National Model 303 - Problem in IF bandwidth switch

4/3/2013 8:22:37 PMEdd

Sir Brian. . . .

Whassamattah . . . . why is it that no one is wanting to respond to your query ?

Let me initially make a start with facilitating the ease of your circuit tracing comprehension 'bouts five hunna' and 'lebenteens per " sense", just by my conversion of that units round about and sectionalized schematic into a Unitized one piece version .

Then, I further initiated tracing by using a color coded RF signal flow path, starting from the antenna terminal, completely on all the way thru to the AM detector diode circuitry at the commode of the 6AL5.

Just start following the arrowed path and then refer to the LEGEND for determining if you are on a plate related path (BLUE) or a 1st grid related path (GREEN).

The plate related sections will have B+ on them, but I made a minimal use of RED (B+) mark up, just enough for you to be able to see the sourcing of their B+ feed points.

Your very first run in with B+ is the plate if the V1 RF amplifier and its WIDE band RF choke, serving as its plate load, and then the RF flows into the C6 interstage coupling cap where it passes on the RF, BUT has NOW been stripped of its DC . . . B+ level component.

(Therefore, now we are seeing the RF traveling the GREEN coded arrow path.)

You will see this occurring again up at the plate circuit of the 1st mixer, but, with the loss of the B+ THIS time, being due to the incorporation of the T-3 transformer interstage RF for accomplishing the coupling aspect.

Finally, further on, you will again see the loss of the DC passage component at the 2nd Mixer, and 1st and 2nd IF's via the C22, C34 and C43 coupling caps.

I just placed the Q-multiplier elemental path in as dotted lines, as it will NOT be something that would STOP the set from operating.

It’s just a tunable VERY high Q circuit that is used for acquiring VERY sharp tuning, if needed for the close
differentiation between some closely adjunct received signals.

Now, you made some query as to there being/or/not being B+ levels on some of the inductors / transformers.

I put a markup of a large ATERISK nearby to all of those mentioned units.

The BLUE ones would have a B + related voltage present upon them.

The GREEN ones would not have B+ voltage, but there could be some low level biasing voltage presence, since the circuitry is feeding onwards into a 1st grid.

A good forthcoming answer to me now, would be, what is the sets actual situation?

Is it a totally dead radio, or is the power supply operational as well as the AF circuitry?

If it hasn’t been done already, need to check for all of the tubes screens and plates and confirm B+ presence, as well as checking cathode resistors to see that none are scorched or burnt open.

In the past, it seems like you usually do quite well in your sleuthing and ferreting out of the problems.

73's de Edd

Diplomacy is the ability to tell someone to "get lost", in such a very unique way, that they look forward to the trip.

National NC-303 Communications Receiver Schematic:

:I have no B voltage on L7 but do have voltages on L9 and 12.
:No B voltage on L13, L10; however, there is B voltage on L5, which I believe feeds L7 through the bandwidth switch?
:I have ohmed L7 and it compares to its counterparts. Am I correct about L7 being fed through the switch and anyone have a suggestion as to what would I be looking for? Just to follow the schematic for these compoents mentioned I am finding a challenge.
:
:
:
:

4/4/2013 12:33:38 PMBrian

Edd,
Thanks very much for this circuit diagram, it helps me immensely to understand this radio.

:

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:

:
:
:
:
:
:
:
:Sir Brian. . . .
:
:
:
:Whassamattah . . . . why is it that no one is wanting to respond to your query ?
:
:
:Let me initially make a start with facilitating the ease of your circuit tracing comprehension 'bouts five hunna' and 'lebenteens per " sense", just by my conversion of that units round about and sectionalized schematic into a Unitized one piece version .
:
:
:Then, I further initiated tracing by using a color coded RF signal flow path, starting from the antenna terminal, completely on all the way thru to the AM detector diode circuitry at the commode of the 6AL5.
:
:
:Just start following the arrowed path and then refer to the LEGEND for determining if you are on a plate related path (BLUE) or a 1st grid related path (GREEN).
:
:
:The plate related sections will have B+ on them, but I made a minimal use of RED (B+) mark up, just enough for you to be able to see the sourcing of their B+ feed points.
:
:
:Your very first run in with B+ is the plate if the V1 RF amplifier and its WIDE band RF choke, serving as its plate load, and then the RF flows into the C6 interstage coupling cap where it passes on the RF, BUT has NOW been stripped of its DC . . . B+ level component.
:
:
:(Therefore, now we are seeing the RF traveling the GREEN coded arrow path.)
:
:
:You will see this occurring again up at the plate circuit of the 1st mixer, but, with the loss of the B+ THIS time, being due to the incorporation of the T-3 transformer interstage RF for accomplishing the coupling aspect.
:
:
:Finally, further on, you will again see the loss of the DC passage component at the 2nd Mixer, and 1st and 2nd IF's via the C22, C34 and C43 coupling caps.
:
:
:I just placed the Q-multiplier elemental path in as dotted lines, as it will NOT be something that would STOP the set from operating.
:
:
:It’s just a tunable VERY high Q circuit that is used for acquiring VERY sharp tuning, if needed for the close
:differentiation between some closely adjunct received signals.
:
:
:
:Now, you made some query as to there being/or/not being B+ levels on some of the inductors / transformers.
:
:
:I put a markup of a large ATERISK nearby to all of those mentioned units.
:
:
:The BLUE ones would have a B + related voltage present upon them.
:
:
:The GREEN ones would not have B+ voltage, but there could be some low level biasing voltage presence, since the circuitry is feeding onwards into a 1st grid.
:
:
:
:
:A good forthcoming answer to me now, would be, what is the sets actual situation?
:
:
:Is it a totally dead radio, or is the power supply operational as well as the AF circuitry?
:
:
:
:If it hasn’t been done already, need to check for all of the tubes screens and plates and confirm B+ presence, as well as checking cathode resistors to see that none are scorched or burnt open.
:
:
:
:In the past, it seems like you usually do quite well in your sleuthing and ferreting out of the problems.
:
:
:
:
:
:
:
:73's de Edd
:
:
:
:
:
:Diplomacy is the ability to tell someone to "get lost", in such a very unique way, that they look forward to the trip.
:
:
:
:
:
:
:

