Unknown Grundig valve portable

[Mikwat]

Hi Folks,
I have a 1950s Grunfig valve batery/Mains portbale that I cannot find information for ...
I think the model number may be 1056 (see photos) but I can find no mention of it !
It is a MW/SW set with the usual sort of Mullard valve line-up DK96,DF96,DAF96,DL96
I like restoring valve portables as they are usually nice and clean inside with less heat damage!
Any help with this one would be appreciated !
Thanks
Mike

[Terry]

Welcome to Golborne!

I wouldn't worry too much at this stage.

There were many sets using this valve line up and most used virtually identical circuitry (although I wouldn't trust Grundig not to do some things differently!)

The main differences were between battery only sets with 1.5V cells supplying parallel filaments and mains/battery sets which usually arranged the filaments in series, fed by a 7.5V battery.

So, if you can find any 4-valve set using the '96 valve range, it will be a useful guide to start with.

Obviously, if you can find the original circuit, that will be a bonus.

[Crackle]

Looks like this one. http://www.radiomuseum.org/r/grundig_mic..._e_kl.html
Mike

[Terry]

The main differences were between battery only sets with 1.5V cells supplying parallel filaments and mains/battery sets which usually arranged the filaments in series, fed by a 7.5V battery.

Well, I did  say usually!

Looking at the diagram in the link that Mike posted, Grundig opted for the parallel filament 1.5V* arrangement in this set.

* Not quite true as, although this is the marked voltage on the cells as sold, this (and slightly higher levels) are only produced for a short time, the output then settling down to around the 1.4V mark for the majority of their life. Thus the valve data always specifies a filament voltage of 1.4V.

It is normal to run these valves at a slightly lower voltage - the Grundig figure is 1.35V - which helps to prolong valve life as they have to function at voltages even lower than this as the cell voltage drops even lower towards the end of their life.

[Mikwat]

Thanks folks as it happens, I already had the schematic for that one
see below if anyone wants a copy ... now back to the man cave :-)


http://thecodemachine.co.uk/Grundig_Radi....Radio.pdf

Mike

[Crackle]

Have I missed something, I cant work out how the HT from the mains transformer gets to the radio circuit.
All the HT seems to connect to is the screen of the DF96 !
I wonder if there is a line or a joining Dot missing somewhere.


Mike

[Mikwat]

Perhaps it is not very obvious but there is a conection from the line going to DL96 screen to HT+ which is unusually drawn at the bottom of the circuit rather than top,
see the junction of C23 and the output transformer primary. Of course the AC PSU circuit is missing but that is straight forward and was perhaps optional !
This may be the confusioin, the mains transformer is not drawn, the tranformer on the circuit is the speaker output transformer.
Mike

[Terry]

Definitely a missing dot, Mike!

The main HT rail runs immediately below the earth, i.e.: from the positive side of the 16uF cap on the right hand side. The dot should be where the feed crosses this rail.

Don't you hate it when the HT rail isn't shown at the top?

[ppppenguin]

Our low voltage cousins across The Pond often have the HT (B+) at the bottom.

[Crackle]

Yes, I dont like this style of schematic.
I have edited the one on RMorg and re-uploaded it, so it now shows the positive line from the rectifier joining the HT rail.

Mike