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 Post subject: Sweep Generator Woes
PostPosted: May Sun 23, 2004 6:55 pm 
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Hi J,<P>Actually, you want to use DC coupling for the vertical input. Depending on the sweep settings of the generator, your input to the scope may be very low in effective frequency, and many scopes don't have good low-frequency response.<P>Also, with DC coupling, you can turn the sweep off and adjust the generator frequency by hand, and watch the signal level change on the scope (using normal horizontal sweep).<P>------------------<BR>73 de Leigh W3NLB | | Leigh@AtwaterKent.Info<BR><A HREF="http://www.AtwaterKent.info" TARGET=_blank>http://www.AtwaterKent.info</A> | | <A HREF="http://www.Synchrophase.info" TARGET=_blank>http://www.Synchrophase.info</A>


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 Post subject: Sweep Generator Woes
PostPosted: May Sun 23, 2004 10:38 pm 
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Location: PA, USA
Dave, good to see you making progress with this thing. <P>The neon lamp is just a power indicator. The wiring configuration in yours sounds odd, though. The lamp in mine is connected across the primary of the power transformer, though it's hard to notice unless one actually traces the circuitry. Take another look. If someone butchered it up, you could always run new wires directly from the transformer primary terminals to the lamp. <P>My unit appears to have the correct tubes. Thanks for clearing that up for me.<P>Johnny and Leigh, thanks for the tips. I'll keep them in mind next time I fire up this thing. <IMG SRC="http://antiqueradios.com/forums/smile.gif"><P><P>------------------<BR>


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 Post subject: Sweep Generator Woes
PostPosted: May Mon 24, 2004 12:18 am 
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Leigh wrote:
<font>quote:</font><HR>Originally posted by J Matahratz:<BR><B>...The lamp in mine is connected across the primary of the power transformer</B><HR>
<P>There should be a resistor in series with the neon. The operating voltage of these is around 65 volts, so putting one directly across the AC line will destroy it.<P>------------------<BR>73 de Leigh W3NLB | | Leigh@AtwaterKent.Info<BR><A HREF="http://www.AtwaterKent.info" TARGET=_blank>http://www.AtwaterKent.info</A> | | <A HREF="http://www.Synchrophase.info" TARGET=_blank>http://www.Synchrophase.info</A>


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 Post subject: Sweep Generator Woes
PostPosted: May Mon 24, 2004 12:59 am 
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J Matahratz wrote:
<font>quote:</font><HR>Originally posted by Leigh:<BR><B> <BLOCKQUOTE><font>quote:</font><HR>Originally posted by J Matahratz:<BR>...The lamp in mine is connected across the primary of the power transformer</B><HR></BLOCKQUOTE><P>There should be a resistor in series with the neon. The operating voltage of these is around 65 volts, so putting one directly across the AC line will destroy it.<P><HR>
<P>OOPS, forgot to mention that. There is a 33k series resistor on one side of the lamp. <P><P>------------------<BR>


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 Post subject: Sweep Generator Woes
PostPosted: May Mon 24, 2004 1:08 am 
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Location: Burbank, CA and Thailand
Well, my turn to check in I guess. <IMG SRC="http://antiqueradios.com/forums/smile.gif"> Man, after soaking that switch rotor in acetone I had to put it in my biggest vise and pound it with a hammer to free the center part, but it finally did come out. (No, I hadn't forgotten to remove the C clip, it was just that stuck.) Alan you were right, the old grease had turned into thread lock. After cleaning and lubing it I reassembled the whole thing. (If anyone here has ever disassembled a multi section rotary switch and then put it back together correctly the first time, congratulations! I've done this before, but still it took me several tries.)<P>I found that I had to clean the switch wafers like crazy, and burnish the finger contacts before the frequencies even came close to agreeing with the dial markings. J, you might check yours and make sure that the ranges are doing what they're supposed to, because mine were pretty far out there. The band switch contacts were black and making very poor contact, I measured each contact individually with an ohm meter and just kept cleaning and cleaning (with acetone, Q tips, and a small burnishing tool) until the resistance and intermittencies were all finally gone.<P>As for the neon lamp, J thanks, I double checked, you were correct, it's just a power indicator. In replacing the power cord with a grounded type and rebuilding the solid state low voltage supply, I had missed a wire that needed to be moved, oops. <P>I now seem to have a working sweep oscillator, but I don't think the marker is working right. The marker oscillator itself is working, I see it on my scope when looking at the cathode of its oscillator tube, but that signal doesn't seem to be making it to the marker level control or the RF output. Will take a closer look and see what I can figure out. Grrr...it's frustrating working with a schematic that's close, but not exactly right.<P>Also I'm confused about using the marker crystal. I assume that the marker function can be used without a crystal, and the marker does seem to oscillate properly without one. There's a socket for an external crystal, but there's no switch. When you plug in a crystal, does it's frequency override the dial setting, or how does that work?<P>J, what do you plan to use your 369 for? Mainly FM radios? I'll use mine for IF alignment of old TV's. Dennis here convinced me that old TV's don't usually need their IF's aligned, but I did want to have some means of checking them, and doing an alignment if needed.<P>This thread reminds me once again how the internet has changed out lives. Pre-www it would have been nearly impossible to hook up with someone else restoring an obscure instrument like this, exchange play-by-play commentary, and get this sort of assistance. Now, it's almost expected. Really amazing, when you stop and think about it.<P>------------------<P>P.S. Just noticed a couple more things. That "Scope" connector is a 2 -pin screw type. Seems to just supply a sample of the HV secondary (60 Hz. sine) for the scope horiz. input. Does this even need to be used, or can you just use "line trig" on the scope. The low side of this connector is not grounded, but goes through a network. Also, there is a "demod in" connector, which is not in the 368 manual we have, no idea what it does.<P>I ordered a manual for this thing a few minutes ago...it's been driving me crazy having one that's almost right.


