Another Dick Smith Q-1280 Oscilloscope. Need Help.

[Hammer_651]

 HI all. I would like to ask the forum if anyone knows about these dick smith oscilloscopes. Yes i have one and i really like it but, two things are different.

1) The POT-R215-5KB on the MPCB from the Horizontal Gain as shown in the schematic has been replaced with a POT on the front panel.
2) There is also a small PCB on the back inside of the panel top RHS above the transformer. This has Blk and Red banana plugs and a small POT connected to it. There is a small coaxial
     cable coming from it going   
     which is floating at the back of the horizontal gain pot previously mentioned. There no indication of this PCB or connections on the scopes schematic. I have no clue what this PCB cct
     does.
Can anyone help with this please?   
Thanks.
Hammer_651

[wilfred]

It looks like a DIY addition to me. I did find a picture of the rear panel of another example at this website. Scroll across to the third picture.

https://www.radiomuseum.org/r/dicksmithe_65mhz_single_channel_oscilloscope_q_1280.html

But as to what the modifications do I wouldn't even try to guess.

[Hammer_651]

 Thanks for your help.

[floobydust]

To me, that looks like someone was building-in a I-V curve tracer into the scope. Sort of a poor man's Huntron tracker.
But these require a dedicated say 6VAC power transformer. You can't use the one in the scope without trouble and this might be why it was abandoned 
Look up "octopus curve tracer" to see the circuit, it is very simple and needs the scope's H and V inputs.
edit: added a typical schematic. The pots might be another addition.