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New to the forum and restoring an SX-71. I'm trying to go through the alignment procedure in the manual.
I'm stuck at Step 2 adjusting the IF coil associated with the 455 kHz crystal (adjusting tank U, aka T9 bottom).
I've watched some YouTubes on the topic, and most I've seen use a sweep generator and spectrum analyzer instead of the legacy Step 2 procedure.
I have an IFR 1200A but it doesn't have a sweep generator, so I attempted to do my adjustment per the manual. I've set the controls per the Step 2 instructions. Per my IFR 1200A the crystal seems to be at 457.9 kHz, so that is what I'm generating with my IFR.
I was able to adjust tank U for a peak, but then I tried to look for dip & second peak on either side of the main peak, and couldn't seem to find it (I understand the adjustment goal is mid-way between the main peak and the dip). At the main peak, adjusting
the frequency +/- 100 Hz resulted in 40 dB drop.
Subsequently, I tried to adjust again for the former peak, but this time the best peak I could get was about???of what I had before, and when 100 Hz off center freq, the drop is far less dramatic.
I fear that I dislodged the ferrite slug from the adjustment screw by going too far one way or the other.
Any ideas?
Thanks,
Randy, W7HMT
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Randy, ? I’ve been working on a SX-110, which uses the same type of instruction, and it’s confusing and seems counter-intuitive for peaking the first IF transformer.? Once you’ve identified the crystal frequency, you want to make sure that adjustment U is tuned for the center of the DIP you found – in other words, a MINIMUM of the beat note at the IF frequency.? At that point, the audio note will be much lower, and you’ll hear much more of a “swishing” sound than the beat note.? If you don’t find it, then you turn adjustment U a little bit one way or the other to try to bring the transformer into the range of the crystal frequency. ? To find the crystal frequency, I connected a VTVM to the 500 ohm speaker output and put my signal generator into a slow sweep between 450 and 460 KHz.? Watching the VTVM, I found a beat note dip on the slope of one of the passes – that got me into the “ballpark”.? I then stopped the sweep and set the generator for the approximate frequency where the dip was found, and then began manually adjusting the generator frequency in very small steps.? Once located (in my case, it was 453.48 KHz), I “peaked” the transformer for “minimum” beat note and maximum swishing sound.? ? Honestly, I believe there are easier ways to find the actual crystal frequency.? The instruction in the manual is too much voodoo for my taste.? My SX-110 is a bit of a fun test radio, and one thing on my agenda (for today, in fact) was to simply discover the crystal frequency by running the signal generator through it and monitoring for a peak on the oscilloscope.? The crystal will have maximum output at its resonant frequency.? Then, I’ll try peaking up the 1st IF using that frequency, using a modulated signal and with the BFO turned off. ? 73 – Steve, KW4H ? ? New to the forum and restoring an SX-71. I'm trying to go through the alignment procedure in the manual. I'm stuck at Step 2 adjusting the IF coil associated with the 455 kHz crystal (adjusting tank U, aka T9 bottom). I've watched some YouTubes on the topic, and most I've seen use a sweep generator and spectrum analyzer instead of the legacy Step 2 procedure. I have an IFR 1200A but it doesn't have a sweep generator, so I attempted to do my adjustment per the manual. I've set the controls per the Step 2 instructions. Per my IFR 1200A the crystal seems to be at 457.9 kHz, so that is what I'm generating with my IFR. I was able to adjust tank U for a peak, but then I tried to look for dip & second peak on either side of the main peak, and couldn't seem to find it (I understand the adjustment goal is mid-way between the main peak and the dip). At the main peak, adjusting the frequency +/- 100 Hz resulted in 40 dB drop. Subsequently, I tried to adjust again for the former peak, but this time the best peak I could get was about???of what I had before, and when 100 Hz off center freq, the drop is far less dramatic. I fear that I dislodged the ferrite slug from the adjustment screw by going too far one way or the other.
