Hi, has anybody had trouble building the ELENCO 108 AM/FM RADIO KIT

In summary, the conversation was about someone seeking help with a radio they were building. They accidentally swapped the battery and speaker, but eventually figured out their mistake. They were asked to provide a schematic and DC voltages measured at various points in the circuit to help troubleshoot the issue. The person also mentioned trying to connect a different speaker to no avail. The conversation then shifted to asking for more information and eventually the person provided a link to the schematic they were using.
  • #1
michael1978
434
19
Hello, i build the radio like they say in the book, and i did everything with VOM(testing with only multimeter),
everything was like in book , but when i finish, i switch to am or fm, i just hear high noise
:doh:
 
Engineering news on Phys.org
  • #2
When I built it, I accidentally got the battery and the speaker swapped. It took me a while to figure out my mistake. o0)

But seriously, how are we supposed to help you with so little information? Post the schematic and label it with the DC voltages you measure in your circuit -- that will give us a starting point to try to help you...
 
  • #3
berkeman said:
When I built it, I accidentally got the battery and the speaker swapped. It took me a while to figure out my mistake. o0)

But seriously, how are we supposed to help you with so little information? Post the schematic and label it with the DC voltages you measure in your circuit -- that will give us a starting point to try to help you...
You had the same, i can tell you the value, you mean the TEST POINT(TP)? i don't know, which value you are interessed? just tell me and i will do it
 
  • #4
michael1978 said:
You had the same, i can tell you the value, you mean the TEST POINT(TP)? i don't know, which value you are interessed? just tell me and i will do it
I was kidding in my first paragraph, making fun of the fact that you posted with so little information and wanted help. Sorry if my humor wasn't obvious.

In my second paragraph, I asked you to Upload a copy of the schematic (as a PDF or JPEG file), and be sure to mark the DC voltages you measure at each node of the circuit on the schematic. That will help us to look for obvious problems (like if you measure a zero voltage at a place in the circuit where the voltage should be non-zero). Mark up the voltage you measure on the schematic that you have, and use the UPLOAD button to Upload a PDF or JPEG copy of that marked-up schematic. Here is an example without the measured voltages marked on it yet...

http://electroschematics.com/wp-content/uploads/2010/07/fm-radio-receiver.gif
fm-radio-receiver.gif
 
  • #5
michael1978 said:
You had the same, i can tell you the value, you mean the TEST POINT(TP)? i don't know, which value you are interessed? just tell me and i will do it
I was kidding in my first paragraph, making fun of the fact that you posted with so little information and wanted help. Sorry if my humor wasn't obvious.

In my second paragraph, I asked you to Upload a copy of the schematic (as a PDF or JPEG file), and be sure to mark the DC voltages you measure at each node of the circuit on the schematic. That will help us to look for obvious problems (like if you measure a zero voltage at a place in the circuit where the voltage should be non-zero). Mark up the voltage you measure on the schematic that you have, and use the UPLOAD button to Upload a PDF or JPEG copy of that marked-up schematic. Here is an example without the measured voltages marked on it yet...

http://electroschematics.com/wp-content/uploads/2010/07/fm-radio-receiver.gif
fm-radio-receiver.gif
 
  • #6
berkeman said:
When I built it, I accidentally got the battery and the speaker swapped. It took me a while to figure out my mistake. o0)

But seriously, how are we supposed to help you with so little information? Post the schematic and label it with the DC voltages you measure in your circuit -- that will give us a starting point to try to help you...
I Measure, Test Point, without connection a speaker(because i thought the speaker was bad, so i desoldeer, and i connect with wire other speaker 8ohm but the same problem stays),
so
i switch to FM
tp15 and tp2=2.74V
tp15 and tp13=1.4V
tp15 and tp11=6.59V
tp15 and tp10=1.20V
tp15 and tp9=7.08V
tp15 and tp8=6.43V
tp15 and tp12=6.74V
i switch to am
tp15 and tp2=0.02V
tp15 and tp3=7.77V
tp15 and tp1=4.21V
tp15 and tp4=8.13V
tp15 and tp5=1.34V
tp15 and tp6=0V
tp15 and tp14'=0.02V
TP15=GND
 
  • #7
michael1978 said:
I Measure, Test Point, without connection a speaker(because i thought the speaker was bad, so i desoldeer, and i connect with wire other speaker 8ohm but the same problem stays),
so
i switch to FM
tp15 and tp2=2.74V
tp15 and tp13=1.4V
tp15 and tp11=6.59V
tp15 and tp10=1.20V
tp15 and tp9=7.08V
tp15 and tp8=6.43V
tp15 and tp12=6.74V
i switch to am
tp15 and tp2=0.02V
tp15 and tp3=7.77V
tp15 and tp1=4.21V
tp15 and tp4=8.13V
tp15 and tp5=1.34V
tp15 and tp6=0V
tp15 and tp14'=0.02V
TP15=GND
Please upload the schematic or link to a copy of it on the Internet. Thank you.
 