:
:
:
:
:

:
:
:
: National NC-303 Communications Receiver Schematic:
:
:
:
:
:

:
:
:
:
:

:
:
:
:
:
:
:
:
::I have no B voltage on L7 but do have voltages on L9 and 12.
::No B voltage on L13, L10; however, there is B voltage on L5, which I believe feeds L7 through the bandwidth switch?
::I have ohmed L7 and it compares to its counterparts. Am I correct about L7 being fed through the switch and anyone have a suggestion as to what would I be looking for? Just to follow the schematic for these compoents mentioned I am finding a challenge.
::
::
::
::
:
:

4/21/2013 2:17:29 PMBrian

Audio section seems OK by touching probe to centre of volume control. To test IF, for this radio would I inject 2295kc at grid of IF amp tube? No far I have not heard a tone. Or am I wrong on this?

:
:Sir Brian. . . .
:
:
:
:Whassamattah . . . . why is it that no one is wanting to respond to your query ?
:
:
:Let me initially make a start with facilitating the ease of your circuit tracing comprehension 'bouts five hunna' and 'lebenteens per " sense", just by my conversion of that units round about and sectionalized schematic into a Unitized one piece version .
:
:
:Then, I further initiated tracing by using a color coded RF signal flow path, starting from the antenna terminal, completely on all the way thru to the AM detector diode circuitry at the commode of the 6AL5.
:
:
:Just start following the arrowed path and then refer to the LEGEND for determining if you are on a plate related path (BLUE) or a 1st grid related path (GREEN).
:
:
:The plate related sections will have B+ on them, but I made a minimal use of RED (B+) mark up, just enough for you to be able to see the sourcing of their B+ feed points.
:
:
:Your very first run in with B+ is the plate if the V1 RF amplifier and its WIDE band RF choke, serving as its plate load, and then the RF flows into the C6 interstage coupling cap where it passes on the RF, BUT has NOW been stripped of its DC . . . B+ level component.
:
:
:(Therefore, now we are seeing the RF traveling the GREEN coded arrow path.)
:
:
:You will see this occurring again up at the plate circuit of the 1st mixer, but, with the loss of the B+ THIS time, being due to the incorporation of the T-3 transformer interstage RF for accomplishing the coupling aspect.
:
:
:Finally, further on, you will again see the loss of the DC passage component at the 2nd Mixer, and 1st and 2nd IF's via the C22, C34 and C43 coupling caps.
:
:
:I just placed the Q-multiplier elemental path in as dotted lines, as it will NOT be something that would STOP the set from operating.
:
:
:It’s just a tunable VERY high Q circuit that is used for acquiring VERY sharp tuning, if needed for the close
:differentiation between some closely adjunct received signals.
:
:
:
:Now, you made some query as to there being/or/not being B+ levels on some of the inductors / transformers.
:
:
:I put a markup of a large ATERISK nearby to all of those mentioned units.
:
:
:The BLUE ones would have a B + related voltage present upon them.
:
:
:The GREEN ones would not have B+ voltage, but there could be some low level biasing voltage presence, since the circuitry is feeding onwards into a 1st grid.
:
:
:
:
:A good forthcoming answer to me now, would be, what is the sets actual situation?
:
:
:Is it a totally dead radio, or is the power supply operational as well as the AF circuitry?
:
:
:
:If it hasn’t been done already, need to check for all of the tubes screens and plates and confirm B+ presence, as well as checking cathode resistors to see that none are scorched or burnt open.
:
:
:
:In the past, it seems like you usually do quite well in your sleuthing and ferreting out of the problems.
:
:
:
:
:
:
:
:73's de Edd
:
:
:
:
:
:Diplomacy is the ability to tell someone to "get lost", in such a very unique way, that they look forward to the trip.
:
:
:
:
:
:
:
:
:
:
:
:

:
:
:
: National NC-303 Communications Receiver Schematic:
:
:
:
:
:
:
:
:
:
:

:
:
:
:
:
:
:
:
::I have no B voltage on L7 but do have voltages on L9 and 12.
::No B voltage on L13, L10; however, there is B voltage on L5, which I believe feeds L7 through the bandwidth switch?
::I have ohmed L7 and it compares to its counterparts. Am I correct about L7 being fed through the switch and anyone have a suggestion as to what would I be looking for? Just to follow the schematic for these compoents mentioned I am finding a challenge.
::
::
::
::
:
:

4/22/2013 9:47:39 PMEdd(106184:106144)

Sir Brian . . .
This is a dual conversion receiver design, with the very end of the receiver using a 80KHZ IF frequency, while the first portion uses a 2215 KHZ as its IF frequency.
Try up at the front of the receiver with that madulated 2215 KHZ test signal.
If it doesn't make it thru, and IF you have 80KHZ generator capabilities (audio generator or Wavetek function generator), move on down to the end of the IF strip.
Then, try to get detected 80KHZ output audio.
73's de Edd

