Figure 21. Heathkit Filters
The lower right photo shows the repair to the broken track on the top right corner of the
PC Board. The top and bottom connections are made to the case and the left and right
hand connections are signal in and out.
As you can see, the filters can be disassembled but the critical trick is to melt the solder
seal around the base without melting the component joints on the PCB. This means
supporting the base of the filter and applying heat quickly to the outside of the base to
soften the solder so that the cover may be pulled off. I use a plumbers gas blowlamp for
this purpose. Once cool, repairs may be made and the unit resealed with a large
soldering iron. Any scorched/burnt paint can be cleaned off and replaced. If you need to
varnish any of the inductors then leave the filter open for several days to dry before
resealing.
Right click on any photo and save it to your hard drive as required.
The AM and CW filters only used four crystals and their performance is not really
adequate for today’s more packed bands. Modification / redesign is possible to add the
additional two crystals as long as the pole zero frequencies are correct for the
application. A new PCB will be required. Another option is to obtain and disassemble
another AM/CW filter in order to use two of the crystals and a tuned circuit to create the
additional filter section.
Heathkit Filters Page 106
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