WOPL 400 Build Problem!
- Thread starter nadude98
- Start date
Those sure look like fake Hitachi filter capacitors. Almost all the HCC FA caps are fake.
More info here:
http://sound.westhost.com/fake/hitachi-caps.htm
More info here:
http://sound.westhost.com/fake/hitachi-caps.htm
Last edited:
That I haven't done..... I'll try that if you think I should tomorrow after my wife goes to work. She wouldn't like me waking her up... 
I had the same (or at least similar) problem on my WOPL 400 that I built a few years ago. It has the Rev. C board, cap kit, etc. It sounded fantastic until I started to crank it up. At that point, the left channel would sound like it was clipping on the bass notes. I swapped the speaker leads and the problem moved to the right speaker so, I figured the problem had to be in the left channel, of the amp.
As I thought about it more, it sounded like the current limiting protection was doing its thing. I had the amp connected to Magnapans 1.7 through an infinity sub which has a built in crossover. I decided to do a static resistance check of the speaker system and it measured 3.2 ohms. Not what I was hoping for. The Magnapans themselves checked out at 4.7 ohms and they are a non reactive load. Hmmmm could the problem be that the amp is not happy with the load it's seeing?
My next step was to hook the amp directly to the Maggie's. I cranked it up until the meters were screaming for dear life and the problem was gone. It sounded fantastic! I went back to the sub/Maggie combo and the problem reappeared.
in my case, I can only assume that the reactive load of the sub being in the system was causing the current limiting protection to kick in. Why only the left channel is a bit of a mystery to me. Maybe the left channel circuitry is a bit more sensitive.
Maybe this information will be of value to you.
Gary
As I thought about it more, it sounded like the current limiting protection was doing its thing. I had the amp connected to Magnapans 1.7 through an infinity sub which has a built in crossover. I decided to do a static resistance check of the speaker system and it measured 3.2 ohms. Not what I was hoping for. The Magnapans themselves checked out at 4.7 ohms and they are a non reactive load. Hmmmm could the problem be that the amp is not happy with the load it's seeing?
My next step was to hook the amp directly to the Maggie's. I cranked it up until the meters were screaming for dear life and the problem was gone. It sounded fantastic! I went back to the sub/Maggie combo and the problem reappeared.
in my case, I can only assume that the reactive load of the sub being in the system was causing the current limiting protection to kick in. Why only the left channel is a bit of a mystery to me. Maybe the left channel circuitry is a bit more sensitive.
Maybe this information will be of value to you.
Gary
Okay, I think we might be getting somewhere...! I checked the the rail voltages under load... I don't believe there is a problem there. They drop from 84.5v to where they fluctuate from 74.5 to about 80 depending on the musical passage.
I also decide to check Bias and 15v test points...
Bias under load on right channel was about 360mvdc and stable under load but left channel was fluctuating all over the place from 100mvdc to 25omvdc... Bias transistor? or something else..? I'm not sure why that would draw the left channel down.
I also decide to check Bias and 15v test points...
Bias under load on right channel was about 360mvdc and stable under load but left channel was fluctuating all over the place from 100mvdc to 25omvdc... Bias transistor? or something else..? I'm not sure why that would draw the left channel down.
- Joined
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That's what I thought. Bias was stable with no input or output connected when I set it. I tried a few different things. With the amp on as soon as I plug the left channel input in at zero volume the bias drops to approx. 001-002 millivolts and as I turn the volume up it rises to about 100-200mvdc but fluctuates all over the place.. Right channel fluctuates a tad but the fluctuation is never more than 010mvdc i.e. 350mv + or - 005mv
- Joined
- Jan 14, 2011
- Messages
- 75,023
- Location
- Gillette, Wyo.
- Tagline
- Halfbiass...Electron Herder and Backass Woof
- Joined
- Jan 14, 2011
- Messages
- 75,023
- Location
- Gillette, Wyo.
- Tagline
- Halfbiass...Electron Herder and Backass Woof
- Joined
- Jan 14, 2011
- Messages
- 75,023
- Location
- Gillette, Wyo.
- Tagline
- Halfbiass...Electron Herder and Backass Woof