[Chris Cusick]

Hi - I'm enjoying my recapped Philco 610, which works pretty well even though the antenna arrangement is less than ideal - but I noticed that the volume level is normally pretty low (you need to turn the volume knob a long way although it is progressive in its increase) . The other day, the volume suddenly increased massively, requiring me to dash across the room, scattering barking dogs and crying children in my wake, to turn it down again. It later dropped right back again. The effect is sudden not gradual.

Poking around, I noticed I can sometimes create the same effect by tapping the top of the 75 tube (second detector). This tube tests rather weak - I would usually have said it would be alright. Does anyone have any experience of this phenomenon, or ideas for what I should check for ?

Its not a big deal really - but has me puzzled.

[TA Forbes]

Is the grid cap on the tube loose? I am talking about the silver cap that should be premanently affixed to the top of the tube, not the wire connector end. If yes, that could be the issue.
Try replacing the 75 with a strong tube and go from there. The 75 is the first audio/2d detector tube, and the volume control feeds the grid of the 75 through a .01mFd cap.

[Arran]

Is the grid cap on the tube loose? I am talking about the silver cap that should be premanently affixed to the top of the tube, not the wire connector end. If yes, that could be the issue.
Try replacing the 75 with a strong tube and go from there. The 75 is the first audio/2d detector tube, and the volume control feeds the grid of the 75 through a .01mFd cap.

It could also be a flakey solder joint on the lead near the clip, or the wire breaking internally near the clip, those are pretty common problems around a grid cap along with the cap itself.
Regards
Arran

[Chris Cusick]

Thanks for the ideas - I'll check all these points - I just want it to work as good as it can !