A few obvious questions about Mullard 3 3 building.

[Diabolical Artificer]

As you already have an EZ80, you may as well stick with valve rectification. Using a bridge rectifier will make your project a 2- 3, not a 3-3. Then why not get rid of the EF86 and use a transistor instead? Joking of course.

The point I'm trying to make is that as the 3-3 is pretty perfect as is, why muck about with it? Silicon rectification also has its place of course.

You can use a bridge rectifier in one package where you connect your AC from your mains transformer to the wavy line symbols (AC), your HT from the + symbol ground to - on the package. Easy.

Or you can use 1N1007 diodes connected in a bridge configuration or other. I suggest you look up rectification. Valve Wizard is a good site to check out for this and other subjects.

Andy.

[mushibu10]

Oh, Well I went with the one stated in the r-type article.

So I went in search on adding a fuse to a radiogram I found, but I soon found out that instead of a fuse it uses lamps - by what I have learnt on heating/powering valves I assume the lamps are also 6.3V. Could I power the bulbs using a 9v battery with a resistor to lower the voltage? If so would a resistor of 27ohms be right?

I have the "Electronics for Dummie"s book, where I got the ohms law equation (rather annoying I hate maths but it was simple).
So while searching I came across this site

[GrimJosef]

Originally Posted by mushibu10

... instead of a fuse it uses Lamps. - Now by what i have learnt on heating/powering valves I assume the lamps are also 6.3V...

They might be, but they might not. Look closely at the metal part and you may well see the bulb's voltage and current stamped in small letters there.

... could I power the bulbs with a 9v battery with a resistor to lower the voltage? ...

Well you could, but if they're 6.3V bulbs wouldn't it be easier to use the 6.3V supply that's already powering the valves' heaters ? Or do you suspect that the gram has a series heater chain ?

... if so would a resistor of 27ohms be right? I have the electronics for dummies book, where i got the ohms law equation, (rather annoying I hate math! haha but it was simple) ...

It doesn't sound right. Do you want to 'show your working' as they used to say in school (at least in my school) ? Then we can see how you arrived at this number.

Cheers,

GJ

[mushibu10]

The bulbs are in series I think. See image.

I was just going to see if it would work.

[GrimJosef]

Nope, that's 'parallel' not 'series'.

In what sense are those lamps "instead of a fuse" ?

Cheers,

GJ

[mushibu10]

Dial Lamps in AC/DC Sets

Dial lights are sometimes connected into the heater chain. There may be a thermistor or resistor in parallel with them, to enable the set to keep working if one of the lamps fail. The dial lamps may alternatively be in series with the supply to the whole set (as in this case), probably shunted by a resistor or thermistor for the same purpose.

Thermistor failure is not common, but it can be a problem when it does occur. The service sheets usually give no information about the cold and hot resistance. You may be able to extract a similar thermistor from a scrap set or obtain one from a dealer. Otherwise, you will probably have to replace it with a resistor or omit it altogether depending on how it is used.

The dial lamps will probably not be running at maximum brightness when the set is warmed up and working normally, although they will (generally) be bright enough to illuminate the tuning scale. This increases the life of the bulbs, which is useful since the set will often not work at all if one of the bulbs has blown. During the initial warming up process the lamps will vary in brightness, and may be very dim or very bright depending on the circuit arrangement.

and this

Occasionally a small mains bulb is used as a dial lamp. This will normally be a 15W pigmy bulb with a BC or SBC base. In some cases, there will be a resistor in series with the lamp to reduce its brightness and extend its life, and this resistor often fails too! In the Bush DAC70 and VHF90A sets the heat from this lamp is sufficient to melt the plastic tuning dial surround. It would be advisable to increase the series resistor to decrease the heat and brightness, thus reducing the risk of further damage. My VHF90A has previously been fitted with a large 1K resistor for this purpose, and the plastic is in good order as a result.

SO I was mis interpreting it? (taken from http://vintage-radio.com/repair-rest...ly-stages.html

[GrimJosef]

The first quote is headed Dial Lamps in AC/DC sets.

The circuit you showed in post #24 has a mains transformer in it, which means it is not an AC/DC set. So none of the stuff in the first quote applies.

I'm still not sure where you've got the idea that the lamps are "instead of a fuse" from. Neither of your bits of text mentions lamps as fuses. They sometimes are used as fuses. But only sometimes.

Cheers,

GJ

[mushibu10]

so i have mis-understood the concept,

[Station X]

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