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Pass F5 Help

MWalt said:
I can assume that the trim pots are the small blue boxes on the circuit boards. Am I correct?

At first, I felt that the whole thing was daunting, but the more advice I receive and the more I read, the more condidence I am getting that I can probably do this myself. You guys are a wealth of knowledge and I truly appreciate the assistance.
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You can definately do it yourself. Heck, alot of guys BUILT this amplifier as a first DIY audio project. :yes:

Yes, the trim pots are the little blue boxes with the gold screws on top. You turn those gold screws to make adjustments. :yes:

Make sure to read and re-read the instructions manual that has been attached to your thread (don't remember if it was westend or russelc that attached it).
 
ashok said:
The other issue that I have read about is the presence of distortions or even dc offsets in the 120V ac input to the toroid. Electronic ballasts, hair dryers and switching supplies can inject asymmetry into the ac input voltage, and it is no longer symmetrical about the horizontal axis. This asymmetry and hash can cause the toroid to buzz.

Rod Elliott has a nice article on this subject: Transformers and dc, and you can find several other discussions on Audiocircle and Diyaudio.

The usual solution (also described in Rod Elliott's article) is to add back-to-back electrolytic capacitors in the ac input in an effort to block the dc offset.

Does this hum/buzz get worse or improve depending on time of day? That could help confirm that it is indeed variations in the ac input that is causing the problem.
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With that solution, I got rid of toroidal buzz which was very irritating. Here are pictures. See those red and green circled parts.

maindc0.jpg


Close up, yellow wire is live wire of main 230V here, this part of the world.

mainsdc1.jpg
 
MWalt said:
The buzzing gets worse as it warms up. It doesn't transmit through the speakers, but it irritates me.
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Also, looking at the pictures of your F5, I don't see any CL-60 thermistors in the primary windings of the toroid. I can see the grey (or blue) colored capacitor across the hot and neutral terminals of the ac inlet. This capacitor should be "line" rated.

The hot terminal is then wired to the fuse. The fuse is then wired to the switch (I think).

The primaries of the toroid are paralleled together and then connected directly to the ac input - gray/brown to the switch, and blue/black to the neutral terminal of the ac inlet.

I don't see any thermistors in there. The F5 build thread referenced above shows these thermistors in the power supply diagram.

The CL-60s are in place to limit the inrush current on powering up the amp. Those 8 x 15,000uF capacitors will cause a large transient inrush current to flow through the toroid on power up. It is likely that this plays havoc with the transformer.

So, I would definitely add them.

I would also add the CL-60 that connects the circuit ground to chassis ground (which is tied to the earth terminal of the ac input). This was suggested earlier by another person.

I wish the original builder had done a better job of wiring this amplifier.
 
ashok said:
I wish the original builder had done a better job of wiring this amplifier.
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Yeah, me too. I was listening to it at home during lunch and it sounds great. I sold a 3k integrated amp because this home brewed amp sounds superior to my ears. I also appreciate your input. Everyone that posts adds some piece of credible evidence of some fault that needs to be corrected. I am in way over my head.

Anyone out there volunteer to get my amp corrected? I'll pay!!
 
By any chance have you found the build threads, here, at AK? I'll link them up because a few of them have really good pictures of the builds and you can see how others have proceeded. Remember what NP said about the difficulty of his amp, "so easy a caveman could do it."

Specialidiot's Ver.1

Specialidiot's Ver.2

Gboneus' F5 build Part Deux

I'd be remiss to not show my first, where you can find out how to toast resistors.

Westend's Part Trois

Marantzfan's take five

Sirbyrds F5 Mono build

I know I missed some other good ones but my search results are tedious.
 
Also, when you begin twiddling the pots, make sure (or at least I did) your amp is unhooked from the speaker cables and input cables. Some short the input, I didnt. This makes it easier to get a nice stable reading. If your pre is dumping even the tiniest ( like my tube pre) amount of trash, the DC offset will vary, and you will be twiddling to adjust the amp for something it has no control over.

With the B-1, it seemed to be stable as a rock, hooked up or not....

Also, make sure and have a look at 6L6's pics over on diyaudio.com, I provided a link above. 6L6 is very nice to contact via PM, and helped me over the phone. He has a way of explaining things on a level that even I can understand! He's been invaluable in the creation of my Pass Pearl 2 phono pre, which should be nearing completion very soon, just need the extra cash for the last few goodies.

