521
Item nr.


Novak 491 Table top

What with the wood case?


Data for Novak 491
ProductionBelgium, 1960.
Price was BF1650.
BandsGO, PO, OC.
TubesUCH81, UBF80, UCL82, UY85.
CabinetWood. Size 30x21.5x15cm.
PowerACDC 110/220V (now 230VAC, 17W).
DocumentsSchema.

The Design

This Novak 491 is a bit unusual, because normally this model has a bakelite case. I first thought that the wood box was made by somebody at home, for example after breaking the cabinet, but the work is just a little too neat for that. On the other hand, it isn't completely professional, for example, the speaker hole was manually jigsawed in the front. So I assume somebody had a small business of upgrading bakelite radio's by producing wood cases for them. In the new cabinet, there was no longer room for the bandswitch knob, so you can's switch the wavelengths anymore. During the repair I found out that the Long Wave works well (two stations) and the Short Wave does nothing, but I didn't bother to repair this.

Obtained8/2020 from Storm via Marktplaats.
Condition7; good sound, nice wood.
DisposedSold 5/2021.

This Object

Repairing and revising the chassis of a small universal (AC/DC) radio isn't too hard. Usually, replacing a few capacitors will do the job, but here there was also serious heat damage to the PCB. This set had wood work that was damaged, there a realy big cuts in the veneer.

I learned that veneer damage can be repaired using a hot iron and damp cloth. You're supposed to iron your radio with the cloth in between, and this will bring back the wood in its original shape (also if there are bumps in it). Subsequently I applied some wood glue under the veneer. After the treatment, the wood didn't look like new, but a lot nicer already.

A small radio like this uses about 40 to 45W when playing on 230V AC. The increased line voltage (the radio was designed for 220V) makes the heaters warmer, which causes all tubes to run a higher current. Extra wear on the tubes is a result, but the effect on the PVB is even worse. The PCB becomes black by carbonization and starts conducting current between the various tracks on the board. A previous repair has scratched out some of the conducting material, but this was not enough. In low light, I could see the sparks jump on the board. So I removed some of the trails completely and connected the components by wire. Also, the PCB has some interruptions, due to mechanical instability.

To reduce heat, I replaced the ballast resistor by a capacitor following the Sanshin-schema. After this modification, the set can only be used on 230V AC, and uses only 17W (and, after power on, requires a minute to start playing, and several minutes to reach full sensitivity). I removed the (very dangerous) pickup connection; it was intended for a fully isolated pickup, and was connected to the mains directly. I replaced the dial light (6.3V @ 300mA) by a suitable light (24V @ 95mA).


Part of Gerard's Radio Corner.
Generated by SiteBuilder on 26/2/2024 by Gerard (g.tel@uu.nl)