:Audio section seems OK by touching probe to centre of volume control. To test IF, for this radio would I inject 2295kc at grid of IF amp tube? No far I have not heard a tone. Or am I wrong on this?
:
::
::Sir Brian. . . .
::
::
::
::Whassamattah . . . . why is it that no one is wanting to respond to your query ?
::
::
::Let me initially make a start with facilitating the ease of your circuit tracing comprehension 'bouts five hunna' and 'lebenteens per " sense", just by my conversion of that units round about and sectionalized schematic into a Unitized one piece version .
::
::
::Then, I further initiated tracing by using a color coded RF signal flow path, starting from the antenna terminal, completely on all the way thru to the AM detector diode circuitry at the commode of the 6AL5.
::
::
::Just start following the arrowed path and then refer to the LEGEND for determining if you are on a plate related path (BLUE) or a 1st grid related path (GREEN).
::
::
::The plate related sections will have B+ on them, but I made a minimal use of RED (B+) mark up, just enough for you to be able to see the sourcing of their B+ feed points.
::
::
::Your very first run in with B+ is the plate if the V1 RF amplifier and its WIDE band RF choke, serving as its plate load, and then the RF flows into the C6 interstage coupling cap where it passes on the RF, BUT has NOW been stripped of its DC . . . B+ level component.
::
::
::(Therefore, now we are seeing the RF traveling the GREEN coded arrow path.)
::
::
::You will see this occurring again up at the plate circuit of the 1st mixer, but, with the loss of the B+ THIS time, being due to the incorporation of the T-3 transformer interstage RF for accomplishing the coupling aspect.
::
::
::Finally, further on, you will again see the loss of the DC passage component at the 2nd Mixer, and 1st and 2nd IF's via the C22, C34 and C43 coupling caps.
::
::
::I just placed the Q-multiplier elemental path in as dotted lines, as it will NOT be something that would STOP the set from operating.
::
::
::It’s just a tunable VERY high Q circuit that is used for acquiring VERY sharp tuning, if needed for the close
::differentiation between some closely adjunct received signals.
::
::
::
::Now, you made some query as to there being/or/not being B+ levels on some of the inductors / transformers.
::
::
::I put a markup of a large ATERISK nearby to all of those mentioned units.
::
::
::The BLUE ones would have a B + related voltage present upon them.
::
::
::The GREEN ones would not have B+ voltage, but there could be some low level biasing voltage presence, since the circuitry is feeding onwards into a 1st grid.
::
::
::
::
::A good forthcoming answer to me now, would be, what is the sets actual situation?
::
::
::Is it a totally dead radio, or is the power supply operational as well as the AF circuitry?
::
::
::
::If it hasn’t been done already, need to check for all of the tubes screens and plates and confirm B+ presence, as well as checking cathode resistors to see that none are scorched or burnt open.
::
::
::
::In the past, it seems like you usually do quite well in your sleuthing and ferreting out of the problems.
::
::
::
::
::
::
::
::73's de Edd
::
::
::
::
::
::Diplomacy is the ability to tell someone to "get lost", in such a very unique way, that they look forward to the trip.
::
::
::
::
::
::
::
::
::
::
::
::

::
::
::
:: National NC-303 Communications Receiver Schematic:
::
::
::
::
::
::
::
::
::
::

::
::
::
::
::
::
::
::
:::I have no B voltage on L7 but do have voltages on L9 and 12.
:::No B voltage on L13, L10; however, there is B voltage on L5, which I believe feeds L7 through the bandwidth switch?
:::I have ohmed L7 and it compares to its counterparts. Am I correct about L7 being fed through the switch and anyone have a suggestion as to what would I be looking for? Just to follow the schematic for these compoents mentioned I am finding a challenge.
:::
:::
:::
:::
::
::
:
:

4/23/2013 4:14:25 PMWhatmoresoevermaybeit . . .(106188:106184)

Sir Brian. . . .

ALSO . . . . . have you checked EVERY RF associative toobies plate and screen grid for its supply voltage presence.

I specifically forget model exclusivity . . . . but those 'ole Nationals have a high proclivity of bypass capacitor failures.

Have one dead short and you lose your supply voltage to its feed.

If the series resistor is small enough the 1/2 watt carbon composition will smoke, or, if on up higher in value, the unit
splits and opens the wires end ball bond termination to the resistive composition mass.

If the split is being on a back side, you don't even visually notice it, unless further found out by testing.

73's de Edd

The meek shall inherit the earth, but NOT it's mineral rights.

:
:Sir Brian . . .
:This is a dual conversion receiver design, with the very end of the receiver using a 80KHZ IF frequency, while the first portion uses a 2215 KHZ as its IF frequency.
:Try up at the front of the receiver with that madulated 2215 KHZ test signal.
:If it doesn't make it thru, and IF you have 80KHZ generator capabilities (audio generator or Wavetek function generator), move on down to the end of the IF strip.
:Then, try to get detected 80KHZ output audio.
:
:73's de Edd
:
:
:
:
:
:
::Audio section seems OK by touching probe to centre of volume control. To test IF, for this radio would I inject 2295kc at grid of IF amp tube? No far I have not heard a tone. Or am I wrong on this?
::
:::
:::Sir Brian. . . .
:::
:::
:::
:::Whassamattah . . . . why is it that no one is wanting to respond to your query ?
:::
:::
:::Let me initially make a start with facilitating the ease of your circuit tracing comprehension 'bouts five hunna' and 'lebenteens per " sense", just by my conversion of that units round about and sectionalized schematic into a Unitized one piece version .
:::
:::
:::Then, I further initiated tracing by using a color coded RF signal flow path, starting from the antenna terminal, completely on all the way thru to the AM detector diode circuitry at the commode of the 6AL5.
:::
:::
:::Just start following the arrowed path and then refer to the LEGEND for determining if you are on a plate related path (BLUE) or a 1st grid related path (GREEN).
:::
:::
:::The plate related sections will have B+ on them, but I made a minimal use of RED (B+) mark up, just enough for you to be able to see the sourcing of their B+ feed points.
:::
:::
:::Your very first run in with B+ is the plate if the V1 RF amplifier and its WIDE band RF choke, serving as its plate load, and then the RF flows into the C6 interstage coupling cap where it passes on the RF, BUT has NOW been stripped of its DC . . . B+ level component.
:::
:::
:::(Therefore, now we are seeing the RF traveling the GREEN coded arrow path.)
:::
:::
:::You will see this occurring again up at the plate circuit of the 1st mixer, but, with the loss of the B+ THIS time, being due to the incorporation of the T-3 transformer interstage RF for accomplishing the coupling aspect.
:::
:::
:::Finally, further on, you will again see the loss of the DC passage component at the 2nd Mixer, and 1st and 2nd IF's via the C22, C34 and C43 coupling caps.
:::
:::
:::I just placed the Q-multiplier elemental path in as dotted lines, as it will NOT be something that would STOP the set from operating.
:::
:::
:::It’s just a tunable VERY high Q circuit that is used for acquiring VERY sharp tuning, if needed for the close
:::differentiation between some closely adjunct received signals.
:::
:::
:::
:::Now, you made some query as to there being/or/not being B+ levels on some of the inductors / transformers.
:::
:::
:::I put a markup of a large ATERISK nearby to all of those mentioned units.
:::
:::
:::The BLUE ones would have a B + related voltage present upon them.
:::
:::
:::The GREEN ones would not have B+ voltage, but there could be some low level biasing voltage presence, since the circuitry is feeding onwards into a 1st grid.
:::
:::
:::
:::
:::A good forthcoming answer to me now, would be, what is the sets actual situation?
:::
:::
:::Is it a totally dead radio, or is the power supply operational as well as the AF circuitry?
:::
:::
:::
:::If it hasn’t been done already, need to check for all of the tubes screens and plates and confirm B+ presence, as well as checking cathode resistors to see that none are scorched or burnt open.
:::
:::
:::
:::In the past, it seems like you usually do quite well in your sleuthing and ferreting out of the problems.
:::
:::
:::
:::
:::
:::
:::
:::73's de Edd
:::
:::
:::
:::
:::
:::Diplomacy is the ability to tell someone to "get lost", in such a very unique way, that they look forward to the trip.
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::

