The AVC circuit is designed to adjust the gain in reference to the input signal to the RF circuit. Too much gain and the circuit reduces it, too little and it's increased. This is to maintain a constant relationship between weak stations and strong stations so the volume control isn't constantly being turned up and down.
Obviously, if the gain is being artificially changed by attempts at alignment, the circuit will constantly try and adjust it to maintain a balance. It is literally a case of the dog chasing it's tail. If one wants to gauge the action, take a voltage reading at the top of the volume control and tune through several stations. The voltage should change very little.
An attempt to describe the steps necessary to achieve a successful alignment is WAY beyond the scope of this thread, but can be found in most service literature. One good reference is Alfred Corbin's "A Modern Look at Antique Radio Repair".
Also, the information is usually included with the specific model service info. This usually includes the correct IF frequency, signal generator settings and type of signal level indicator, (Like an RCA Voltohmist).
An alignment is a VERY difficult procedure and should only be attempted if ABSOLUTELY necessary. Even then it should only be attempted by someone with a lot of experience and understanding of the circuitry involved.
This message is not meant to make any assumptions or denigrate anyone's ability, but to simply inform. I hope that it is taken in that context.
Terry Decker
:There seems to be a common misunderstanding about the relationship between AVC, (automatic voltage control, or AGC, automatic gain control as it in now called), and alignment.
:
:The AVC circuit is designed to adjust the gain in reference to the input signal to the RF circuit. Too much gain and the circuit reduces it, too little and it's increased. This is to maintain a constant relationship between weak stations and strong stations so the volume control isn't constantly being turned up and down.
:
:Obviously, if the gain is being artificially changed by attempts at alignment, the circuit will constantly try and adjust it to maintain a balance. It is literally a case of the dog chasing it's tail. If one wants to gauge the action, take a voltage reading at the top of the volume control and tune through several stations. The voltage should change very little.
:
:An attempt to describe the steps necessary to achieve a successful alignment is WAY beyond the scope of this thread, but can be found in most service literature. One good reference is Alfred Corbin's "A Modern Look at Antique Radio Repair".
:
:Also, the information is usually included with the specific model service info. This usually includes the correct IF frequency, signal generator settings and type of signal level indicator, (Like an RCA Voltohmist).
:
:An alignment is a VERY difficult procedure and should only be attempted if ABSOLUTELY necessary. Even then it should only be attempted by someone with a lot of experience and understanding of the circuitry involved.
:
:This message is not meant to make any assumptions or denigrate anyone's ability, but to simply inform. I hope that it is taken in that context.
:Terry Decker
:
:
:
:
:
Over simplified, maybe-Hogwash, I don't think so. Sure, for those of us who have done a lot of these, it's easy, for a beginner-not so much. For instance anyone who knows what they are doing wouldn't ask how to use the AVG for alignment. Also, accidentally messing with the oscillator is probably going to cause some MAJOR problems.
And yeah, there are a couple of mistakes in my explanation. It IS automatic volume control, not automatic voltage control, and the top of the volume control not the best place to measure the voltage change.
However, I stand by my statement that using the AVC voltage to do an alignment ain't gonna work.
:
::There seems to be a common misunderstanding about the relationship between AVC, (automatic voltage control, or AGC, automatic gain control as it in now called), and alignment.
::
::The AVC circuit is designed to adjust the gain in reference to the input signal to the RF circuit. Too much gain and the circuit reduces it, too little and it's increased. This is to maintain a constant relationship between weak stations and strong stations so the volume control isn't constantly being turned up and down.
::
::Obviously, if the gain is being artificially changed by attempts at alignment, the circuit will constantly try and adjust it to maintain a balance. It is literally a case of the dog chasing it's tail. If one wants to gauge the action, take a voltage reading at the top of the volume control and tune through several stations. The voltage should change very little.
::
::An attempt to describe the steps necessary to achieve a successful alignment is WAY beyond the scope of this thread, but can be found in most service literature. One good reference is Alfred Corbin's "A Modern Look at Antique Radio Repair".
::
::Also, the information is usually included with the specific model service info. This usually includes the correct IF frequency, signal generator settings and type of signal level indicator, (Like an RCA Voltohmist).
::
::An alignment is a VERY difficult procedure and should only be attempted if ABSOLUTELY necessary. Even then it should only be attempted by someone with a lot of experience and understanding of the circuitry involved.
::
::This message is not meant to make any assumptions or denigrate anyone's ability, but to simply inform. I hope that it is taken in that context.
::Terry Decker
::
::
::
::
:
:
:However, I stand by my statement that using the AVC voltage to do an alignment ain't gonna work.
:
Hi Terry:
Sorry to sound like I am contradicting you.
...and I can see that you feel strongly about the AVC indication not being able to tweak the IFs. ....but I am puzzled why you think that?
What is it about the idea of watching the AVC voltage go more negative when the IFs are being properly tuned-in ... that you don't seem to agree with?
I have done this many many times with no trouble.
It works very nicely for me.
In fact (I think) it was Norm Leal that I learned it from when he explained the method some years ago on here.
So maybe I'm missing something that you are saying.
Can you just enlighten me a little Terry, and elaborate you thoughts a bit more so it doesn't look like we are butting heads here?
::However, I stand by my statement that using the AVC voltage to do an alignment ain't gonna work.
::
:
:Hi Terry:
:Sorry to sound like I am contradicting you.