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Forgot to mention – it will be interesting to see if the 453.48 MHz frequency I allegedly “located” on that dip is, in fact, the actual frequency of the crystal – and if the 1st IF is already properly peaked using the method in the Hallicrafters manual.? I’ll post the results later today.? ? Interestingly, National uses a similar “find the crystal frequency” game in its IF alignment for the HRO-60, but it’s the peak they want.? The setup is similar – signal generator to the mixer section of the main tuning capacitor, and a VTVM on the audio output.? Turn on the BFO and adjust for some beat note between 400 and 1000 Hz, and then vary the tuning control of the signal generator very slowly until a peak is found on the meter.? That, per National, is the frequency of the crystal.? Interesting how Hallicrafters has you do the same thing, but they’re looking for a dip on the slope.? Huh?? Anyone have comments on that? ? Like I said, it will be interesting to see what’s really going on. ? 73 – Steve, KW4H ? Randy, ? I’ve been working on a SX-110, which uses the same type of instruction, and it’s confusing and seems counter-intuitive for peaking the first IF transformer.? Once you’ve identified the crystal frequency, you want to make sure that adjustment U is tuned for the center of the DIP you found – in other words, a MINIMUM of the beat note at the IF frequency.? At that point, the audio note will be much lower, and you’ll hear much more of a “swishing” sound than the beat note.? If you don’t find it, then you turn adjustment U a little bit one way or the other to try to bring the transformer into the range of the crystal frequency. ? To find the crystal frequency, I connected a VTVM to the 500 ohm speaker output and put my signal generator into a slow sweep between 450 and 460 KHz.? Watching the VTVM, I found a beat note dip on the slope of one of the passes – that got me into the “ballpark”.? I then stopped the sweep and set the generator for the approximate frequency where the dip was found, and then began manually adjusting the generator frequency in very small steps.? Once located (in my case, it was 453.48 KHz), I “peaked” the transformer for “minimum” beat note and maximum swishing sound.? ? Honestly, I believe there are easier ways to find the actual crystal frequency.? The instruction in the manual is too much voodoo for my taste.? My SX-110 is a bit of a fun test radio, and one thing on my agenda (for today, in fact) was to simply discover the crystal frequency by running the signal generator through it and monitoring for a peak on the oscilloscope.? The crystal will have maximum output at its resonant frequency.? Then, I’ll try peaking up the 1st IF using that frequency, using a modulated signal and with the BFO turned off. ? 73 – Steve, KW4H ? ? New to the forum and restoring an SX-71. I'm trying to go through the alignment procedure in the manual. I'm stuck at Step 2 adjusting the IF coil associated with the 455 kHz crystal (adjusting tank U, aka T9 bottom). I've watched some YouTubes on the topic, and most I've seen use a sweep generator and spectrum analyzer instead of the legacy Step 2 procedure. I have an IFR 1200A but it doesn't have a sweep generator, so I attempted to do my adjustment per the manual. I've set the controls per the Step 2 instructions. Per my IFR 1200A the crystal seems to be at 457.9 kHz, so that is what I'm generating with my IFR. I was able to adjust tank U for a peak, but then I tried to look for dip & second peak on either side of the main peak, and couldn't seem to find it (I understand the adjustment goal is mid-way between the main peak and the dip). At the main peak, adjusting the frequency +/- 100 Hz resulted in 40 dB drop. Subsequently, I tried to adjust again for the former peak, but this time the best peak I could get was about???of what I had before, and when 100 Hz off center freq, the drop is far less dramatic. I fear that I dislodged the ferrite slug from the adjustment screw by going too far one way or the other.
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I had a broken slug on my Sx-71, I discovered it because it would tune when upside down, and rite side up it wouldn't.
it was on the subchassis in the left rear.
toggle quoted message
Show quoted text
Randy,
?
I’ve been working on a SX-110, which uses the same type of instruction, and it’s confusing and seems counter-intuitive for peaking the first IF transformer.? Once you’ve identified the crystal frequency, you want to make sure that adjustment U is tuned for
the center of the DIP you found – in other words, a MINIMUM of the beat note at the IF frequency.? At that point, the audio note will be much lower, and you’ll hear much more of a “swishing” sound than the beat note.? If you don’t find it, then you turn adjustment
U a little bit one way or the other to try to bring the transformer into the range of the crystal frequency.
?
To find the crystal frequency, I connected a VTVM to the 500 ohm speaker output and put my signal generator into a slow sweep between 450 and 460 KHz.? Watching the VTVM, I found a beat note dip on the slope of one of the passes – that got me into the “ballpark”.?