:::
:::
:::
::: National NC-303 Communications Receiver Schematic:
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::

:::
:::
:::
:::
:::
:::
:::
:::
::::I have no B voltage on L7 but do have voltages on L9 and 12.
::::No B voltage on L13, L10; however, there is B voltage on L5, which I believe feeds L7 through the bandwidth switch?
::::I have ohmed L7 and it compares to its counterparts. Am I correct about L7 being fed through the switch and anyone have a suggestion as to what would I be looking for? Just to follow the schematic for these compoents mentioned I am finding a challenge.
::::
::::
::::
::::
:::
:::
::
::
:
:

6/19/2013 9:00:53 AMBrian(107134:106188)

Well,finally I am now picking up some AM and SSB talk on 3 bands with a longwire aerial, and B voltages are stable now, likely within tolerance too. Thanks to Edd for his diagram, I found some sloppy solder connections on my part and replaced older capacitors. To conduct an alignment now, would one of those modern pocket audio generators be adequate for aligning at the 80 khz IF?
:
:
:
:

:
:
:
:
:
:
:
:
:
:
:
:Sir Brian. . . .
:
:
:ALSO . . . . . have you checked EVERY RF associative toobies plate and screen grid for its supply voltage presence.
:
:
:I specifically forget model exclusivity . . . . but those 'ole Nationals have a high proclivity of bypass capacitor failures.
:
:
:Have one dead short and you lose your supply voltage to its feed.
:
:
:If the series resistor is small enough the 1/2 watt carbon composition will smoke, or, if on up higher in value, the unit
:splits and opens the wires end ball bond termination to the resistive composition mass.
:
:
:If the split is being on a back side, you don't even visually notice it, unless further found out by testing.
:
:
:
:
:
:
:73's de Edd
:
:
:
:
:
:The meek shall inherit the earth, but NOT it's mineral rights.
:
:
:
:
:
:

:
:
:
:
:
::
::Sir Brian . . .
::This is a dual conversion receiver design, with the very end of the receiver using a 80KHZ IF frequency, while the first portion uses a 2215 KHZ as its IF frequency.
::Try up at the front of the receiver with that madulated 2215 KHZ test signal.
::If it doesn't make it thru, and IF you have 80KHZ generator capabilities (audio generator or Wavetek function generator), move on down to the end of the IF strip.
::Then, try to get detected 80KHZ output audio.
::
::73's de Edd
::
::
::
::
::
::
:::Audio section seems OK by touching probe to centre of volume control. To test IF, for this radio would I inject 2295kc at grid of IF amp tube? No far I have not heard a tone. Or am I wrong on this?
:::
::::
::::Sir Brian. . . .
::::
::::
::::
::::Whassamattah . . . . why is it that no one is wanting to respond to your query ?
::::
::::
::::Let me initially make a start with facilitating the ease of your circuit tracing comprehension 'bouts five hunna' and 'lebenteens per " sense", just by my conversion of that units round about and sectionalized schematic into a Unitized one piece version .
::::
::::
::::Then, I further initiated tracing by using a color coded RF signal flow path, starting from the antenna terminal, completely on all the way thru to the AM detector diode circuitry at the commode of the 6AL5.
::::
::::
::::Just start following the arrowed path and then refer to the LEGEND for determining if you are on a plate related path (BLUE) or a 1st grid related path (GREEN).
::::
::::
::::The plate related sections will have B+ on them, but I made a minimal use of RED (B+) mark up, just enough for you to be able to see the sourcing of their B+ feed points.
::::
::::
::::Your very first run in with B+ is the plate if the V1 RF amplifier and its WIDE band RF choke, serving as its plate load, and then the RF flows into the C6 interstage coupling cap where it passes on the RF, BUT has NOW been stripped of its DC . . . B+ level component.
::::
::::
::::(Therefore, now we are seeing the RF traveling the GREEN coded arrow path.)
::::
::::
::::You will see this occurring again up at the plate circuit of the 1st mixer, but, with the loss of the B+ THIS time, being due to the incorporation of the T-3 transformer interstage RF for accomplishing the coupling aspect.
::::
::::
::::Finally, further on, you will again see the loss of the DC passage component at the 2nd Mixer, and 1st and 2nd IF's via the C22, C34 and C43 coupling caps.
::::
::::
::::I just placed the Q-multiplier elemental path in as dotted lines, as it will NOT be something that would STOP the set from operating.
::::
::::
::::It’s just a tunable VERY high Q circuit that is used for acquiring VERY sharp tuning, if needed for the close
::::differentiation between some closely adjunct received signals.
::::
::::
::::
::::Now, you made some query as to there being/or/not being B+ levels on some of the inductors / transformers.
::::
::::
::::I put a markup of a large ATERISK nearby to all of those mentioned units.
::::
::::
::::The BLUE ones would have a B + related voltage present upon them.
::::
::::
::::The GREEN ones would not have B+ voltage, but there could be some low level biasing voltage presence, since the circuitry is feeding onwards into a 1st grid.
::::
::::
::::
::::
::::A good forthcoming answer to me now, would be, what is the sets actual situation?
::::
::::
::::Is it a totally dead radio, or is the power supply operational as well as the AF circuitry?
::::
::::
::::
::::If it hasn’t been done already, need to check for all of the tubes screens and plates and confirm B+ presence, as well as checking cathode resistors to see that none are scorched or burnt open.
::::
::::
::::
::::In the past, it seems like you usually do quite well in your sleuthing and ferreting out of the problems.
::::
::::
::::
::::
::::
::::
::::
::::73's de Edd
::::
::::
::::
::::
::::
::::Diplomacy is the ability to tell someone to "get lost", in such a very unique way, that they look forward to the trip.
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::