:...and I can see that you feel strongly about the AVC indication not being able to tweak the IFs. ....but I am puzzled why you think that?
:
:What is it about the idea of watching the AVC voltage go more negative when the IFs are being properly tuned-in ... that you don't seem to agree with?
:
:I have done this many many times with no trouble.
:It works very nicely for me.
:
:In fact (I think) it was Norm Leal that I learned it from when he explained the method some years ago on here.
:So maybe I'm missing something that you are saying.
:
:Can you just enlighten me a little Terry, and elaborate you thoughts a bit more so it doesn't look like we are butting heads here?
:
:
No, you are right, it CAN be done, if you know what you're doing. However, it could be misleading to a novice. This post was in response to two other threads about using sweep generators, etc. and AVC to do alignments. As I said in one of them, I had three books open in front of me at the time, Alfred's "Antique Radio Repair", Marcus' "Elements of Radio servicing", and Audel's "Radioman's Guide". I was paraphrasing all of them in my statement. And the summation of them all was that the AVC should ALWAYS be disengaged during alignment, or the generator output should be kept at the lowest possible setting to produce a signal without activating the AVC. They also said, exactly what I said, about the fact that as the signal voltage increased during alignment, the AVC would keep trying to catch up. Therefore the signal would just be going 'round robin. Most service info strongly suggests putting an ACVTVM across the speaker, or primary of the output transformer, and then how and where to inject the signal. In fact I'm looking at a schematic right now that explains how to disable the AVC.
Actually, I've never used the AVC voltage to do an alignment either. And trust me, I've done my share of alignments.
As I implied in my post, I'm not trying to tell anyone else what to do, just sharing my own experience and the descriptions I've read of the circuits involved.
Terry
::
:::However, I stand by my statement that using the AVC voltage to do an alignment ain't gonna work.
:::
::
::Hi Terry:
::Sorry to sound like I am contradicting you.
::...and I can see that you feel strongly about the AVC indication not being able to tweak the IFs. ....but I am puzzled why you think that?
::
::What is it about the idea of watching the AVC voltage go more negative when the IFs are being properly tuned-in ... that you don't seem to agree with?
::
::I have done this many many times with no trouble.
::It works very nicely for me.
::
::In fact (I think) it was Norm Leal that I learned it from when he explained the method some years ago on here.
::So maybe I'm missing something that you are saying.
::
::Can you just enlighten me a little Terry, and elaborate you thoughts a bit more so it doesn't look like we are butting heads here?
::
::
:No, you are right, it CAN be done, if you know what you're doing. However, it could be misleading to a novice. This post was in response to two other threads about using sweep generators, etc. and AVC to do alignments. As I said in one of them, I had three books open in front of me at the time, Alfred's "Antique Radio Repair", Marcus' "Elements of Radio servicing", and Audel's "Radioman's Guide". I was paraphrasing all of them in my statement. And the summation of them all was that the AVC should ALWAYS be disengaged during alignment, or the generator output should be kept at the lowest possible setting to produce a signal without activating the AVC. They also said, exactly what I said, about the fact that as the signal voltage increased during alignment, the AVC would keep trying to catch up. Therefore the signal would just be going 'round robin. Most service info strongly suggests putting an ACVTVM across the speaker, or primary of the output transformer, and then how and where to inject the signal. In fact I'm looking at a schematic right now that explains how to disable the AVC.
:
:Actually, I've never used the AVC voltage to do an alignment either. And trust me, I've done my share of alignments.
:As I implied in my post, I'm not trying to tell anyone else what to do, just sharing my own experience and the descriptions I've read of the circuits involved.
:Terry
:
Thanks for pointing that out. I love you too. Have a good one.
Terry
:
:::
::::However, I stand by my statement that using the AVC voltage to do an alignment ain't gonna work.
::::
:::
:::Hi Terry:
:::Sorry to sound like I am contradicting you.
:::...and I can see that you feel strongly about the AVC indication not being able to tweak the IFs. ....but I am puzzled why you think that?
:::
:::What is it about the idea of watching the AVC voltage go more negative when the IFs are being properly tuned-in ... that you don't seem to agree with?
:::
:::I have done this many many times with no trouble.
:::It works very nicely for me.
:::
:::In fact (I think) it was Norm Leal that I learned it from when he explained the method some years ago on here.
:::So maybe I'm missing something that you are saying.
:::
:::Can you just enlighten me a little Terry, and elaborate you thoughts a bit more so it doesn't look like we are butting heads here?
:::
:::
::No, you are right, it CAN be done, if you know what you're doing. However, it could be misleading to a novice. This post was in response to two other threads about using sweep generators, etc. and AVC to do alignments. As I said in one of them, I had three books open in front of me at the time, Alfred's "Antique Radio Repair", Marcus' "Elements of Radio servicing", and Audel's "Radioman's Guide". I was paraphrasing all of them in my statement. And the summation of them all was that the AVC should ALWAYS be disengaged during alignment, or the generator output should be kept at the lowest possible setting to produce a signal without activating the AVC. They also said, exactly what I said, about the fact that as the signal voltage increased during alignment, the AVC would keep trying to catch up. Therefore the signal would just be going 'round robin. Most service info strongly suggests putting an ACVTVM across the speaker, or primary of the output transformer, and then how and where to inject the signal. In fact I'm looking at a schematic right now that explains how to disable the AVC.
