Hey there Alwyn.....Sad to hear about the problem with your 2.4 conversion....Three Gens HL has provided to date....and really ...though I might be a tad bias ...they are getting better and better
If the one you installed was the first gen....the manual volume was actually not all that good...at it's loudest setting it was still quite soft ....HL improved that with the 2nd and 3rd remote controlled units ....not sure what they did ...but the amplification is quite good I would go as far to say it's about 3 times louder than any of the earlier "manual" adjusted units
Now...with that said....you might want to contact a couple of members who have just finished working on their M1s.....as a couple of them have changed out the internals
Good Luck with your quest
ALPHA