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Here is how I measure and adjust an oscillator frequency without loading down the circuit. I have my frequency counter connected to the vertical output of an oscilloscope, using the amplifier in the oscilloscope to boost the level to my counter. Turn the scope sensitivity all the way up and...

this is new to me. what is this "VFO windup" circuit about? ? causing your frequency to sweep. what is the application? on one radio I disconnected what appeared to be a faulty roger beep board. I was told it was working normally, and put it back in circuit. I was told it is a "duck fart"...

. Yes, I remember back in the Los Angeles area as a kid in the 1970's. Kraco auto electronics was sold at K-Mart. Maybe also at White Front stores. Maybe Zody's. (the memories of them places!) That there gave their products a stigma right from the start. Us kids would get our fake "waffle...

I have my old A-99 mounted to a five-foot mast with the coax going at a right angle to my house and radio room. I will put it back on a taller mast again. Works great on "27 MHz CB" 29.000 MHz AM and 29.600 MHz FM. the mast / radials / CP are the other half of the antenna. the antenna...

keep this thread from 2008 going. :) these types of tools.

I worked on an older Saturn with the 013Z board in it a few weeks ago. I had just over 40 W PEP output SSB. Set it to 10 W carrier for AM. works good. I posted my RF out bias circuit change. for the weak receive, tune up the receiver front end RF amp coil L6. it may have been messed with...

got a 939 for repair. it is modified for "TX audio direct injection" on the back of the radio, and had a "golden screwdriver" turning this and that. :oops: It worked but ran so hot I was told they had to put a fan in place of the speaker to keep it cool. :mad::mad: so yes, the "520's" bias...

playing "armchair technician" just checked out the schematic to that radio. so with a regular mic plugged in, does the PA work? loud audio there? and receiver audio in the speaker? If yes, then maybe a problem in the ALC circuit. for TX modulation, and that audio ALC circuit. turn RV102 to...

brandon7861 says - - "*Someone* should redraw that AGC path and the detector circuit in a way that makes it easier on the eyes (and brain)." yes! much agreed. it is hard to see clearly on the schematic. but on the old 2970 I successfully got working on strong SSB signals. I found, I think...

just got home from a long day at work. yes C73 on the 14B board, going to the product detector. for TP6 I added more RF osc signal on this older 2970 with a 013 board and the cap is C90. I could see on the scope that the carrier level was low, so put in a 100 pico-F and strong SSB signals are...

transistor TR30 should be good. don't mess with it. TX in SSB and AM is working. you can see that the AGC is working. the S-meter is moving is a good indication of that, and it works in AM receive.

transistor TR30 should be good. don't mess with it.

hold everything.... the SSB receive signal in this design takes a different path at the end. there is extra gain and transformers to tune (L13 and L14). and AGC is separate at the end. there is not enough carrier injection from the transistor TR30 carrier oscillator to the SSB receiver...

- about that diode D90 in the Saturn. Yesterday I was working on a RCI-2950 (013Z board) and it has diode D93 in that same place. And with full negative going modulation causing the voltage at the TP 7/8/9 shorting board to go to zero, the bias going to the RF driver to drops out, as...

so is your problem in SSB receive? these RCI/Galaxy radios have a problem there. I posted a solution not long ago.

hey, yeah, brandon7861 just got on my computer this evening. I knew what I did and said would get replies. Messing with that "sacred" bias circuit. I was keeping it short, and may not have explained things properly. we are not arguing, it's all cool. We will all learn something. And then...

-"function of D90 and C174 was to keep the collector from going below 8v." if it did that, then the collectors on the other transistor collectors would not go below 8 V, and it would not modulate correctly, as is done with that "NPC mod" that I clip out of radios so they get full modulation...

-- "Was removing galaxy's attempt at negative peak control necessary for the simplified bias at the finals to work? Can you tell us about the journey that led you to yanking those parts?" You must be referring to diode D90 and capacitor C174. this circuit is in most of their radios. I always...

I got this old Galaxy Saturn radio to bring back to life. Working on the RF output. It had several watts of carrier for AM, and SSB was "rough" "scratchy" sounding bad I was told. did the usual RF output transistor bias level check at first. at driver transistor TR44 the bias would barely...

OK, I just repaired an old Galaxy Saturn days ago. (014B board) It was golden screw driver-ed to death, and had various modifications. Just got my new RF output bias circuit tested last night. I ripped out the MV1Y diodes that failed and made a more reliable bias circuit. Just some resistor...