Hi everyone,

I have an R-390a. When tuning "through" a CW signal, the CW signal
warbles and is distorted. Once I've stopped tuning and set the audio
response to "NARROW" and the bandwith to about 200hz,, the signal
sounds like a pure DC note.

A friend of mine who services lots of boatanchors including the R-390a
says this is normal. He says I've got the RF Gain set too high and
that's causing the signal to be distorted. I'm not so sure. Even
with the RF gain set lower, I still hear the warbling and distortion
as I tune "through" a CW signal. If I turn the RF gain *way* down, I
don't hear it (but I don't hear the CW signal much either).

AM reception is just fine and SSB reception using the BFO is just
fine...no distortion or warbling as I tune through a SSB signal.

So...my question for those of you that have R-390As or know them well,
when I tune "through" a CW signal, should I hear a nice DC note all
the way through or should it warble and show some distortion.

I *am* using a matching transfomer with my 8 ohm speaker.

73 and thanks for any help you guys can give me!

Derek
WB0TUA

mecograph wrote:
Hi everyone,

I have an R-390a. When tuning "through" a CW signal, the CW signal
warbles and is distorted. Once I've stopped tuning and set the audio
response to "NARROW" and the bandwith to about 200hz,, the signal
sounds like a pure DC note.

A friend of mine who services lots of boatanchors including the R-390a
says this is normal. He says I've got the RF Gain set too high and
that's causing the signal to be distorted. I'm not so sure. Even
with the RF gain set lower, I still hear the warbling and distortion
as I tune "through" a CW signal. If I turn the RF gain *way* down, I
don't hear it (but I don't hear the CW signal much either).

AM reception is just fine and SSB reception using the BFO is just
fine...no distortion or warbling as I tune through a SSB signal.

So...my question for those of you that have R-390As or know them well,
when I tune "through" a CW signal, should I hear a nice DC note all
the way through or should it warble and show some distortion.

You should hear a nice pure tone that changes pitch smoothly as you tune...
no warble.

The AGC and all that is fine, because you don't hear warble when you tune
the bfo knob.

The warble could be caused by the PTO needing a lube job, or it could be
caused by the gear train for the main knob needing cleaning and lubing.

The main tuning knob should tune smoothly without any "gear" feeling...
when was the last time I used an R390A that felt that way!

Chuck

Hi everyone,

I have an R-390a. When tuning "through" a CW signal, the CW signal
warbles and is distorted. Once I've stopped tuning and set the audio
response to "NARROW" and the bandwith to about 200hz,, the signal
sounds like a pure DC note.

A friend of mine who services lots of boatanchors including the R-390a
says this is normal. He says I've got the RF Gain set too high and
that's causing the signal to be distorted. I'm not so sure. Even
with the RF gain set lower, I still hear the warbling and distortion
as I tune "through" a CW signal. If I turn the RF gain *way* down, I
don't hear it (but I don't hear the CW signal much either).

AM reception is just fine and SSB reception using the BFO is just
fine...no distortion or warbling as I tune through a SSB signal.

So...my question for those of you that have R-390As or know them well,
when I tune "through" a CW signal, should I hear a nice DC note all
the way through or should it warble and show some distortion.

I *am* using a matching transfomer with my 8 ohm speaker.

73 and thanks for any help you guys can give me!

Derek
WB0TUA

Derek,

What you describe is a common problem with PTO. There is a small "finger"
that rides on the shaft near the front of the PTO. There are one or two
small screws that hold the finger in place. Remove it, clean it and the
shaft with something like DeoxIT and reassemble. I don't remember if any
grease is recommended but a conductive lubricant would probably help. It
should definitely NOT warble when tuning through a signal like that.

By the way, you will probably need to remove the PTO to do this. If so, be
very careful not to lose the Oldham coupling spring and if you do turn the
PTO shaft, try to remember how far (how many turns, etc.) you turn it and
put it back in the same position before reassembling it or your dial
calibration will be way off.

73,
Barry - N4BUQ

mecograph wrote:

So...my question for those of you that have R-390As or know them well,
when I tune "through" a CW signal, should I hear a nice DC note all
the way through or should it warble and show some distortion.

Depends on your PTO. Who made your R-390A? Some model PTOs are better
than others, and some will wobble while being tuned.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

So...my question for those of you that have R-390As or know them well,
when I tune "through" a CW signal, should I hear a nice DC note all
the way through or should it warble and show some distortion.

I had an identical problem with another boatanchor receivers.

In my case the problem was with one of the anti-backlash gears driving the VFO.
The spring was not in tension enough.

73

Tony I0JX

Hi Scott,

It's a Capehart R-390A. I'm not sure who made the PTO....I don't have
anyone to help me lift it out of the case so I can look at it this
evening.

I hope to have a friend help me extract it from the cabinet in the
next few days...I'll try to figure out which PTO it is.

Thanks!

Derek
WB0TUA

On Sep 6, 10:16*am, (Scott Dorsey) wrote:
mecograph wrote:

So...my question for those of you that have R-390As or know them well,
when I tune "through" a CW signal, should I hear a nice DC note all
the way through or should it warble and show some distortion.

Depends on your PTO. *Who made your R-390A? *Some model PTOs are better
than others, and some will wobble while being tuned.
--scott

--
"C'est un Nagra. *C'est suisse, et tres, tres precis."

mecograph wrote:
Hi Scott,

It's a Capehart R-390A. I'm not sure who made the PTO....I don't have
anyone to help me lift it out of the case so I can look at it this
evening.

Don't lift it out of the cabinet, lift the cabinet off of it. Turn it face
down on the bench, and lift up the case.

I hope to have a friend help me extract it from the cabinet in the
next few days...I'll try to figure out which PTO it is.

Thanks!

Derek
WB0TUA

On Sep 6, 10:16 am, (Scott Dorsey) wrote:
mecograph wrote:

So...my question for those of you that have R-390As or know them well,
when I tune "through" a CW signal, should I hear a nice DC note all
the way through or should it warble and show some distortion.
Depends on your PTO. Who made your R-390A? Some model PTOs are better
than others, and some will wobble while being tuned.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On Sun, 7 Sep 2008, mecograph wrote:

Hi Scott,

It's a Capehart R-390A. I'm not sure who made the PTO....I don't have
anyone to help me lift it out of the case so I can look at it this
evening.

I hope to have a friend help me extract it from the cabinet in the
next few days...I'll try to figure out which PTO it is.


I don't know how much of it might apply to the R-390, but Ham Radio
magazine ran a couple of articles about Collins PTOs, that might provide
some background information or help.

Bill Orr had an article in the December 1969 issue about the PTO in
the 51J-series receivers, including if I recall properly how to get
the PTO out and open it up.

Then, there was an article in the December 1974 issue about the PTO
in the 75A4.

The only Collins PTOs I've looked inside of were some 1 to 1.5MHz
ones I got at a hamfest decades ago. The circuit was really simple,
of course the mechanics were what made them really good.

Michael VE2BVW