French radio problem

[humphrey]

I have a Integra 60 for which I have been unable to find a schematic. Valves are AZ1, EL3, EF9, EBF2, EK3.
I can only get faint sound but when I touch the top cap of EBF2,(g1) it gets loud. MW and LW are ok but not SW. I took the cover off the coil covers and checked them for continuity. All the caps are new and the resistors are all good. Any ideas? I expect I made a mistake somewhere.

[maitiustandun]

hi humphrey, i dont know the set in question, but an aerosol containing switch gear oil , sprayed into the valve base connections , and the valve pins cleaned as well, also check the solder joints at base as well , for dry joints , regards maitiu.

[Herald1360]

Is the EBF2 acting as detector and first AF or is the pentode section used as something else (2nd IF or RF amp)?

If it's the AF amp, maybe the biassing is wrong and touching the grid restores a high resistance to chassis.

If it's an IF, maybe something wrong with AGC, or oscillation?

If it's RF, possibly trouble with the front end tuning or oscillation. Touching grid will just damp oscillation / introduce wideband signals tunable with the mixer/LO tuned circuits- resultant second channel problems would not be immediately obvious.

[geofy]

Originally Posted by humphrey

I have a Integra 60 for which I have been unable to find a schematic. Valves are AZ1, EL3, EF9, EBF2, EK3.
I can only get faint sound but when I touch the top cap of EBF2,(g1) it gets loud. MW and LW are ok but not SW. I took the cover off the coil covers and checked them for continuity. All the caps are new and the resistors are all good. Any ideas? I expect I made a mistake somewhere.

Did the radio work before the mods, did you draw the circuit before fitting new components, are the components the correct values.
The valve line up is the same as some Philips sets. Whatever you do, DO NOT make any adjustments to the coils. If you have some sound getting though it could be that you have wired a component wrongly somewhere, recheck your work.

Geof

[humphrey]

So far I have only found one set with the same valves. An ORA 69 (1938) which is not quite the same.

[georgesgiralt]

hi Humphrey,
Have a look here :
http://www.grandlivre.doctsf.com/fic...q=466433&idx=1
could it be that a modification had been made ?

[humphrey]

The EBF2 grid (top cap) runs to a coil in a can which goes

EBF2 grid---\--------coil------/-----r500k-------> to EBF2 pin5 (D2)
\ /
\--8pf--------/----0.05uf cap to earth

I disconnected the 0.05uf cap from earth and it worked with no cap so I changed it to 0.02uf which might have been nearer the original but it made no difference.

[Herald1360]

That sounds like the EBF2 might be IF amp. D2 acting as AGC detector with the 500K and 0.05u removing the audio from the recovered DC. Not clear why it would work without a capacitor and not with, though.

Is the 500K actually 500K?

Any chance of a circuit sketch showing all of the EBF2 and surrounding components?

[humphrey]

Its actually 540k but marked 500k (It's in the can)

[geofy]

The 8pf capacitor is the agc feed to the agc diode, this value would stop audio getting through but there should not be a 0.05 uf connected to this, it would charge up and stop the agc from working at a guess.

Geof

[humphrey]

Does this help?
http://i208.photobucket.com/albums/b...circuit002.jpg

[geofy]

It would be better if you could send pictures as jpeg thumbnails.

The 8pf is not the agc coupler, it is just the tuning cap across the secondary of the IF

the 20pf on pins 5, 6 of EBF2 could be the agc coupler.

The 0.05 is killing the IF as far as I can see so should be removed.

Geof

[humphrey]

It only works when it is disconnected, but there was one there before I started changing them. Strange. It was marked 50,000cm and went from the tag to earth. It cuts out when connected. Is it possible that a later valve was introduced? I still dont know what the original lineup was.

[geofy]

If you have the original piece try putting that back to see what happens, I don't know what the markings are. The set was probably designed just for use with this valve.

Some pictures (jpeg thumbnails, not bitmaps) would be helpful.

Geof

[humphrey]

This is the link http://i208.photobucket.com/albums/b...tegra60024.jpg

You can see the base or the coil unit to the right of the central earth bus. The two 500,000cm caps are to the right at the bottom.
I have seen other EBF2 circuits where the ends or the coil and 8pf are actually earthed.
I could try to do a circuit diagram, but it will take time.

[humphrey]

Here is a diagram that took a long time to do as I am afraid that Summer jobs took precedence.
I hope it is of some use. The disconnected cap is marked with an X.
If you have time to spare a redraw would be appreciated.
http://i208.photobucket.com/albums/b...circuit018.jpg
or...

[Herald1360]

Hmmmmmmm.....

there's rather a lot of that circuit which doesn't make sense- g1 and g2 on the EL3 seem to be reversed; is there really a variable resistor in the cathode circuit of the EF9?

Tracing spaghetti is difficult, isn't it?

Probably between us it will eventually make sense

[humphrey]

Perhaps I had better come back to it when I have more time. Looking again, I can't see a cathode to a vr either.

[humphrey]

Here are five pictures of underneath.
http://s208.photobucket.com/albums/b...2060%20layout/

[Herald1360]

Aaargh!

That's enough to make you go seriouslycrosseyed. At least there's room to work in!