::
::Actually, I've never used the AVC voltage to do an alignment either. And trust me, I've done my share of alignments.
::As I implied in my post, I'm not trying to tell anyone else what to do, just sharing my own experience and the descriptions I've read of the circuits involved.
::Terry
::
:
:
Superheterodyne Alignment
By Bruce McCalley
...."Output meters are generally of two types: one is an indicator across the speaker voice coil (which might even by your ear!); and the other is an indicator across the AVC line at the detector. The indicator might be a meter, an oscilloscope, a tuning eye, or whatever. The best is the one on the AVC line. AVC voltage increases with signal level and is therefore a positive indication of a peak in adjustment. The output at the speaker, and particularly just listening for maximum, is far less accurate. Why? Because if the set has AVC, the increasing AVC voltage tends to reduce the audio output (that's why it's there; for Automatic Volume Control!) so the "peak" is apparently broader. On early sets with no AVC, of course, there is no choice"
REF: http://www.antiqueradios.org/gazette/align.htm
:
:The AVC circuit is designed to adjust the gain in reference to the input signal to the RF circuit. Too much gain and the circuit reduces it, too little and it's increased. This is to maintain a constant relationship between weak stations and strong stations so the volume control isn't constantly being turned up and down.
:
:Obviously, if the gain is being artificially changed by attempts at alignment, the circuit will constantly try and adjust it to maintain a balance. It is literally a case of the dog chasing it's tail. If one wants to gauge the action, take a voltage reading at the top of the volume control and tune through several stations. The voltage should change very little.
:
:An attempt to describe the steps necessary to achieve a successful alignment is WAY beyond the scope of this thread, but can be found in most service literature. One good reference is Alfred Corbin's "A Modern Look at Antique Radio Repair".
:
:Also, the information is usually included with the specific model service info. This usually includes the correct IF frequency, signal generator settings and type of signal level indicator, (Like an RCA Voltohmist).
:
:An alignment is a VERY difficult procedure and should only be attempted if ABSOLUTELY necessary. Even then it should only be attempted by someone with a lot of experience and understanding of the circuitry involved.
:
:This message is not meant to make any assumptions or denigrate anyone's ability, but to simply inform. I hope that it is taken in that context.
:Terry Decker
:
:
:
:
Good post Terry. Gives food for thought and should cause folks to take a look at the AVC circuit as opposed to the alignment procedure. I have to at least check the alignment of my Crosley that Warren helped me with on the rebuild of the IF cans. The info from the schematic is very explicite about the test points, signal generator and using a VTVM and what i should be looking for.
Mitch
.. but it's been my experience that aligning an AM radio is really not very hard to do at all.
As long as you clearly understand what you are trying to accomplish...
A signal generator and a few tweaks.. and that's it.
::
::The AVC circuit is designed to adjust the gain in reference to the input signal to the RF circuit. Too much gain and the circuit reduces it, too little and it's increased. This is to maintain a constant relationship between weak stations and strong stations so the volume control isn't constantly being turned up and down.
::
::Obviously, if the gain is being artificially changed by attempts at alignment, the circuit will constantly try and adjust it to maintain a balance. It is literally a case of the dog chasing it's tail. If one wants to gauge the action, take a voltage reading at the top of the volume control and tune through several stations. The voltage should change very little.
::
::An attempt to describe the steps necessary to achieve a successful alignment is WAY beyond the scope of this thread, but can be found in most service literature. One good reference is Alfred Corbin's "A Modern Look at Antique Radio Repair".
::
::Also, the information is usually included with the specific model service info. This usually includes the correct IF frequency, signal generator settings and type of signal level indicator, (Like an RCA Voltohmist).
::
::An alignment is a VERY difficult procedure and should only be attempted if ABSOLUTELY necessary. Even then it should only be attempted by someone with a lot of experience and understanding of the circuitry involved.
::
::This message is not meant to make any assumptions or denigrate anyone's ability, but to simply inform. I hope that it is taken in that context.
::Terry Decker
::
::
::
::
:Good post Terry. Gives food for thought and should cause folks to take a look at the AVC circuit as opposed to the alignment procedure. I have to at least check the alignment of my Crosley that Warren helped me with on the rebuild of the IF cans. The info from the schematic is very explicite about the test points, signal generator and using a VTVM and what i should be looking for.
:Mitch
:
Hey Mitch-
As you know, we've been trading information for a while now. I've watched you grow from a novice into a good tech. You've paid attention and learned a lot in a short time. I have no doubt that you are going to do a great job and have the set up an running in no time. And I also know from experience that Warren is one of the best.
I hope you took my 'disclaimer' in a better spirit than some.
Good luck and keep us posted.
Terry
:::
:::The AVC circuit is designed to adjust the gain in reference to the input signal to the RF circuit. Too much gain and the circuit reduces it, too little and it's increased. This is to maintain a constant relationship between weak stations and strong stations so the volume control isn't constantly being turned up and down.
:::
:::Obviously, if the gain is being artificially changed by attempts at alignment, the circuit will constantly try and adjust it to maintain a balance. It is literally a case of the dog chasing it's tail. If one wants to gauge the action, take a voltage reading at the top of the volume control and tune through several stations. The voltage should change very little.
:::
:::An attempt to describe the steps necessary to achieve a successful alignment is WAY beyond the scope of this thread, but can be found in most service literature. One good reference is Alfred Corbin's "A Modern Look at Antique Radio Repair".
