#61
|
||||
|
||||
Nice! - but I hope you didn't buy that poncho <grin>
|
#62
|
|||
|
|||
Quote:
Thanks. . |
#63
|
||||
|
||||
Its from Advance Receiver Research http://www.advancedreceiver.com/
It has to be a custom model. Its similar to P470VDG or P902VDG. You just order a different center frequency. Price is $90 to $130. Specs (at about ch 39) NF 0.6 dB Gain 18 dB 1 dB Comp dBm +12 1 dB BW 30 MHz Type: GaAsFET Power: 10-16 VDC Mine's ordered for Ch. 44 so depending on how it was tuned it is likely a little bit down in gain at Ch. 39. For indoor use there are no cons except need for a wallwart. Outdoors, it needs weather protection and power sent to it. Doug |
#64
|
|||
|
|||
Thanks, Doug. I'll have to study those to see if they'll help me here.
. |
#65
|
||||
|
||||
Quote:
ordinary broadband ones, even good ones. Ch. 44 is 68 miles from me over a hill, and without that preamp, its over the digital cliff. With it, 99.95% reliable. (That's not with the bowtie ... it with a 20 element single channel YAgi). |
Audiokarma |
#66
|
||||
|
||||
Original circuit be damned ... I've ordered 20 200v Zeners for the focus.
So far, I have not changed the circuit functionality, as I don't consider replacing a selenium with a silicon and series resistor changed functionality. It really needs regulated focus. |
#67
|
||||
|
||||
I installed 2800 volts worth of Zener regulating the focus this evening.
As an earlier restorer said, it works. Focus is perfect from black to bloom. |
#68
|
||||
|
||||
I'm curious - does it maintain focus if you vary the line voltage (so other things are varying while focus voltage is constant)?
|
#69
|
||||
|
||||
Quote:
regulated and the convergence electrode runs off that. The small difference in screen voltages likely won't make any difference. My Variac can take the rather large power need. |
#70
|
||||
|
||||
I tested focus versus line voltage.
Yes, focus varies. +-5 volts is "OK" but needs adjustment. +-10 volts is not OK and the height changes wildly as the line voltage is changed. However color and overall picture quality stay good. |
Audiokarma |
#71
|
||||
|
||||
If you have problems with AC mains voltage fluctuations then I would recommend looking in to obtaining a saturable reactor 120V isolation transformer. Those supply regulated 120V AC output as long as the input voltage is between ~85-155V.
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#72
|
||||
|
||||
I used to have one of those transformers which I used on
my photo enlarger lamps. It weighed like 30 pounds but still probably didn't have the power for a CT-100. However, where I live the voltage is rock solid at about 120, and I set the adjustable the B+ resistors for that voltage. |
#73
|
||||
|
||||
One more niggling problem: horizontal ringing.
That is, ringing in the horizontal sweep waveform. I see it in a scope waveform with a probe dangling near the yoke. It looks to be about 175 kHz. This is very clear. I see it as waviness in a diagonal line pattern across the screen, barely visible. I see it as bright bars in a black background, barely visible. I see it as scrunching up or spreading out in the bars as a scene pans across the screen. This actually is clearer than on the diagonal bars. I've tried finding this problem in the archives here and find two suggestions: replace the damper tube and the 270 pF capacitor in the yoke. I have no mica caps in a high enough voltage ... would two 130 pF 6 kV ceramics in parallel do? I don't know if our stock has the 6AU4GT. Question: are there other things to check, especially ones I can just "test" to see if they are good? |
#74
|
||||
|
||||
I looked at the 270 pF capacitor in the yoke .... its the
biggest dogbone ceramic capacitor I have ever seen! |
#75
|
||||
|
||||
I replaced the damper and it fixed the problem say 90%, which is
plenty good enough. It turns out that the "shunt" pot in the tube tester was dirty and it was giving wrong results for diodes. |
Audiokarma |
|
|