Brandes B15 High pitch dog wistle sound from speaker

2/6/2007 7:41:23 PMGreg

Hi,

I am working on a Brandes B15. I have replaced all the power resistors and filter caps. The tubes glow brightly and have been tested. When I turn it on and it warms up, I get a very high pitched consistant sound that could be defined as the sound of a dog whistle. Can any one tell me what this could be coming from?

Thanks

Greg

2/7/2007 1:44:16 PMRadiodoc

Greg,

Have you tested and/or replaced the paper caps in the set? This looks like a regenerative receiver. Some of the paper caps may be enclosed in a metal can filled with wax or tar. Regardless, they are probably leaky and need to be replaced.

Radiodoc

:Hi,
:
:I am working on a Brandes B15. I have replaced all the power resistors and filter caps. The tubes glow brightly and have been tested. When I turn it on and it warms up, I get a very high pitched consistant sound that could be defined as the sound of a dog whistle. Can any one tell me what this could be coming from?
:
:Thanks
:
:Greg

2/8/2007 1:35:01 AMMark

With most regenerative sets you adjust the feedback control just below the point of oscillation. This is the most sensitive spot. Try adjusting your feedback control.

MRO

:Greg,
:
:Have you tested and/or replaced the paper caps in the set? This looks like a regenerative receiver. Some of the paper caps may be enclosed in a metal can filled with wax or tar. Regardless, they are probably leaky and need to be replaced.
:
:Radiodoc
:
:
::Hi,
::
::I am working on a Brandes B15. I have replaced all the power resistors and filter caps. The tubes glow brightly and have been tested. When I turn it on and it warms up, I get a very high pitched consistant sound that could be defined as the sound of a dog whistle. Can any one tell me what this could be coming from?
::
::Thanks
::
::Greg

2/8/2007 3:04:59 PMGreg

Hi,

Please keep in mind I am new at this and am learning. All the caps have been replaced as well as all wirewound resistors. 2 days ago I found that the secondary winding of the transfomer that wires directly into the Phonograph Tip-Jack per the schematic is open. Could this be the cause of the whistle? The transformer was placed in a metal can and epoxy filled. I tested it before I removed it. (Definately open). I then I put the can in in the oven at 300 degrees for 10 minutes which softened up the black epoxy which allow me to remove the transformer from the can. I guess the next question is how do I either find a replacement or get it re-wound?

Thanks

Greg

:With most regenerative sets you adjust the feedback control just below the point of oscillation. This is the most sensitive spot. Try adjusting your feedback control.
:
:MRO
:
:
:
:
::Greg,
::
::Have you tested and/or replaced the paper caps in the set? This looks like a regenerative receiver. Some of the paper caps may be enclosed in a metal can filled with wax or tar. Regardless, they are probably leaky and need to be replaced.
::
::Radiodoc
::
::
:::Hi,
:::
:::I am working on a Brandes B15. I have replaced all the power resistors and filter caps. The tubes glow brightly and have been tested. When I turn it on and it warms up, I get a very high pitched consistant sound that could be defined as the sound of a dog whistle. Can any one tell me what this could be coming from?
:::
:::Thanks
:::
:::Greg
:

2/9/2007 2:18:46 AMMark

Greg:
It is yet to be seen if the oscillation is caused by an open interstage transformer. You can use the 3 to 1 or 4 to 1 transformers sold by Antique Electronic Supply. They should work fine. You could as a temporary measure use resistive and capacitive coupling. For a coupling capacitor .05 uf is commonly used and the grid resistor is often 470k. The plate resistor for a #27 tube could be around 27k to 47k. It is better, in this case, to use the transformer coupling as it gives more gain and to my tinny ear sounds better. The R/C coupling is temporary and the values given are close enough to get the audio stages working. Just some suggestions.

MRO

:Hi,
:
:Please keep in mind I am new at this and am learning. All the caps have been replaced as well as all wirewound resistors. 2 days ago I found that the secondary winding of the transfomer that wires directly into the Phonograph Tip-Jack per the schematic is open. Could this be the cause of the whistle? The transformer was placed in a metal can and epoxy filled. I tested it before I removed it. (Definately open). I then I put the can in in the oven at 300 degrees for 10 minutes which softened up the black epoxy which allow me to remove the transformer from the can. I guess the next question is how do I either find a replacement or get it re-wound?
:
:Thanks
:
:Greg
:
:
:
:
::With most regenerative sets you adjust the feedback control just below the point of oscillation. This is the most sensitive spot. Try adjusting your feedback control.
::
::MRO
::
::
::
::
:::Greg,
:::
:::Have you tested and/or replaced the paper caps in the set? This looks like a regenerative receiver. Some of the paper caps may be enclosed in a metal can filled with wax or tar. Regardless, they are probably leaky and need to be replaced.
:::
:::Radiodoc
:::
:::
::::Hi,
::::
::::I am working on a Brandes B15. I have replaced all the power resistors and filter caps. The tubes glow brightly and have been tested. When I turn it on and it warms up, I get a very high pitched consistant sound that could be defined as the sound of a dog whistle. Can any one tell me what this could be coming from?
::::
::::Thanks
::::
::::Greg
::

2/9/2007 8:25:17 AMGreg

Thanks Mark. I will order the transformer and give this a try and let you know how it goes.

Greg

:Greg:
:It is yet to be seen if the oscillation is caused by an open interstage transformer. You can use the 3 to 1 or 4 to 1 transformers sold by Antique Electronic Supply. They should work fine. You could as a temporary measure use resistive and capacitive coupling. For a coupling capacitor .05 uf is commonly used and the grid resistor is often 470k. The plate resistor for a #27 tube could be around 27k to 47k. It is better, in this case, to use the transformer coupling as it gives more gain and to my tinny ear sounds better. The R/C coupling is temporary and the values given are close enough to get the audio stages working. Just some suggestions.
:
:MRO
:
:
:
::Hi,
::
::Please keep in mind I am new at this and am learning. All the caps have been replaced as well as all wirewound resistors. 2 days ago I found that the secondary winding of the transfomer that wires directly into the Phonograph Tip-Jack per the schematic is open. Could this be the cause of the whistle? The transformer was placed in a metal can and epoxy filled. I tested it before I removed it. (Definately open). I then I put the can in in the oven at 300 degrees for 10 minutes which softened up the black epoxy which allow me to remove the transformer from the can. I guess the next question is how do I either find a replacement or get it re-wound?
::
::Thanks
::
::Greg
::
::
::
::
:::With most regenerative sets you adjust the feedback control just below the point of oscillation. This is the most sensitive spot. Try adjusting your feedback control.
:::
:::MRO
:::
:::
:::
:::
::::Greg,
::::
::::Have you tested and/or replaced the paper caps in the set? This looks like a regenerative receiver. Some of the paper caps may be enclosed in a metal can filled with wax or tar. Regardless, they are probably leaky and need to be replaced.
::::
::::Radiodoc
::::
::::
:::::Hi,
:::::
:::::I am working on a Brandes B15. I have replaced all the power resistors and filter caps. The tubes glow brightly and have been tested. When I turn it on and it warms up, I get a very high pitched consistant sound that could be defined as the sound of a dog whistle. Can any one tell me what this could be coming from?
:::::
:::::Thanks
:::::
:::::Greg
:::