:::
:::Also, the information is usually included with the specific model service info. This usually includes the correct IF frequency, signal generator settings and type of signal level indicator, (Like an RCA Voltohmist).
:::
:::An alignment is a VERY difficult procedure and should only be attempted if ABSOLUTELY necessary. Even then it should only be attempted by someone with a lot of experience and understanding of the circuitry involved.
:::
:::This message is not meant to make any assumptions or denigrate anyone's ability, but to simply inform. I hope that it is taken in that context.
:::Terry Decker
:::
:::
:::
:::
::Good post Terry. Gives food for thought and should cause folks to take a look at the AVC circuit as opposed to the alignment procedure. I have to at least check the alignment of my Crosley that Warren helped me with on the rebuild of the IF cans. The info from the schematic is very explicite about the test points, signal generator and using a VTVM and what i should be looking for.
::Mitch
::
:Hey Mitch-
:As you know, we've been trading information for a while now. I've watched you grow from a novice into a good tech. You've paid attention and learned a lot in a short time. I have no doubt that you are going to do a great job and have the set up an running in no time. And I also know from experience that Warren is one of the best.
:I hope you took my 'disclaimer' in a better spirit than some.
:Good luck and keep us posted.
:Terry
:
It's people like you and Warren that keep people like me going. All that contribute on NA are appreciated, it is my hope that some day i will be able to help others. As for now i have the first IF can installed in my Crosley with the new caps and have taken a pic to insure it is right, will send to Warren? He has my one line mechanacial drawings and can say Mitch this is right. Second can tomorrow if i can see through the day, maybe at the evening hours. Would like to hear this radio work at some time in my life.
Remember the time you were almost through with me and said, well you could buy a 100 foot wave antenna from radio shack to solve the reception problem? You worked with me to find the bad capacitor in the circuit, alas, i listen to the radio today.
Your are blessed, just know it yet Terry.
Mitch
Here's a clear description for reference:
http://www.vias.org/basicradio/basic_radio_33_10.html
:Here's a clear description for reference:
:http://www.vias.org/basicradio/basic_radio_33_10.html
:
Below is a partial excerpt from the above referenced website:
Automatic Volume Control
Author: J.B. Hoag
"Due to fading, the carrier frequency often varies in amplitude. This causes undesirable changes in the volume of sound radiated from the loudspeaker. The fading sometimes occurs too rapidly to be compensated for manually by a gain-control system. Within limits, an a.v.c. circuit automatically keeps the output at constant volume.
In Fig. 32 N, the diode-detector rectifies the r.f. (or the i.f.) currents and develops a d.c. voltage across resistor R1, with negative at its ungrounded end, and of an amount proportionate to the audio signal plus the fading modulation on the carrier. The audio component is bypassed through C2 (the r.f. goes through C1 and is kept out of C2 by resistor R2), leaving the undesired fading voltage to continue to the left as indicated by the arrow marked a.v.c. If the carrier strength increases, the voltage across R1 increases proportionately, and that part due to the undesired changes (fading) is fed back as a negative value onto the grids of the r.f. and i.f. amplifiers, to undo the increase. "
::Here's a clear description for reference:
::http://www.vias.org/basicradio/basic_radio_33_10.html
::
:Below is a partial excerpt from the above referenced website:
:Automatic Volume Control
:Author: J.B. Hoag
:
:"Due to fading, the carrier frequency often varies in amplitude. This causes undesirable changes in the volume of sound radiated from the loudspeaker. The fading sometimes occurs too rapidly to be compensated for manually by a gain-control system. Within limits, an a.v.c. circuit automatically keeps the output at constant volume.
:
:In Fig. 32 N, the diode-detector rectifies the r.f. (or the i.f.) currents and develops a d.c. voltage across resistor R1, with negative at its ungrounded end, and of an amount proportionate to the audio signal plus the fading modulation on the carrier. The audio component is bypassed through C2 (the r.f. goes through C1 and is kept out of C2 by resistor R2), leaving the undesired fading voltage to continue to the left as indicated by the arrow marked a.v.c. If the carrier strength increases, the voltage across R1 increases proportionately, and that part due to the undesired changes (fading) is fed back as a negative value onto the grids of the r.f. and i.f. amplifiers, to undo the increase. "
:
:
:
It's people like you and Warren that keep people like me going. All that contribute on NA are appreciated, it is my hope that some day i will be able to help others. As for now i have the first IF can installed in my Crosley with the new caps and have taken a pic to insure it is right, will send to Warren? He has my one line mechanacial drawings and can say Mitch this is right. Second can tomorrow if i can see through the day, maybe at the evening hours. Would like to hear this radio work at some time in my life.
Remember the time you were almost through with me and said, well you could buy a 100 foot wave antenna from radio shack to solve the reception problem? You worked with me to find the bad capacitor in the circuit, alas, i listen to the radio today.
Your are blessed, just know it yet Terry.
:
:The AVC circuit is designed to adjust the gain in reference to the input signal to the RF circuit. Too much gain and the circuit reduces it, too little and it's increased. This is to maintain a constant relationship between weak stations and strong stations so the volume control isn't constantly being turned up and down.
:
:Obviously, if the gain is being artificially changed by attempts at alignment, the circuit will constantly try and adjust it to maintain a balance. It is literally a case of the dog chasing it's tail. If one wants to gauge the action, take a voltage reading at the top of the volume control and tune through several stations. The voltage should change very little.
