06-10-2017, 07:26 PM
A good idea with PP3's as it would likely be easier than the 'lash up' I often have at present. It would be an idea to wire them together in a box with just 2 leads. I do have several 12V 'gel' batteries so could use those, although would need fusing because of potential current flow if shorted. I can see the possibility of HT on the heaters so I will give it some thought (bearing in mind that the diodes would effectively short HT) The convertors are cheap so not too big an issue, but fused gel batteries would sort both issues.. The past few day's experiments have given me food for thought anyway, and as I have learned quite a bit in the time I have been using these valves I may change my approach (at least try).
The blown module problem came along after I decided to tidy things up and mount the anode tuned circuit on my module board. At that point things were much tidier but the oscillator failed to work. Any subsequent lash up of wiring brought it back into life (sporadically). After twenty minutes or so of tinkering, the one thought that came to me was that I had no shielding on the valve, and I new from previous things I had read that lack of shielding invited problems (Joe Sousa and Mike). Yesterday I bought some tinplate and today made a shield. My oscillator module is now outputting stabily on the 7th Harmonic. I have since checked and the nearest station of any note seems to be a Spanish one around 5kHz higher.
I have made rough checks for a buffer amplifier, but found similar stability issues with the amplifiers (funnily less so with the oscillator in it's initial state), so now plan to fit shielding to all valves and fully fit tuned circuits before testing, hence hopefully getting more reliable results. With far less croc leads the prospect of a wrong connection should be far less likely. I will do this to them all over the next few days so they are more ready for tests.
See attached photo of oscillator board. The metal screen is close, but I have fitted internal rubber strips, the intention of which to dampen any mechanical vibration of the screen which may cause unwanted modulation of signals.
The blown module problem came along after I decided to tidy things up and mount the anode tuned circuit on my module board. At that point things were much tidier but the oscillator failed to work. Any subsequent lash up of wiring brought it back into life (sporadically). After twenty minutes or so of tinkering, the one thought that came to me was that I had no shielding on the valve, and I new from previous things I had read that lack of shielding invited problems (Joe Sousa and Mike). Yesterday I bought some tinplate and today made a shield. My oscillator module is now outputting stabily on the 7th Harmonic. I have since checked and the nearest station of any note seems to be a Spanish one around 5kHz higher.
I have made rough checks for a buffer amplifier, but found similar stability issues with the amplifiers (funnily less so with the oscillator in it's initial state), so now plan to fit shielding to all valves and fully fit tuned circuits before testing, hence hopefully getting more reliable results. With far less croc leads the prospect of a wrong connection should be far less likely. I will do this to them all over the next few days so they are more ready for tests.
See attached photo of oscillator board. The metal screen is close, but I have fitted internal rubber strips, the intention of which to dampen any mechanical vibration of the screen which may cause unwanted modulation of signals.
