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Old 6th December 2008, 02:55 PM   #2121
rdk845 is offline rdk845  United States
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Default Re: Re: firing up but fuse blowing

Quote:
Originally posted by cviller
Sounds like you have a short or have connected your power fets wrongly (if connected wrong, they are just power diodes). Try monitoring the voltage across the source power resistors (r11 and r12) when you turn up the voltage slowly. Otherwise post some detailed pictures and people in here might be able to help you.
The apparent resistance accross + - 24 / 0 is about 40-50Ohm for both channels, so I don't know whether a short would be. The voltage across R11 and 12 is 0 for both channel, but for left channel the current through +24 -24 is 0 and for right channel the current reaches 1.5A at when rail voltage is as low as + - 2 V.
Attached is picture of a mian board. I printed PCB layout on paper, pasted it on perforated board, and followed traces. I checked a couple times with oringinal schematics and can't find what is wrong.....

I'd appreciate any help!
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Old 6th December 2008, 02:56 PM   #2122
rdk845 is offline rdk845  United States
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Default top picture

top view.
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Old 6th December 2008, 03:09 PM   #2123
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rdk845--are the boards mounted to a heatsink when you blow a fuse?
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Old 6th December 2008, 03:29 PM   #2124
rdk845 is offline rdk845  United States
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Quote:
Originally posted by bubba177
rdk845--are the boards mounted to a heatsink when you blow a fuse?
yes. I had mica insulations between Mosfet and Heatsinks.
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Old 6th December 2008, 03:41 PM   #2125
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Default Re: Re: firing up but fuse blowing

Quote:
Originally posted by cviller

If I had to get the boards manufactured, I might throw in another layer to reduce board size, but then the old farts in here might have troubles stuffing the boards.


LOL, CVILLER, how would you compare the sound of the F5 to your J-Fish? I'm afraid to admit I etched and stuffed your JFish boards, but still haven't connected them (2SJ109BL sitting there wasted).

The task that poses the biggest obstacle for me is drilling and mounting to heatsink, so after having all those problems lining up the output device holes for my F4 and A30 (6 per channel), I started to procrastinate but I did build an F5 (at least to running state).

RDK845: I'm sure you can already see this question coming but are you sure the back traces are not touching the heatsink?
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Old 6th December 2008, 04:01 PM   #2126
rdk845 is offline rdk845  United States
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Default Re: Re: Re: firing up but fuse blowing

Quote:
Originally posted by twitchie
RDK845: I'm sure you can already see this question coming but are you sure the back traces are not touching the heatsink?
Yea. I have stand offs between heat sinks and boards. Measurs discontinuisty, when I disconnect the current limiter between PSU ground and chassis.
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Old 7th December 2008, 10:24 PM   #2127
culture is offline culture  Netherlands
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Default and an other f5 pcb design :)

Hello everyone,

Past few days i've been buzzy designing my own F5 PCB. Quite interesting because its the first time i really tried. I used DipTrace.
I'm wondering if anybody is willing to take a look at it. My main goal is it to make it the same size as Peter's F4 PCB's and locate the FETs on the same position so i can easily fit it in a F4 chassis.

few notes/questions:
- i intend to use cadock resistors in he signal path
- i want to have PCB's professionally made, that's why i used two layers (any suggestions where i can have a few samples made without paying the jackpot...)
- small traces are 1mm thick traces are 4mm. is this enough?
- does anybody know where i can get get those nice blue Panasonic .47r and 100r 3watt resistors in europe.. or does anyone have some spares i could buy?


thanks in advance!!

cheers,

c.
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Old 8th December 2008, 05:06 AM   #2128
cviller is offline cviller  Denmark
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Default Re: Re: Re: firing up but fuse blowing

Quote:
Originally posted by twitchie



LOL, CVILLER, how would you compare the sound of the F5 to your J-Fish? I'm afraid to admit I etched and stuffed your JFish boards, but still haven't connected them (2SJ109BL sitting there wasted).

The task that poses the biggest obstacle for me is drilling and mounting to heatsink, so after having all those problems lining up the output device holes for my F4 and A30 (6 per channel), I started to procrastinate but I did build an F5 (at least to running state).
I think the sound of F5 is better than the jfish (babbelfish modified) and perhaps even better than the aleph j, but new toys are always more fun.


Quote:
Originally posted by rdk845

The apparent resistance accross + - 24 / 0 is about 40-50Ohm for both channels, so I don't know whether a short would be. The voltage across R11 and 12 is 0 for both channel, but for left channel the current through +24 -24 is 0 and for right channel the current reaches 1.5A at when rail voltage is as low as + - 2 V. Attached is picture of a mian board. I printed PCB layout on paper, pasted it on perforated board, and followed traces. I checked a couple times with oringinal schematics and can't find what is wrong.....
Your right channel appears to be shorted... try focusing on only one channel at a time - disconnect the right channel. Are you sure you haven't mirrored one of the channels?
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Old 8th December 2008, 05:40 AM   #2129
Variac is offline Variac  United States
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Quote:
My main goal is it to make it the same size as Peter's F4 PCB's and locate the FETs on the same position so i can easily fit it in a F4 chassis.
I salute this idea!
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Old 8th December 2008, 06:02 AM   #2130
cviller is offline cviller  Denmark
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Quote:
Originally posted by Variac


I salute this idea!

Why? The board has only two transistors and this way is about the only bad way to place them...
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