::::
::::
::::
:::: National NC-303 Communications Receiver Schematic:
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::

::::
::::
::::
::::
::::
::::
::::
::::
:::::I have no B voltage on L7 but do have voltages on L9 and 12.
:::::No B voltage on L13, L10; however, there is B voltage on L5, which I believe feeds L7 through the bandwidth switch?
:::::I have ohmed L7 and it compares to its counterparts. Am I correct about L7 being fed through the switch and anyone have a suggestion as to what would I be looking for? Just to follow the schematic for these compoents mentioned I am finding a challenge.
:::::
:::::
:::::
:::::
::::
::::
:::
:::
::
::
:
:

10/4/2013 9:45:45 AMBrian(108751:107134)

Using a Heathkit audio generator and injecting 80KHZ as called for I cannot get a strong enough signal through the "S" IF band to register movement on the s-meter. Other bands have varying s-meter readings but the meter simply falls dead in "S" position. Tube voltages appear OK, can someone point me to particular components in that IF circuit that might be checked?
:Well,finally I am now picking up some AM and SSB talk on 3 bands with a longwire aerial, and B voltages are stable now, likely within tolerance too. Thanks to Edd for his diagram, I found some sloppy solder connections on my part and replaced older capacitors. To conduct an alignment now, would one of those modern pocket audio generators be adequate for aligning at the 80 khz IF?
:
::
::
::
::

::
::
::
::
::
::
::
::
::
::
::
::Sir Brian. . . .
::
::
::ALSO . . . . . have you checked EVERY RF associative toobies plate and screen grid for its supply voltage presence.
::
::
::I specifically forget model exclusivity . . . . but those 'ole Nationals have a high proclivity of bypass capacitor failures.
::
::
::Have one dead short and you lose your supply voltage to its feed.
::
::
::If the series resistor is small enough the 1/2 watt carbon composition will smoke, or, if on up higher in value, the unit
::splits and opens the wires end ball bond termination to the resistive composition mass.
::
::
::If the split is being on a back side, you don't even visually notice it, unless further found out by testing.
::
::
::
::
::
::
::73's de Edd
::
::
::
::
::
::The meek shall inherit the earth, but NOT it's mineral rights.
::
::
::
::
::
::

::
::
::
::
::
:::
:::Sir Brian . . .
:::This is a dual conversion receiver design, with the very end of the receiver using a 80KHZ IF frequency, while the first portion uses a 2215 KHZ as its IF frequency.
:::Try up at the front of the receiver with that madulated 2215 KHZ test signal.
:::If it doesn't make it thru, and IF you have 80KHZ generator capabilities (audio generator or Wavetek function generator), move on down to the end of the IF strip.
:::Then, try to get detected 80KHZ output audio.
:::
:::73's de Edd
:::
:::
:::
:::
:::
:::
::::Audio section seems OK by touching probe to centre of volume control. To test IF, for this radio would I inject 2295kc at grid of IF amp tube? No far I have not heard a tone. Or am I wrong on this?
::::
:::::
:::::Sir Brian. . . .
:::::
:::::
:::::
:::::Whassamattah . . . . why is it that no one is wanting to respond to your query ?
:::::
:::::
:::::Let me initially make a start with facilitating the ease of your circuit tracing comprehension 'bouts five hunna' and 'lebenteens per " sense", just by my conversion of that units round about and sectionalized schematic into a Unitized one piece version .
:::::
:::::
:::::Then, I further initiated tracing by using a color coded RF signal flow path, starting from the antenna terminal, completely on all the way thru to the AM detector diode circuitry at the commode of the 6AL5.
:::::
:::::
:::::Just start following the arrowed path and then refer to the LEGEND for determining if you are on a plate related path (BLUE) or a 1st grid related path (GREEN).
:::::
:::::
:::::The plate related sections will have B+ on them, but I made a minimal use of RED (B+) mark up, just enough for you to be able to see the sourcing of their B+ feed points.
:::::
:::::
:::::Your very first run in with B+ is the plate if the V1 RF amplifier and its WIDE band RF choke, serving as its plate load, and then the RF flows into the C6 interstage coupling cap where it passes on the RF, BUT has NOW been stripped of its DC . . . B+ level component.
:::::
:::::
:::::(Therefore, now we are seeing the RF traveling the GREEN coded arrow path.)
:::::
:::::
:::::You will see this occurring again up at the plate circuit of the 1st mixer, but, with the loss of the B+ THIS time, being due to the incorporation of the T-3 transformer interstage RF for accomplishing the coupling aspect.
:::::
:::::
:::::Finally, further on, you will again see the loss of the DC passage component at the 2nd Mixer, and 1st and 2nd IF's via the C22, C34 and C43 coupling caps.
:::::
:::::
:::::I just placed the Q-multiplier elemental path in as dotted lines, as it will NOT be something that would STOP the set from operating.
:::::
:::::
:::::It’s just a tunable VERY high Q circuit that is used for acquiring VERY sharp tuning, if needed for the close
:::::differentiation between some closely adjunct received signals.
:::::
:::::
:::::
:::::Now, you made some query as to there being/or/not being B+ levels on some of the inductors / transformers.
:::::
:::::
:::::I put a markup of a large ATERISK nearby to all of those mentioned units.
:::::
:::::
:::::The BLUE ones would have a B + related voltage present upon them.
:::::
:::::
:::::The GREEN ones would not have B+ voltage, but there could be some low level biasing voltage presence, since the circuitry is feeding onwards into a 1st grid.
:::::
:::::
:::::
:::::
:::::A good forthcoming answer to me now, would be, what is the sets actual situation?
:::::
:::::
:::::Is it a totally dead radio, or is the power supply operational as well as the AF circuitry?
:::::
:::::
:::::
:::::If it hasn’t been done already, need to check for all of the tubes screens and plates and confirm B+ presence, as well as checking cathode resistors to see that none are scorched or burnt open.
:::::
:::::
:::::
:::::In the past, it seems like you usually do quite well in your sleuthing and ferreting out of the problems.
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::73's de Edd
:::::
:::::
:::::
:::::
:::::
:::::Diplomacy is the ability to tell someone to "get lost", in such a very unique way, that they look forward to the trip.
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::

