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Jadis DA30: fuse keeps blowing

Since 8 months I own a 2nd hand Jadis integrated class A tube amplifier. It has worked fine until recently, when the left channel stopped playing, some 60 seconds after power-up. I opened the case, checked for any blown/ destroyed/ burned component, but the only thing blown was the left channel fuse. This I replaced and all was well again. Unfortunately, a few days later the left channel fuse blew again, within 60 seconds after power-up...

I have switched all the tube pairs (left pair to right and vice versa), but the left channel fuse keeps blowing, ruling out a faulty tube. Please note that after replacing the fuse, the amp is playing fine, but after some on/off cycles the fuse pops within a minute after power-up.

Has anyone experienced a similarly vague problem with a (Jadis) tube amp? What could be causing this?

Thanks for your assistance! Bernhard
dudok12
dudok12 OP
2 posts
 
Thanks for your helpful comments! The DA30 is currently being serviced by the Jadis importer in the Netherlands...

@Polk431: The tubes were tested and were found to be OK: no shorts.

@Mcfarland: the DA30 is an autobias push-pull design. I swapped the left tubes (A+B) with the right tubes (C+D), but again the left channel fuse blew, ruling out that the left tubes were defective...

Will report back once the amp is working fine again!
mattzack2's avatar
mattzack2
175 posts
 
I have the exact same problem on an Jadis Orchestra Reference. I also replaced the left channel internal fuse, which again blew in just a couple of minutes. I rearranged KT88 tubes from ABCD to CDAB. Fuse did not blow, but bias was way off and sound was horrible. I tried to rebias the tubes but the 120 mV DC was floating up over 200 mV as it warmed up. I have several calls into Pierre Gabriel with no response, and also tried Jadis France. They told me that Pierre was moving locations but would be in touch soon. Right now system is completely down. Please contact me or make your solution public in the Audiogon discussions. Thanks - Matt
missioncoonery
1,237 posts
 
If your within sticking distance contact Brooks Berdan in Monrovia CA and dont mess around with distributors..Brooks is authorized Jadis since day one it seems and his bench tech is spot on with Jadis gear(they have all Jadis parts as well, which really makes a difference)..good luck
mattzack2's avatar
mattzack2
175 posts
 
Dudok -

Did you resolve your fuse problem? My Orchestra is still in the shop. Tech found one of the Jadis KT88's shorted. I bought a matched quad of Gold Lions and had them installed and biased. Got it home and the KT88's started glowing red when I cranked it up, the sound quality was terrible, and finally blew the external fuse. I brought it back to tech, swapped tubes, and as of today, they are feeding a square wave into it and seeing a lot of distortion. Did Jadis offer you any suggestions?
Matt
dudok12 OP
2 posts
 
The DA30 has been repaired by the Jadis importer in the Netherlands and now is well again. It turned out that the left output transformer was malfunctioning: when is was heating up, for some reason it started to pull more current than it should, causing the fuse (160mA fast) to blow after some 15 minutes...

I now have a new one and all is well again. Hope this helps, and good luck to Mattzack2!
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