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Discussion in 'General CB Services Discussion' started by kopcicle, Oct 5, 2018.
Anyone know the case screw sizes ?
Pretty sure they're #8 coarse self-tapping.
A friend of yours?
I found a crack in the VFO capacitor support that would not under any circumstances allow for correct VFO output.
A note for future Radio wrenches that attack linearity of this VFO. You'll note that the moving and stationary plates are not quite parallel .
Until you actually find the ends of the 27 and 28 dial don't even try to straighten it out. I think you'll find that it is by design.
Tisha I didn't convert to a solid state regulator as these original parts seem very stable.
I managed to get all the voltages where they are supposed to be but I'm leaving the PA for last. I have a limited number of 8950's so I'm making sure.
One last note for those that seldom work on tube gear. Sacrificing a scope probe to these rigs is a real possibility. You see, a high impedance location in the oscillator chain that won't load the oscillator usually equates with a High voltage. Couple this with a DC coupled probe and the results can be tears if not shocking.
I'm off to plotting a filter on a piece of paper to find out where the carrier insertion points "should" be. In a rig this old the as written specs are meaningless. Don't ask why I have to do this the hard way :-/ (parts are on the way)
I'm hoping to check into the weekend 10m nets but I know better than to get in a hurry. Thank You to all as it is difficult to get answers or information without multiple sermons from the "Church of St Hiram" . Your assistance was and is very much appreciated
1) if left open and powered on the bench with a half eaten snack in near proximity it makes a serious rat trap.
Tripped the bench iso and power strip but not after thoroughly cooking the rodent
2) DC coupled scope probes and looking for a high impedance point in a circuit that won't load the oscillator usually points to a high voltage.
3) There is a reason for DDS instead of PLL instead of PTO instead LMO instead of VFO instead of ...
Getting this low budget VFO linear over any semblance of of it's width is voodoo that I rarely do. Now I remember why .
4)Mentioning a piece of equipment that is even remotely considered "CB" quickly separates the pontificating minions of the "Church of St Hiram" from some of the best people I have met here and on "teh 'Zed" . It was my welcome introduction to Tisha and Dale among others.
5) just because a carbon resistor measures within tolerance on initial diagnosis does not mean that it will survive even initial turn on.
6) Same holds true for HV capacitors. See above. Nothing like a HV party popper to get your heart started (or stopped) and spread confetti all over the bench.
7) input impedance of a 12AX7 grid is NOT 500 ohms. In my defense I have two identical mic bodies, one with a ceramic element and another with a 500 ohm voice coil. At least it was a 500 ohm voice coil. I didn't properly check the mic jack.
8) Show me a radio that is idiot proof and I'll prove you wrong. In the words of Robert Anson Heinlein, "Never underestimate the power of human stupidity. This includes your own."
9) There are very good reasons for a non conductive bench top. Setting the radio down with the bottom exposed , on tools left on the bench , negates this careful preparation .
Have one of these 1011D's where can I find tubes for mine? Blew the final tubes and am unable to find any. Been told there is a solid state conversion for the finals, I would guess those would be set up with pins for tube sockets.
8950 tubes do show up on Ebay.
This guy is quite dependable.
He shows 8950 for 50 bucks used, 85 bucks new, near the bottom of the page.
Another source is here: http://www.vacuumtubes.net/prices.htm
His price is 95 bucks.
It's also possible to substitute a 6LF6 for the final tube, if you take the heater-power wire loose from the final-tube socket and put a 6-Amp rectifier diode between the wire and the tube socket. Pretty well cuts the heater voltage in half.
And I thought I had an uphill battle with this "Made in The Malaysia" 148.
My sympathies to the family of the deceased.
"It's also possible to substitute a 6LF6 for the final tube, if you take the heater-power wire loose from the final-tube socket and put a 6-Amp rectifier diode between the wire and the tube socket. Pretty well cuts the heater voltage in half. "
Gotta dig around and see if have any of the 6LF6 tubes out in the barn. Does this have any positive effect on the drift issues with the 1011D? Decent radio, just won't stay on freq., doesn't wander much, but have to keep an eye on it. Placed a brooder light over the radio and that helped some by keeping it warm and cozy like a wittle chicken.
Its doubtful a different tube (number) in the final output socket will cure the VFO drift issue of this classic-but I'm no expert!
Are those vintage mice from the sixtys?.
my assalt cat is on duty at my house
The mouse drifted a bit close to the vfo and got a shock of his life guess he called his last call sign lol
You have discovered the basis of the VFO's drift.
Anything that stabilizes the temperature inside the VFO compartment will reduce frequency drift.
The choice of final tube won't have much influence on the stability of the VFO.
Until it gets hot enough to raise the temperature inside the VFO box.