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AES SE-1 Blowing Fuses

108.180.143.102
Posted on September 13, 2014 at 12:25:10
returntohifi
Audiophile

Posts: 13
Joined: August 17, 2009
 Hello,

I am new to this forum forum and I am hoping if someone can shed some light on a recent problem I have with my AES SE-1(not Signature) amplifier. I purchased this about a year ago and other than the drifting bias with using either Sovtek 2A3s or Audio Note 300Bs, the amp has been working until a it recently blew the 2A slowblow fuse. I replaced the fuse with the same but the fuse only lasts a couple of minutes before it blows again. Also during the time when it is on I do not get any bias current when I plug in the ammeter.

I appreciate any input where I should start troubleshootng the problem.

Thank you.

Alex

 

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RE: AES SE-1 Blowing Fuses, posted on September 14, 2014 at 14:54:00
returntohifi
Audiophile

Posts: 13
Joined: August 17, 2009
 I have taken a look at the inside of the SE-1 and found the BN102 bridge rectifier(on the schematic) was charred. I have removed the 15,000µF 16V cap and snipped off all the wires and confirmed the bridge rectifier is shot (it is a TGI TB102G - 10A single phase according to the component data sheet). The two green wires from the transformer that were connected to each of the AC legs of the rectifier were almost melted together along the length. I tested the capacitor and it appears to be fine.

I hope I can get some input on what would cause this problem? Is it a transformer problem? or just the rectifier failing?

Any insight would be very much appreciated.

Alex

 

RE: AES SE-1 Blowing Fuses, posted on September 14, 2014 at 15:15:31
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 It could be a number of things. That cap could be shorted, the diode bridge could've failed, there are ways that a tube could fail to take this out (unlikely).

Replace the bridge and cap, then fire up the amp and see what happens. I would also recommend measuring the resistance between the green wires. It should be low, but no 0.

 

RE: AES SE-1 Blowing Fuses, posted on September 14, 2014 at 16:10:24
returntohifi
Audiophile

Posts: 13
Joined: August 17, 2009
 Hi BP,

Thanks for the info. I measured the resistance between the two green wires at 0.5 ohms. Is that OK? If not I will separate them and put on new heatshrink. I will replace the parts as you suggest.

Thanks again.

Alex

 

RE: AES SE-1 Blowing Fuses, posted on September 15, 2014 at 08:36:01
Palustris
Audiophile

Posts: 2408
Location: Cape Cod
Joined: September 12, 2008
 Why take a chance with that wire? Cut them at the transformer and add new wire and heat shrink the splice. You can turn on the amp in "standby" (or remove all the tubes) and measure the voltage on the filament wires to ensure the transformer is OK.

 

RE: AES SE-1 Blowing Fuses, posted on September 15, 2014 at 17:02:49
returntohifi
Audiophile

Posts: 13
Joined: August 17, 2009
 Hi Palustris,

Thanks for the suggestion. I will splice on some new wire. I needed to cut 3 inches off the old wires since the insulation melted along that length. The rest of the green wires to the transformer are clean and fully separated from each other. I am still wondering what could have caused such high temperatures. Could the failure of the bridge rectifier cause this?

Alex

 

RE: AES SE-1 Blowing Fuses, posted on September 16, 2014 at 09:26:54
Palustris
Audiophile

Posts: 2408
Location: Cape Cod
Joined: September 12, 2008
 It is clear that too much current caused the failure. We could speculate endlesly about what 'might' have happended; now is the time to start trouble shooting. What voltage did you measure when you turned on the amp in "standby" (or remove all the tubes) and measured the the filament wires?

 

RE: AES SE-1 Blowing Fuses, posted on September 16, 2014 at 17:34:10
returntohifi
Audiophile

Posts: 13
Joined: August 17, 2009
 Hi Palustris,

I am a novice when it comes to troubleshooting tube amps and I am doing a lot of research and asking a lot of questions right now. I am proceeding slowly and cautiously. I will get the new bridge rectifier in a week or so. I will reassemble and retest.
Thanks for the suggestions.

Alex

 

RE: AES SE-1 Blowing Fuses, posted on September 27, 2014 at 21:07:50
returntohifi
Audiophile

Posts: 13
Joined: August 17, 2009
 Hi Palustris,

I replaced the original (102) rectifier was 10A/200V with a (1010) rectifier 10A/1000V. I have tested the filament voltage (between pin1 and Pin4) with the power tube removed and it is 8.1 VDC. This should only be 5.3 V according the schematic.

I hope you or other members can shed some light on this. Thanks.

Alex

 

RE: AES SE-1 Blowing Fuses, posted on September 29, 2014 at 16:00:51
returntohifi
Audiophile

Posts: 13
Joined: August 17, 2009
 Hi,

I put the tubes in remeasured the filament voltage which is now 5.3 v for the 300B as per their schematic and the plate voltage is 337V also per schematic. I still don't know what caused the original problem but the failed bridge rectifier and hot transformers has occurred with a couple of other owners of the se-1.

Alex

 

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