blown delta force

alexthegasman · Post by **alexthegasman** » Tuesday 30th Dec 2008, 11:17

hi all, happy new year to everyone.

I've been asked to look at a magnum delta force that apparently has had the centre pin on the mike plug shorted out (dodgy mic soldering by the sound of it!!), A couple of wires inside the plug were touching, including the centre one, and now he tells me that radio will not even turn on (completly dead). my question is, is it worth having a look at or will the damage be too great or un-economical to repair? has anyone seen this problem before? any help would be gratefully received. cheers.

zodiac · Post by **zodiac** » Saturday 3rd Jan 2009, 12:23

Alex,
Check L123 4.7uH coil at the front corner of the board, you should have 13v both sides of it.
Dave.

alexthegasman · Post by **alexthegasman** » Sunday 4th Jan 2009, 8:04

thanks zodiac, that part checks out ok. closer inspection revealed a burnt out track between q153 and the audio i.c. Will post exact position soon. Once repaired it fired up beautifully. No other apparent damage!!! Other problem is low output power, less than 1 watt on my dummy load, but have been told this was already a problem, r383,376 (22ohm?? schematic difficult to read!!) both burnt out, replaced with no effect. pre-driver removed and checked ok, two 1969's removed and checked, both u/s!!! b300p + high swr=burnt outputs!!! thanks all.

hotrod · Post by **hotrod** » Friday 30th Jan 2009, 4:50

i know this is oldjust curious if ya got it up and running

alexthegasman · Post by **alexthegasman** » Friday 30th Jan 2009, 8:39

sorry hotrod, forgot to update, yes, got it going. Only a blown track from the middle leg of the smaller transistor (q153) bolted to the side casing, just down from the audio i.c. No other faults found. Apart from 2 blown output trannys' 2sc1969 in this case, and replacing the above mentioned components, Radio is working perfectly.