  • #8
berkeman said:
Please upload the schematic or link to a copy of it on the Internet. Thank you.
 

Attachments

  • schematic.pdf
    903.4 KB · Views: 251
  • #9
berkeman said:
I was kidding in my first paragraph, making fun of the fact that you posted with so little information and wanted help. Sorry if my humor wasn't obvious.

In my second paragraph, I asked you to Upload a copy of the schematic (as a PDF or JPEG file), and be sure to mark the DC voltages you measure at each node of the circuit on the schematic. That will help us to look for obvious problems (like if you measure a zero voltage at a place in the circuit where the voltage should be non-zero). Mark up the voltage you measure on the schematic that you have, and use the UPLOAD button to Upload a PDF or JPEG copy of that marked-up schematic. Here is an example without the measured voltages marked on it yet...

http://electroschematics.com/wp-content/uploads/2010/07/fm-radio-receiver.gif
fm-radio-receiver.gif
i post schematic
 
  • #10
michael1978 said:
i post schematic
Thank you, that helps a lot. I think I'll move this thread to the EE forum, to get more specialized help.

It looks like there are several adjustable components in the schematic. Was there an "alignment procedure" included in the instructions? Also, did you assemble this from a kit with a PC board included?
 
  • #11
michael1978 said:
I Measure, Test Point, without connection a speaker(because i thought the speaker was bad, so i desoldeer, and i connect with wire other speaker 8ohm but the same problem stays),
so
i switch to FM
tp15 and tp2=2.74V
tp15 and tp13=1.4V
tp15 and tp11=6.59V
tp15 and tp10=1.20V
tp15 and tp9=7.08V
tp15 and tp8=6.43V
tp15 and tp12=6.74V
i switch to am
tp15 and tp2=0.02V
tp15 and tp3=7.77V
tp15 and tp1=4.21V
tp15 and tp4=8.13V
tp15 and tp5=1.34V
tp15 and tp6=0V
tp15 and tp14'=0.02V
TP15=GND
It looks like TP17 (lower right of the schematic) is Ground. Can you please measure the voltages of the other test points with respect to TP17 Ground? That would be helpful. Just keep you meter's negative test lead on TP17, and measure the voltages of the other test points with your meter's positive lead. Thank you.
 
  • #12
berkeman said:
It looks like TP17 (lower right of the schematic) is Ground. Can you please measure the voltages of the other test points with respect to TP17 Ground? That would be helpful. Just keep you meter's negative test lead on TP17, and measure the voltages of the other test points with your meter's positive lead. Thank you.
berkeman said:
It looks like TP17 (lower right of the schematic) is Ground. Can you please measure the voltages of the other test points with respect to TP17 Ground? That would be helpful. Just keep you meter's negative test lead on TP17, and measure the voltages of the other test points with your meter's positive lead. Thank you.
I don't use transistor amplifier, but i use lm386,
 
  • #13
michael1978 said:
I don't use transistor amplifier, but i use lm386,
Please post the schematic for what you have built, and post the test point voltages. Thank you.
 
  • #14
berkeman said:
Please post the schematic for what you have built, and post the test point voltages. Thank you.
I show you tomorow maybe, because i go to sleep, here is 24:10 goodnight berkeman
 
  • Like
Likes berkeman
  • #15
berkeman said:
It looks like TP17 (lower right of the schematic) is Ground.
TP15 is also GND; that's below Q5 in the FM section.

@michael1978
I have only looked at the AM section because that part is easier. Let's get that and the earphone working first.
Page 34 of the manual says the battery should measure 8.5V or more with the power switch turned on. Your measurements show around 7.8V to 8.1V. Please replace the battery.

This test can be done with the old battery. It will give you something to do until you get a new one.
There is a problem at TP6, it reads 0V but should be about 8V or higher (about the same voltage as at TP4).
Check the wiring at the primary (left) side of T6, around L5 and around Q7. There is probably a bad or missing connection to T6.

