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9th November 2007, 04:22 PM
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#1 |
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diyAudio Member
Join Date: Jun 2004
Location: Hong Kong
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Help needed with Lectron JH 50 Amp
Hello,
I have a Lectron JH 50 amp which I love but recently has stopped working. Opening up I noticed that the power supply board under the power transformer has burnt out (see the attached picture). There is an ic chip with the number erased. I believe that this power supply board eventually fails. I have tried to contact the Swiss manufacturers of the Lectron JH 60 amps and Nick Doshi who I believe modifies these amps but have had no reply to my queries. I believe that other members have had similar problems. Does anyone have a schematic for this amp? Or if anyone has a working replacement for the damaged board in question I would be glad to follow your design with kind permission. Any suggestions are welcome. Many thanks. |
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9th November 2007, 08:25 PM
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#2 |
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diyAudio Member
Join Date: Aug 2006
Location: Taxland, New Jersey
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I really hate it when manufactures put power resistors on circuit boards like that without proper ventilation. But I'll bet that IC is a 555 timer for the relay.
__________________
"The supercomputer is technologically impossible. It would take all of the water that flows over Niagara Falls to cool the heat generated by the number of vacuum tubes required." ~ Professor of Electrical Engineering, New York University |
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9th November 2007, 10:39 PM
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#3 |
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diyAudio Member
Join Date: Jan 2005
Location: South Florida
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There is one for sale on FleaBay. You may want to ask the seller if he/she has a schematic...
http://cgi.ebay.de/ws/eBayISAPI.dll?...m=160177144324 -- josé k. |
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11th November 2007, 04:53 AM
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#4 |
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diyAudio Member
Join Date: Jun 2004
Location: Hong Kong
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HollowState, yes you are probably right about it being a 555. It is a timer for the relay.
Jose, thank you for the info. Unfortunately the eBay seller does not have a schematic. I wonder if anyone has a copy of the old French magazine L'Audiophile. Apparently there was a schematic in issue #41 or 42 (I forget which). If someone has a copy I will be glad to purchase this. An alternative is to redesign the whole power supply. |
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14th November 2007, 03:10 PM
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#5 |
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diyAudio Member
Join Date: Sep 2006
 
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I'm guessing
I think the resistors and relay are combined to form a slow turn-on circuit. The 55 delays the relay, which bypasses the resistors after a preset time. Maybe delays the B+ while the tubes are warming up.
Doesn't look that complex,. from what I can see. |
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