Hi, I have recently bought a Heathkit AD1013 audio-scope from ebay (for £260). I have been waiting for one of these to come up for years and pounced on it. I am going to use it with my sansui QRX-6001 that I bought on a recommendation from mr. Quadrasaurus. The trouble is the display seem quite dim to me. At first I assumed it was just that it needed re-capping, especially as the waveforms wobbled about a bit but I have just finished replacing all the electrolytics and it is still the same. Does anyone have any ideas? I have a circuit diagram which doesn't show any adjustable pre-sets. Do old tubes just decay?