Yaesu FT-902DM "Restoration" Part Three

Hi,

So onto the second one the PB-1708A Rectifier A board.

Here it is ;

As you can see if you look carefully - overall not in bad condition but the two capacitor on the right look a slightly different colour and so that might indicate that they have a problem.

Either way they will get replaced with new quality 105deg electrolytics.

On the underside of the board (right) you will see the

 usual Yaesu soldering but look more closely. I've circled in red a 'blobby' or poor solder joint. Being entirely fair about it - it might have been due to heat but I think its been like this from the start 

So work starts - removed the four vertical electrolytics - again be careful they have the yaseu 'glue' to hold them still when the unit was subject to vibration when it was used mobile (!!!).

Here are the capacitors as removed, as you might be able to see the two on the left have a slight 'bulge' - they were the Atwo with the slightly different colour tops.

Below  is the ESR value for one of the axial capacitors removed from the board - as you can see not too bad with and ESR of 0.19 Ohms and 3473uF  but they will get changed anyway!

Here is the replacement capacitor an ESR of 0.06 Ohms and a capacitance of 3235uF.

Remember the bottom of the board - well after a little rework etc. this is what it turned out like :-

Not perfect but pretty good, I also cleaned and re-flowed the edge connectors, if you do this make sure that the re-flow is as thin as possible - or you might open up the edge connector in the chassis and cause intermittent problems. When I put any of the boards into the chassis I use the cleaning solution that I mentioned earlier to protect and ensure a good connection.

Finally here is the completed board :-

One final note - TAKE CARE with the insertion of the vertical capacitors !! - look at the above picture - this board is a little different - the capacitors are not all in the same orientation - check and re-check - as if you get this wrong it will not be pleasant !! - I also noted that the board itself has the orientation marked on the board - but you can't see them when you put the capacitors in - so checking is a bit difficult !!