30-08-2021, 02:36 PM
Brilliant work Trevor. I like your circuit. I do like your construction too. Good for stability.
With a recent circuit of mine I used Manhattan style too but with a slightly different slant. I have built a 1j37b mixer driving a 455kHz ceramic filter via a transistor. With this I had most of the 1j37b components on a copper board using surace mount components with all the tube base components connected into that. The copper board was connected by a short lead to the tube shield that I usually use. The only connection seperate from this was the anode connection which which was to a small piece of stripboard complete with anode tuning. The transistor / ceramic circuit was on stripboard, somewhat alongside but screened by the valve screen. I am working toward superhet ideas but not specifically pure rod pentode. I have tested this with just a 455kHz signal and through a 2 x 1j24b IF strip which I put together some time ago. The setup performed well with no sign of instability even though there was pretty high gain. It's early days though and somewhat experimental. The mixer circuit box is 3" x 2". I am hoping that the use of 'Manhattan Style' will much reduce the need for fully screened boxes but I have looked into solutions if required.
I do look on ebay from time to time for these 1J42A's but have yet to see any. It's perhaps a good thing though as I am pretty much fixed to 60V for a supply, generally varying this between 24V and 75V for testing. My preference is to avoid falling into the 12V and lower HT as, apart from some of these somewhat special valves, traditional types are getting to require somewhat specialist techniques to operate well whereas, at the voltages I use I can reasonably intermix transistors and valves well although battery power is not really sensible in the normal sense (without invertors etc).
With a recent circuit of mine I used Manhattan style too but with a slightly different slant. I have built a 1j37b mixer driving a 455kHz ceramic filter via a transistor. With this I had most of the 1j37b components on a copper board using surace mount components with all the tube base components connected into that. The copper board was connected by a short lead to the tube shield that I usually use. The only connection seperate from this was the anode connection which which was to a small piece of stripboard complete with anode tuning. The transistor / ceramic circuit was on stripboard, somewhat alongside but screened by the valve screen. I am working toward superhet ideas but not specifically pure rod pentode. I have tested this with just a 455kHz signal and through a 2 x 1j24b IF strip which I put together some time ago. The setup performed well with no sign of instability even though there was pretty high gain. It's early days though and somewhat experimental. The mixer circuit box is 3" x 2". I am hoping that the use of 'Manhattan Style' will much reduce the need for fully screened boxes but I have looked into solutions if required.
I do look on ebay from time to time for these 1J42A's but have yet to see any. It's perhaps a good thing though as I am pretty much fixed to 60V for a supply, generally varying this between 24V and 75V for testing. My preference is to avoid falling into the 12V and lower HT as, apart from some of these somewhat special valves, traditional types are getting to require somewhat specialist techniques to operate well whereas, at the voltages I use I can reasonably intermix transistors and valves well although battery power is not really sensible in the normal sense (without invertors etc).
