Brandes B15 No Sound from speaker

12/1/2006 4:40:28 PMGreg

Hi,

I am tinkering with an old Brandes B15 floor model. I have replaced all the electrolytics but am only getting a hum from the transformer. Absolutely nothing is coming from the speaker. Can someone tell me how to bypass the speaker and speaker transformer and put a tempory working speaker on just to make sure I am actually getting some kind of output from the radio?

Sorry if this seems like a dumb question. I'm new at this.

Thanks

Greg

12/1/2006 6:56:35 PMMark

:Hi,
:
:I am tinkering with an old Brandes B15 floor model. I have replaced all the electrolytics but am only getting a hum from the transformer. Absolutely nothing is coming from the speaker. Can someone tell me how to bypass the speaker and speaker transformer and put a tempory working speaker on just to make sure I am actually getting some kind of output from the radio?
:
:Sorry if this seems like a dumb question. I'm new at this.
:
:Thanks
:
:Greg
Hi greg
Well I wouldn't reccomend bypassing the audio output transformer, what you could do is connect a large wattage 8 Ohm permanent magnet speaker to the output side of the audio output transformer to see if your getting any audio, with the volume turned way down and gradually turn it up.
Mark

12/2/2006 6:27:46 PMDoug Criner

Greg: when the symptom is no audio, it's tempting to suspect the speaker, but you'd be wrong many more times than not.

Best to troubleshoot the radio in a systematic manner. Check all voltages.

::Hi,
::
::I am tinkering with an old Brandes B15 floor model. I have replaced all the electrolytics but am only getting a hum from the transformer. Absolutely nothing is coming from the speaker. Can someone tell me how to bypass the speaker and speaker transformer and put a tempory working speaker on just to make sure I am actually getting some kind of output from the radio?
::
::Sorry if this seems like a dumb question. I'm new at this.
::
::Thanks
::
::Greg
:Hi greg
: Well I wouldn't reccomend bypassing the audio output transformer, what you could do is connect a large wattage 8 Ohm permanent magnet speaker to the output side of the audio output transformer to see if your getting any audio, with the volume turned way down and gradually turn it up.
:Mark

12/3/2006 10:55:24 PMThomas Dermody

If you are getting hum at the speaker, then it is obvious that the output stage is getting through to the speaker. Why not check the 1st audio interstage transformer? You can pipe in music through the phonograph terminals from a portable CD player or phonograph. If this works, get busy with the RF section. If not, then you need to attend to the audio section, and possibly that 1st interstage transformer.

Thomas

12/4/2006 5:08:43 PMGreg

I will take a deeper look this weekend and let you all know how it goes.

Many thanks for the input! :-)

Greg

:If you are getting hum at the speaker, then it is obvious that the output stage is getting through to the speaker. Why not check the 1st audio interstage transformer? You can pipe in music through the phonograph terminals from a portable CD player or phonograph. If this works, get busy with the RF section. If not, then you need to attend to the audio section, and possibly that 1st interstage transformer.
:
:Thomas

12/4/2006 7:02:47 PMDoug Criner

Greg, here's the schematic: http://www.nostalgiaair.org/PagesByModel/473/M0039473.pdf

Agree with Thomas -- check the audio interstage xfmrs for continuity (primary and secondary windings).

Are all the tubes' filaments lighted?

The schematic has all the voltages you should need to troubleshoot this set. Interesting receiver. With two 45s in push-pull, this should have plenty of power.

:I will take a deeper look this weekend and let you all know how it goes.
:
:Many thanks for the input! :-)
:
:Greg
:
::If you are getting hum at the speaker, then it is obvious that the output stage is getting through to the speaker. Why not check the 1st audio interstage transformer? You can pipe in music through the phonograph terminals from a portable CD player or phonograph. If this works, get busy with the RF section. If not, then you need to attend to the audio section, and possibly that 1st interstage transformer.
::
::Thomas

2/1/2007 9:52:33 AMGreg

Hi again,

Finally I've had some time to get back on this project!! I removed the 3 in 1 resistor bar and found that getting readings way off the mark. I temporarily replaced it with 3 old wire wound resistors I had lying around. Put it all back together and got very high pitched dog whistle sounding whistle which leveled out to a low frequency hum in the speker. As I turned the dial (with volume on Max) I could here sublte changes in frequency in the speaker. I measured the voltage the detector plate and ground. I got about 25 volts. I'm thinking it is because of the spare resistors were a bit higher in resistance than what is specified in the schematic. I am planning on replacing all the old wires in the power supply as well as the resistors. Can someone tell me what would be an acceptable resistor wattage rating would be for these types of resistors. Also can someone tell me what the temporary high pitched whistle means?

Thanks

Greg

:Greg, here's the schematic: http://www.nostalgiaair.org/PagesByModel/473/M0039473.pdf
:
:Agree with Thomas -- check the audio interstage xfmrs for continuity (primary and secondary windings).
:
:Are all the tubes' filaments lighted?
:
:The schematic has all the voltages you should need to troubleshoot this set. Interesting receiver. With two 45s in push-pull, this should have plenty of power.
:
:
::I will take a deeper look this weekend and let you all know how it goes.
::
::Many thanks for the input! :-)
::
::Greg
::
:::If you are getting hum at the speaker, then it is obvious that the output stage is getting through to the speaker. Why not check the 1st audio interstage transformer? You can pipe in music through the phonograph terminals from a portable CD player or phonograph. If this works, get busy with the RF section. If not, then you need to attend to the audio section, and possibly that 1st interstage transformer.
:::
:::Thomas

12/4/2006 7:06:49 PMDoug Criner

If you want to check the speaker, measure the resistance of the field coil and the voice coil. Neither should be open.

,
::
::I am tinkering with an old Brandes B15 floor model. I have replaced all the electrolytics but am only getting a hum from the transformer. Absolutely nothing is coming from the speaker. Can someone tell me how to bypass the speaker and speaker transformer and put a tempory working speaker on just to make sure I am actually getting some kind of output from the radio?
::
::Sorry if this seems like a dumb question. I'm new at this.
::
::Thanks
::
::Greg
:Hi greg
: Well I wouldn't reccomend bypassing the audio output transformer, what you could do is connect a large wattage 8 Ohm permanent magnet speaker to the output side of the audio output transformer to see if your getting any audio, with the volume turned way down and gradually turn it up.
:Mark

2/1/2007 10:27:38 AMGreg

Hi again,

Finally I've had some time to get back on this project!! I removed the 3 in 1 resistor bar and found that getting readings way off the mark. I temporarily replaced it with 3 old wire wound resistors I had lying around. Put it all back together and got very high pitched dog whistle sounding whistle which leveled out to a low frequency hum in the speker. As I turned the dial (with volume on Max) I could here sublte changes in frequency in the speaker. I measured the voltage the detector plate and ground. I got about 25 volts. I'm thinking it is because of the spare resistors were a bit higher in resistance than what is specified in the schematic. I am planning on replacing all the old wires in the power supply as well as the resistors. Can someone tell me what would be an acceptable resistor wattage rating would be for these types of resistors. Also can someone tell me what the temporary high pitched whistle means?

Thanks

Greg

:Hi,
:
:I am tinkering with an old Brandes B15 floor model. I have replaced all the electrolytics but am only getting a hum from the transformer. Absolutely nothing is coming from the speaker. Can someone tell me how to bypass the speaker and speaker transformer and put a tempory working speaker on just to make sure I am actually getting some kind of output from the radio?
:
:Sorry if this seems like a dumb question. I'm new at this.
:
:Thanks
:
:Greg