Mike Bryce
prosolar@sssnet.com
> On Nov 10, 2016, at 6:29 PM, rick@dj0ip.de <Rick@DJ0IP.de> wrote:
>
> If not the tubes, then it sounds like the something in the tank circuit is
> wrong.
> When you build an amp from scratch and are searching for the best place for
> the band taps, as you move from turn to turn and then around the coil to find
> the best spot, you see the same scenario you are describing.
>
> It sounds like it is failing to find a resonance.
> Are you dipping the plate current as you tune or are you just tuning for
> maximum output power?
dip the plate and then load for max power. Always trying to keep current around
500/550 ma. On the higher bands, current exceeds 600+ ma.
> I don't have the circuit in front of me and it's way too late at night to
> pull it out and look, but perhaps there are some fixed caps normally switched
> by band and one has blown, or the switch is burned or has a bad or no solder.
There is a small pcb that holds come capacitors that are switched in depending
on band. I will take a complete teardown to get at them.
>
> Also, have you checked the signal level into the tube itself, after passing
> through the input filter?
> If something is bad in there, that would cause this.
seems okay
Mike, WB8VGE
>
> Just for a test you can completely bypass those switched filters, disconnect
> them and apply power to the finals just through a capacitor. This should
> give you similar output power on all bands. If not then the problem is
> probably not in the input filters, so you can reconnect them.
>
> At the end of the day, the only way to fix it is to get in there and fix it.
> You have to try things and eventually you will come across the significant
> clue that leads you to the source of the problem.
>
> Gud luk Mike.
>
> BTW, there is a phenomenon I have discovered... I am 10x better at fixing
> other people's radio than I am at fixing my own. I can only imagine that I am
> subconsciously too emotional, too worried, something, and my mind doesn’t
> think as freely as it does when working on other people's radio.
>
> 73 - Rick, DJ0IP
> (Nr. Frankfurt, Germany)
>
>
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