Old School President Jackson drifting after clarifier mod

[Lkaskel]

Good Day Men,
So, I have this 1985 President Jackson that I wanted to open the fine tune clarifier (course clarifier is open from the factory). I used the method shown below for this. The radio drifts more than I expected so I was wondering if anyone has seen this before or has a solution.

Thanks as always!!!

 

[nomadradio]

So, how much did it drift before? Is this only a transmit-side problem, or does it drift on receive as well?

All this mod does is to unook the fine control from the receive-only power source and connect it to the same one that powers the Coarse control. Any chance the clarifier only needs cleaning?

73

 

[MKwrench]

Is it more on LSB than in the other modes?
The LB209 adjustable coils drift like a bum in the sun, and some are worse than others.
I'm wondering if recentering their adjustment height because of our disabling VR6 and using the 470 ohm in ground has anything to do with it.
The only other thing I can think of is the 8v regulator voltage might be cruising around.
I havn't looked into these things on my own radios yet, ....but soon.....
Drift bugs the hell out of me! Good luck, let us know what you find..

 

[Lkaskel]

So, how much did it drift before? Is this only a transmit-side problem, or does it drift on receive as well?

All this mod does is to unook the fine control from the receive-only power source and connect it to the same one that powers the Coarse control. Any chance the clarifier only needs cleaning?

73

The radio was stable before but I am going to return it to its factory default as a test. The drift is on both transmit and receive. I did clean (deoxit green) the control and it seems to work fine. The drift is interesting. It is always center to low, never high. It will move down to 9 o'clock (fine tune control) and all around 9-12.

 

[Lkaskel]

Is it more on LSB than in the other modes?
The LB209 adjustable coils drift like a bum in the sun, and some are worse than others.
I'm wondering if recentering their adjustment height because of our disabling VR6 and using the 470 ohm in ground has anything to do with it.
The only other thing I can think of is the 8v regulator voltage might be cruising around.
I havn't looked into these things on my own radios yet, ....but soon.....
Drift bugs the hell out of me! Good luck, let us know what you find..

I will set up a meter and monitor the 8vdc point I connected the control to. I'll let you know what I find. I love these older radios so I am hoping this one can become more manageble. I will say that when I talk on it (always LSB) It worlks great. I just need to keep making the adjustment as I am using it..

 

[Onelasttime]

Not likely to be from the mod.

I would suspect a part is bad or going bad. I have had voltage regulators going bad that had not yet failed cause this. I have had crystal filter go bad on one radio cause this. I had a cap go bad on VFO caused this.

My point is that a lot of things can cause this. Know if it was dead on before or also drifted is one thing to know. The other thing is looking at this as a reason to look for something going bad that might not be bad yet.

Often attempting to do a factory alignment is a good place to start. Old radio's often recapping is the best place to start before you do anything else if the radio is more than 20 years old. Not all radio's are built like a Hammerlund.

 

[Onelasttime]

In fact I had one radio my favorite at the time that had multiple failures.

As the radio would heat up the main voltage regulator was allowing double the current to flow into the radio. The next voltage regulator looked fine but when I removed it to test it, it was already craked and the corner fell off as I removed the screw. I upgraded both and the problem was much better but still there and that is when I found the crystal filter was bad.

The radio in question was a 1991 or 1992 RCI2950. It was around 1997 or 1998 when it failed. So I upgraded the voltage regulators with Mitsubish and Fuji voltage regulators. Installed matched 1969's and upgraded the driver, pre-driver, the crystal filter and a few low voltage caps. Kind of like the TIP36 mod of today.

If you have to replace a part might as well upgrade as you go. Not for more power but to make them more rugged and stabil.