Item nr.

Philips B2X12A/79K Mini Radio

FM Mini in useable or donor condition

Data for Philips B2X12A/79K
ProductionBenelux, 1961.
BandsLW (1050-2000m), MW (186-580m), FM (3-3,43m); IF is 452kHz, 10.7MHz. LW/MW are disabled.
TubesECC85, ECH81, EF89, UABC80, UL84, UY85; dial 8045D (6.3V/0.32A); fuses 500mA, 2000mA, 315mA, 63mA.
CabinetPlastic. Size 30x15.5x14cm.
PowerACDC 100/120/220V, 40W.
DocumentsService docs.

The Design

A nice little set from an era in which even small and cheap sets were expected to come with FM.

There are a few common problems with this type (and my set has them all). First, the plastic front parts (grill and knobs) tend to discolor badly. They also disappear and replacing the knobs with metal ones is very dangerous (picture) because the chassis is connected to mains! Second, the bandswitch breaks because of the fragile construction. Capacitors, tubes and resistors from the sixties often keep themselves remarkably well.

Obtained6/2017 from Techniekbeurs Hoenderloo; sn=WA13334.
Condition5 (plays FM a bit, but bad cabinet).
DisposedSold 6/2020.

This Object

When starting to work on a set like this, it is advisable to replace a few capacitors that can cause harm when leaking: the Boucherot C41, the coupler C39, the rattler C4. After replacing these (and a few more) and a check of the tubes (which all measured OK), the radio came to life and with an external MP3 player I found out that the LF amplifier and loudspeaker work fine.

No stations could be received, however, and I found out that the moving strip in the band switch was broken, something that easily happens considering how it is moved. Rather, given the construction of the switch, it is a miracle that any of these switches survived the first year of operation. It was suggested to me that a new slider could be made from epoxy print but I didn't follow this suggestion.

I tried to rewire the set as an FM only set by soldering those contacts which normally connect in FM position. Some debugging was still required because I found out that some of the switch contacts touch each other and cause shorts when the slider isn't there. With an external receiver tuned to 10.7MHz I could verify that the FM tuner works, that 10.7MHz signals are present at the grid of the two IF tubes (ECH81 and EF89) and at the detector (pin 2 of UABC80). But unfortunately, no FM sounds are heard from the speaker. This was probably caused by B+ leaking to the detector circuit (through band switch contacts). After opening the switch and placing some cardboard between the contacts, the set gave a clear sound on FM. She won't let you fool around with AC voltage, though: with a 40W series bulb is wont play at all and with a 75W bulb it works opoorly.

Meanwhile I also received a suggestion that discolored plastics can be refreshed using an agent called Cillit Bang Bleach. I worked Cillit on the grill but without any appreciable effect.

The radio now works on FM, but isn't a strong performer: there is a quite noticeable hum, and sensitivity is low (produces some stations on a wire antenna in my attic, but the antenna in my living is too weak for acceptable reception). Also given the deplorable looks and disfunction of the LW/MW, no one need to feel ashamed when using it as a parts set. The cabinet is intact, though with some paint chips. Back panel is there. PCB and loud speaker are there. Dial, FM unit, transformer, fuses, etc are there. Knops are there, though the volume knob is not original and the others are discolored.

Part of Gerard's Radio Corner.
Generated by SiteBuilder on 12/8/2021 by Gerard (g.tel@uu.nl)