resistor gets hot and voltage drop across it is too high

Thread Starter

Roque

Joined Sep 16, 2014
147
Hello guys,
thank you for your valuable input you have given me ever since ive joined this forum.
am addicted to all abou circuits thats why i keep comming back..... currently got a Velodyne subwoofer CHT 8R and one of the resistor in the 15V rail gets which was tested open ....replaced with a new one the newly installed 330ohms gets real hot replaced the TIP transistor even though it tested good also all the caps around the area the subwoofer workst fine ....but the resistor gets real hot whereas the voltage drop which should be around 5v is 22v the transformer heats up too.....if i disconnect the preamp control board the resistor is cool and the voltage drop across it is 5v ....not sure if the preamp is playing up or if its the main powr am cum owersupply board
what am i overlooking or doin wrong any advice or input is very much appreciated

thank you will attach a schematic of the powersupply and amp board couldnt fine a schematic for the control board. the resistor tat is the issue is R801
 

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thedoc8

Joined Nov 28, 2012
128
Hello guys,
thank you for your valuable input you have given me ever since ive joined this forum.
am addicted to all abou circuits thats why i keep comming back..... currently got a Velodyne subwoofer CHT 8R and one of the resistor in the 15V rail gets which was tested open ....replaced with a new one the newly installed 330ohms gets real hot replaced the TIP transistor even though it tested good also all the caps around the area the subwoofer workst fine ....but the resistor gets real hot whereas the voltage drop which should be around 5v is 22v the transformer heats up too.....if i disconnect the preamp control board the resistor is cool and the voltage drop across it is 5v ....not sure if the preamp is playing up or if its the main powr am cum owersupply board
what am i overlooking or doin wrong any advice or input is very much appreciated

thank you will attach a schematic of the powersupply and amp board couldnt fine a schematic for the control board. the resistor tat is the issue is R801

What is the emitter voltage (q801) when it is not working correct. You say it is supposed to have 5 volts across R801 normal, but you are getting 22 volts across when not working. Is the -15 working correctly
 

Thread Starter

Roque

Joined Sep 16, 2014
147
What is the emitter voltage (q801) when it is not working correct. You say it is supposed to have 5 volts across R801 normal, but you are getting 22 volts across when not working. Is the -15 working correctly
The subwoofer works fine it plays well but the resistor gets real hot can’t touch it’s got burn marks already and if I play it for a couple of hours the mains transformer gets hottt too
If I leave the preamp or control board disconnected the voyage across the resistor is normal ... the -15v resistor shows 5v drop across it that’s when the control board is connected
 
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