[ARC5] 10 meter BC-454 - more

[Kenneth G. Gordon]

Talk about problems:

OK. I have been dealing with what I consider to be a major instability issue with this thing. I'll 
try to detail those below.

Over the last few days, I have liberally coated the HFO coil with clear lacquer and allowed it 
to dry thoroughly. I have been working on the assumption that this instability problem was 
centered in the HFO coil. However, from the below, it appears that I was wrong. Trouble is, I 
don't know what to do about it, or even if I CAN do anything about it

Results of "solidifying" the HFO coil are Interesting:

1) There appears to have been no difference made in the overall mechanical stability of the 
receiver. The slightest mechanical jar can be heard, very vividly in the audio, whether the 
BFO is on or off. The receiver literally "rings" like a struck bell.

2) Judiciously tapping, very lightly, on various bits has confirmed that the instability is NOT, 
repeat NOT, associated solely with the HFO coil, if at all. In fact, tapping very lightly on the 
aluminum can which holds the HFO coil can hardly be heard.

3) Pushing very slightly on any IF can, or on the chassis anywhere results in severe wobble 
and/or jumping of the frequency tuned to. Manipulating the resistors on the four resistor 
"blocks" very obviously favors only that one nearest the 1st IF can as being close to the 
source.

4) Further judicious tapping and pushing appears to point to the main-tuhning capacitor as 
the most likely culprit, or to something inside its "can". Touching the main-tuning knob, even 
slightly, results in major wobble.

5) I have swapped both the RF amp tube and the Mixer tube with new ones. No difference.

Conclusion:

At this point, I am very suspicious that the main tuning capacitor is the main source of this 
problem, but I have no idea how to confirm or eliminate this, or if it is there, what to do about 
it.

As I mentioned earlier, the tuning cap has been very badly treated.

Ken W7EKB