312
Item nr.


Tesla 420U Mini Radio

Banska Bystrica Souvenir


Data for Tesla 420U
ProductionCzechoslovakia, 1957.
BandsDlouhe Vlny (750-2060m), Stredny Vlny (185-590m), Kratke Vlny (16.6-52.6m).
Tubes12H31, 12F31, 12BC32, 35L31, 35Y31.
CabinetBakelite. Size 32x22x19cm. Weight 4.3kg.
PowerACDC, 120V@230mA or 220V@270mA.
DocumentsService Docs.

The Design

A standard radio in most respect. In the early fifties, Tesla mainly produced the little Talisman, versions 306U, 307U, and 308U, as cheap ACDC sets. But in the late fifties, they introduced a few more models.

What distinguishes this radio from the dozen of almost similar models is the use of tubes with 150mA heater current, like is usual in the US. Another surprising feature is the placement of the tuning capacitor with its axis vertical. I have seen this in no other set; for the user, this is unnoticeable.


Obtained11/2008 from Antik Bazar, Banska Bystrica.
Condition8.
DisposedSold 6/2018.
Sound samplePLAY SOUND   The radio is from Slovakia and I completed its revision just before Chrismas 2008, so you hear Vianocna Hviezda.

This Object

I bought this radio as a souvenir to my trip to Banska Bystrica, and selected a radio with this station on the dial. The evening of purchase I tried the radio in my hotel room and it produced some stations, so I didn't expect much problems with the repair. I replaced the paper capacitors. After putting the set together again, I found out that it is not a good idea to have a metal dial pointer running close to a dial lamp that carries mains voltage relative to the chassis.

When tuning I found out that the pointer had to take a hump every time it passed the dial light, then I saw a bright flash inside the radio, heard a loud bang, and everything became silent and dark (including my workshop lights). The photo shows the dial light after eating 230V at a current high enough to activate my 16A circuit breakers.

Of the 23 stations on the dial, I visited 17 places (as per 2011).

In 2015 a cake was made to celebrate the birthday of a fellow collector. The baker asked my assistence.


Part of Gerard's Radio Corner.
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