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-   -   My F5 blew up!! (http://www.diyaudio.com/forums/pass-labs/217286-my-f5-blew-up.html)

musicfan49 3rd August 2012 05:15 PM

My F5 blew up!!
 
Greetings,

I just picked up a F5 amp and played it for hours and was thrilled. After about 4 hours I switched from my EAR 834L LINESTAGE PREAMP to my Heedroom SS preamp and when I turned on the F5 a funny smell started things off and about 15 seconds later the amp started to smoke!!

What did I do wrong......and does anybody have a clue as to what got fried. I was guessing that it was one or more of those huge caps......just a guess.....I purchased this amp completely built. I don't know how to work on stuff (I'm disabled)........so I'll need someone else to fix it, BUT I need to know what I did wrong!!

Any help from the community would be greatly appreciate. The fellow who sold it to me wasn't willing to help mt trouble shoot......so I'm really in the dark........help please !!

Thanks, musicfan49 (newbie)

WithTarragon 3rd August 2012 08:12 PM

Out of curiosity, was the builder of this F5 clone named Tim Rawson?

Zen Mod 3rd August 2012 08:22 PM

pics , please

if builder is TR , even pics will not help

Loudthud 3rd August 2012 09:25 PM

Could it be DC on the output of your preamp?

musicfan49 3rd August 2012 10:02 PM

Quote:

Originally Posted by WithTarragon (Post 3114038)
Out of curiosity, was the builder of this F5 clone named Tim Rawson?

No, the gent that built my F5 was a fellow by the name of Paul Trautmann.

Uunderhill 3rd August 2012 10:10 PM

To review

Your F5 worked great for 4 hours with one preamp.

When another preamp was used - your F5 smoked.

As LoudThud as alluded to - the F5 is a DC coupled amplifier.
Which means if your Headroom preamp put out a line signal + DC voltage,
the F5 will try to amplify both the signal + DC.

As I recall, the EAR preamp is a tube pre - so the output would have a DC blocking cap.
It would put out the signal only.

If your Headroom pre does not block DC it could get passed along to the F5
which would pass it along to the speakers.

The F5 has few components and should be very easy for a service tech to fix.
The parts are easy to get and the schematic is on line.

The bad news is that I hope your bass drivers on your speakers didn't get cooked.

Do you have a receiver to test your speakers ?
.

musicfan49 3rd August 2012 10:14 PM

F5 blow-up ....some pics
 
3 Attachment(s)
Quote:

Originally Posted by Zen Mod (Post 3114050)
pics , please

if builder is TR , even pics will not help


musicfan49 3rd August 2012 10:20 PM

[QUOTE=Uunderhill;3114122]To review

Your F5 worked great for 4 hours with one preamp.

When another preamp was used - your F5 smoked.

As LoudThud as alluded to - the F5 is a DC coupled amplifier.
Which means if your Headroom preamp put out a line signal + DC voltage,
the F5 will try to amplify both the signal + DC.

As I recall, the EAR preamp is a tube pre - so the output would have a DC blocking cap.
It would put out the signal only.

If your Headroom pre does not block DC it could get passed along to the F5
which would pass it along to the speakers.

The F5 has few components and should be very easy for a service tech to fix.
The parts are easy to get and the schematic is on line.

The bad news is that I hope your bass drivers on your speakers didn't get cooked.

Do you have a receiver to test your speakers ?



I have single drivers (Terry Cain's Abbys) and they're just fine. I'm listening to music a 2A3 SET, which I've had for 12 years.

musicfan49

Uunderhill 3rd August 2012 10:43 PM

Quote:

Originally Posted by musicfan49 (Post 3114128)
I have single drivers (Terry Cain's Abbys) and they're just fine. I'm listening to music a 2A3 SET, which I've had for 12 years.

musicfan49

Good news your speakers are safe.

Your 2A3 SET amp will block DC .

The F5 will let DC through.

If you do not have electronics experience - its best to let a service tech fix the F5.

The F5 has only 4 transistors per side - its has to be the simplest amp in the
world to diagnose and fix.
Plus the parts are very common (all this reminds me of a Dodge slant 6).

To speed things up get a print out of the schematic.
Its on Page 12 here
http://www.firstwatt.com/pdf/prod_f5_man.pdf


BTW: Its kind of a complement to Mr. Pass that this amp is in the company of a 2A3 SET amp.
.

Zen Mod 3rd August 2012 10:47 PM

it looks pretty decent

in any case - it needs thorough checking by someone who knows his drek

I can't see NTC's besides output mosfets - are they beneath pcb's ?


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