:
:An attempt to describe the steps necessary to achieve a successful alignment is WAY beyond the scope of this thread, but can be found in most service literature. One good reference is Alfred Corbin's "A Modern Look at Antique Radio Repair".
:
:Also, the information is usually included with the specific model service info. This usually includes the correct IF frequency, signal generator settings and type of signal level indicator, (Like an RCA Voltohmist).
:
:An alignment is a VERY difficult procedure and should only be attempted if ABSOLUTELY necessary. Even then it should only be attempted by someone with a lot of experience and understanding of the circuitry involved.
:
:This message is not meant to make any assumptions or denigrate anyone's ability, but to simply inform. I hope that it is taken in that context.
:Terry Decker
:
:
:
:
There has been some heated discussion about my statements in this this thread. Discussion is good, vitriolic dialog-not so much.
It has been pointed out that there is a way to use the AVC circuit to aid in alignment. It would be safe to say that I was not aware of this.
However, I would like to refer to some of the service information that I have used as my guide in this matter.
RCA 65X1-"Keep the oscillator output as low as possible to avoid AVC action".
GE 202- "...readings taken with low signal input so that the AVC is not effective".
RCA BP-10- "For all alignment operations keep the output as low as possible to avoid AVC action".
RCA 66X11- "Keep the output signal as low as possible to avoid AVC action".
These are quotes just from the schematics I have on hand. It would seem that the gist of my original statements stand on they're own merit. Perhaps there ARE other approaches to this, but they do NOT seem to be supported by the manufacturers recommendations.
Once again, in my defense, I have used nothing but published information to make my statements. I hope this will satisfy those who have seen fit to lambast me in this forum.
Have a nice day. :-o
Terry
::An alignment is a VERY difficult procedure and should only be attempted if ABSOLUTELY necessary. Even then it should only be attempted by someone with a lot of experience and understanding of the circuitry involved.
:::An alignment is a VERY difficult procedure and should only be attempted if ABSOLUTELY necessary. Even then it should only be attempted by someone with a lot of experience and understanding of the circuitry involved.
:
:
:
:
::::An alignment is a VERY difficult procedure and should only be attempted if ABSOLUTELY necessary. Even then it should only be attempted by someone with a lot of experience and understanding of the circuitry involved.
::
::
::
::
:
:
If you are a novice and barely understand the circuit, or if somehow the oscillator is changed instead of the IF, or one ties to use a sweep generator, then I'd say yes, it CAN be very difficult.
Geez, WHAT is your problem?
T.
Bear in mind that most shops were not run by guys with a lot of training in electronics theory. They often learned their trade on the job. After a while they learned which part to change if a certain model had a particular problem. There were also technicians who did completely understand what they were doing, but these were somewhat fewer in number. Both types could and often did have very successful businesses. The manufacturers defined alignment procedures that led to the best results for all.
Study each step of the written alignment procedure,and positively ID the physical location of each adjustment point in the procedure on the radio chassis. (Label it on the chassis if its not labeled already)
If a step in the procedure is not clear, you may want to ask someone what it means.
Mark the starting location of all adjustment points so you can go back to the original setting if you have to.
Positively ID the location of each point on the set where a voltage measurement it to be taken.
Confirm that your signal generator, AC voltmeter,test cables, and any other test equipment is working AND that you know how to set it up and use it correctly.
All these steps can help a novice or even expert technicians avoid problems, and should be done before making first adjustment.
I would agree that the actual alignment part is fairly simple, but it is also to easy to make errors if you don't do the preliminary steps above.
Most experienced technicians do a lot of these steps so often they become automatic, and we don't even think about them.
:There seems to be a common misunderstanding about the relationship between AVC, (automatic voltage control, or AGC, automatic gain control as it in now called), and alignment.
:
:The AVC circuit is designed to adjust the gain in reference to the input signal to the RF circuit. Too much gain and the circuit reduces it, too little and it's increased. This is to maintain a constant relationship between weak stations and strong stations so the volume control isn't constantly being turned up and down.
:
:Obviously, if the gain is being artificially changed by attempts at alignment, the circuit will constantly try and adjust it to maintain a balance. It is literally a case of the dog chasing it's tail. If one wants to gauge the action, take a voltage reading at the top of the volume control and tune through several stations. The voltage should change very little.
:
:An attempt to describe the steps necessary to achieve a successful alignment is WAY beyond the scope of this thread, but can be found in most service literature. One good reference is Alfred Corbin's "A Modern Look at Antique Radio Repair".
:
:Also, the information is usually included with the specific model service info. This usually includes the correct IF frequency, signal generator settings and type of signal level indicator, (Like an RCA Voltohmist).
:
:An alignment is a VERY difficult procedure and should only be attempted if ABSOLUTELY necessary. Even then it should only be attempted by someone with a lot of experience and understanding of the circuitry involved.
:
:This message is not meant to make any assumptions or denigrate anyone's ability, but to simply inform. I hope that it is taken in that context.
:Terry Decker
:
:
:
:
:
:Study each step of the written alignment procedure,and positively ID the physical location of each adjustment point in the procedure on the radio chassis. (Label it on the chassis if its not labeled already)
:
:If a step in the procedure is not clear, you may want to ask someone what it means.
:
:Mark the starting location of all adjustment points so you can go back to the original setting if you have to.
