Navy RCH Receiver

[W2TRH]

Hi i am working on a very clean EH Scott RCH Receiver from the USS Slater DE-766 museum ship here in Albany N.Y . Band one works fine, band 2 which is only supposed to go to 550mhz is only receiving one station, 590mhz no mater where you turn the dial,a local station here in albany, bands 3 and 4 work perfectly, band 5 is dead. All of the filter caps have been replaced as well as out of tolerance resistors. After the parts where replaced the same issue with bands 2 and 5 is still going on. The underside of the chassis is clean as well as the top. What could e going ob here, out of alligment or what, thanks for your time,
Steve

[KA0HCP]

For band 5, the dead band, check/clean bandswitch contacts..

For those who haven't memorized the RCH schematic, located at BAMA:
http://bama.edebris.com/manuals/scott/

[W2TRH]

Hi William, thank you for replying, the underside is very clean but i will try that with some better contact cleaner, still very strange on band 2 that only receives on station that is out of band, (590 am) no matter where you turn the dial, nice boat anchors on your qrz page, i'll keep you posted on the RCH.

[KA0HCP]

The schematic is giving my eyes a workout.  

I'm not an expert, but given that Band 2 is so far off frequency; my guess is that the problem is high level. That is very early in the RF chain probably the RF IF.  So I suggest looking at C-164, 20 mmF/pF, Mica, in the T-107 IF transformer.  You might check the T-107 xfmr resistances per Table II, Section 7.1.  Pri: 25.9Ohm, Sec: 45.4Ohm.

That's a first stab.  Good luck, bill.  

My first suspect for components in Band 2 chain would be a bad capacitor, second a Coil, third resistor (but less likely).  

Depending on the local station strength it may be helpful to build a 'wave trap"/band stop filter for that frequency as work around.  You can build a crude one with just a few junk box components. Google will help.  This would be placed at the antenna input; first thing.

I suggest always going thru any BA and check ALL resistors for gross out of tolerance.  All paper & electrolytic caps replaced.  "Micamold" (encapsulated paper caps) are always suspect if things are wrong.  b.  

[K7MCG]

The IF of the RCH radio is 585KHz !   That strong local station at 590 KHz is direct feedthru or stay pickup - not a properly received signal. 
1) RTFM
2) Check whether the LO is oscillating.

73
Chuck K7MCG

[W2TRH]

Hi Bill And Chuck, i have another RCH in a case that works perfectly, receives a few beacons that are around e.t.c. 590 is a local station,, a few kw i think, been around for decades, missed gtting its old tube transmitter, , bill that mica cap you mentioned is waay off, going to replace that, chuck i will check what you mentioned and i am going to run it through a full alligement after i re[lace afew more caps and such, thank you again for time and advise, i'll keep you posted.

[W2TRH]

Hi Bill And Chuck Again, i checked out that 20mfd mica cap, dead i say a few others where in the same shape. I also replaced all of the resistors except for a few that where ok, caps also. Band five came back to life so 1,3,4,5 are working very well now.On band two with the dial turned all the way counter clock wise you can just barley hear that station on 590AM. I will run it through anouther allighnment before bringing it back abored the USS Slater musueun ship hear in albany. Thanks again for you time and help with this,
Steve