I then stopped the sweep and set the generator for the approximate frequency where the dip was found, and then began manually adjusting the generator frequency in very small steps.? Once located (in my case, it was 453.48 KHz), I “peaked” the transformer for
“minimum” beat note and maximum swishing sound.?
?
Honestly, I believe there are easier ways to find the actual crystal frequency.? The instruction in the manual is too much voodoo for my taste.? My SX-110 is a bit of a fun test radio, and one thing on my agenda (for today, in fact) was to simply discover the
crystal frequency by running the signal generator through it and monitoring for a peak on the oscilloscope.? The crystal will have maximum output at its resonant frequency.? Then, I’ll try peaking up the 1st IF using that frequency, using a modulated
signal and with the BFO turned off.
?
73 – Steve, KW4H
?
?
New to the forum and restoring an SX-71. I'm trying to go through the alignment procedure in the manual.
I'm stuck at Step 2 adjusting the IF coil associated with the 455 kHz crystal (adjusting tank U, aka T9 bottom).
I've watched some YouTubes on the topic, and most I've seen use a sweep generator and spectrum analyzer instead of the legacy Step 2 procedure.
I have an IFR 1200A but it doesn't have a sweep generator, so I attempted to do my adjustment per the manual. I've set the controls per the Step 2 instructions. Per my IFR 1200A the crystal seems to be at 457.9 kHz,
so that is what I'm generating with my IFR.
I was able to adjust tank U for a peak, but then I tried to look for dip & second peak on either side of the main peak, and couldn't seem to find it (I understand the adjustment goal is mid-way between the main peak
and the dip). At the main peak, adjusting the frequency +/- 100 Hz resulted in 40 dB drop.
Subsequently, I tried to adjust again for the former peak, but this time the best peak I could get was about???of what I had before, and when 100 Hz off center freq, the drop is far less dramatic.
I fear that I dislodged the ferrite slug from the adjustment screw by going too far one way or the other.
|
Thanks Scott. The subchassis sounds like it's the 2.0xx MHz converter. Did you try to repair the loose slug? If so, how did you do it?
toggle quoted message
Show quoted text
I had a broken slug on my Sx-71, I discovered it because it would tune when upside down, and rite side up it wouldn't.
it was on the subchassis in the left rear.
Randy,
?
I’ve been working on a SX-110, which uses the same type of instruction, and it’s confusing and seems counter-intuitive for peaking the first IF transformer.? Once you’ve identified the crystal frequency, you want to make sure that adjustment U is tuned for
the center of the DIP you found – in other words, a MINIMUM of the beat note at the IF frequency.? At that point, the audio note will be much lower, and you’ll hear much more of a “swishing” sound than the beat note.? If you don’t find it, then you turn adjustment
U a little bit one way or the other to try to bring the transformer into the range of the crystal frequency.
?
To find the crystal frequency, I connected a VTVM to the 500 ohm speaker output and put my signal generator into a slow sweep between 450 and 460 KHz.? Watching the VTVM, I found a beat note dip on the slope of one of the passes – that got me into the “ballpark”.?
I then stopped the sweep and set the generator for the approximate frequency where the dip was found, and then began manually adjusting the generator frequency in very small steps.? Once located (in my case, it was 453.48 KHz), I “peaked” the transformer for
“minimum” beat note and maximum swishing sound.?
?
Honestly, I believe there are easier ways to find the actual crystal frequency.? The instruction in the manual is too much voodoo for my taste.? My SX-110 is a bit of a fun test radio, and one thing on my agenda (for today, in fact) was to simply discover the
crystal frequency by running the signal generator through it and monitoring for a peak on the oscilloscope.? The crystal will have maximum output at its resonant frequency.? Then, I’ll try peaking up the 1st IF using that frequency, using a modulated
signal and with the BFO turned off.
?
73 – Steve, KW4H
?
?
New to the forum and restoring an SX-71. I'm trying to go through the alignment procedure in the manual.
I'm stuck at Step 2 adjusting the IF coil associated with the 455 kHz crystal (adjusting tank U, aka T9 bottom).
I've watched some YouTubes on the topic, and most I've seen use a sweep generator and spectrum analyzer instead of the legacy Step 2 procedure.
