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 Post subject: Eico 369: Measuring frequency of marker generator
PostPosted: Jun Thu 13, 2019 11:53 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 302
Location: Windsor, CT USA
I have (another) 369, which I picked up at a swap meet for $10. After a recap, it seems to work very well! Part of my success is that I think I am finally understanding how sweep generators work (and how to connect them). Anyway, I have a couple of questions which I am hoping someone could help me with.

1) The manual says to use the external trigger which I understand is a line level trigger. However, my scope has a line level trigger, and when I use it, everything works fine. Am I missing something by not using the external trigger output of the 369?

2) I would like monitor the frequency of the marker generator with an external digital frequency counter. I am not sure where to connect the frequency counter. Here is the schematic:

Image

Can someone advise me as to where and how to tap-in to monitor the frequency of the marker?

Thanks!


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 Post subject: Re: Eico 369: Measuring frequency of marker generator
PostPosted: Jun Fri 14, 2019 1:18 am 
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Joined: May Thu 14, 2015 4:15 pm
Posts: 1778
Location: Dallas, TX
I wish you didn't make the image quiet so wide. Scrolling sideways is a pain.
First The output from the 396 to the scope horizontal is not a trigger, it is a sweep signal.
The frequency sweep is not linear with time like a normal scope sweep. The scope is used in
the X-Y mode, do not use the time per division scope sweep.
For the counter output, try adding a 150 pF cap between the cathode of V5 and the center pin of a
BNC that you will have to add somewhere. You may have to experiment with the cap value.

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It's not the Destination, It's the Journey.


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 Post subject: Re: Eico 369: Measuring frequency of marker generator
PostPosted: Jun Fri 14, 2019 5:16 am 
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Joined: Jun Sat 09, 2007 8:14 am
Posts: 3816
Location: Florida
Try connecting a counter between one of the crystal socket pins (try both) and ground. I was able to use my counter this way.

RRM


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 Post subject: Re: Eico 369: Measuring frequency of marker generator
PostPosted: Jun Fri 14, 2019 5:33 am 
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Joined: Jan Sun 18, 2015 5:01 am
Posts: 1406
Location: Waxahachie Texas
Yup, pin 3 of V5 is where I did my pick-off.

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Crist


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 Post subject: Re: Eico 369: Measuring frequency of marker generator
PostPosted: Jun Fri 14, 2019 5:38 am 
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Joined: Jan Sun 18, 2015 5:01 am
Posts: 1406
Location: Waxahachie Texas
Look here for the details.

viewtopic.php?f=8&t=307433&p=2573569&hilit=eico+369#p2573569

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 Post subject: Re: Eico 369: Measuring frequency of marker generator
PostPosted: Jun Fri 14, 2019 7:05 am 
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Joined: Jan Tue 10, 2012 8:39 am
Posts: 610
That should work okay but use a coupling capacitor to the counter to avoid screwing up the circuit.


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 Post subject: Re: Eico 369: Measuring frequency of marker generator
PostPosted: Jun Fri 14, 2019 11:32 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 302
Location: Windsor, CT USA
I woke up this morning with a novel approach to the problem of monitoring the marker frequency. I put a tube shield around the 12at7 marker oscillator. I then ran a probe between the tube shield and my frequency counter. The result was perfect. No direct coupling to the oscillator circuit needed. No possible interference. No soldering. I applied some pieces of electrical tape to the hole where the 12at7 passes through to the socket. I verified that this works by plugging-in the 4.5mhz crystal. The counter showed exactly 4.5mhz. I'm now going to run a small RG316 cable from the tube shield to a female coax connector at the back of the chassis. I'll post pictures when I'm done.


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 Post subject: Re: Eico 369: Measuring frequency of marker generator
PostPosted: Jun Fri 14, 2019 12:45 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 302
Location: Windsor, CT USA
I'm just not getting anywhere trying to use my 369 in x y mode. When I choose "AC line" I get this:

Image

When I move the marker frequency, I can see the marker move from left to right.

When I set it up in x y mode (i.e. connecting the 369 per the diagram in the manual), I get this:

Image

The trace is rotated 90 degrees to the right. And it looks funny!

I have a wavetek sweep generator that works great in x y mode. It's just not suitable for FM IF. I checked the 'Y' waveform from the 369; it's a perfect 59-60hz AC sine wave. My RCA WR-50b works great with an AC line sweep. Do I really have to run this in X Y mode?