:
:Positively ID the location of each point on the set where a voltage measurement it to be taken.
:
:Confirm that your signal generator, AC voltmeter,test cables, and any other test equipment is working AND that you know how to set it up and use it correctly.
:
:All these steps can help a novice or even expert technicians avoid problems, and should be done before making first adjustment.
:
:I would agree that the actual alignment part is fairly simple, but it is also to easy to make errors if you don't do the preliminary steps above.
:
:Most experienced technicians do a lot of these steps so often they become automatic, and we don't even think about them.
:
:
:
:
Excellent advice. I would only add a couple of tips. If using a tube type generator, like the Heathkit IG-102, you should let both the generator and the radio warm up for about 15 minutes to stabilize. Start with the last transformer and work forward. Use an "Alignment" tool, NOT a regular screwdriver. The metal of the screwdriver will interact with the inductance of the transformer coil. Go over the instructions, and advice in these tutorials, until totally confident. DO NOT touch anything in the oscillator circuit unless absolutely necessary. Once the oscillator is detuned, it's very difficult to get it back on track.
Have fun.
Terry
::There seems to be a common misunderstanding about the relationship between AVC, (automatic voltage control, or AGC, automatic gain control as it in now called), and alignment.
::
::The AVC circuit is designed to adjust the gain in reference to the input signal to the RF circuit. Too much gain and the circuit reduces it, too little and it's increased. This is to maintain a constant relationship between weak stations and strong stations so the volume control isn't constantly being turned up and down.
::
::Obviously, if the gain is being artificially changed by attempts at alignment, the circuit will constantly try and adjust it to maintain a balance. It is literally a case of the dog chasing it's tail. If one wants to gauge the action, take a voltage reading at the top of the volume control and tune through several stations. The voltage should change very little.
::
::An attempt to describe the steps necessary to achieve a successful alignment is WAY beyond the scope of this thread, but can be found in most service literature. One good reference is Alfred Corbin's "A Modern Look at Antique Radio Repair".
::
::Also, the information is usually included with the specific model service info. This usually includes the correct IF frequency, signal generator settings and type of signal level indicator, (Like an RCA Voltohmist).
::
::An alignment is a VERY difficult procedure and should only be attempted if ABSOLUTELY necessary. Even then it should only be attempted by someone with a lot of experience and understanding of the circuitry involved.
::
::This message is not meant to make any assumptions or denigrate anyone's ability, but to simply inform. I hope that it is taken in that context.
::Terry Decker
::
::
::
::
:
:
:........ DO NOT touch anything in the oscillator circuit unless absolutely necessary. Once the oscillator is detuned, it's very difficult to get it back on track.
:Have fun.
:Terry
No it isn't. Anyone who can follow simple instructions can do a complete alignment without difficulty. Contintuing to make a big deal of it and saying how hard everything is only brings your competence as into question.
A lot of inexperienced folks read this site. Having someone who knows very little continually saying how difficult everything is can discourage them from pursuing a very entertaining hobby.
::........ DO NOT touch anything in the oscillator circuit unless absolutely necessary. Once the oscillator is detuned, it's very difficult to get it back on track.
::Have fun.
::Terry
:
:
:No it isn't. Anyone who can follow simple instructions can do a complete alignment without difficulty. Contintuing to make a big deal of it and saying how hard everything is only brings your competence as into question.
:
:A lot of inexperienced folks read this site. Having someone who knows very little continually saying how difficult everything is can discourage them from pursuing a very entertaining hobby.
:
:
:::........ DO NOT touch anything in the oscillator circuit unless absolutely necessary. Once the oscillator is detuned, it's very difficult to get it back on track.
:::Have fun.
:::Terry
::
::
::No it isn't. Anyone who can follow simple instructions can do a complete alignment without difficulty. Contintuing to make a big deal of it and saying how hard everything is only brings your competence as into question.
::
::A lot of inexperienced folks read this site. Having someone who knows very little continually saying how difficult everything is can discourage them from pursuing a very entertaining hobby.
::
::
:
:
Whatever,
Enough members have left comments that they appreciate what I'm trying to say. I don't think any of these disparaging remarks about my experience, or stupidity, or how I wash my hog, are really doing anything but showing the arrogance of someone who won't sign their name trying to ruin my day.
Good luck-
I have a VERY thick skin.
An possibly a LOT more experience.
Terry
:Good luck-
:I have a VERY thick skin.
:An possibly a LOT more experience.
:Terry
The only person that can ruin your day is you. If you had any confidence in your own knowledge you would just give your advice and go away like the really knowledgeble and mature contributors do. If someone contradicts it with something you don't understand, instead of arguing that your way is the only way, ask what they mean and why. You might just learn something that way.
If you great experience is what it seems to be it consisted of "connect the red cable to jack number three". If the system goes "whoop, whoop, whoop, move it to jack four. Not really very impressive.
:
:The AVC circuit is designed to adjust the gain in reference to the input signal to the RF circuit. Too much gain and the circuit reduces it, too little and it's increased. This is to maintain a constant relationship between weak stations and strong stations so the volume control isn't constantly being turned up and down.
:
:Obviously, if the gain is being artificially changed by attempts at alignment, the circuit will constantly try and adjust it to maintain a balance. It is literally a case of the dog chasing it's tail. If one wants to gauge the action, take a voltage reading at the top of the volume control and tune through several stations. The voltage should change very little.