:::::
:::::
:::::
::::: National NC-303 Communications Receiver Schematic:
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::

:::::
:::::
:::::
:::::
:::::
:::::
:::::
:::::
::::::I have no B voltage on L7 but do have voltages on L9 and 12.
::::::No B voltage on L13, L10; however, there is B voltage on L5, which I believe feeds L7 through the bandwidth switch?
::::::I have ohmed L7 and it compares to its counterparts. Am I correct about L7 being fed through the switch and anyone have a suggestion as to what would I be looking for? Just to follow the schematic for these compoents mentioned I am finding a challenge.
::::::
::::::
::::::
::::::
:::::
:::::
::::
::::
:::
:::
::
::
:
:

10/4/2013 9:06:22 PMClifton(108759:108751)

Brian,
You might want to use an RF signal generator and apply 80kHz RF signal.
Clifton

:Using a Heathkit audio generator and injecting 80KHZ as called for I cannot get a strong enough signal through the "S" IF band to register movement on the s-meter. Other bands have varying s-meter readings but the meter simply falls dead in "S" position. Tube voltages appear OK, can someone point me to particular components in that IF circuit that might be checked?
:
:
:
::Well,finally I am now picking up some AM and SSB talk on 3 bands with a longwire aerial, and B voltages are stable now, likely within tolerance too. Thanks to Edd for his diagram, I found some sloppy solder connections on my part and replaced older capacitors. To conduct an alignment now, would one of those modern pocket audio generators be adequate for aligning at the 80 khz IF?
::
:::
:::
:::
:::

:::
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::Sir Brian. . . .
:::
:::
:::ALSO . . . . . have you checked EVERY RF associative toobies plate and screen grid for its supply voltage presence.
:::
:::
:::I specifically forget model exclusivity . . . . but those 'ole Nationals have a high proclivity of bypass capacitor failures.
:::
:::
:::Have one dead short and you lose your supply voltage to its feed.
:::
:::
:::If the series resistor is small enough the 1/2 watt carbon composition will smoke, or, if on up higher in value, the unit
:::splits and opens the wires end ball bond termination to the resistive composition mass.
:::
:::
:::If the split is being on a back side, you don't even visually notice it, unless further found out by testing.
:::
:::
:::
:::
:::
:::
:::73's de Edd
:::
:::
:::
:::
:::
:::The meek shall inherit the earth, but NOT it's mineral rights.
:::
:::
:::
:::
:::
:::

:::
:::
:::
:::
:::
::::
::::Sir Brian . . .
::::This is a dual conversion receiver design, with the very end of the receiver using a 80KHZ IF frequency, while the first portion uses a 2215 KHZ as its IF frequency.
::::Try up at the front of the receiver with that madulated 2215 KHZ test signal.
::::If it doesn't make it thru, and IF you have 80KHZ generator capabilities (audio generator or Wavetek function generator), move on down to the end of the IF strip.
::::Then, try to get detected 80KHZ output audio.
::::
::::73's de Edd
::::
::::
::::
::::
::::
::::
:::::Audio section seems OK by touching probe to centre of volume control. To test IF, for this radio would I inject 2295kc at grid of IF amp tube? No far I have not heard a tone. Or am I wrong on this?
:::::
::::::
::::::Sir Brian. . . .
::::::
::::::
::::::
::::::Whassamattah . . . . why is it that no one is wanting to respond to your query ?
::::::
::::::
::::::Let me initially make a start with facilitating the ease of your circuit tracing comprehension 'bouts five hunna' and 'lebenteens per " sense", just by my conversion of that units round about and sectionalized schematic into a Unitized one piece version .
::::::
::::::
::::::Then, I further initiated tracing by using a color coded RF signal flow path, starting from the antenna terminal, completely on all the way thru to the AM detector diode circuitry at the commode of the 6AL5.
::::::
::::::
::::::Just start following the arrowed path and then refer to the LEGEND for determining if you are on a plate related path (BLUE) or a 1st grid related path (GREEN).
::::::
::::::
::::::The plate related sections will have B+ on them, but I made a minimal use of RED (B+) mark up, just enough for you to be able to see the sourcing of their B+ feed points.
::::::
::::::
::::::Your very first run in with B+ is the plate if the V1 RF amplifier and its WIDE band RF choke, serving as its plate load, and then the RF flows into the C6 interstage coupling cap where it passes on the RF, BUT has NOW been stripped of its DC . . . B+ level component.
::::::
::::::
::::::(Therefore, now we are seeing the RF traveling the GREEN coded arrow path.)
::::::
::::::
::::::You will see this occurring again up at the plate circuit of the 1st mixer, but, with the loss of the B+ THIS time, being due to the incorporation of the T-3 transformer interstage RF for accomplishing the coupling aspect.
::::::
::::::
::::::Finally, further on, you will again see the loss of the DC passage component at the 2nd Mixer, and 1st and 2nd IF's via the C22, C34 and C43 coupling caps.
::::::
::::::
::::::I just placed the Q-multiplier elemental path in as dotted lines, as it will NOT be something that would STOP the set from operating.
::::::
::::::
::::::It’s just a tunable VERY high Q circuit that is used for acquiring VERY sharp tuning, if needed for the close
::::::differentiation between some closely adjunct received signals.
::::::
::::::
::::::
::::::Now, you made some query as to there being/or/not being B+ levels on some of the inductors / transformers.
::::::
::::::
::::::I put a markup of a large ATERISK nearby to all of those mentioned units.
::::::
::::::
::::::The BLUE ones would have a B + related voltage present upon them.
::::::
::::::
::::::The GREEN ones would not have B+ voltage, but there could be some low level biasing voltage presence, since the circuitry is feeding onwards into a 1st grid.
::::::
::::::
::::::
::::::
::::::A good forthcoming answer to me now, would be, what is the sets actual situation?
::::::
::::::
::::::Is it a totally dead radio, or is the power supply operational as well as the AF circuitry?
::::::
::::::
::::::
::::::If it hasn’t been done already, need to check for all of the tubes screens and plates and confirm B+ presence, as well as checking cathode resistors to see that none are scorched or burnt open.
::::::
::::::
::::::
::::::In the past, it seems like you usually do quite well in your sleuthing and ferreting out of the problems.
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::73's de Edd
::::::
::::::
::::::
::::::
::::::
::::::Diplomacy is the ability to tell someone to "get lost", in such a very unique way, that they look forward to the trip.
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::

