Imgur photo gallery: imgur.com/gallery/dKxPMXp
Got this radio off the internet as still functional but with some pretty damning defects, so... I took a chance on it.
The main thing that was wrong with it - the dial string was all out of place, snapped off... not broken, still whole but just off. This radio has a weird tuning arrangement - the dial string and pulleys are off, away from the tuning cap+variable resistor combo. The connection between them is made by some small plastic lever. One of the previous owners, probably trying to re-string this radio had lost that lever somewhere on the floor and then had no idea that the piece was even needed. It is however pointed out in the exploded parts view from the service manual. I have improvised some plastic part myself, but without the proper tools and dimensions... the result is that now the dial string and cap combo works but the needle moves around about three quarters of the whole scale coverage... eh, I don't mind it as long as all wavebands work.
This radio is designed by Philips, and it shows in all its documentation but practical realization is done in Japan. It is a Japanese product and it shows at the quickest look over its PCB - components look like they've been thrown from a plane all over the place, wires look like a spaghetti mess and the big electrolytic caps are glued in place (Japanese earthquake law of the 70s). it also had a bunch of Nichicon caps.
I did replace all of the electrolytic caps and increased the mains filtering.
The antenna was missing, Ive added one myself, looks pretty okay.
Otherwise the radio looks pretty well kept, aesthetically, there are only a few scratches here and there, and the cover for the FM preset adjusting pots is missing.
Some peculiar things about this radio -
The AM is tuned classically, with a variable capacitor but the FM is Varicap Diode tuned. Hence, the radio has a voltage converter circuit - provides 12 V stabilized (up from the 9 V the batteries give) for the tuning. This voltage has to be very stable and temperature compensated, otherwise the FM stations will drift away. And it is, the stations are kept without a problem.
The FM has 4 presets, plus the fifth tuning position at the Variable capacitor (a variable resistor mounted on its axis). The presets work all the same, all the 5 tuner circuits are the same quality.
There are 5 capacitive touch buttons on top of the radio with which you can switch between the stations wit a feather light touch. It is a pleasure to do it... When the thing works. The radio uses a MC14174 IC for the switching and the lighting of the indicator LEDs but the problem is that the whole hing is a bit too sensitive to moisture in my opinion. I often have sweaty palms and that messes up the whole switching process... it sometimes refuses to switch between the presets or gets stuck on a particular one. Apparently the Philips engineers had sweaty palms too, because in later revisions of this model they have added additional IC just to deal with the whole switching errors ordeal.
The reception quality is very good, no problems encountered. This radio is no DX-er, but it ain't no slouch either.
The audio quality though is where it excels - it outputs 2 Watts (real watts) running on batteries and 3 watts from the mains. The audio IC is the classical, well known and well loved for the age - TBA 810S. The volume potentiometer has 2 loudness taps for the physiological volume correction. The radio has a 16.5 cm mid-woofer and a 5 cm tweeter. The highs and lows on it are just lovely, you an listen to it for a whole day without getting tired :)
The radio is powered by mains or 6 d cells. There's a tuning indicator LED, the ones for the presets and also one that shows the selected band. It has switchable dial lighting as well.
Overall, a really nice piece of Tech that I hope I'll be enjoying for many more years to come.
7 сен 2022
