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Old 26th August 2010, 06:46 AM   #8781
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Patrik

do you have balanced F5 pcb to sell
what trafo and heatsink you are using
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Old 26th August 2010, 09:31 AM   #8782
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Franz - nice job! Great looking pair of speakers too!
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Old 26th August 2010, 03:57 PM   #8783
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Quote:
Originally Posted by Bartemus View Post
My apologies if this has been covered but my search has not helped.

After originally getting a good bias setting on my left channel, I made a dumb error and cooked some components. In particular, R111/R112 on cviller v2.0 board got red hot and other components seem to have died.

I am now am trying to isolate the bad components and would love to do this without unsoldering everything on the board. However, I'm getting different resistance readings between the good board and bad one in a number of places so I'm not making much progress.

Has anyone posted any guidance on this? E.g., the expected resistance values at different points or how to check the active components.

Sorry if this is a dumb question, I'm new at this.

Any help is appreciated.
check resistance of the center pin of the transistors to ground to make sure it is not 0.
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Old 26th August 2010, 04:33 PM   #8784
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The first time in operation: my full F5 to drive the FW250 midwoofers

Click the image to open in full size.

Boahhhh!!!!!

Just on the right time: after one year beeing unemployed (I had to solve my shock loosing the job by Studer), I will begin a new job next week.

As you can see: I needed this year also to consolidate my HiFi.

In the rare free time in the future, I gonna finish some enclosures and cleanup the whole setup....

Franz
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Old 26th August 2010, 05:10 PM   #8785
NYCOne is offline NYCOne  United States
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Quote:
Originally Posted by EUVL View Post
You should bridge like I posted -- at lower rail voltage (+/-16V) and higher bias (2A per FET).
That means each half of the bridge is now optmised for 3 ohms.

(I always deduct 4V from the rail voltage as my "clipping" voltage.)


Patrick
I saw your schematic with the Toshiba outputs.

If I use the IRFs, can I "X" the spot between two sets of boards at R1-R2 and get a balanced board (and use 16V), or do I need bigger changes than that in terms of resistor values?
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Old 26th August 2010, 05:32 PM   #8786
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Quote:
Originally Posted by Franz Gysi View Post
The first time in operation: my full F5 to drive the FW250 midwoofers
......

Franz
Looking good and congrats on your new job.

Cheers,
Dennis
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Old 26th August 2010, 05:51 PM   #8787
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Default Troubleshooting

Thanks Westend. I probably should have been more specific. The only troubleshooting I've done before is with tube amps where I could pull and test the tubes separately.

I did replace the burned resistors and was measuring the differences between the boards. For example, the differences I'm seeing across some resistors are:
Bad Good
R114 1.6 47.4
R22 130 165
R5-8 11.8 28.4
R113 1.8 47.4

Also, there are big differences across the legs of Q103 and Q104.

I guess the question is whether there is an easy way to check whether the active components are good either in or out of the circuit. I'll go ahead and start checking the resistors individually.

Regards,

Stuart
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Old 26th August 2010, 08:06 PM   #8788
alazira is offline alazira  United States
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Quote:
Originally Posted by NYCOne View Post
I took out R6 and R7. Mr. Pass has a post on this and says you loose very little. It's not really clear to me what I lost vs. what I gained.

If this simple change in the feedback resistors is so helpful and has so little downside, why not make it the original design? There must be an issue or a lot more people would do it.

If someone understands the real changes in removing R6 and R7, I'd appreciate understanding it better.
Hi,

The reason for paralleling R5/R7 and R6/R8 was to enable the use of lower wattage resistors. You could replace each 100ohm 3W pair with a 50ohm 5watt+ resistor. Removing a 100R without changing the remaining 100R effectively reduces feedback (increasing gain/distortion). You should also change R1 & R2 from 10R to 20R in order to keep the ratio of feedback:source at 5:1. (50R:10R, 100R:20R, etc.)
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Old 26th August 2010, 08:23 PM   #8789
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Quote:
You should also change R1 & R2 from 10R to 20R in order to keep the ratio of feedback:source at 5:1.
You may have overseen, that R1 and R2 are the source resistors for the input fets and are responsible for the gain of the first stage (just read Papa's pdf). Dont change their value only looking at the feedback voltage divider!!!

Removing one of the 100R resistors simply reduces feedback and gives you 6dB more gain (dont forget to justify the idle current after the mod).

You can be sure: the distortion is still very very low (your speakers will have higher distortion). Should you like it this way: everything is green!

Franz

Last edited by Franz Gysi; 26th August 2010 at 08:28 PM.
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Old 26th August 2010, 08:33 PM   #8790
cjkpkg is offline cjkpkg  United States
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Question on added MOSFET pair for F5 - Peter Daniel's boards.

I have a spare set of IRF MOSFETS and figured I would play around and see how I like the sound/power with another pair per channel.

Is it as simple as this ? One end shown for example...
Click the image to open in full size.
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