I am fixing this unit for a Ham radio person. I did restore the filter circuit and the B+ is good. Tubes also test good.
Bands A,B,C, & D track the correct frequency with my frequency counter, amazingly almost directly with the dial scale.
The response on the D band is erratic, the frequency that does stabelize is only the 50 MHz. All other response on the dial comes and goes (erratic output).
All ideas are welcome for a soultion.
Thank you,
Mitch
Rich
:Hello everyone,
:
:I am fixing this unit for a Ham radio person. I did restore the filter circuit and the B+ is good. Tubes also test good.
:
:Bands A,B,C, & D track the correct frequency with my frequency counter, amazingly almost directly with the dial scale.
:
:The response on the D band is erratic, the frequency that does stabelize is only the 50 MHz. All other response on the dial comes and goes (erratic output).
:
:All ideas are welcome for a soultion.
:
:Thank you,
:
:Mitch
:
Rich
:The D band operates on harmonics, so it will actually be at half frequency. One of the compromises of a low-priced kit design.
:How are you checking the frequency? With a receiver?
:Can you turn on an FM radio and set the SG-8 to the same frequency and hear the sig? It should wipe out any local FM radio station signal.
:
:Rich
:
:
::Hello everyone,
::
::I am fixing this unit for a Ham radio person. I did restore the filter circuit and the B+ is good. Tubes also test good.
::
::Bands A,B,C, & D track the correct frequency with my frequency counter, amazingly almost directly with the dial scale.
::
::The response on the D band is erratic, the frequency that does stabelize is only the 50 MHz. All other response on the dial comes and goes (erratic output).
::
::All ideas are welcome for a soultion.
::
::Thank you,
::
::Mitch
::
:
:
A,B,C and D bands work perfect. I am testing the unit with a frequency counter.
It is the E Band that is erratic.
Ideas appreciated,
Mitch
If it is erratic, you might try a new 12AT7 (or is it a 12AU7? Can't remember).
I gave away my SG-8 about 5 yrs. ago.
Rich
::PS: you can more useful info and lots of help on vintage equipment from Antique Radio Forum.
::http://www.antiqueradios.com/forums/viewforum.php?f=8
::
::Rich
::
::
:::The D band operates on harmonics, so it will actually be at half frequency. One of the compromises of a low-priced kit design.
:::How are you checking the frequency? With a receiver?
:::Can you turn on an FM radio and set the SG-8 to the same frequency and hear the sig? It should wipe out any local FM radio station signal.
:::
:::Rich
:::
:::
::::Hello everyone,
::::
::::I am fixing this unit for a Ham radio person. I did restore the filter circuit and the B+ is good. Tubes also test good.
::::
::::Bands A,B,C, & D track the correct frequency with my frequency counter, amazingly almost directly with the dial scale.
::::
::::The response on the D band is erratic, the frequency that does stabelize is only the 50 MHz. All other response on the dial comes and goes (erratic output).
::::
::::All ideas are welcome for a soultion.
::::
::::Thank you,
::::
::::Mitch
::::
:::
:::
::
::
:Sorry, error in message.
:
:A,B,C and D bands work perfect. I am testing the unit with a frequency counter.
:
:It is the E Band that is erratic.
:
:Ideas appreciated,
:
:Mitch
:
:
:At higher frequencies the least little poor connection would cause this erratic operation.
:While on band E and your frequency counter connected wiggle the band switch, see if that makes the counter change. Also wiggle the tubes for dirty sockets. Tap around the components and grounding points. You may find more that one area that is causing this.
:
:
Use an oscilloscope to check signal on the upper band. For most signal generators quality is very poor. Once seeing the signal you may wonder how it could be usable for aligning a radio.
Norm
:If you are using a freq. counter, the output on the highest freq. band of the SG-8 may not be sufficiently high to trigger the counter correctly. Do you have a 'scope?
:Rich
:
:
::
::At higher frequencies the least little poor connection would cause this erratic operation.
::While on band E and your frequency counter connected wiggle the band switch, see if that makes the counter change. Also wiggle the tubes for dirty sockets. Tap around the components and grounding points. You may find more that one area that is causing this.
::
::
:
:
My Heathkit SG-8 has a strange phenomenon - The filament voltage is only 5 vac! I swear! the 12AU7 and 6C4 tubes are quite happy with the low voltage and I guess they will last forever.
I sometimes use mine as a low power AM transmitter. Feed music in, hang a 6 foot wire on the output. I'm sure your buddy will have fun with it. John
:Mitch
:
: Use an oscilloscope to check signal on the upper band. For most signal generators quality is very poor. Once seeing the signal you may wonder how it could be usable for aligning a radio.
:
:Norm
:
::If you are using a freq. counter, the output on the highest freq. band of the SG-8 may not be sufficiently high to trigger the counter correctly. Do you have a 'scope?
::Rich
::
::
:::
:::At higher frequencies the least little poor connection would cause this erratic operation.
:::While on band E and your frequency counter connected wiggle the band switch, see if that makes the counter change. Also wiggle the tubes for dirty sockets. Tap around the components and grounding points. You may find more that one area that is causing this.
:::
:::
::
::
:
:
You probably have this manual, but I'll post it for lurkers :>)
:http://pdf.textfiles.com/manuals/SCANNERS-F-R/Heathkit-SG-8.pdf
:
:My Heathkit SG-8 has a strange phenomenon - The filament voltage is only 5 vac! I swear! the 12AU7 and 6C4 tubes are quite happy with the low voltage and I guess they will last forever.
:I sometimes use mine as a low power AM transmitter. Feed music in, hang a 6 foot wire on the output. I'm sure your buddy will have fun with it. John
:
:
:
::Mitch
::
:: Use an oscilloscope to check signal on the upper band. For most signal generators quality is very poor. Once seeing the signal you may wonder how it could be usable for aligning a radio.
::
::Norm
::
:::If you are using a freq. counter, the output on the highest freq. band of the SG-8 may not be sufficiently high to trigger the counter correctly. Do you have a 'scope?
:::Rich
:::
:::
::::
::::At higher frequencies the least little poor connection would cause this erratic operation.
::::While on band E and your frequency counter connected wiggle the band switch, see if that makes the counter change. Also wiggle the tubes for dirty sockets. Tap around the components and grounding points. You may find more that one area that is causing this.
::::
::::
:::
:::
::
::
:
: