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On 20200324 09:37:19, Martin - G8JNJ via Groups.Io wrote:
On Tue, Mar 24, 2020 at 10:19 AM, jdow wrote:
If somebody has managed to un-pot the circuit they might discover the pot is
an adjustment for operating current
It's not a bias current adjustment, the MLA-30 uses a video op-amp and the pot in the head unit is a gain (feedback) control.
Unfortunately the whole design is very flawed, and increasing the gain simply rolls off the performance at HF, as the gain bandwidth product is inadequate in this application.
An outline circuit can be found on this webpage (when it's working).