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 Post subject: Re: Eico 369: Measuring frequency of marker generator
PostPosted: Jun Fri 14, 2019 2:23 pm 
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Joined: May Wed 18, 2011 2:40 am
Posts: 4142
Location: Littleton, MA
mstamper wrote:
When I set it up in x y mode (i.e. connecting the 369 per the diagram in the manual), ...
The trace is rotated 90 degrees to the right. And it looks funny!

Looks like you have X and Y swapped.

mstamper wrote:
Do I really have to run this in X Y mode?

Only if you want the horizontal deflection to be proportional to frequency, rather than the arcsine of the frequency.

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 Post subject: Re: Eico 369: Measuring frequency of marker generator
PostPosted: Jun Fri 14, 2019 4:32 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1613
Location: Canyon Lake, TX
My Radio Shack counter is sensitive enough to read the marker frequency by just sticking an insulated wire into the crystal socket.
No direct electrical connection is necessary . . .


Attachments:
RSCounter-1.JPG
RSCounter-1.JPG [ 285.08 KiB | Viewed 522 times ]

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 Post subject: Re: Eico 369: Measuring frequency of marker generator
PostPosted: Jun Fri 14, 2019 4:59 pm 
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Joined: Feb Sun 02, 2014 9:13 pm
Posts: 2025
Location: Roanoke, VA
Notimetolooz wrote:
I wish you didn't make the image quiet so wide. Scrolling sideways is a pain.

I will second that. Please resize your images to no more than 800 pixels wide before posting them.

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 Post subject: Re: Eico 369: Measuring frequency of marker generator
PostPosted: Jun Fri 14, 2019 5:42 pm 
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Joined: May Thu 14, 2015 4:15 pm
Posts: 1778
Location: Dallas, TX
You want the 60 Hz to be on the 'X' axis (horizontal).
If you do not take the 60 Hz from the 369 then the "Phase" control has no effect.

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Tim
It's not the Destination, It's the Journey.


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 Post subject: Re: Eico 369: Measuring frequency of marker generator
PostPosted: Jun Thu 27, 2019 3:04 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 302
Location: Windsor, CT USA
Well, I can see now why x-y mode is needed. If you use a 60hz trigger, the sweep is not linear. For example, if I set the marker frequency at 10.7mhz and put the marker in the center of the sweep trace, in "triggered" mode, the marker is displaced .5mhz at one end of the trace, but only .4mhz at the other end of the trace. If I do the same thing in x-y mode, the marker is displaced by an equal amount at both ends of the trace. In triggered mode, the sweep is not linear. In x-y mode, the sweep is linear. So, I have to use x-y mode.

Trouble is, in x-y mode the display is turned 90 degrees to the right! I suppose I could just turn the scope on it's side; however, that seems pretty stupid! I don't think my x-y connections are reversed. "to scope" is plugged into 'x'. The 60hz 'y' is plugged into 'y'. When I reverse the connections, I get no trace at all. My wavetek sweep generator exhibits none of these symptoms. It works perfectly in x-y mode; the trace is normal. I'm at my wit's end! What could be wrong with my 369 that it would not produce a normal sweep trace in x-y mode? It works great in 60hz triggered mode. However, that's not linear. Could it be PEC PC2 (part number 29756)? The schematic shows no component values for PC2. Has anyone ever tried to reconstruct PC2 using discrete components? Does anyone know the actual component values in PC2?


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 Post subject: Re: Eico 369: Measuring frequency of marker generator
PostPosted: Jun Thu 27, 2019 5:53 pm 
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Joined: May Thu 14, 2015 4:15 pm
Posts: 1778
Location: Dallas, TX
Sounds like it may be a issue related to DC offset. Also maybe the cable is labeled wrong. Just to clarify "triggering" is not involved at all.
You do not use the timebase generator in the scope, that is the only place that would involve triggering. The horizontal "sweep" comes
from the "X" drive of the sweep generator. The "X" drive is a 60Hz sinewave that can be phase shifted by a control on the generator.

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Tim
It's not the Destination, It's the Journey.


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 Post subject: Re: Eico 369: Measuring frequency of marker generator
PostPosted: Jun Thu 27, 2019 10:07 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 302
Location: Windsor, CT USA
To: Notimetolooz Thank you for explaining x versus y. I switched the BNC connectors on the scope. Presto! I now have a horizontal sweep! I can see the marker. I performed the phase adjustment. Looking good! Digital scopes are so slow! I may go back to using my Tektronix 465b. I now have a correct, linear horizontal sweep. I can see the marker. I can monitor the marker frequency. Time to start aligning some tuners.


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