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Old 3rd Apr 2008, 10:28 pm   #1
paulridgeon
Retired Dormant Member
 
Join Date: Apr 2008
Location: yorkshire
Posts: 2
Default Thurlby PL320 circuit or service data

Hello I wonder if anyone can help with a fault I have on a Thurlby pl320 this is a dual power supply.
The unit is quite old brown case but any info would be appreciated.
Fault is one side of the psu is unable to supply any current.
Voltage is present and is adjustable but current limit operates on a tiy ammount of load.
I did find the large 47 ohm power resistor on the pcb was burnt out.
Circuit appreciated.
Many thaks Paul
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Old 4th Apr 2008, 9:43 pm   #2
hysteresis
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Join Date: Feb 2007
Location: Liverpool, Merseyside, UK.
Posts: 99
Default Re: Thurlby PL320 circuit or service data

Hi Paul,

If the burnt out resistor was R8 (please see the attached PCB layout diagram) then that could explain the fault. The output current passes through R8. The resultant voltage drop is used as an input to the current regulator circuit (2nd attached diagram).

The original value of R8 would have been 0.5Ω. Substituting a 0.47Ω wirewound resistor would be fine, as the output current range can be adjusted during calibration.

Just in case you missed the service manual link in the other thread, here it is again:
http://k1.dyndns.org/Vintage/Sinclai...cs%20Products/

John
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Old 5th Apr 2008, 8:19 pm   #3
paulridgeon
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Join Date: Apr 2008
Location: yorkshire
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Default Re: Thurlby PL320 circuit or service data

Thanks very much I really appreciate your help with this.
Thanks
Paul
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