Let us know what you find.

Cheers,
Tom
 
  • #16
Tom.G said:
TP15 is also GND; that's below Q5 in the FM section.

@michael1978
I have only looked at the AM section because that part is easier. Let's get that and the earphone working first.
Page 34 of the manual says the battery should measure 8.5V or more with the power switch turned on. Your measurements show around 7.8V to 8.1V. Please replace the battery.

This test can be done with the old battery. It will give you something to do until you get a new one.
There is a problem at TP6, it reads 0V but should be about 8V or higher (about the same voltage as at TP4).
Check the wiring at the primary (left) side of T6, around L5 and around Q7. There is probably a bad or missing connection to T6.

Let us know what you find.

Cheers,
Tom
GoodMorning, i was wrong, because now between T6 is 8.7V, now is not anymore so high noise, but low noise, and when i rotate the VARcapacitor
i don't hear nothing changes, i can't pickup any fm or am radio station?
what do you think where is problem?
have a nice day
 
  • #17
berkeman said:
Thank you, that helps a lot. I think I'll move this thread to the EE forum, to get more specialized help.

It looks like there are several adjustable components in the schematic. Was there an "alignment procedure" included in the instructions? Also, did you assemble this from a kit with a PC board included?
yes
 
  • #18
Tom.G said:
TP15 is also GND; that's below Q5 in the FM section.

@michael1978
I have only looked at the AM section because that part is easier. Let's get that and the earphone working first.
Page 34 of the manual says the battery should measure 8.5V or more with the power switch turned on. Your measurements show around 7.8V to 8.1V. Please replace the battery.

This test can be done with the old battery. It will give you something to do until you get a new one.
There is a problem at TP6, it reads 0V but should be about 8V or higher (about the same voltage as at TP4).
Check the wiring at the primary (left) side of T6, around L5 and around Q7. There is probably a bad or missing connection to T6.

Let us know what you find.

Cheers,
Tom
I see one video, all collector of fm have the same value, he show in the video and i tested my the same they have,
but like in am and fm sometimes is high noise, sometime little bit noise, but i can't catch any signal,
 
  • #19
now is low NOISE like in am or fm but i can get any signal, what do you think , where is problem:bow:
 
  • #20
Does anything you do make a change in the high noise or low noise?
If yes, tell use what you do to make that change.
 
  • #21
Tom.G said:
Does anything you do make a change in the high noise or low noise?
If yes, tell use what you do to make that change.
I think maybe, i soldeer it one more lm386 WITH bypass capacitor at pin 2 and 6, and also i change the battery little bit old,
and also i can hear nothing from earphony, totaly nothing,
 
  • #22
michael1978 said:
WITH bypass capacitor at pin 2 and 6
That should be pin 4 and 6.

Do you have any test equipment besides the voltmeter?
 
  • #23
Tom.G said:
That should be pin 4 and 6.

Do you have any test equipment besides the voltmeter?
how not, how i measure til now?, but in the book is between pin 2 and 6 capacitor, how come now pin 4 and 6(are you sure)?
 
  • #24
michael1978 said:
how not, how i measure til now?, but in the book is between pin 2 and 6 capacitor, how come now pin 4 and 6(are you sure)?
i have dvm
 
  • #25
michael1978 said:
how not, how i measure til now?, but in the book is pin 2 and 6, how come now pin 4 and 6(are you sure)?
The image below is from the datasheet for the LM386 made by National Semiconductor. As you can see, the supply voltage is on pin 6, Ground is pin 4, and -Input is pin 2. Your circuit has pin 2 connected to Ground, probably as a short circuit trace between pins 2 and 4. I said pin 4 for the bypass capacitor just to be very safe (conservative). If there is a bad connection on the board between pins 2 and 4, the bypass might not connect to Ground if soldered to pin 2.

If the connection between pins 2 and 4 are good, for your circuit it probably will not make much difference. For other circuits it can make a difference, so we all get in the habit of connecting bypass capacitors to the power and Ground pins just to avoid problems.

OK, you have DVM. What make and model is it?

upload_2018-7-15_15-14-38.png
 

Attachments

  • upload_2018-7-15_15-14-38.png
    upload_2018-7-15_15-14-38.png
    8.5 KB · Views: 942
  • #26
Tom.G said:
The image below is from the datasheet for the LM386 made by National Semiconductor. As you can see, the supply voltage is on pin 6, Ground is pin 4, and -Input is pin 2. Your circuit has pin 2 connected to Ground, probably as a short circuit trace between pins 2 and 4. I said pin 4 for the bypass capacitor just to be very safe (conservative). If there is a bad connection on the board between pins 2 and 4, the bypass might not connect to Ground if soldered to pin 2.

