brownlee: Restoration

The circuit isn't complicated and as stated in the notes, is a variation of the UK Pilot Blue Peter, but location of smoothing capacitors swapped with audio transformer and valve bases changed from Octal / Loctal to similar B7G and B9A types. One band less. The fourth RF trimmer position is used for IF trap.

Removal:

Set set on back on sponges or cushion with rear panel off. Unplug speaker. Pull off knobs. Remove four screws at base.

If removing the baffle board for woodworm treatment: Unscrew speaker. One baffle board screw is under it.

Alignment:

Front  <-------------------> Rear

Top view.

|
|
| Local Oscillator HF end trim
| ...(LW)
| ...(MW)
| ...(SW)
|
|
| Main Tuning unit
|
| (LW) (MW) (IF trap) (SW)
|___________________

I used a switchable MW/LW Loop aerial  with screen wire connected to 10m wire for Shortwave. Only connect signal generator by loose coupling of a separate loop on its output (I use about 10 turns 15cm diameter).

There is a 32uF + 32uF 350V capacitor for main HT and a 25uF 25V capacitor on 6BW6 output cathode resistor. These were checked using 32V current limited PSU and didn't even need reformed.

There were the following SIX paper dielectric types in waxed card tubes, all very leaky:

3 x 0.1uF (100nF 300V)  (One is AGC, so actually a 50V ceramic part is fine, it's obvious by being on first IFT and resistors going to second IF (detector) and feeding Magic Eye.

1 x 0.001uF (1nF 250V), purpose unknown but goes from valve base to wavechange.

1 x 0.002uF (2.2nF 1kV XY Ceramic) 800V, probably on 6BW6 anode / audio transformer primary, so called "tone correction" (Snubber). A 250V part here will die as peak is HT plus peak to peak audio transient, potentially!

1 x 0.025uF (27nF 400V), near 6AT6 and 6BW6.

EDIT: Figures in brackets are replacements used. Replacements all plasitc film / met poly types except for 2.2nF.

The rest of the capacitors are mica or ceramic and unlikely to be a problem. Don't worry about resistors maybe 20% to 30% out. However the 6U6G 470K load resistor was close to 2M Ohms. This was repllaced with two series resistors to have adequate voltage rating. I've found that the 470K are the least reliable composite resistors.

The Russian Magic eye 6e5s is availble NOS easily rather than rarer x5 price Octal 6U5G on eBay. Do not buy "used" as life is short on Magic eyes. The target phosphor is the issue. It needs a small wiring change or an Octal to Octal adaptor if you want to keep radio original (6e5s is pin 6 target and 6U5G is pin 4 Target). Note that the 1M resistor on the 6U5G base is using a "no connection" pin (used as Target on 6e5s!) and is actually in series with grid!

The second scale lamp is almost hidden under the magic eye.

Grease the drive cord, top edge and drive shaft with petrolium jelly. The fullly meshed position is marked on the glass scale.

Avoid touching IF cores unless they have been "got at". They are double tuned, so 2nd core is accessible only under chassis when chassis out of case.

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