So if the old radio like that dies - can you just replace head unit or do you need new GS/VOR indicators too?
KX170B W/KI209 and KN75 - used about $375-$1000 for a pristine one (don't buy the old 360 channel King units)
RT328T w/VOR indicator- about $200 on ebay if it works
KMA 20 Audio panel- $200-$300
2- place intercom- new from about $150 on up
KT76A Xponder- $worthless if weak or dead cavity tube to maybe $800 for one that works. A new Garmin slide in replacement is about $1500 with adapter, ACK A30 encoder is about $200 if you don't have a blind encoder
All these radios that are in the plane are still perfectly good for functional Cessna 150 flying, and all are readily available very inexpensively on eBay or in avionic shops in good working condition as removed from customer planes for upgrades as well as other used avionics sources. Sometimes it is better to find a cheap yet functional identical replacement rather than have your existing unit repaired should it fail.That way you simply slide in/out the radio unit and you probably wouldn't even need to document the swap. Also, the KX170 series have slide-in replacement radios (Michel MX170B)available or the MAC conversion that converts the old reliable King radio to digital tuning by changing the face plate. Michel also makes slide -in replacements for the old Cessna Rt series 12V and Narco Mk-12A as well.These units also show up on ebay for cheap as well. The VOR heads can be swapped for like units as well, they have a connector on the back you can unplug.Ask your radio shop guy which units to avoid, as some early heads are belt drive for the OBS, are difficult to align, and parts may be obsolete or not available- but for swapping, just get a unit that works. All this is fine and dandy for VFR, and for IFR you might want to upgrade to the newer units. The KT76A XPDR is a good unit if it works, but it has a cavity tube that is pricey to fix if it fails-BUT, Garmin's GX320A is a slide in solid state replacement with the appropriate adapter.
You can always replace your radios with low cost units like the ICOMA200 or the new ICOM A210. Right now there's a King KX125 NAV/COM on ebay for around $800, but it may go higher. That unit has the built-in VOR display in the faceplate- nice for a 2nd unit or if you don't have space for two VOR indicators.
Just be aware that there is a lot of junk sold on eBay, so you have to know what you are looking for or want. Make sure you get a guarantee or refund option if it fails.Anything other than direct replacements will incur additional cost to rewire the planes radio rack for the new equipment.It all depends on what you want the plane for or how long you plan on keeping it.If you want to build flight time quickly then sell the plane, leave as-is, otherwise plane on getting new stuff in the not too distant future.
-Brian