:
:An attempt to describe the steps necessary to achieve a successful alignment is WAY beyond the scope of this thread, but can be found in most service literature. One good reference is Alfred Corbin's "A Modern Look at Antique Radio Repair".
:
:Also, the information is usually included with the specific model service info. This usually includes the correct IF frequency, signal generator settings and type of signal level indicator, (Like an RCA Voltohmist).
:
:An alignment is a VERY difficult procedure and should only be attempted if ABSOLUTELY necessary. Even then it should only be attempted by someone with a lot of experience and understanding of the circuitry involved.
:
:This message is not meant to make any assumptions or denigrate anyone's ability, but to simply inform. I hope that it is taken in that context.
:Terry Decker
:
:
:
:
I don't feel the need to justify myself. But there is one statement that I would like to make. To the best of my ability to do so, there is not ONE SINGLE statement in this thread that I have not substantiated beforehand by checking with acknowledged and published information.
My sources have included, but were not limited to:
"Elements of Radio servicing" by Marcus and Levy
"A Modern Look at Antique Radio Repair" Third edition- by Alfred Corbin
"Audel's Radioman's Guide" by E.P. Anderson
"Elementary Radio Servicing" by William R. Wellman
"Radio Troubleshooting Handbook" by Ghirardi
and MANY years as the owner of Reliable Sound and Video.
Some of my comments have been augmented by new information, and I ALWAYS appreciate being educated.
And as I said at the beginning-
"This message is not meant to make any assumptions or denigrate anyone's ability, but to simply inform. I hope that it is taken in that context."
Thanks to all who HAVE taken it in that context, and were proud to sign their names. You know who you are.
Terry
::
::The AVC circuit is designed to adjust the gain in reference to the input signal to the RF circuit. Too much gain and the circuit reduces it, too little and it's increased. This is to maintain a constant relationship between weak stations and strong stations so the volume control isn't constantly being turned up and down.
::
::Obviously, if the gain is being artificially changed by attempts at alignment, the circuit will constantly try and adjust it to maintain a balance. It is literally a case of the dog chasing it's tail. If one wants to gauge the action, take a voltage reading at the top of the volume control and tune through several stations. The voltage should change very little.
::
::An attempt to describe the steps necessary to achieve a successful alignment is WAY beyond the scope of this thread, but can be found in most service literature. One good reference is Alfred Corbin's "A Modern Look at Antique Radio Repair".
::
::Also, the information is usually included with the specific model service info. This usually includes the correct IF frequency, signal generator settings and type of signal level indicator, (Like an RCA Voltohmist).
::
::An alignment is a VERY difficult procedure and should only be attempted if ABSOLUTELY necessary. Even then it should only be attempted by someone with a lot of experience and understanding of the circuitry involved.
::
::This message is not meant to make any assumptions or denigrate anyone's ability, but to simply inform. I hope that it is taken in that context.
::Terry Decker
::
::
::
::
:I don't feel the need to justify myself. But there is one statement that I would like to make. To the best of my ability to do so, there is not ONE SINGLE statement in this thread that I have not substantiated beforehand by checking with acknowledged and published information.
:My sources have included, but were not limited to:
:"Elements of Radio servicing" by Marcus and Levy
:"A Modern Look at Antique Radio Repair" Third edition- by Alfred Corbin
:"Audel's Radioman's Guide" by E.P. Anderson
:"Elementary Radio Servicing" by William R. Wellman
:"Radio Troubleshooting Handbook" by Ghirardi
:and MANY years as the owner of Reliable Sound and Video.
:Some of my comments have been augmented by new information, and I ALWAYS appreciate being educated.
:And as I said at the beginning-
:
:"This message is not meant to make any assumptions or denigrate anyone's ability, but to simply inform. I hope that it is taken in that context."
:
:Thanks to all who HAVE taken it in that context, and were proud to sign their names. You know who you are.
:Terry
:
:
:
:
:
Terry,
Alignment and AVC.
I installed the IF cans and new capacitors that Warren worked on for me last night. Connected loop antenna and turned the radio on. Got a volume controlled noise through the tuning cap. Touching the antenna increased the noise level. Warren says this means i have gain through the stages, i agree. Before the alignment i will retest all tubes and check all tube voltages to insure all is right. I have a signal generator and VTVM to perform the alignment. It is my first one.
The last line in the alignment instructions read:
Turn the voume control on full and adjust the signal generator output to produce approximately midscale deflection of the output meter, BUT maintain signal generator output as low as possible to prevent AVC action in the receiver.
Your point made very well.
Mitch
:::
:::The AVC circuit is designed to adjust the gain in reference to the input signal to the RF circuit. Too much gain and the circuit reduces it, too little and it's increased. This is to maintain a constant relationship between weak stations and strong stations so the volume control isn't constantly being turned up and down.
:::
:::Obviously, if the gain is being artificially changed by attempts at alignment, the circuit will constantly try and adjust it to maintain a balance. It is literally a case of the dog chasing it's tail. If one wants to gauge the action, take a voltage reading at the top of the volume control and tune through several stations. The voltage should change very little.
:::
:::An attempt to describe the steps necessary to achieve a successful alignment is WAY beyond the scope of this thread, but can be found in most service literature. One good reference is Alfred Corbin's "A Modern Look at Antique Radio Repair".
:::
:::Also, the information is usually included with the specific model service info. This usually includes the correct IF frequency, signal generator settings and type of signal level indicator, (Like an RCA Voltohmist).
