Grampian 506

[Newgirl2013]

Well all the components have arrived this morning, just one more item to find

[PJL]

I have seen some AC/DC sets where metalwork is accessible but the -ve rail is separated from the chassis and coupled using a capacitor. Given that house mains sockets of that period were not polarised, you have to wonder if this was designed for an environment where the mains supply was already isolated.

I would strongly recommend you run this off an isolation transformer!

[ms660]

Reverse engineered attempt for the radio section, bits might be right, bits might be wrong...based on the photo's here:

https://www.vintage-radio.net/forum/...2&d=1277330178

https://www.vintage-radio.net/forum/...1&d=1277330178

In the schematic, note the capacitor with the question mark above it....In the photo's there's no actual component/connection between the output of the detector and the input to the tone/volume controls (it looks to have been removed) so I've shown a capacitor in the schematic to serve that purpose.

Lawrence.

[Newgirl2013]

Hi Laurence
Thanks for the diagrams
Shaz

[Newgirl2013]

Hi Laurence
About the missing capacitor you mention
Looking at circuits for other amplifiers I find the capacitors are usually .1mfds 350v
Shaz

[ms660]

In yours it appears to be a resistor, I drew a capacitor just to show that there is a connection between the detector and audio amp, in the photo's I was working from no component or connecting wire is shown and I concluded that whatever it was, was missing.

Lawrence.

[Newgirl2013]

Hi Laurence
Ah ho right
Shaz

[Newgirl2013]

Got stuck into the Grampian
Contrary to earlier belief the Neutral does not go to chassis it's connected to a tag stip and connected to the Mains transformer

[ms660]

That must mean that the Neutral of the outlet socket isn't connected to the chassis either?

Lawrence.

[Newgirl2013]

Hi Laurence
That's right it isn't
Sharon

[ms660]

Ok, panic over.

If you can work out what's what with the transformer and heater circuit I can amend the reverse engineered schematic I did.

Lawrence.

[Newgirl2013]

Hi Laurence
On disconnecting all the secondarys from the transformer and plugging in I have smoke from the transformer
It sounds very much like the Mains Transformer has popped its clogs
Going by your circuit diagrams it would appear that the Grampian has two heater chains
Sharon