MM144/200W linear - how to change drive power - UK Vintage Radio Repair and Restoration Discussion Forum

onewatt · 5th Feb 2018, 1:42 am

Hi all,
I have a microwave modules linear amp with no instructions! Ok, I don't normally read instructions unless desperate anyway but here's the query.
It can be driven by 3, 10 or 25 watts.
At the moment it is set to 10 watts drive. I've seen a brochure that states it's a manual selection of input power, and I can see a blind grommet on the underside and when removed it looks like a VR, but it could be a switch, can anyone recall if this is the drive adjustment before I trash it please and throw it out of alignment!
ATB
Chris

Terry_VK5TM · 5th Feb 2018, 6:16 am

Don't twiddle the pot - it's likely to be the bias adjustment (turned the wrong way will junk the unit).

Can't find a user manual, but schematic attached.

onewatt · 5th Feb 2018, 7:09 am

Thank you for info Terry, much appreciated!
Looks like I need to open it up.
Vy 73
Chris
G1rpo

5th Feb 2018, 1:42 am	#1
onewatt Hexode Join Date: Jun 2005 Location: Buntingford, Hertfordshire, UK. Posts: 362	MM144/200W linear - how to change drive power Hi all, I have a microwave modules linear amp with no instructions! Ok, I don't normally read instructions unless desperate anyway but here's the query. It can be driven by 3, 10 or 25 watts. At the moment it is set to 10 watts drive. I've seen a brochure that states it's a manual selection of input power, and I can see a blind grommet on the underside and when removed it looks like a VR, but it could be a switch, can anyone recall if this is the drive adjustment before I trash it please and throw it out of alignment! ATB Chris __________________ BVWS, VMARS, RSGB, DEHS, RAOTA Nothings too big or too heavy, otherwise it wouldn't be where it is!

5th Feb 2018, 7:09 am	#3
onewatt Hexode Join Date: Jun 2005 Location: Buntingford, Hertfordshire, UK. Posts: 362	Re: MM144/200W linear - how to change drive power Thank you for info Terry, much appreciated! Looks like I need to open it up. Vy 73 Chris G1rpo __________________ BVWS, VMARS, RSGB, DEHS, RAOTA Nothings too big or too heavy, otherwise it wouldn't be where it is!