Sporting set of WS315 and MDS415

I'm sitting in my office and suddenly phone is ringing. 10 minutes later, he comes to the clinic. Holding sport's bag in his hands, he is comming closer. In very weak street light I'm getting this patient directly into my hands. I can hear silent ask: "Can you take a look on it? Maybe there is still some hope". Whithout waiting any minute longer, I'm taking this patient upstairs. I must confess, it weights. I'm putting this bag on my desk and opening. At the very first glance it doesn't look that bad, but after more detailed it is turning out that it lost its voice and willing to live. This is how we got DIORA's devices.


Power amplifier

As a first on our table landed power amplifier WS315. Its dimensions reminds a bit PW8010 but electronic construction is completely different. Extremaly cleverly they figured out how to put heatsinks inside, which in clasical way of montage would take two times more space. Also putting PCBs vertically allowed to achieve very copact device.

General viewHeatsinks

In this case, main problem were borken transistors in power end. We could finish after replacing demaged parts, but after measurements it turne out, that constans voltage on output has not been as close to zero as should, so we have replaced original transistors from differential pair with more modern and also have adjust bias current. To avoid getting complains from family on some dissfunctions, we have checked all electrolitic capacitors and those bad were also replaced.

Corrected PCBs 1-after 2-beforePre-amplifierOld and new transistorsAfter monage

Switchesz during cleaningmeasuring main capacitor 2x4700uFCleaning pcbCleaning potentiometer

Of course, device is not only electronic, but also mechanic part. In front panel, there is a silver plactic under volume control knob. Here it was kept by black tape. We have reap this out and put a dose of glue similar to original. After a years of using this equipment has a right to be dirty, so cleaning up was very necessery thing to fully recover.

Tape recorder

As a part of this set, there was also the MDS415 tape recorder.


Here, the main problem was in rubber belts passing the drive strength. As one can see on picture, one of them has stucked to wheel's surface. These leftovers had to vanish before mounting new one. After further investigation, it turned out, that second belt is not original. It has been replaced with shorten one and hadn't drive mechanical counter. New one was long enough to make it possible.

New belts

Patient's family raised also a problem with quality of produced sound. This kind of effect is mostly caused by skewed reading head or inappropriate tape pressing force. Using service tape, we have fixed these interal problems and MDS415 has spoken with normal voice again. Of course, cleaning was mandatory to get shining look.

Service casetteSignal in left and right channelCoroded fuseCorroded fuse


During surgery we have found small piece of paper with date of manufacturing this device. This was like some kind of "time box". 1987 makes impression. It was nice to take a part in extending its life time. I'm afraid not many modern devices will last so long. Bravo for those models

Message from the past


Schematic WS315Schemat mds415

Download schematcis.zip

Pictures of mounting details:

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