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F5 build power on with smoke from R19 and R20
F5 build power on with smoke from R19 and R20
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Old 27th August 2014, 10:39 PM   #1
kj123 is offline kj123  Canada
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Default F5 build power on with smoke from R19 and R20

Hi there,

Beginner here, so I could use all the help I could get

I started building my F5.. Power supply tested good. So I fired on with a dim bulb attached. The bulb lit for a second or 2 and dimmed completely but I saw some smoke coming out of R19 and R20... Here is a picture where you see R20 discolored ... any advice before I do more damage

Edit: One channel attached, I have not yet assembled the other board. The short ti,e it was up, I read 0V across R11 R12

Thanks

KJ
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Last edited by kj123; 27th August 2014 at 10:48 PM.
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Old 27th August 2014, 10:53 PM   #2
Zen Mod is online now Zen Mod  Serbia
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F5 build power on with smoke from R19 and R20
bjt orientation ?

however - post or link ref. schmtc
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Old 27th August 2014, 11:09 PM   #3
kj123 is offline kj123  Canada
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Hi Zen Mod,

I am using the "official" F5 build (schematics) with 2SK170, 2SJ74, IRFP9240, IRFP240, ZTX550 and ZTX450 ... I followed the pinout on the board using the build guide as a reference - on page 13, they gave the pin orientation of the different parts that can be used for the build.

Here is another picture, maybe someone more knowledgeable like yourself will spot what I am doing wrong

Thanks

KJ
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Old 27th August 2014, 11:15 PM   #4
Zen Mod is online now Zen Mod  Serbia
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F5 build power on with smoke from R19 and R20
why JFets are backwards ?

also bjts are looking backwards

and left NTC is dangerously close to mosfet washer , with naked legs
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Last edited by Zen Mod; 27th August 2014 at 11:17 PM.
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Old 27th August 2014, 11:20 PM   #5
e_fortier is offline e_fortier  Canada
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F5 build power on with smoke from R19 and R20
Reverse Q6 like ZM mentioned. Can't see Q5 but it's probably the same.

Q1, Q2 are also reversed, why ?

Rgds,
Eric

Last edited by e_fortier; 27th August 2014 at 11:24 PM.
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Old 27th August 2014, 11:31 PM   #6
Zen Mod is online now Zen Mod  Serbia
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F5 build power on with smoke from R19 and R20
well - OP didn't read build guide enough times

check Jfets just in case ( common Idss test with 9V battery and mAmeter)

replace them if needed , even if I believe that they're good

replace small bjts without hesitation

replace R19 and R20

triple check pinout of parts prior to powering up ....... post pic here , so we can check together
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Old 27th August 2014, 11:32 PM   #7
kj123 is offline kj123  Canada
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Thank you Eric and ZM,

I will recheck/reposition Q5 Q6 and report back... also push NTC away from the washer.

Thanks again
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Old 28th August 2014, 01:17 AM   #8
kj123 is offline kj123  Canada
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As FYI to other extreme newbies like me, here are the pinouts for Q1 Q2 Q5 and Q6 (2SK170, 2SJ74, ZTX550, ZTX450)

I am going to fix the mess and will post the picture here before powering as ZM suggested in case I do another monumental mistake

Thank you again gentlemen for your help

KJ
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Old 28th August 2014, 04:56 PM   #9
kj123 is offline kj123  Canada
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Hi,

I turned around the transistors (replaced ZTXs and resistors). Does the board look ok now? Can I go ahead and power it on?

PS. I will probably replace the whole board but I want to make sure that it's fine the way it is so I do not waste another pcb/parts

Many thanks

KJ
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File Type: jpg 20140828_123418.jpg (474.3 KB, 252 views)
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Old 28th August 2014, 05:23 PM   #10
e_fortier is offline e_fortier  Canada
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F5 build power on with smoke from R19 and R20
Based on your latest pics I would give it a try.

Keep us posted.

BR,
Eric
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