Has anyone had any experience with this model? I have replaced a few caps and resistors and the 6SJ7. The oscillator is running at the correct frequency on all bands but, I'm not entirely happy with the quality of the output sigal.
I particularily want to know details about this generators output characteristics:
1. What is the maximum amplitude of the output signal?
2. What is the unmodulated waveform characteristics? 3. Is it supposed to be a clean sine wave etc?
Thanks,
GWP
:I've just acquired a Precision Apparatus E-200-C RF Signal Generator.
:
:Has anyone had any experience with this model? I have replaced a few caps and resistors and the 6SJ7. The oscillator is running at the correct frequency on all bands but, I'm not entirely happy with the quality of the output sigal.
:
:I particularily want to know details about this generators output characteristics:
:
:1. What is the maximum amplitude of the output signal?
:2. What is the unmodulated waveform characteristics? 3. Is it supposed to be a clean sine wave etc?
:
:Thanks,
:GWP
HI: I have used and rebuilt a dozen or so of this model mover the years. You have an older version of the 200C with the 6SJ7 - the later version used a 6AU6 and both were electron coupled oscillators. The electron coupled oscillator is stable but due to its nature does generate some harmonics. I have never rebuilt one of these that would produce a nice pure sine wave on RF. However, it should be pretty good and will suffice for alignment purposes just fine. I would suggest one test for you. Crank up the generator on band "A" about 150 KC and use you scope on the power supply main filter cap to see if any RF is "floating" around on the B+. If it is, and you have replaced the filter caps, install a high quality capacitor .1 mf across the filter caps. All electrolytics have inductance (L), some more than others, so by bypassing them to ground will indeed get rid of any regeneration due to the B+ not being at true AC ground.
Another good thing to know on this model is that the AVC voltage supply is a function of power supply current on the center tap of the power transformer. It should approximate 50 volts. Connect a voltmeter to your AVC supply terminals and see if it cranks up to 50 volts DC. This is a very good test to see if the power supply is drawing the correct amount of current. Good luck with it. Tom.
Hi Tom:
Thanks for the tips. I will check the AVC and do the Band A 150kHz test you suggested.
I'll let you know how it turns out.
Again, thanks.
Gary
I did that check on the AVC and the maximum is about 16V? You had mentioned that it should put out about 50.
I noticed that the voltage on the grid of the 6SJ7 is about -21V. This seems a bit high.
I did the 150KHz test you suggested. There is no appreaciable RF on the DC bus.
Gary
::Most lower cost signal generators use harmonics to generate the output signal, and therefore the signal is full of many frequencies. The genarator will be accurate to alighn/test most radio receiving equipment, but will not produce the quality of signal that would be obtained from a "lab" type generator. (and doesn't cost nearly as much).
::
:::I've just acquired a Precision Apparatus E-200-C RF Signal Generator.
:::
:::Has anyone had any experience with this model? I have replaced a few caps and resistors and the 6SJ7. The oscillator is running at the correct frequency on all bands but, I'm not entirely happy with the quality of the output sigal.
:::
:::I particularily want to know details about this generators output characteristics:
:::
:::1. What is the maximum amplitude of the output signal?
:::2. What is the unmodulated waveform characteristics? 3. Is it supposed to be a clean sine wave etc?
:::
:::Thanks,
:::GWP
:
:HI: I have used and rebuilt a dozen or so of this model mover the years. You have an older version of the 200C with the 6SJ7 - the later version used a 6AU6 and both were electron coupled oscillators. The electron coupled oscillator is stable but due to its nature does generate some harmonics. I have never rebuilt one of these that would produce a nice pure sine wave on RF. However, it should be pretty good and will suffice for alignment purposes just fine. I would suggest one test for you. Crank up the generator on band "A" about 150 KC and use you scope on the power supply main filter cap to see if any RF is "floating" around on the B+. If it is, and you have replaced the filter caps, install a high quality capacitor .1 mf across the filter caps. All electrolytics have inductance (L), some more than others, so by bypassing them to ground will indeed get rid of any regeneration due to the B+ not being at true AC ground.
: Another good thing to know on this model is that the AVC voltage supply is a function of power supply current on the center tap of the power transformer. It should approximate 50 volts. Connect a voltmeter to your AVC supply terminals and see if it cranks up to 50 volts DC. This is a very good test to see if the power supply is drawing the correct amount of current. Good luck with it. Tom.
I've did all the usual checks. The cap is not leaky and the pot is bang on 4K. The pot has a fixed tap at about 2K. The B+ is in the range of 310, which may be a bit low compared to your estimate. I've checked the recifier tube on my AVO MKIII Valve Characteristic Meter. It checks out fine. I haven't checked the ac voltage from the secondary of the power transformer yet.For that matter, I haven't verified that the filament voltages are up to snuff.
Thanks for your input.
I'll keep ya posted.
Gary
::Gary: With the AVC supply having a maximum of only 16 volts something is rotten in Denmark. This AVC supply voltage is derived from the center tap of the power transformer going to ground through the AVC control resistance which is about 4,000 ohms. If the AVC voltage is low then you are probably not drawing enough current through the power supply OR the control itsself could be changed by someone. Measure the value of the control and change the .01mf cap soldered across the AVC output terminals. B+ should be in the neighborhood of 340 or to ground. Keep'em flying --tTom. Hi Tom:
::
::I did that check on the AVC and the maximum is about 16V? You had mentioned that it should put out about 50.