::::::
::::::
::::::
:::::: National NC-303 Communications Receiver Schematic:
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::

::::::
::::::
::::::
::::::
::::::
::::::
::::::
::::::
:::::::I have no B voltage on L7 but do have voltages on L9 and 12.
:::::::No B voltage on L13, L10; however, there is B voltage on L5, which I believe feeds L7 through the bandwidth switch?
:::::::I have ohmed L7 and it compares to its counterparts. Am I correct about L7 being fed through the switch and anyone have a suggestion as to what would I be looking for? Just to follow the schematic for these compoents mentioned I am finding a challenge.
:::::::
:::::::
:::::::
:::::::
::::::
::::::
:::::
:::::
::::
::::
:::
:::
::
::
:
:

10/5/2013 7:37:00 AMBill G.(108760:108751)

:Using a Heathkit audio generator and injecting 80KHZ as called for I cannot get a strong enough signal through the "S" IF band to register movement on the s-meter. Other bands have varying s-meter readings but the meter simply falls dead in "S" position. Tube voltages appear OK, can someone point me to particular components in that IF circuit that might be checked?
:
Hi Brian,
Using the audio generator is fine.
As for components that could be problematic in the IF, well, the IF as you can see has few components.
Check your voltages on the tubes. Pay special attention to the grids. They should not be positive. That is an indication of silver mica disease. It is a problem that can effect the IF cans of radios of this vintage.
Of course check the tubes. Sometimes tubes test OK but are not good. 6AL5 rarely fail, but it does happen and they are cheap.
Best Regards,
Bill Grimm

10/5/2013 12:54:50 PM*** Edd ***(108761:108760)

Sir Brian. . . .

Me thinks that you are now all right, with NO problems, it’s just you’re not yet being FULLY knowledgeable of the specific intricacies of the settings involved on that 303's bottom
left corner " IF selectivity switch " .

Its purpose is geared towards the blocking out of any potentially interfering nearby signals,
right next door to the one which you are tuned into.

This radio is not grand dad’s typical old AM receiver with its reception bandwidth, as wide as a barn door.
Instead it is chopped up into specific frequency segments related to Radio Amateur Bands.

Now, for its setting options:

The B setting is the broadest setting of 8000hz bandwidth, and is adequate for listening to common AM radio IF it was even receivable, but alas, this sets low end limit of 1800 KC is being just above the AM broadcast band.
You will have to do with some of the FEW hams still operating AM mode on 160 meters, or other bands, usually on popular weekend operational times, or at some regular occurring net contact times.

The M setting is a bit narrower setting of 3500 cycles and quite a bit more selective in blocking down adjunct operating stations.

The SB1 and SB2 positions are for receiving SSB stations after you have turned on your BFO,
and then with proper tuning onto them, you will be able to switch between the upper and lower sidebands of that tuned in frequency with the flip between that switch’s 1 SB and 2 SB positions.

Now the S setting . . . . and that means sharp . . . like a razor blade . . . with it having a pass band of a mere 400 cycles.
This S option is where you are receiving stations operating in CW . . .. code mode.
You know . . . . dit dit dit dit . . dit . . .dit.dah.dit.dit . . . dit dah dit dit . . dah dah dah
When you happen to end up with another station almost sitting right on top of the station that you are trying to receive.
If you then switch to S mode that should appreciably sharpen the tuning to then differentiate between the two signals if you slightly tune further away from the interfering secondary signal.
Sooooooooooo the way I see it being, is that you were set up with your signal generator, all set up to that 80 Khz frequency, with your signal generator and with its "certifiable" accuracy of plus or minus a foot.
But you were NOT actually sending out a PRECISE IF signal, with it needing to be above > 79600~ . .or right on at 80000~ . .or, less than < 80400 ~.

In reality, if you were to listen for the sig gens signal, you would just hear a "swooosh" as tuning by with the signal generator, however you might "micro-grip" and try to position the frequency dial of the sig generator.

(Frankly, if even using a yardstick C clamped onto the freq dial and manipulating the end of the stick for a "vernier" control, I still perceive of a "whoooooooooooooooosh" in passing by in tuning.)
This is being an accuracy setting requirement in the order of the need of a synthesized generator to get that precise of a degree of accuracy.
Sooooooo . . . as I said, I feel that you are adequately close enough in aligning at those wider bandwidth setting, as the 400 cycle final specs are acquired / final trimmed in using silver mica caps in that specific mode.
Plus . . . . how many times you gonna be using CW reception and experience next door interference. Ops use VFO's now a days and can dither to either side of a frequency.
Thereby, there is no more being rigidly locked down to the precise specs of a fixed crystals output frequency. .
Thassssssit . . . .

