Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Reduction => Topic started by: ALL212 on October 04, 2019, 01:39:57 PM
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A friend of mine purchased a Reduction from the 'bay. Nice build, well done, however...
After some time horrible noises would come from one channel and in one case the speaker fuse blew.
I found a cold solder joint at 60 on the resistor. The wire had solder all around it but was not making a solid connection. If this resistor lost connection would it have done what he described as the symptoms?
I've reflowed the joint, ran all resistance checks and all voltage checks - everything checks fine.
Thanks!
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Yes, a loose connection there would cause the high DC voltage to be there intermittently, which could make low frequency transients to annoy a solid state amp and blow a speaker fuse.
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Ouch...
I didn't want to test it live until I had confirmation.
As always much appreciated Paul!
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Follow up:
While "in the shop" I took the liberty of pulling some parts from my stock and I did some updates. The owner reported he heard an improvement so I thought I'd list what I did here. To be honest I didn't expect any audible improvement.
All three power supply caps replaced with Nichicon. In doing this I discovered the issue with the cold solder joint. I replaced one diode with a Cree Shotkey and the 3300 uF with another Nichicon. The last power supply cap got a 2.2uf WIMA attached to it.
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The last power supply cap got a 2.2uf WIMA attached to it.
There's some interesting points/ideas about bypassing large capacitance electrolytic power supply caps with small capacitance film cap in the recent "Bypassing Capacitors" thread on the Tube DIY Asylum sub-board ... but they are interspersed amongst a lot of totally off the rails bickering.
Lower ESR and ESL, and faster transient response are mentioned as possible benefits.
cheers, Derek