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Discussion in 'Amateur Radio Modifications' started by 743SEPA, Nov 22, 2018.
Is it necessary to have a radio aligned or checked after replacing finals or installing a max mod?
Depends on radio. in SSB rig bias need to be checked/adjusted.
For maxmod, nope.
When a final transistor fails, it tends to short internally. Frequently this causes the 12-Volt DC power on the final transistor's output collector to come shooting out the base terminal, the input side.
Sometimes parts in the final's input circuit will be damaged. Might only be a 10-ohm resistor that gets scorched, like in a Cobra 29LTD. Or if it's a sideband radio the bias diode, bias trimpot and a resistor or two will all get blown out.
In some radios, like those made by RCI the modulator transistor can get popped as well. The Max-Mod may require a notch to be ground off the lower-left corner of the Max-Mod's plastic package to clear the anchor lug to the rear from it.
The new final won't work properly until all collateral damage is repaired as well.
Just replacing the final alone might fix a problem. But only if the final transistor is the only component that got damaged.
What kind of radio is this? Makes a big difference.
Installing a MaxMod should not affect any adjustments, if the radio was working normally before the swap.
But a side note here and not to hi-jack, the Max-Mod won’t work in a 497HPC. Been there and done that, not as a drop-in replacement. Myself and Key CB shop know this first hand.
Otherwise, I agree 110% with Nomad. Check supporting components.
So far I have done the max mod in a 2970 and an AT5555. Easy replacement.