I have a like new around 2 year old 2995dx with power supply problem. It hums when on and gets louder the higher power is turned up? It dont flicker or dim when talking just annoying hum. I touch the transformer and feel it vibrating when I crank it up about 40 watts on high? Could something else be making it do that or is the transformer itself bad? Where can I buy a good transformer if needed? Thanks.
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2995dx power supply problem
- Thread starter zinger827
- Start date
The transformer windings might be an bit loose and start to vibrate when you pull an big load off it.
One pointer should be that the voltage doesn't change when under load, meaning the output and rectification and voltage regulation is oke.
What's left is the mechanical sound from the windings/core of the transformer, i used to put the whole transformer in an bath of epoxy to cure that, only leaving the connector(s) free of it.
This doesn't mean the transformer is bad, just sloppy work making it...
If you can get into the windings with an syringe or an hot glue gun, that would work too, do DISCONNECT from the MAINS before doing any work on it..
If the core is visible, treat the metal core the same.
Then, mount the transformer on rubber feet to dampen the vibrations.
Or mount an replacement good tranformer, same voltage, same amps output, higher amps is no problem, but keep the output voltage the same.
Cor
One pointer should be that the voltage doesn't change when under load, meaning the output and rectification and voltage regulation is oke.
What's left is the mechanical sound from the windings/core of the transformer, i used to put the whole transformer in an bath of epoxy to cure that, only leaving the connector(s) free of it.
This doesn't mean the transformer is bad, just sloppy work making it...
If you can get into the windings with an syringe or an hot glue gun, that would work too, do DISCONNECT from the MAINS before doing any work on it..
If the core is visible, treat the metal core the same.
Then, mount the transformer on rubber feet to dampen the vibrations.
Or mount an replacement good tranformer, same voltage, same amps output, higher amps is no problem, but keep the output voltage the same.
Cor
Where or which wires do I put volt meter on to test voltage output? Thanks for the info. My display stays nice and bright dont dim any high or low power whih makes me think its good. Even on SSB high 100+ watts dont dim which is a good sign right? Thanks for the info.
The manual for the radio should provide information on voltage readings and such. If you didn't get a manual with the radio, you should get one from an aftermarket supplier.
I DOUBT THE PROBLEM IS WITH THE TRANSFORMER..AS TRANSFORMERS
RARELY GO BAD.AND IF THEY DO,IT WILL GIVE OFF A SMELL LIKE
BURNING TAR.AND IF THE TRANSFORMER SHORTS PRIMARY TO SECONDARY
WINDINGS,ID WILL DO MORE THAN JUST HUM.AND THE LIGHTS WILL
DIFFENTILY DIM.ID SUSPECT AS THE FIRST GUY SAID.IT PROBABLY WILL
BE A BAD FILTER CAPACITOR.
RARELY GO BAD.AND IF THEY DO,IT WILL GIVE OFF A SMELL LIKE
BURNING TAR.AND IF THE TRANSFORMER SHORTS PRIMARY TO SECONDARY
WINDINGS,ID WILL DO MORE THAN JUST HUM.AND THE LIGHTS WILL
DIFFENTILY DIM.ID SUSPECT AS THE FIRST GUY SAID.IT PROBABLY WILL
BE A BAD FILTER CAPACITOR.
Also just a thought,but on the galaxy dx 2527,2517 had similar
problem with power supply hum.Which was caused by TR-602
oscillating.The cure was to replace C-602 with a .01 uf cap.
and remove C-608.I dont know off hand if your radio uses
the EPT690010Z pcb or not.But thats just a thought.
Even if it uses different pcb,,it might be the same problem.
The cap. numbers might be different.Also i think your radio
has the built in amp,yes..If so the problem might be with it.
Easy to determine,just disconnect one of the power wires
to it..I believe on the 2970,it has a brown and black wire
going to amp board.Just disconnect one wire.If the buzzing
stops.Youve isolated it too the amp board.Reason i say i think
has black and brown wires..There was a mod awhile back
for making the 2970 amp switchable.By placing a spdt toggle
in series with these wires
problem with power supply hum.Which was caused by TR-602
oscillating.The cure was to replace C-602 with a .01 uf cap.
and remove C-608.I dont know off hand if your radio uses
the EPT690010Z pcb or not.But thats just a thought.
Even if it uses different pcb,,it might be the same problem.
The cap. numbers might be different.Also i think your radio
has the built in amp,yes..If so the problem might be with it.
Easy to determine,just disconnect one of the power wires
to it..I believe on the 2970,it has a brown and black wire
going to amp board.Just disconnect one wire.If the buzzing
stops.Youve isolated it too the amp board.Reason i say i think
has black and brown wires..There was a mod awhile back
for making the 2970 amp switchable.By placing a spdt toggle
in series with these wires
The Galaxy Saturns without the built in amp had the same problems
the transformer was not properly built from factory either isolate the
transformer ie rubber pads or replace it , i just repaired one with the exact same problem
73
the transformer was not properly built from factory either isolate the
transformer ie rubber pads or replace it , i just repaired one with the exact same problem
73
sounds like the transformer has bad or loose plates or windings could be from a surge or just from the heat transfer braking down the glue this is a known problem with some transformers if your hearing the hum in your audio this could be the filter caps that have been mentioned hope you figure it out
check to make sure the transformer is bolted tight to the chassis, sometimes they get loose and vibrate too. probably the hum is caused because the power supply is too small and dont have a high enough current rating or because it needs new filter caps. Or one diode could be open in the rectifier circuit making it a halfwave supply instead of a fullwave supply.
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