:::
:::An alignment is a VERY difficult procedure and should only be attempted if ABSOLUTELY necessary. Even then it should only be attempted by someone with a lot of experience and understanding of the circuitry involved.
:::
:::This message is not meant to make any assumptions or denigrate anyone's ability, but to simply inform. I hope that it is taken in that context.
:::Terry Decker
:::
:::
:::
:::
::I don't feel the need to justify myself. But there is one statement that I would like to make. To the best of my ability to do so, there is not ONE SINGLE statement in this thread that I have not substantiated beforehand by checking with acknowledged and published information.
::My sources have included, but were not limited to:
::"Elements of Radio servicing" by Marcus and Levy
::"A Modern Look at Antique Radio Repair" Third edition- by Alfred Corbin
::"Audel's Radioman's Guide" by E.P. Anderson
::"Elementary Radio Servicing" by William R. Wellman
::"Radio Troubleshooting Handbook" by Ghirardi
::and MANY years as the owner of Reliable Sound and Video.
::Some of my comments have been augmented by new information, and I ALWAYS appreciate being educated.
::And as I said at the beginning-
::
::"This message is not meant to make any assumptions or denigrate anyone's ability, but to simply inform. I hope that it is taken in that context."
::
::Thanks to all who HAVE taken it in that context, and were proud to sign their names. You know who you are.
::Terry
::
::
::
::
::
:Terry,
:Alignment and AVC.
:I installed the IF cans and new capacitors that Warren worked on for me last night. Connected loop antenna and turned the radio on. Got a volume controlled noise through the tuning cap. Touching the antenna increased the noise level. Warren says this means i have gain through the stages, i agree. Before the alignment i will retest all tubes and check all tube voltages to insure all is right. I have a signal generator and VTVM to perform the alignment. It is my first one.
:
:The last line in the alignment instructions read:
:
:Turn the voume control on full and adjust the signal generator output to produce approximately midscale deflection of the output meter, BUT maintain signal generator output as low as possible to prevent AVC action in the receiver.
:
:Your point made very well.
:Mitch
:
You'll do fine. Some of my statements might have appeared too strongly worded, but that was just to put everything in perspective. Alignment CAN be easy, but like anything else in this hobby, it's easy to make a mistake, lose confidence and throw up your hands in disgust. A recent post showed that. A radio worked before being re-capped, then didn't. Some of us stepped in and that person found the problem pretty quickly. As far as I'm concerned, that's what we, all of us, are here for.
Have fun.
T.
:::........I don't feel the need to justify myself.................
However I just have to make another post to try to convince myself and everyone else that I know what I'm doing.
::::........I don't feel the need to justify myself.................
:
:However I just have to make another post to try to convince myself and everyone else that I know what I'm doing.
:
YEP!
What IS your problem? If you have something personal against me-get to it. And have the cahones to let me know who you are. Or are you going to remain an arrogant butthead?
Geez-
Terry
T
::
::The AVC circuit is designed to adjust the gain in reference to the input signal to the RF circuit. Too much gain and the circuit reduces it, too little and it's increased. This is to maintain a constant relationship between weak stations and strong stations so the volume control isn't constantly being turned up and down.
::
::Obviously, if the gain is being artificially changed by attempts at alignment, the circuit will constantly try and adjust it to maintain a balance. It is literally a case of the dog chasing it's tail. If one wants to gauge the action, take a voltage reading at the top of the volume control and tune through several stations. The voltage should change very little.
::
::An attempt to describe the steps necessary to achieve a successful alignment is WAY beyond the scope of this thread, but can be found in most service literature. One good reference is Alfred Corbin's "A Modern Look at Antique Radio Repair".
::
::Also, the information is usually included with the specific model service info. This usually includes the correct IF frequency, signal generator settings and type of signal level indicator, (Like an RCA Voltohmist).
::
::An alignment is a VERY difficult procedure and should only be attempted if ABSOLUTELY necessary. Even then it should only be attempted by someone with a lot of experience and understanding of the circuitry involved.
::
::This message is not meant to make any assumptions or denigrate anyone's ability, but to simply inform. I hope that it is taken in that context.
::Terry Decker
::
::
::
::
:I don't feel the need to justify myself. But there is one statement that I would like to make. To the best of my ability to do so, there is not ONE SINGLE statement in this thread that I have not substantiated beforehand by checking with acknowledged and published information.
:My sources have included, but were not limited to:
:"Elements of Radio servicing" by Marcus and Levy
:"A Modern Look at Antique Radio Repair" Third edition- by Alfred Corbin
:"Audel's Radioman's Guide" by E.P. Anderson
:"Elementary Radio Servicing" by William R. Wellman
:"Radio Troubleshooting Handbook" by Ghirardi
:and MANY years as the owner of Reliable Sound and Video.
:Some of my comments have been augmented by new information, and I ALWAYS appreciate being educated.
:And as I said at the beginning-
:
:"This message is not meant to make any assumptions or denigrate anyone's ability, but to simply inform. I hope that it is taken in that context."
:
:Thanks to all who HAVE taken it in that context, and were proud to sign their names. You know who you are.
:Terry
:
:
:
:
:
Dear Terry,
I thank you for the information, that is one area of the tube radio I had a hard time in understanding, but after reading your post I have a much better understanding of the system and what it does. Thank you kindly!!!
Daniel M.