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 Post subject: Sweep Generator Woes
PostPosted: May Mon 24, 2004 5:47 am 
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Location: PA, USA
Dave,<P>I will take another look at my switch. The contacts may need to be cleaned, though they look brand new.<P>Funny you're having trouble seeing the marker pips on the scope, because it's a problem I seem to be having also. The oscillator runs fine and the dial scale is dead accurate, yet the pip is barely perceptible on fundamental frequencies and invisible when harmonics are used (above about 80 Mhz). I have not tried using a crystal, so I have no idea if it would work any better. As for the DEMOD IN jack... I'm sure someone here knows what it's for, because I don't. <IMG SRC="http://antiqueradios.com/forums/smile.gif"><P>Once I get this going I, like you, plan to use it to check and align FM and TV IFs. I have a couple of TVs that undoubtedly had the IFs tampered with. I have some FM sets that I just couldn't get to sound right either.<P>One last thing, turning the TRACE SIZE control on my unit has no effect whatsoever. Does it do anything for you?<P><BR>------------------<BR>


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 Post subject: Sweep Generator Woes
PostPosted: May Mon 24, 2004 6:01 am 
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Location: Waukegan, IL
Unfortunately, I don't have a working tv to try all this on, or have I even tried this before. But, I'm reading about aligning tv's and certain if alignment procedures call for disabling the agc otherwise it will distort the response curve. Check your sets algnment instruction if this is called for. Could this be the problem you are having? <P>------------------<BR>Tony


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 Post subject: Sweep Generator Woes
PostPosted: May Mon 24, 2004 7:30 am 
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Location: Burbank, CA and Thailand
I think Trace Size just affects the Scope connector, which the 368 manual says gets connected to the Horizontal input of your scope, and only seems to have a 60 Hz. sine wave on it. I'm still scratching my head over how this unit really works.<P>You were lucky your bandswitch connector was in good shape, mine was totally trashed though I think it's fully repaired now. The good news is that my unit was clearly factory built, not a kit, and is super clean inside. I'll post pictures soon.


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 Post subject: Sweep Generator Woes
PostPosted: May Tue 25, 2004 1:17 am 
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Location: Pocasset, Cape Cod, MA
<B>>>P.S. Just noticed a couple more things. That "Scope" connector is a 2 -pin screw type. Seems to just supply a sample of the HV secondary (60 Hz. sine) for the scope horiz. input. Does this even need to be used, or can you just use "line trig" on the scope. The low side of this connector is not grounded, but goes through a network.</B><P>This probably adjusts the phase of the 60Hz, so the center frequency winds up in the middle of the scope display.<P>For cleaning tarnished silver rotary switch contacts, DeOxit works really well, applied with homebrew Q-tips.<P>------------------<BR>


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 Post subject: Sweep Generator Woes
PostPosted: Aug Fri 13, 2004 3:28 am 
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Location: Herkimer, NY, USA
I have a Precision Apparatus E-410C Sweep Generator and Marker Adder. I believe the sweep generator circuit in this instrument is very similar to the one in the EICO 368 and 369. The only difference between the EICO 368 and 369 circuitry is, I believe, that the 369 has a post-injecton marker-adder circuit where the 368 has pre-injection markers. All of these instruments have an output-leveling circuit which is an attempt to maintain the output voltage at a constant level as the RF is varied to produce the sweep signal. These circuits are fa from perfect, and there can be considerable variation in the output level depending on the sweep center frequency and the sweep width. This is especially true in these service-grade type instruments. Perhaps the problem you are having is with the leveling circuit in your instrument. The circuit usually samples the sweep oscillator grid voltage and adjusts the sweep oscilator plate voltage to counteract the grid voltage change.<P>------------------<BR>


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