An illustrated guide to building an F5

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#1,102
I'm back at it again.....

I put together a bulb limiter using the diagram in the beginning of the post. Here is a picture. I tested it on low power devices and it worked fine but the bulb didn't light up. I tested it on my computer which draws a ton of power and the computer would fail to post and the bulb would just flash on and off while the computer repeatedly failed to post, so i have no idea if it's working properly.

When I used it on the amp with one channel connected, the bulb lights up and stays the exact same brightness which is unlike either video previously posted. It looks exactly like a fully lit bulb. I tried both channels and they both do the same thing.

Here is a video - YouTube

The video makes it appear to be a flash but it's just the camera adjusting the exposure. If I keep it on for a minute it stays exactly the same.

Is the bulb limiter working right and do I have a short?
 

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#1,103
Mrshazbot said:
I'm back at it again.....

I put together a bulb limiter using the diagram in the beginning of the post. Here is a picture. I tested it on low power devices and it worked fine but the bulb didn't light up. I tested it on my computer which draws a ton of power and the computer would fail to post and the bulb would just flash on and off while the computer repeatedly failed to post, so i have no idea if it's working properly.

When I used it on the amp with one channel connected, the bulb lights up and stays the exact same brightness which is unlike either video previously posted. It looks exactly like a fully lit bulb. I tried both channels and they both do the same thing.

Here is a video - YouTube

The video makes it appear to be a flash but it's just the camera adjusting the exposure. If I keep it on for a minute it stays exactly the same.

Is the bulb limiter working right and do I have a short?
Click to expand...

Are you sure the amp is not biased up? You sure your trimpots are set to minimum? If the amp is biased up it will draw current even if there is no short.
 
#1,104
Your response helped me figure it out. I fell for the “turn the pots counter-clockwise” trick in the manual despite a previous post mentioning to ignore it.

I measured R7 and R8 on both channels and they were pulling current. I turned them clockwise until they all went back to zero and the bulb turned off.

I guess that’s a good sign that it’s working like it’s supposd to and I’ve regained a bit of confidence.

I’ll bias them up tomorrow!
 
#1,105
Mrshazbot said:
Your response helped me figure it out. I fell for the “turn the pots counter-clockwise” trick in the manual despite a previous post mentioning to ignore it.

I measured R7 and R8 on both channels and they were pulling current. I turned them clockwise until they all went back to zero and the bulb turned off.

I guess that’s a good sign that it’s working like it’s supposd to and I’ve regained a bit of confidence.

I’ll bias them up tomorrow!
Click to expand...

....and the bulb tester saves another amplifier.
 
#1,108
Had a hell of a time getting one of the channels biased properly. One of the pots wasn’t responding the same as the others but I finally got it close enough.

That being said, it sounds incredible! I went from a crappy class D, to an ACA and now this F5 and each step has been crazy to listen to the improvement. This one sounds so clear, impossible to describe.

It’s only been burning in for about 4 hours so it’s probably gonna get even better.

Thanks for everyone answering my questions and helping me get over the problems I was having. Couldn’t have done it without the help.

Kevin
 
#1,114

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#1,117
Hi Kevin,

I've only spent a little time with the F5 and won't be able to get back to
it again until the weekend. But my first impression is that it has a very clean
sound, and perhaps less forgiving of poor materials.

After the ACA and F5, you might want to read up a bit about the M2 (or M2x)
and Aleph j.

Also, keep your eyes open for the next Vfet kit. I suspect it will be
very interesting.

Be seeing you at the AA (Amplifier Anonymous) meetings. 🙂

Dennis
 
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