Old tube radios
17.01.2008 20:59
Some time ago I was writing about two big wooden boxes full of vacuum tubes. It turned out they were old radios that were brought by my dad's colleague to be repaired.
The first one was RIZ 634 UKV, the last radio made by Radioindustrija Zagreb that used tubes (designed in 1963 according to one source).
This one was pretty easy to fix. The schematic is actually available on the internet, but we didn't need it much. The radio required new electrolytic capacitors for the rectifier and some tuning of the RF circuitry (since someone obviously tried to fix the radio before us by turning all those little trimmer capacitors and coils because all seals on them were broken).
My dad wanted to preserve the authentic look of the circuitry, so he hid modern capacitors in the emptied case of the original capacitor.
The other radio is more of a mystery. It's obviously a lot older than RIZ 436. It only has a long and middle wave receiver and my dad puts its design around 1935 - 1940. A sticker on the back says "Philips AL 394 HU" while all text in the front is in Spanish, so I'm curious how it ended here. I couldn't find any info about it on the internet, so if you know anything about it, I would happy if you dropped me a mail.
Most of the passive components (capacitors and resistors) were heavily damaged because of age and we decided that it would ruin the historical value if we attempted to replace them with modern equivalents. So we basically just cleaned up the interior and took a few pictures.
Here's a nice example of simple instructions that anyone could follow. This is a picture of the back plate with pictograms showing what to plug into various connectors on that side. It seems that you should connect one wire to the water pipe (ground) and another to your clothes line (antenna).
If you're wondering, two connections on the right are for the gramophone and external speakers.