Russellc
 
I appreciate all the great links and the help here, guys. I am going to try and clean the amp up myself, so be prepared for some dumb questions along the way. I really like the way it sounds, almost to the point where I was considering buying an original Pass F5 that I found on the asylum. I just don't have the coin at the moment. Again, thanks to all.

Mark
 
MWalt said:
I appreciate all the great links and the help here, guys. I am going to try and clean the amp up myself, so be prepared for some dumb questions along the way. I really like the way it sounds, almost to the point where I was considering buying an original Pass F5 that I found on the asylum. I just don't have the coin at the moment. Again, thanks to all.

Mark
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Good on you Mark; it really isn't as daunting as it might appear at first. :thmbsp:
 
To be clear here, the issue is mechanical buzzing, correct?

MWalt I'm fairly sure that the suggestion to make sure the rubber isolators are in place and the center bolt is snug will take care of it. If the rubber stuff is missing, find an old inner tube or similar and fit it in there. Rawson didn't care about looks, so why fuss now.

Don't listen to any other suggestions until that's taken care of.

No current inrush stuff on any of my builds. AFAIK they are all going strong, including my personal amp after 3.5 years of nearly daily use.
 
specialidiot said:
To be clear here, the issue is mechanical buzzing, correct?

MWalt I'm fairly sure that the suggestion to make sure the rubber isolators are in place and the center bolt is snug will take care of it. If the rubber stuff is missing, find an old inner tube or similar and fit it in there. Rawson didn't care about looks, so why fuss now.

Don't listen to any other suggestions until that's taken care of.

No current inrush stuff on any of my builds. AFAIK they are all going strong, including my personal amp after 3.5 years of nearly daily use.
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Jeff, thanks for weighing in. I'm communicating with the OP via PM and we will be on "less is more" train.

I think, sometimes, when questions about wire schema and layout come up on the Forums, there can be a host of different ideas about how it should or could be done, what's best practice, etc. I wish I could find the pictures of that Deutsch fella's F5. Talk about precision wiring.:ntwrthy:

BTW, hope you and yours are having a happy Thanksgiving.
 
westend said:
Jeff, thanks for weighing in. I'm communicating with the OP via PM and we will be on "less is more" train.

I think, sometimes, when questions about wire schema and layout come up on the Forums, there can be a host of different ideas about how it should or could be done, what's best practice, etc. I wish I could find the pictures of that Deutsch fella's F5. Talk about precision wiring.:ntwrthy:

BTW, hope you and yours are having a happy Thanksgiving.
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Wasn't his handle komi or something like that? That was the most beautiful F5 build I have seen. :yes:
 
marantzfan said:
Wasn't his handle komi or something like that? That was the most beautiful F5 build I have seen. :yes:
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I dunno, I agree, it was artful.
Bingo! Found it:F5 Settima Parte He even got in the AK "numbering queue", :thmbsp:

Damn, Anthony, you've got a good memory * starts looking for bottle of Echinacea*:D
 
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Yo Lance life is good because my F5 is back in the system and is doing a great job heating my little office on a cold MN morning.

I think one thing most builders would say about the F5 is that it is quite forgivable in terms of noise.

If that toroid is buzzing, I think a replacement can be ordered for around $50, right?

Keep it simple? I like the way you think.... any progress?
 
specialidiot said:
Yo Lance life is good because my F5 is back in the system and is doing a great job heating my little office on a cold MN morning.

I think one thing most builders would say about the F5 is that it is quite forgivable in terms of noise.

If that toroid is buzzing, I think a replacement can be ordered for around $50, right?

Keep it simple? I like the way you think.... any progress?
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Hey Jeff, good to hear your F5 is doing the winter warm up!:thmbsp:

Yeah, a new toroid could be a solution but I think the buzzing is probably just a mounting issue. I've had them buzz and a realignment is the trick, most of the time. I don't know if the windings get loose and a point of pressure in a different direction is the cure or if there are some rattling on the outer sheath and they are pressed back in.

The OP is going to try some wire management. I think our griping and bitching is more than he could take. I hope he keeps us up to date on the progress.
 
westend said:
I think our griping and bitching is more than he could take. I hope he keeps us up to date on the progress.
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*Laughing* No, it's cool. The crappy workmanshiop is what drives me crazy. I'll do my best with it and keep everyone updated. Now I just have to make some time to work on it.
 
OK, we need an update with successes or failures, even. Let's keep it all in this thread so others can learn. More pictures if possible, too.
 
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