::
::I noticed that the voltage on the grid of the 6SJ7 is about -21V. This seems a bit high.
::
::I did the 150KHz test you suggested. There is no appreaciable RF on the DC bus.
::
::Gary
::
::
::::Most lower cost signal generators use harmonics to generate the output signal, and therefore the signal is full of many frequencies. The genarator will be accurate to alighn/test most radio receiving equipment, but will not produce the quality of signal that would be obtained from a "lab" type generator. (and doesn't cost nearly as much).
::::
:::::I've just acquired a Precision Apparatus E-200-C RF Signal Generator.
:::::
:::::Has anyone had any experience with this model? I have replaced a few caps and resistors and the 6SJ7. The oscillator is running at the correct frequency on all bands but, I'm not entirely happy with the quality of the output sigal.
:::::
:::::I particularily want to know details about this generators output characteristics:
:::::
:::::1. What is the maximum amplitude of the output signal?
:::::2. What is the unmodulated waveform characteristics? 3. Is it supposed to be a clean sine wave etc?
:::::
:::::Thanks,
:::::GWP
:::
:::HI: I have used and rebuilt a dozen or so of this model mover the years. You have an older version of the 200C with the 6SJ7 - the later version used a 6AU6 and both were electron coupled oscillators. The electron coupled oscillator is stable but due to its nature does generate some harmonics. I have never rebuilt one of these that would produce a nice pure sine wave on RF. However, it should be pretty good and will suffice for alignment purposes just fine. I would suggest one test for you. Crank up the generator on band "A" about 150 KC and use you scope on the power supply main filter cap to see if any RF is "floating" around on the B+. If it is, and you have replaced the filter caps, install a high quality capacitor .1 mf across the filter caps. All electrolytics have inductance (L), some more than others, so by bypassing them to ground will indeed get rid of any regeneration due to the B+ not being at true AC ground.
::: Another good thing to know on this model is that the AVC voltage supply is a function of power supply current on the center tap of the power transformer. It should approximate 50 volts. Connect a voltmeter to your AVC supply terminals and see if it cranks up to 50 volts DC. This is a very good test to see if the power supply is drawing the correct amount of current. Good luck with it. Tom.
This one has got me baffled????
Every resistor, pot & capacitor checks out.
The secondary of the power transformer is pumping out 275VAC per side. Filament voltages are good and all of the tubes check out. Yet, the AVC is still around 16V??? The B+ is 336 VDC at the rectifier and 300V after the 3K resistor. There's about 3Vpp of ripple, does this seem reasonable to you?
Still working on it.
Gary
::Gary: With the AVC supply having a maximum of only 16 volts something is rotten in Denmark. This AVC supply voltage is derived from the center tap of the power transformer going to ground through the AVC control resistance which is about 4,000 ohms. If the AVC voltage is low then you are probably not drawing enough current through the power supply OR the control itsself could be changed by someone. Measure the value of the control and change the .01mf cap soldered across the AVC output terminals. B+ should be in the neighborhood of 340 or to ground. Keep'em flying --tTom. Hi Tom:
::
::I did that check on the AVC and the maximum is about 16V? You had mentioned that it should put out about 50.
::
::I noticed that the voltage on the grid of the 6SJ7 is about -21V. This seems a bit high.
::
::I did the 150KHz test you suggested. There is no appreaciable RF on the DC bus.
::
::Gary
::
::
::::Most lower cost signal generators use harmonics to generate the output signal, and therefore the signal is full of many frequencies. The genarator will be accurate to alighn/test most radio receiving equipment, but will not produce the quality of signal that would be obtained from a "lab" type generator. (and doesn't cost nearly as much).
::::
:::::I've just acquired a Precision Apparatus E-200-C RF Signal Generator.
:::::
:::::Has anyone had any experience with this model? I have replaced a few caps and resistors and the 6SJ7. The oscillator is running at the correct frequency on all bands but, I'm not entirely happy with the quality of the output sigal.
:::::
:::::I particularily want to know details about this generators output characteristics:
:::::
:::::1. What is the maximum amplitude of the output signal?
:::::2. What is the unmodulated waveform characteristics? 3. Is it supposed to be a clean sine wave etc?
:::::
:::::Thanks,
:::::GWP
:::
:::HI: I have used and rebuilt a dozen or so of this model mover the years. You have an older version of the 200C with the 6SJ7 - the later version used a 6AU6 and both were electron coupled oscillators. The electron coupled oscillator is stable but due to its nature does generate some harmonics. I have never rebuilt one of these that would produce a nice pure sine wave on RF. However, it should be pretty good and will suffice for alignment purposes just fine. I would suggest one test for you. Crank up the generator on band "A" about 150 KC and use you scope on the power supply main filter cap to see if any RF is "floating" around on the B+. If it is, and you have replaced the filter caps, install a high quality capacitor .1 mf across the filter caps. All electrolytics have inductance (L), some more than others, so by bypassing them to ground will indeed get rid of any regeneration due to the B+ not being at true AC ground.
::: Another good thing to know on this model is that the AVC voltage supply is a function of power supply current on the center tap of the power transformer. It should approximate 50 volts. Connect a voltmeter to your AVC supply terminals and see if it cranks up to 50 volts DC. This is a very good test to see if the power supply is drawing the correct amount of current. Good luck with it. Tom.