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Technics Sl-P550 Reconstruction & Mods
Technics Sl-P550 Reconstruction & Mods
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Old 9th June 2019, 09:21 PM   #1
Trident is offline Trident  Spain
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Default Technics Sl-P550 Reconstruction & Mods

After some time without being here, I start this small project.

It is a total reconstruction, and modification of an old Technics SL-P555 player. I've been away from home for a month, and I've felt the impulse that I had to do it.

It is curious the small history of this model, the manufacturer in 1989 announced it as a "4DAC linear 18 Bits" but in reality it is one of the first 1 bit DACs.

The project has been started, and as soon as it resolves the hosting of images, I will put it here.

The idea is to leave the unit in a cosmetic and functional state again, just as it left the factory 30 years ago, and go a little further.

This model is ideal because it is attractive, and has 40% of the space available inside to accept mods.

Basically it is divided into ten stages:

1.- Complete dismantling of the unit (part to part), washing and deep cleaning, new lubrication.
2.- Replacement and readjustment of the pick-up by a new and fresh unit.
3.- Replacement of the Display, and cosmetic pieces with stripes or marks by new components.
4.- Replacement of all capacitors.
5.- Installation of a new clock (it depends on determining if with or without oven), with independent power supply.
6.- Installation of a metal separator panel in the chassis (to insulate from heat and dirt).
7.- Installation of a new power supply for vacuum tubes
8.- Construction and installation of a new outlet circuit with vacuum tubes, and output by transformer.
9.- Installation of bitumen and cork against vibrations and resonances.
10.- Comparison against another unmodified twin unit.

The first three stages are completed, and at this moment the project is waiting for the delivery of the kit for changing capacitors.

I just did a quick test comparing with an old Sony CDP-222-ESD with 1541 (not A) and it sounded quite flat, nice sound (I would not get tired of listening to it) but flat sound, the Technics to my ears seemed to have much more dynamic.

This is just a personal opinion, nothing more.

Greetings to all

Last edited by Trident; 9th June 2019 at 10:04 PM.
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Old 13th June 2019, 03:56 PM   #2
StewartH83 is offline StewartH83  England
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How are you getting on with the mods?

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Old 13th June 2019, 10:26 PM   #3
Trident is offline Trident  Spain
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I have finished the disassembly, cleaning and lubrication part of the player, I have also replaced the laser pickup and completed the correct adjustment.

Dropbox - VID-20190611-WA0012.mp4 - Simplify your life

Now I'm waiting for the arrival from "Audio High End Store" of this capacitor kit:

URL: Technics SL-P555 Upgrade Kit Audio Capacitors

They are € 39 and are original components, as soon as I receive them I will make this mod.

Yesterday I received the toroidal transformer (50VA) for heaters and plate from AnTek USA, but I will not be able to use it due to a problem of dimensions and weight.

I try to find another unit in the range of 20 VA and that is not Chinese. Lamentably Lampizator closed the sale of components.

I have completed and tested the circuit for the temperature control of the TXCO (finally I will go with an oven for stability of temperatures and frequencies)

Basically the oscillator will go in a closed chamber of stable temperature and controlled at 35 degrees, with a circuit with outlet by miniature vacuum tube (Telefunken 5678) controlled by an LM35

And tonight I have solved the issue of the storage of images and videos.

It can be said that the thing advances ... to the rhythm of the post office.

I will surely perform some action with the power supply (AC input), I do not finish seeing it that way.

Last edited by Trident; 13th June 2019 at 10:46 PM. Reason: Add comments
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Old 13th June 2019, 11:02 PM   #4
Trident is offline Trident  Spain
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Additional mod: change the operational headphone output by two OPA627 (with the associated calculations) and others in the adders +/- inputs of the output DAC, the rest will be completed by four 12ax7 and a pair of Lundahl transformers.

And this combining with work ...
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Old 13th June 2019, 11:22 PM   #5
Trident is offline Trident  Spain
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It is a DAC 1bit without a doubt, without the MASH brand but it sounds great, huge dynamics without mods, pick-ups available, not easy to adjust, temperamental, but reliable.

At the time, going from 16 (TDA1541) to 18 and 20 linear bits was an important economic and complex effort. You could not continue on that line. 1 bit was an elegant solution to a complex problem.

It's just a historical review, nothing more

Last edited by Trident; 13th June 2019 at 11:32 PM.
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Old 17th June 2019, 06:45 PM   #6
Trident is offline Trident  Spain
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Advances in the project, with the change of the display and the replacement of different plastic parts of the front.





Last edited by Trident; 17th June 2019 at 07:02 PM.
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