AM stage in NAD 7020E. Constant farting.

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I got a loop antenna for it.

Then i opened it up and noticed the osc coil was split in half so i got another one and popped it in. The osc still doesnt do anything when i turn it and the if just goes through a whole bunch of pulsating noises that dont show even faint signs of a signal.

Any clue how else i could trouble shoot this bad boy? Im kind of a newb but have a multimeter and can read schematics (7020e manual didnt help much). Should i start taking voltages around am stage?


Thanks!!
 
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DC voltages are always a good place to start.

What do you mean by 'split in half'? Don't try to adjust the coils unless you understand how to do radio alignment.

Coils have been turned but I ive done alignments before and theyve been put back to somewhat the same spot. The adjuster on the inside was parted in two.

Should be noted that everything else on the receover is sounding great..fm phono cd etc
 
You can check a coil for DC continuity. If OK you could measure inductance and Q, but this is rarely necessary. Coils usually either fail open circuit or stay OK.

I am wondering what sort of coil you just "popped in" - you located and bought an exact replacement for the original?

Thank you for your input thus far! I am beginning to think it may be the coil...the one that was broken was a SUMIDA oscillator that was a black dot but STRIPED red and 7mm (cant find exact replacements anywhere). I replaced it with a red dot SUMIDA osc with no stripes. Could that make a difference? The red dots were not having any impact when turned and the black dots (tried 2 black dot coils..no red stripes tho) had much more impact on the signal when in the oscillator position)

I wasbtold the am osc is always red

Still pretty lost �� looking forward to the learning this could bring tho!
 
The oscillator coil, like all radio coils, must be replaced by one which has the same inductance and the same secondaries or taps. You can't even just swap one MW AM coil for another MW AM coil unless they are the same inductance and intended for the same circuit design. Some adjustment is possible, of course, but you need to be close to start with.

What are these "dots" which you are turning? Do you mean the adjustable ferrite cores?

I have no idea whether in a particular manufacturer's range of coils the AM oscillator coils are always red. This may not be useful information, as you also have to choose the right frequency range and right inductance etc. In post 3 you implied that you are familiar with radio alignment; I am beginning to doubt this.
 
The oscillator coil, like all radio coils, must be replaced by one which has the same inductance and the same secondaries or taps. You can't even just swap one MW AM coil for another MW AM coil unless they are the same inductance and intended for the same circuit design. Some adjustment is possible, of course, but you need to be close to start with.

What are these "dots" which you are turning? Do you mean the adjustable ferrite cores?

I have no idea whether in a particular manufacturer's range of coils the AM oscillator coils are always red. This may not be useful information, as you also have to choose the right frequency range and right inductance etc. In post 3 you implied that you are familiar with radio alignment; I am beginning to doubt this.
Yes the ferrite cores.
I was under the impression the red coils were all am oscillators. How can i check what i had before if the ferrite core is broken? Ive checked the schematic and it doesnt say amy speca. Just refers to it as the AM OSC.
 
Are you now saying that the coil is intact but the core was broken? If so, that is not what you told us in post 1. I was puzzled how a coil could break in two! Broken cores are usually the result of using the wrong trimming tool, or too much heavy handling.

If you need to replace the coil you need to find the spec for the original and find an exact replacement. Alternatively, dismantle the original coil and replace the broken core. Do whichever is easier for you.

Alternatively, to stop things getting any worse, find someone who knows about radio repair and tell him exactly what you have done.
 
Are you now saying that the coil is intact but the core was broken? If so, that is not what you told us in post 1. I was puzzled how a coil could break in two! Broken cores are usually the result of using the wrong trimming tool, or too much heavy handling.

If you need to replace the coil you need to find the spec for the original and find an exact replacement. Alternatively, dismantle the original coil and replace the broken core. Do whichever is easier for you.

Alternatively, to stop things getting any worse, find someone who knows about radio repair and tell him exactly what you have done.
Thanks
 
coil1.jpg
Which part is broken ?.

Dan.
 
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