If the connection between pins 2 and 4 are good, for your circuit it probably will not make much difference. For other circuits it can make a difference, so we all get in the habit of connecting bypass capacitors to the power and Ground pins just to avoid problems.

OK, you have DVM. What make and model is it?

View attachment 228076
Thnx man i go to change, and i will let you know, i will let you know direct
 
  • #27
michael1978 said:
Thnx man i go to change, and i will let you know, i will let you know direct
I have DVM9915, i soldeer it, now the earphone is working i hear noise but i don't get SIGNAL:cry:
 
  • #28
Does anything you do make a change in the high noise or low noise?
If yes, tell use what you do to make it change.
Does it just get louder and softer or does it sound different?
 
  • #29
Tom.G said:
Does anything you do make a change in the high noise or low noise?
If yes, tell use what you do to make it change.
Does it just get louder and softer or does it sound different?
the earphone is working, and i have a little bit louder, but not like in begin
 
  • #30
Does the sound change when you turn down the volume control?
How does it change?
 
  • #31
Tom.G said:
Does the sound change when you turn down the volume control?
How does it change?
Tom.G said:
Does the sound change when you turn down the volume control?
How does it change?
Yes it go faster and faster, or i hear low noise
 
  • #32
What is the battery voltage when you can hear the noise?
Is the noise the same for both AM and FM?
Does the noise change when you connect TP2 to TP15? If yes, how does it change?
With the switch set for AM.
Does the noise change when you connect the Cathode (K) of D4 to TP15? If yes, how does it change?
 
  • #33
Tom.G said:
What is the battery voltage when you can hear the noise?
Is the noise the same for both AM and FM?
Does the noise change when you connect TP2 to TP15? If yes, how does it change?
With the switch set for AM.
Does the noise change when you connect the Cathode (K) of D4 to TP15? If yes, how does it change?
Sir can i tell you tomorow, i am sorry because is 2 hours nights, i am tired, i want to sleep, thnx for time and help, goodnight…..
 
  • #34
Tom.G said:
What is the battery voltage when you can hear the noise?
Is the noise the same for both AM and FM?
Does the noise change when you connect TP2 to TP15? If yes, how does it change?
With the switch set for AM.
Does the noise change when you connect the Cathode (K) of D4 to TP15? If yes, how does it change?
Googmorning Tom, i did now the test, yes the noise is the same,
FM voltage is 8.6V at the battery, the TP2 AND TP15 stay at 2.6V, and the
AM cathode does not change but the value at cathode is 0V, and TP2 and TP15, are 0 volt at AM
 
  • #35
michael1978 said:
Googmorning Tom, i did now the test, yes the noise is the same,
FM voltage is 8.6V at the battery, the TP2 AND TP15 stay at 2.6V, and the
AM cathode does not change but the value at cathode is 0V, and TP2 and TP15, are 0 volt at AM
michael1978 said:
Sir can i tell you tomorow, i am sorry because is 2 hours nights, i am tired, i want to sleep, thnx for time and help, goodnight…..
Goodmorning Tom are you here somewhere….
 

Similar threads

Variable capacitor q factor for fm radio jammer
    • Electrical Engineering
Replies
4
Views
4K
First Project - Simple FM Radio/Receiver made Complex
    • Electrical Engineering
Replies
1
Views
10K
Modern Digital Audio: Understanding Dither and Oversampling in Hi-Res Age"
    • Computing and Technology
Replies
9
Views
1K
Building Dana lived in in Ghostbusters was built as an antenna
    • Electrical Engineering
Replies
24
Views
3K
RadioInstigator: Building a SIGINT
    • DIY Projects
Replies
5
Views
2K
Building a physical circuit from a transfer function
    • Electrical Engineering
Replies
17
Views
6K
Is it safe to run laptop and router on modified sine wave inverter?
    • Electrical Engineering
Replies
3
Views
14K
Admissions Opening the door to an Astrophysics PhD after a 5 year gap
    • STEM Academic Advising
Replies
11
Views
668
Planning on studying math for the college entrance exam, help needed
    • STEM Academic Advising
Replies
4
Views
1K
What do you think of my site idea?
    • General Discussion
Replies
7
Views
1K

Hot Threads

Recent Insights

Back
Top