[R-390] Filter Repair

[quartz55]

Well, I've installed the repaired filters in the IF module that had the 2 and 4 K ones dead, and rebuilt the other 2 while I was at it.  I'ts now working just like the other IF that appears to have good filters.  Measuring the R at S503 rear pin 8 which should be the AGC line at the filters, I measure ~300 Meg ohms on both IF's now (out of the RX).  That's a pretty good trick, pulling out those filters and replacing them and it works first time, if I do say so myself.  Of course I did a bunch of measurements compared to the other IF before I put it in.  I guess I'm anal enough.  I notice the 14MHz band is dead though, must be a loose crystal.

 

The carrier meter drops off with the 4 and 2 K filters, much expected as they have almost 15 dB more loss than the 8 and 16.  Now I need to tune it up.

 

Anyhow, I've gotten most of my write up done for 'filter repair' and since I don't have a web page, I'll post it here as text and links to my photobucket account for the pictures.  If it can be added to the 'Pearls', I don't mind.

 

It was a project; I'm not sure how many hours I had in it, maybe a week or 2.  Was it worth it?  No, but so what, maybe it will benefit someone else.



Dave
N3DT