[TenTec] Orion 565 Main Receiver Issue

[art N4UC]

Here's a brain teaser for all you Orion experts. My 565 running ver 3.032 has developed a couple of problems that I was hoping would be a firmware issue but it's looking more and more like a hardware problem. I'm looking for some ideas about where to start troubleshooting.

In a nutshell the two problems (which may just be different symptoms of one problem) are these:

1. All signals received by the main rcvr on 20M only are extremely garbled and distorted. This condition is not dependent on mode and all other receiver functions such as S-meter operation, AGC, BW and PBT functions seem to be unaffected. Operation of the sub-receiver is normal.  One interesting note is that a signal disappears when I engage the hardware NB, which is probably just an indicator that the NB thinks it's seeing noise and just doing its job.

2. When both VFO's display the same frequency, there is a difference in received frequency between the two receivers. This is present regardless of band, but the difference is not the same from band to band. The worst I've noticed is 200 hz offset on 20M, but other bands exhibit 50-100 hz delta between the receivers in spite of displaying the same  frequencies.   It doesn't matter how the two receivers arrive at the same frequency, either by pressing the A>B button or configuring both Main and Sub recvrs to be controlled by VFO-A.


This all came on as an intermittent condition. I would notice that during operation on 20M, received signals would suddenly jump by 100-200 hz and I would have to re-tune to get back on frequency. I was assuming that the transmitted frequency was jumping as well, but I haven't verified that as yet. Anyway, after the "jump" occurred, the signals would sound warbly and quivery (technical terms for "trashy"). No matter their signal strength they sounded watery like they were coming from over the North Pole. If I were to select a different band and then return , the receiver would "slide" a few hertz back onto frequency before settling.

I have 
sometimes noticed that just before this would happen there would be a rise in noise
 level, like precipitation static. While the rcvr  is off-frequency,  there is a
 lot of noise/hash that is in sync with other signals some as far 
away as 50 khz. It resembles being at field day in close proximity to 
several
 transmitters. Even though they are way out of the bandpass of the 
filters and too far away to hear a cw tone, I 
can copy them by listening to the hash. 

I have re-flashed the firmware and performed a few master-resets, etc... with no change. The problem is no longer intermittent and I'm looking for ideas while I decide how much $$$ I want to put into repairing a really fine, but old, radio.

73, Art/N4UC