Posts: 101
Threads: 5
Joined: Jul 2020
City: Pelzer
State, Province, Country: SC, USA
Still fairly new at tube type radio repair. Just completed alignment on an Olympic model 411. Was impressed with it's final sensitivity and volume. Decided to use it to preform my first stage gain measurements to both increase my knowledge of stage operation and strengthen my troubleshooting skills. Ran into my problem fairly quickly when instructions guide me to adjust my sig-gen output to 3500 microvolts. That value is a bit difficult to locate on my HP 8640B. Had read some where many months ago of a difference between older and newer sig-gen output terminology and values. Seems my search engine skills are lacking worse than my sig-gen skills. After considerable time at research my success was zero. Could someone please give me a heads up on conversion from old to new terminology and values.
Take Care
Tim
Posts: 7,215
Threads: 266
Joined: Dec 2009
City: Roslyn Pa
3500 microvolts is a ridiculous amount of signal. A decent average sensitivity for a run of the mill 5 tube BC set will be around 40-100 microvolts. Would think if it was badly out of alignment maybe double that to start out to do the alignment.
Generally what I do is feed the the IF signal thru the grid of the mixer tube (with the generator set @ the IF frequency). Set the output level so I can just barely hear it. Adjust the IF for max speaker volume or minimum avc voltage. As it gets louder and louder I turn down the generator's level. Set the oscillator @ the top end of the BC band. Peak the ant trimmer.
GL
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 09-07-2020, 04:40 PM by
Radioroslyn.)
Posts: 101
Threads: 5
Joined: Jul 2020
City: Pelzer
State, Province, Country: SC, USA
Thanks Radioroslyn, I have aligned the radio and am happy with it's performance. What I'm trying to do is establish the gain of the Second AF, First AF, IF and Converter stages. Following the instructions in the Elements of Radio Servicing by Marcus and Levy. I have tuned many solid state radios so I have the experience to make up my own intake, output values to determine each stage gain. Just for my own enlightenment and entertainment I am trying to follow the instructions that a tech would have followed over 70 years ago. When the instructions make reference to the 35000 microvolt level of input from the RF Sig-gen I had a small amount of memory recall of something I read on a thread some where, that made this statement. The word microvolt 70 years ago did not mean 1\ 1000000 but rather some other value. If I am wrong, please let me know. Don't want to be jumping down a rabbit hole because of a foggy memory.
