This was a strange coincidence, but I went to go open my front door near my dynaco pas-3 and all of the sudden it started humming/buzzing incredibly loud. Switching the input selector did not make the problem go away. Even with the volume down all the way it was still making a loud buzz. I turned the unit off and noticed a smell of burning. I opened up the unit and cannot find any signs of damage. Where should I start troubleshooting?
2 posters
PAS-3 problem, hum and smells like burning
lobby- Posts : 18
Join date : 2011-02-15
peterh- Posts : 1833
Join date : 2012-12-25
Location : gothenburg, sweden
power supply, including filtering caps, selenium diodes etc.lobby wrote:This was a strange coincidence, but I went to go open my front door near my dynaco pas-3 and all of the sudden it started humming/buzzing incredibly loud. Switching the input selector did not make the problem go away. Even with the volume down all the way it was still making a loud buzz. I turned the unit off and noticed a smell of burning. I opened up the unit and cannot find any signs of damage. Where should I start troubleshooting?
A radical but effective operation is to purchase a "Z-Mod PAS3 Power Supply Upgrade kit" from :
http://www.tubenirvana.net/pas3-power-supplies.html
That would eliminate all of the above components and keep your power for the next decade.
It could however be that case that your power transformer is bad ( they do stink). You still want to
replace the above and then consult :
http://www.triodeelectronics.com/pa2powtrandy.html
and buy a pa211 ( or pa522 ) to replace the broken one.
Last edited by peterh on Fri Nov 06, 2015 3:58 am; edited 1 time in total (Reason for editing : spelling)
lobby- Posts : 18
Join date : 2011-02-15
peterh wrote:power supply, including filtering caps, selenium diodes etc.lobby wrote:This was a strange coincidence, but I went to go open my front door near my dynaco pas-3 and all of the sudden it started humming/buzzing incredibly loud. Switching the input selector did not make the problem go away. Even with the volume down all the way it was still making a loud buzz. I turned the unit off and noticed a smell of burning. I opened up the unit and cannot find any signs of damage. Where should I start troubleshooting?
A radical but effective operation is to purchase a "Z-Mod PAS3 Power Supply Upgrade kit" from :
http://www.tubenirvana.net/pas3-power-supplies.html
That would eliminate all of the above components and keep your power for the next decade.
It could however be that case that your power transformer is bad ( they do stink). You still want to
replace the above and then consult :
http://www.triodeelectronics.com/pa2powtrandy.html
and buy a pa211 ( or pa521 ) to replace the broken one.
I already did the Z-Mod PAS3 Power Supply Upgrade kit probably about 5 years ago. The transformer seemed kinda hot to the touch, but then again, i dont know how hot it normally gets under operation.
peterh- Posts : 1833
Join date : 2012-12-25
Location : gothenburg, sweden
the transformer is not (very) hot .lobby wrote:peterh wrote:power supply, including filtering caps, selenium diodes etc.lobby wrote:This was a strange coincidence, but I went to go open my front door near my dynaco pas-3 and all of the sudden it started humming/buzzing incredibly loud. Switching the input selector did not make the problem go away. Even with the volume down all the way it was still making a loud buzz. I turned the unit off and noticed a smell of burning. I opened up the unit and cannot find any signs of damage. Where should I start troubleshooting?
A radical but effective operation is to purchase a "Z-Mod PAS3 Power Supply Upgrade kit" from :
http://www.tubenirvana.net/pas3-power-supplies.html
That would eliminate all of the above components and keep your power for the next decade.
It could however be that case that your power transformer is bad ( they do stink). You still want to
replace the above and then consult :
http://www.triodeelectronics.com/pa2powtrandy.html
and buy a pa211 ( or pa521 ) to replace the broken one.
I already did the Z-Mod PAS3 Power Supply Upgrade kit probably about 5 years ago. The transformer seemed kinda hot to the touch, but then again, i dont know how hot it normally gets under operation.
check the voltages on the power supply , they should coincidence with the pas3 manual. If any
discrepancies you might have found your problem. ( or if both B+ and DC filament is low it hints
to the transformer)
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