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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Randell amp
I'm working on a Randell amp...I changed the 2 electrolitic caps in the
power supply..but it still has a hum when the volume is turned up alittle...I esr'ed the other caps in circuit and they look ok......help ....... any suggestions ? thanks |
#2
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Randell amp
On Apr 22, 11:27 pm, "lurk" wrote:
I'm working on a Randell amp...I changed the 2 electrolitic caps in the power supply..but it still has a hum when the volume is turned up alittle...I esr'ed the other caps in circuit and they look ok......help ...... any suggestions ? thanks Are you able to point to a schematic? I am thinking hum-loop, dirty controls or a leaking bypass cap. As to the two electrolytics you did replace, make sure that you followed the schematic exactly. In some cases these caps are part of a voltage-doubler circuit, so (at least) one will be above ground on both ends. Similarly for an LC circuit. Peter Wieck Wyncote, PA |
#3
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Randell amp
Peter...thanks for your answer....I got this unit to repair and
whoever ...... replaced the 2 large caps in the pwr supply... but they had them reversed....and it kept kicking the breaker out...I rewired them and it don't kick the breaker now but the hum is there..I checked the caps with an ESR meter and they look ok...but I wonder if wiring them backwards ruined the caps....what other test can I do on them.....thanks wrote in message oups.com... On Apr 22, 11:27 pm, "lurk" wrote: I'm working on a Randell amp...I changed the 2 electrolitic caps in the power supply..but it still has a hum when the volume is turned up alittle...I esr'ed the other caps in circuit and they look ok......help ...... any suggestions ? thanks Are you able to point to a schematic? I am thinking hum-loop, dirty controls or a leaking bypass cap. As to the two electrolytics you did replace, make sure that you followed the schematic exactly. In some cases these caps are part of a voltage-doubler circuit, so (at least) one will be above ground on both ends. Similarly for an LC circuit. Peter Wieck Wyncote, PA |
#4
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Randell amp
On Apr 25, 1:18 am, "lurk" wrote:
Peter...thanks for your answer....I got this unit to repair and whoever ...... replaced the 2 large caps in the pwr supply... but they had them reversed....and it kept kicking the breaker out...I rewired them and it don't kick the breaker now but the hum is there..I checked the caps with an ESR meter and they look ok...but I wonder if wiring them backwards ruined the caps....what other test can I do on them.....thanks wrote in message oups.com... On Apr 22, 11:27 pm, "lurk" wrote: I'm working on a Randell amp...I changed the 2 electrolitic caps in the power supply..but it still has a hum when the volume is turned up alittle...I esr'ed the other caps in circuit and they look ok......help ...... any suggestions ? thanks Are you able to point to a schematic? I am thinking hum-loop, dirty controls or a leaking bypass cap. As to the two electrolytics you did replace, make sure that you followed the schematic exactly. In some cases these caps are part of a voltage-doubler circuit, so (at least) one will be above ground on both ends. Similarly for an LC circuit. Peter Wieck Wyncote, PA- Hide quoted text - - Show quoted text - It is quite likely that the caps are ruined. In any case, I would not trust them given the (relatively) low cost of replacements. Additional tests that I perform even on new caps right out of the box/bag is a full-voltage test on a cap checker, as well as a simple confirmation of basic capacitance. Good luck with it. Peter Wieck Wyncote, PA |
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