How to build the F5

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M

Mallard

Member
Joined 2003
Here you see how the chassis gnd connection is made.

In the 1st pic you see the filter plug I'm using, it incooperates the fuse. The chassis gnd is done via the chassis connection of this filter.

The 2nd pic describes a little bit the leads and where they coming and going.

Thanks all of oyur for looking into this! It really helps to get me on the right way!

Cheers,
Mallard
 
M

Mallard

Member
Joined 2003
???

Ok I did the next step. Connected the cap bank, put a light bulb in series the the hot lead -> switched on!!

Nothing was exploding, no firework so far so good but what's that:
At the output of the cap bank I meassure only ~2V!!! :eek: to less for powering the amp circuit.

The light bulb was on all the time.

Has anybody an idea where this voltage shrink comes from?

Thanks,
Mallard
 
M

Mallard

Member
Joined 2003
AndrewT said:
Bks is right to be concerned.
The orientation of the caps does not look right.

Starting with the near row of 4 caps.
The two middle terminals are labeled. 4 in from left is -ve, 5 in from left is +ve.
Number the terminals 1 at extreme left and 8 at extreme right.

The capacitor terminals at each of the connections 1 through to 8 are.
1=-
2=+
3=+
4=- , as labeled
5=+ , as labeled
6=-
7=-
8=+

Are you using a dual bridge rectifier fed from a dual secondary transformer?

rectifier left -ve goes to 1, rectifier left +ve goes to 2.
rectifier right +ve goes to 8, rectifier right -ve goes to 7.

Relabel the StarGND as Zero Volts. This is not the Audio Ground.
The 3 wires from the PSU, +ve, 0, -ve, are conveniently close together to combine into a twisted triplet.
Click to expand...

Andrew, where would you recommend to put the star gnd? I mean the point I named StartGnd is the point where the PSU gets it's earth -> chassis earth connection. I personally see no problem in using this point as gnd for the amp.

Cheers,
Mallard
 
Zen Mod

Zen Mod

Official Court Jester
Joined 2003
zenmod.in.rs/
Paid Member
Mallard said:
Andrew, where would you recommend to put the star gnd? I mean the point I named StartGnd is the point where the PSU gets it's earth -> chassis earth connection. I personally see no problem in using this point as gnd for the amp.

Cheers,
Mallard
Click to expand...

exactly

middle of horizontal part of big copper U

put those blue wires , coming from bridges to big U , in same spot

there is a cleaner solution , but that one is impossible with that physical layout of gnd plate ( big U )
 
Last edited:
Andersonix

Andersonix

Member
Joined 2004
Paid Member
AndrewT said:
Mallard,
put a ring tag on each and every wire that needs to connect to the Main Audio Ground (MAG).
Use a nut and bolt to connect all the ring tags together.

The stack of ring tags is your MAG.
Click to expand...
On this topic, where any stranded wire is connected to a barrier block, it should be terminated with a ring (or spade) terminal, as a screw and washer (can't tell from pics?) is not reliable enough. Or use a "Euro" type terminal block which accepts bare wire (see snip from Apex jr.)
 
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Bksabath

Bksabath

Banned
Joined 2007
Well the firs take on my F5 saw sunshine light for the first time yesterday.

Few minor issues to sort out.

Scary moment at first power up HUM LOADS OF IT

Got rid of it by plugin in Pre and F5 on same extension lead
Just a bit of mechanical noise from Trafo not much but realy anoing will be sorted eventualy.

Apart from that picture on How to Move an F5 enclosed
 
Bksabath

Bksabath

Banned
Joined 2007
Progress report
No much to say 60 hours weeks on Nights
Which I love as I can play loud music during the day
And loud it goes
Tweaked the phono stage to get more out put.
And tested the speaker protection a couple of times.
I am stuck with the Polks as it works.
Now this may be fearless by same to me is bit stupid thing to do.

Any way got 12 lovely volts peak and way to loud for my taste.

I have the option to change the taps on the traffo from 20 to 24 V
Once filtered and rectified at present I have 26 V rails and clipping at 20 V
For now it will stay as is 3.5 A Bias till I drag it back in the loft and make balanced version

Now Trafo is a bit of a problem as mechanical hum is really annoying
I know is there and this is a problem closed box may be different but my is not so …

Traffo supplier blaming hi voltage on my supply (246V)
But tried with Variac and no difference and all the rest of my stuff is quite happy with it so I am not
One of the transformers is going back to get same extra things done to it and then we will se.

But when I bought them I told them the use and that I wanted sometink really quiet now they tell me that they can make them better or build new ones with better cores.
I wanted and asked for the better ones to start with so no naming and shaming jet I like to give them a chance

The moral is no point in skimping on the transformers.
 
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