TRC-449 - weak AM receive, no SSB output

[Ironhorsenva]

Hey folks, I have a TRC-449 with weak AM receive and very little meter deflection unless there is a strong signal nearby. Transmits normal AM carrier and modulation but no SSB output shown on the external meter. I can hear AM and SSB output from the radio on a nearby CB. Wondering if I have two separate problems or something common to both symptoms.

Unless I missed something, all power supply voltages are correct. The radio had these problems when I got it off eBay. Recapped it, other than the .01mf and .1PF caps which I have not been able to find. I put a new relay in it just to test and that wasn't it. All voltages on IC4 check out but I didn't try swapping it.

Any ideas on what I should take a closer look at?

Thanks in advance.

 

[nomadradio]

If the radio has not been aligned, that would be the next troubleshooting step.

If someone simply twisted adjustments randomly, this will cripple it. And if there are one or more circuit faults, the behavior (or misbehavior) of the adjustment at one or more alignment steps can point you to where the problem is located.

A coil that won't peak like it should may be a bad coil, or a bad part in that circuit making the coil respond incorrectly when it's adjusted.

It's like "my car won't idle smoothly". More than one possible cause. Might be more than just one fault behind it.

73

 

[Ironhorsenva]

Hi Nomadradio, that makes sense and I will see how far I can get. Right now I just have a scope, signal generator, frequency counter, DVM, 50 ohm load, and power supply. Enough to do the PLL alignment according to the service manual. I still need to locate and purchase a second AF oscillator, AF VTVM, RF VTVM and a spectrum analyzer is on the list as well. Those would allow me to do the transmit and receive alignments. Not sure on what more modern items I could purchase to sub for some of the items currently not on hand that were listed in the service manual.
This radio doesn't appear to have any mods but I know that doesn't verify that someone hasn't tweaked something else in the radio. The wax is still in the coils for the finals. Comparing it visually to another/working TRC-449 that I have, the only two trimmers that I can see that are off from the working unit is VR1 and VR5.
End goal is to have all equipment needed for full alignments. Just don't have that at present. Thanks for your input. 73's

 

[Mike Stand]

Try changing the relay, it switches the 13.8v supply on for SSB TX, wheras AM is controlled by a seperate regulator.

 

[kopcicle]

okay, I'll follow along. I'm a sucker for an 858 thread.

 

[Mike Stand]

Your RX problem is probably TR5, the first RF amp blown, it’s a 2sc1730L, common cause of weak RX.