Laney HCM160B's transistor

zvir · 2nd February 2009, 11:18 AM

Hi fellas.

Sorry about this kind of question, it's probably basic, but i am a newbie, and just learning.

I got a used bass amplifier. You can see the model name in the title. anyway, i turned it on and cranked the volume way up. When I started playing, the result was not a least bit pleasant. Distortion and crackling noises were ruining the sound. But, when the volume is not way up, the amp sounds OK. So, i opened it up and i saw that a pair of power transistors had been replaced. The originals were Sanken's SAP16P and SAP16N, but inside i found SAP15's. I found some datasheets on the internet which say that SAP15's are weaker than SAP16. So, what i want to know, can this be the sole reason for that bad sound i mentioned? Or is there anything else i should be careful about? I am planing to try and get a pair of SAP16's and change them.

zvir · 16th February 2009, 11:45 AM

I have some new information. I o'scoped the preamp output, and by the traces, I think it is distorting. I can post screenshots if someone can look at them and tell me anything useful...

kevvywevvywoo · 16th February 2009, 10:23 PM

Yep put em up, but feed the amp with a 200Hz sine wave will you? Dont just play music through..it'll be confusing on the scope.

2nd February 2009, 11:18 AM	#1
zvir diyAudio Member Join Date: Feb 2009	Laney HCM160B's transistor Hi fellas. Sorry about this kind of question, it's probably basic, but i am a newbie, and just learning. I got a used bass amplifier. You can see the model name in the title. anyway, i turned it on and cranked the volume way up. When I started playing, the result was not a least bit pleasant. Distortion and crackling noises were ruining the sound. But, when the volume is not way up, the amp sounds OK. So, i opened it up and i saw that a pair of power transistors had been replaced. The originals were Sanken's SAP16P and SAP16N, but inside i found SAP15's. I found some datasheets on the internet which say that SAP15's are weaker than SAP16. So, what i want to know, can this be the sole reason for that bad sound i mentioned? Or is there anything else i should be careful about? I am planing to try and get a pair of SAP16's and change them.

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16th February 2009, 11:45 AM	#2
zvir diyAudio Member Join Date: Feb 2009	I have some new information. I o'scoped the preamp output, and by the traces, I think it is distorting. I can post screenshots if someone can look at them and tell me anything useful...

16th February 2009, 10:23 PM	#3
kevvywevvywoo diyAudio Member Join Date: Aug 2008	Yep put em up, but feed the amp with a 200Hz sine wave will you? Dont just play music through..it'll be confusing on the scope.

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