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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders. |
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2nd Aug 2021, 9:47 pm | #1 |
Pentode
Join Date: Jul 2012
Location: Cambridge, Cambridgeshire, UK.
Posts: 135
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Thurlby PL320 R8 current sense resistor.
Hi,
I have 2 0f these dual output supplies, acquired from different places,,with faults. One has a broken voltage control pot. The left hand supply works on both, where as, on both right hand boards the R8 0.5R resister has been chopped out. Is that normal? |
2nd Aug 2021, 10:45 pm | #2 |
Pentode
Join Date: Jul 2012
Location: Cambridge, Cambridgeshire, UK.
Posts: 135
|
Re: Thurlby PL320 R8 current sense resistor.
Right, I have put in a 0.5r resistor, and now I get current, but the voltage is bouncing around. am confused.
few minutes. PR1 intermittent...replaced with a 470r and all is peaceful.... |
2nd Aug 2021, 10:57 pm | #3 |
Nonode
Join Date: Dec 2012
Location: Stockport, Greater Manchester, UK.
Posts: 2,085
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Re: Thurlby PL320 R8 current sense resistor.
Quick work Dave! I don't have any info on this model
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3rd Aug 2021, 1:15 am | #4 |
Dekatron
Join Date: Jul 2007
Location: Evesham, Worcestershire, UK.
Posts: 4,241
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Re: Thurlby PL320 R8 current sense resistor.
If it's a QMD - with the 4 switches in the middle - then the current sense resistor is moved off the board for the master (RH) supply. An aluminium-clad type is bolted to the bottom of chassis. This is because it needs to cope with 4A rather than 2A when working in parallel mode. Perhaps a wire has broken between it and the board?
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3rd Aug 2021, 8:10 am | #5 | |
Pentode
Join Date: Jul 2012
Location: Cambridge, Cambridgeshire, UK.
Posts: 135
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Re: Thurlby PL320 R8 current sense resistor.
Yes that must be it. I looked at the circuits and no mention. To investigate what has happened. I know one of them had an "accident" with a car battery .
Quote:
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3rd Aug 2021, 10:45 am | #6 |
Dekatron
Join Date: Jul 2007
Location: Evesham, Worcestershire, UK.
Posts: 4,241
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Re: Thurlby PL320 R8 current sense resistor.
One of mine came to me with a missing track on the switch PCB. It had been vaporised by a gross overload - no idea what caused it, but suspected it was something like a car battery...
I can't remember how that affected the operation - it was 20 years ago - but since then, I've always made a point of inspecting that PCB. It's easy to overlook as there's not much on it, but it does carry a fair bit of current in certain modes. |
3rd Aug 2021, 9:36 pm | #7 |
Pentode
Join Date: Jul 2012
Location: Cambridge, Cambridgeshire, UK.
Posts: 135
|
Re: Thurlby PL320 R8 current sense resistor.
The first unit is working now, just waiting for some parts. I had a look at the other one, and the right hand channel has a current limit fault. PR3 1K tweaker has failed open circuit like PR1 on the other unit. Feeling quietly pleased with my self.
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6th Aug 2021, 12:15 pm | #8 |
Nonode
Join Date: Mar 2008
Location: Virginia Water, Surrey, UK.
Posts: 2,872
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Re: Thurlby PL320 R8 current sense resistor.
Well done Dave, very satisfying!
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