief for her: oh (

And you are not on services.
Find a newspaper with classified ads and call them.
If you also have a passport with a diagram for this product, then it's very good. Imho, any sane repairer will fix your device without any problems, this technique is very repairable.

Thanks! We will also try this option. Simply, suddenly someone has a reliable and sensible dock - they would be very happy: o)

It seems to me that buying a working copy of this Electronics will now cost less than repairing it.

If everything is spinning, but there is no sound, then the problem is in the contacts or electronics. The parts cost a penny, so the cost of the repair is almost entirely the cost of the work.
And domestic audio equipment of grades 0 and 1 really cost cheap a few years ago, but now the prices for it have risen sharply, people realized that it is much better in quality than Chinese soap dishes.

is wrote:
in terms of quality, it is much better than Chinese soap dishes.

I'll clarify: the sound quality. Inside there is a traditional sovdepovsky kick-ass