Small but crazy - PW8010

This is one of the pearls in my collection. This project took me very long time, but it was worth to wait and now I can say: I'm proud of final effect. For the first time, I saw this model on my colleque desk at work, many years ago. I liked its small size. For playing music and voice on a deskspace you don't need huge power. I decided to buy this device for myself one day. Some time has passed and finally I was ready to hunt on one for me in the internet. I didn't look for model from the shelf. The most important was to have main parts like: transformer, heatsink, knobs and not demaged metal case. I was searching through different offers but often price was somewhere from end of universe. Finaly one day I caught this one.

I bid it, for about 20 PLN as broken. As you can see, it was far from perfect. Owner was from Cracov. Fortunatelly, at that time, one girl from my job (Małgorzata) was visiting her family in that city and she agreed to pick it up for me. After the weekend, I had it in my hands. Also at that time, I was in the middle of moving to the new flat, so this troubadur had had to wait a few months more. Finaly his day has come. When I opened it, I saw a picture as after D-day in France. I could easily noticed that previous owner was trying introduce some modifications with no luck at the end. Dust inside is more or less natural, but greasy layer all over PCB is rather not. I suspected, that it was from potentiometers. Some wires were isolated with tape. In some places pads on PCB were torn. Main capacitor was missing. On/Off swith was mounted on one screw. Basically, everything needed some care and work, but this is what I like in such projects.

On the beggining I downloaded the schematic. Then I made some notes about wires and inside connection, so after all I could eaisly turn back to original. Of course I was checking them agains schematem. I didn't trust previous owner and its talent.

Then only cleaning, cleaning and cleaning left. I have disassembled it to single parts. Construction of input and output selectors has one drawback. Its conacts are complately uncovered, so they oxidize very eaisly and after couple of years they starts to cause problems. To clean them we can use mechanical way, bath in ultrasonic cleaner or in acid for cleaning silver. After each one of them, it is good to cover contacts with special lubricant that will protect them against oxidization. The next thing were speakers terminals and input sockets. I didn't have to touch them, but because everything was put on parts and I had some time and I knew it will stay on my desk I decided to put new, straight wires with new solder.

Board, after washing it in ultrasonic cleaner, got new colour and shine. It was much easier to locate places that can cause problems. In this model, power ending is made from separate transistors connected into Darlington's circuit. Only big power transistors were attached to heatsink. I thought, why to not put them all there. Especially those small ones from temperature compensation. I also didn't like this method of interleacing and bending its legs in triangle holes. This is why I preprared some special pins that make easier (dis)assembling.

Another mechanical step was rebuilding holders for on/off switch. I cut aluminium pipe for this purpose.

Next were capacitors. Some people blindly replace all with new one. Apart from that it is expensive, in many cases it has no sense. Most of them still keep theris capacitance and ESR on good level. This is why I always measure them and replace only broken one. As I already mentioned, main capacitor was missing. It was hard to get similar one, so I have rebuilt it with 6x2200uF connecting them into one 2x6600uF. This is how was made this blue piece of art in the middle of PCB.

Another step was more cosmetic then really needed but I had some time and I like when elements lay straight.

Of course, I wouldn't be me if I didn't check potentiometers inside. And it turned out, that this greasy cover was really from them. Cleaned and lubricated were put on their place.

A lot of work, isn't it? The worst were still ahead. When electronic part was ready, I could close the cover and use it. But how could I put it into such one? Personally, I consider this as barbaric removing original description with sandpaper, but what I could do? I took the challange and decided to recreate original look. Three evenings with photos downloaded from web, caliper and InkScape app for vector graphis and skatch was ready. I asked myself: but how to put it on aluminium? First thought: thermotransfer, but I wasn't sure, that quality will be really good and since this is front that make the first impression, I couldn't risk. Second thought was: graver. That could be even interesting effect, but owner of the company, that was supposed to ddo it for me, proposed me screen painting by his friend. For cost of about 100zł I got perfectly printed overlay.

But befor that I had to prepare surface, because I wanted to have effect of scratched aluminium. For this purpose I use belt sender. Top cover I painted on black, because I really like this combination of colorus.

On the end volume knob has left. Previous owner made ugly hole in it. I thought it will be nice looking if I put a small diode inside. I will know from a distance what is volume level. Rest of hole is filled with epoxy resin. I knew that from the begining that it will shine with orange or yellow light.

Final efect:

Files to download:

- schematic : schemat_PW8010.zip

- panel graphic: panel_pw8010.zip

Piotrek 2022-09-18
Mnóstwo starannej pracy - szanuje:) ale czy było warto? Porównaj kiedyś brzmienie z praktycznie jakimkolwiek Japończykiem z tamtych lat który w cenie poniesionych na unitre kosztów (serio) wciągnie go nosem. Chcąc zachować wyglad chyba wolałbym przerobić elektronikę stawiając na jakość.
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PW8010, Unitra

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