I have an IFR 1200A but it doesn't have a sweep generator, so I attempted to do my adjustment per the manual. I've set the controls per the Step 2 instructions. Per my IFR 1200A the crystal seems to be at 457.9 kHz,
so that is what I'm generating with my IFR.
I was able to adjust tank U for a peak, but then I tried to look for dip & second peak on either side of the main peak, and couldn't seem to find it (I understand the adjustment goal is mid-way between the main peak
and the dip). At the main peak, adjusting the frequency +/- 100 Hz resulted in 40 dB drop.
Subsequently, I tried to adjust again for the former peak, but this time the best peak I could get was about???of what I had before, and when 100 Hz off center freq, the drop is far less dramatic.
I fear that I dislodged the ferrite slug from the adjustment screw by going too far one way or the other.
|
Hi Randy
Yes it was the converter.
???? I removed the transformer, and the top end cap and broken slug? pieces. The slug was broken where the lighter colored material meets the darker material , I carefully aligned the broken pieces and crazy glued them together. I lightly sanded the slug down
to fit smoothly in the tube, and I then switched it with the lower slug, thinking if the glue ever failed, the slug wouldn't fall like the top one did
Scott
toggle quoted message
Show quoted text
Thanks Scott. The subchassis sounds like it's the 2.0xx MHz converter. Did you try to repair the loose slug? If so, how did you do it?
I had a broken slug on my Sx-71, I discovered it because it would tune when upside down, and rite side up it wouldn't.
it was on the subchassis in the left rear.
Randy,
?
I’ve been working on a SX-110, which uses the same type of instruction, and it’s confusing and seems counter-intuitive for peaking the first IF transformer.? Once you’ve identified the crystal frequency, you want to make sure that adjustment U is tuned for
the center of the DIP you found – in other words, a MINIMUM of the beat note at the IF frequency.? At that point, the audio note will be much lower, and you’ll hear much more of a “swishing” sound than the beat note.? If you don’t find it, then you turn adjustment
U a little bit one way or the other to try to bring the transformer into the range of the crystal frequency.
?
To find the crystal frequency, I connected a VTVM to the 500 ohm speaker output and put my signal generator into a slow sweep between 450 and 460 KHz.? Watching the VTVM, I found a beat note dip on the slope of one of the passes – that got me into the “ballpark”.?
I then stopped the sweep and set the generator for the approximate frequency where the dip was found, and then began manually adjusting the generator frequency in very small steps.? Once located (in my case, it was 453.48 KHz), I “peaked” the transformer for
“minimum” beat note and maximum swishing sound.?
?
Honestly, I believe there are easier ways to find the actual crystal frequency.? The instruction in the manual is too much voodoo for my taste.? My SX-110 is a bit of a fun test radio, and one thing on my agenda (for today, in fact) was to simply discover the
crystal frequency by running the signal generator through it and monitoring for a peak on the oscilloscope.? The crystal will have maximum output at its resonant frequency.? Then, I’ll try peaking up the 1st IF using that frequency, using a modulated
signal and with the BFO turned off.
?
73 – Steve, KW4H
?
?
New to the forum and restoring an SX-71. I'm trying to go through the alignment procedure in the manual.
I'm stuck at Step 2 adjusting the IF coil associated with the 455 kHz crystal (adjusting tank U, aka T9 bottom).
I've watched some YouTubes on the topic, and most I've seen use a sweep generator and spectrum analyzer instead of the legacy Step 2 procedure.
I have an IFR 1200A but it doesn't have a sweep generator, so I attempted to do my adjustment per the manual. I've set the controls per the Step 2 instructions. Per my IFR 1200A the crystal seems to be at 457.9 kHz,
so that is what I'm generating with my IFR.
I was able to adjust tank U for a peak, but then I tried to look for dip & second peak on either side of the main peak, and couldn't seem to find it (I understand the adjustment goal is mid-way between the main peak
and the dip). At the main peak, adjusting the frequency +/- 100 Hz resulted in 40 dB drop.
Subsequently, I tried to adjust again for the former peak, but this time the best peak I could get was about???of what I had before, and when 100 Hz off center freq, the drop is far less dramatic.
I fear that I dislodged the ferrite slug from the adjustment screw by going too far one way or the other.
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Randy - W7HMT - North Bend WA