73's de Edd

Hmmmmmm . . . I wonder . . . .What hair color do they put on the driver's licenses of bald men?

::Using a Heathkit audio generator and injecting 80KHZ as called for I cannot get a strong enough signal through the "S" IF band to register movement on the s-meter. Other bands have varying s-meter readings but the meter simply falls dead in "S" position. Tube voltages appear OK, can someone point me to particular components in that IF circuit that might be checked?
::
:Hi Brian,
: Using the audio generator is fine.
: As for components that could be problematic in the IF, well, the IF as you can see has few components.
: Check your voltages on the tubes. Pay special attention to the grids. They should not be positive. That is an indication of silver mica disease. It is a problem that can effect the IF cans of radios of this vintage.
: Of course check the tubes. Sometimes tubes test OK but are not good. 6AL5 rarely fail, but it does happen and they are cheap.
:
:Best Regards,
:
:Bill Grimm
:

10/6/2013 3:15:33 PMBrian(108775:108761)

Edd,
Thanks for the instruction on those IF bandwidth settings. I have been able to enjoy listening to some occasional AM on the HF bands. Regarding the AG-9A audio generator, what what be the typical setting on the output, to do a final peak alignment on the broader IF band settings?
:
:
:

:
:
:
:
:
:
:
:
:
:
:
:Sir Brian. . . .
:
:
:
:
:Me thinks that you are now all right, with NO problems, it’s just you’re not yet being FULLY knowledgeable of the specific intricacies of the settings involved on that 303's bottom
: left corner " IF selectivity switch " .
:
:
:Its purpose is geared towards the blocking out of any potentially interfering nearby signals,
:right next door to the one which you are tuned into.
:
:
:
:
:This radio is not grand dad’s typical old AM receiver with its reception bandwidth, as wide as a barn door.
:Instead it is chopped up into specific frequency segments related to Radio Amateur Bands.
:
:
:
:
:Now, for its setting options:
:
:
:
:
:The B setting is the broadest setting of 8000hz bandwidth, and is adequate for listening to common AM radio IF it was even receivable, but alas, this sets low end limit of 1800 KC is being just above the AM broadcast band.
:
:
:
:You will have to do with some of the FEW hams still operating AM mode on 160 meters, or other bands, usually on popular weekend operational times, or at some regular occurring net contact times.
:
:
:
:
:The M setting is a bit narrower setting of 3500 cycles and quite a bit more selective in blocking down adjunct operating stations.
:
:
:
:
:The SB1 and SB2 positions are for receiving SSB stations after you have turned on your BFO,
:and then with proper tuning onto them, you will be able to switch between the upper and lower sidebands of that tuned in frequency with the flip between that switch’s 1 SB and 2 SB positions.
:
:
:
:
:Now the S setting . . . . and that means sharp . . . like a razor blade . . . with it having a pass band of a mere 400 cycles.
:
:
:
:This S option is where you are receiving stations operating in CW . . .. code mode.
:
:
:
:You know . . . . dit dit dit dit . . dit . . .dit.dah.dit.dit . . . dit dah dit dit . . dah dah dah
:
:
:
:When you happen to end up with another station almost sitting right on top of the station that you are trying to receive.
:
:
:
:If you then switch to S mode that should appreciably sharpen the tuning to then differentiate between the two signals if you slightly tune further away from the interfering secondary signal.
:
:
:
:
:
:Sooooooooooo the way I see it being, is that you were set up with your signal generator, all set up to that 80 Khz frequency, with your signal generator and with its "certifiable" accuracy of plus or minus a foot.
:
:
:
:But you were NOT actually sending out a PRECISE IF signal, with it needing to be above > 79600~ . .or right on at 80000~ . .or, less than < 80400 ~.
:
:
:
:
:In reality, if you were to listen for the sig gens signal, you would just hear a "swooosh" as tuning by with the signal generator, however you might "micro-grip" and try to position the frequency dial of the sig generator.
:
:
:(Frankly, if even using a yardstick C clamped onto the freq dial and manipulating the end of the stick for a "vernier" control, I still perceive of a "whoooooooooooooooosh" in passing by in tuning.)
:
:
:
:This is being an accuracy setting requirement in the order of the need of a synthesized generator to get that precise of a degree of accuracy.
:Sooooooo . . . as I said, I feel that you are adequately close enough in aligning at those wider bandwidth setting, as the 400 cycle final specs are acquired / final trimmed in using silver mica caps in that specific mode.
:
:
:Plus . . . . how many times you gonna be using CW reception and experience next door interference. Ops use VFO's now a days and can dither to either side of a frequency.
:
:
:
:Thereby, there is no more being rigidly locked down to the precise specs of a fixed crystals output frequency. .
:
:
:
:Thassssssit . . . .
:
:
:
:
:
:
:
:
:
:
:
:
:
:
:
:73's de Edd
:
:
:
:
:
:Hmmmmmm . . . I wonder . . . .What hair color do they put on the driver's licenses of bald men?
:
:
:
:
:
:
:

:
:
:
:
:
:
:
:
:::Using a Heathkit audio generator and injecting 80KHZ as called for I cannot get a strong enough signal through the "S" IF band to register movement on the s-meter. Other bands have varying s-meter readings but the meter simply falls dead in "S" position. Tube voltages appear OK, can someone point me to particular components in that IF circuit that might be checked?
:::
::Hi Brian,
:: Using the audio generator is fine.
:: As for components that could be problematic in the IF, well, the IF as you can see has few components.
:: Check your voltages on the tubes. Pay special attention to the grids. They should not be positive. That is an indication of silver mica disease. It is a problem that can effect the IF cans of radios of this vintage.
:: Of course check the tubes. Sometimes tubes test OK but are not good. 6AL5 rarely fail, but it does happen and they are cheap.
::
::Best Regards,
::
::Bill Grimm
::
:
: