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Old 19th January 2013, 04:25 PM   #1
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Default JRDG Coherence One Series I & II powersupply

Dear Pro's

What causes the brown (heat) coloring on the PCB's of the powersupply's of this beautifull preamp?
I'm biased so I won't suggest my amature opinion..

Thanks.
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Old 19th January 2013, 04:28 PM   #2
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It's Heat.

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Old 19th January 2013, 04:32 PM   #3
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Quote:
Originally Posted by Nelson Pass View Post
It's Heat.

Wrong it's molten caramel for to induce the mellow sound of Rowland equipment.
You should try it out on your brainchilds..
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Old 19th January 2013, 04:48 PM   #4
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Let's rephrase the question.
What's causing the brown heatstains on the PCB of the powersupply and how can I avoid the generating heat in the future?
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Old 19th January 2013, 05:22 PM   #5
hm4nine is offline hm4nine  Europe
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I suggest to increase distance between parts and board and substitute coloured resistors with those of higher wattage.
Of course this will cause some solder and mechanical work
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Old 19th January 2013, 05:56 PM   #6
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Quote:
Originally Posted by hm4nine View Post
I suggest to increase distance between parts and board and substitute coloured resistors with those of higher wattage.
Of course this will cause some solder and mechanical work
I already installed six new higher wattage (2 Watts) resistors at some greater distance and ordered two Microsemi VJ247m bridges with a metal topsurface that can be heatsinked for the plus/minus 20 volts rails (the other bridge is only used for the 12 Volts necessary for operating the relays in the main unit) in my series II.
But I'm curious what causes this (surplus) heat in your opinion. Not in the sense that the components radiate heat and that decolours the epoxy layer on the fiberglass, but why do they generate so much heat.
At the first 1 Ohm resistor that's directly connected to one of the bridges I measured more then 55 degrees Celcius. The second one which is much further away but also connected to the other bridge stays just under the 50 degrees.
It's not a quiz but a real interest why these parts radiate so much heat. i suppose Jeff Rowland did not intend or forsee this behaviour/decoloring when he designed thos powersupply.
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Old 19th January 2013, 06:40 PM   #7
hm4nine is offline hm4nine  Europe
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Sent you a PM
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Old 26th November 2013, 05:06 PM   #8
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check out also this thread:
Jeff Rowland Coherence 1 - Schematic for the Modules wanted
here I have an interesting question.

Last edited by tiefbassuebertr; 26th November 2013 at 05:16 PM.
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Old 26th January 2015, 04:47 PM   #9
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Quote:
Originally Posted by RobertS61 View Post
Let's rephrase the question.
What's causing the brown heatstains on the PCB of the powersupply and how can I avoid the generating heat in the future?
The main reason for heating of the resistors between rectifier and first capacitor is a much more higher value for the AC current as through the other 1R resistors behind the first capacitor (saw-tooth 100Hz).
The schematic, which I have create, you will find here:
Jeff Rowland Coherence 1 - Schematic for the Modules wanted
I use 4 pcs 3R9 (3W) or 10 pcs 10R (1W) in parallel mode.
Additional it is important to remove the connectors from transformer and to the male connector (mounted on rear panel). The reason therefore you will find by the last image of
http://www.audiocircle.com/index.php?topic=93368.0
The solder solution provides higher reliability.
In the last step I replace the bridge rectifiers through single diodes with fast recovery time (RGP30G):
http://www.vishay.com/docs/88704/rgp30a.pdf
This step provides a strong audible enhancement in sonic performance, particularly in such cases, where the mains is contaminated with any high frequency stuff.

P.S.: I am looking for phono modules (I+II) for opening to find out the internal circuit topology (I prefer faulty ones therefore)

Last edited by tiefbassuebertr; 26th January 2015 at 05:02 PM.
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