F5X -- the EUVL Approach - The Build Thread

If you can fit an equal number of Pchannel devices and Nchannel devices on a heatsink then OK.
If you fit all the Pchannel on one heatsink and all the Nchannel on the other heatsink then you are virtually guaranteed to have one hotter than the other. When the hot one has a lower Vds, it will start to cool and change over to eventually become the cooler one. During the changeover the output offset will change. I fear this swapping over of hot to cold could become unstable. And worse, what happens to the output offset if it does become unstable?
 
Can anyone tell me the spacing for the diodes on the heatsink?

After discovering the quasimodo thread I am looking to snub the transformers as well as replacing the diodes. Pre-building the bridges (PTP) would reduce the time the amp is out of commission. Anyone snub the primrose tx with the quasimodo?

Well, I disassembled the amp only to find a different spacing/orientation than expected. The measurement is 16mm x 45mm, and the longer "B" lengths are in series instead of parallel.

Quasimodo snubbing findings for Sumr/primrose 600VA 2x15V:
with Cx=0.01uF, Cs=0.2uF
Rs= optimal somewhere between 15Ω and 20Ω

From left to right: Rs=1K, Rs=50Ω, Rs=25Ω, Rs=15Ω
 

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One out of two amp units up and running

After countless hours of trying forth and back how to solve the integration puzzle the first of my twin amps is integrated, powered up and running.

Fitting a proper wiring into the tight design volume was a particuallar challenge. Those who are looking for wiring ideas may find my approach based on the very traditional technique of wire lacing interesting enough to give it a thought. No plastic cable ties, no glued-in tie bases, only PTFE wires and lacing cord.

Markus
 

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what Is bias
which type Is regulator heatsink - look very big

Currently I am running the pwr FETs on 1.5A bias each in thermally settled state. The supply voltage I reduced to +/- 12V, hence the regulators are actually running in cap multiplier mode. SQ I still need to work on, something is odd. Its not close to what I remember from the various protos we build previously. It is the classical error of doing to many changes at once.
The point I´d like to make is I have not found a setting yet which I can recommend.

As for regulators heat sinks. This is the standard size of the batch #2 GB, but this is different in size and shape compared to the batch #1.

Markus
 
I am starting to build the F5X....again. A few questions :

1) Please take a look at the attached drawings. Is the fuse rating for the auxiliary transformer okay?
2) Is a thermistor necessary for the N mains?
3) I have the newest V4 protection board and I intend to use it. The hardwire is fixed in this version and I only have to change the value of reistors R32 to 2k ohm and R33/R34 to 120 ohm. Correct?
4) What is the initial value setting of the trimpot before biasing? I read through fitzfish build guide but there was no mention of this initial value.
5)The labelling (circled as 'A' & 'B') on the regulator board correspond with the schematic and where does the J2(D)goes to?

Thank you.
 

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Firstly I cannot read any of your attached figures. Way too small.
Secondly this is umteen years old, and my memory is not that good these days.
But I try my best. Maybe Markus is more up to date since he is still building lately.

1) Please take a look at the attached drawings. Is the fuse rating for the auxiliary transformer okay?

I use myself 0.3A slow blow.

2) Is a thermistor necessary for the N mains?

I use one, but on the L side.
In theory no difference whether L or N.

3) I have the newest V4 protection board and I intend to use it. The hardwire is fixed in this version and I only have to change the value of reistors R32 to 2k ohm and R33/R34 to 120 ohm. Correct?

The info has been posted before.
I don't have it with me right now, so cannot answer you directly.

4) What is the initial value setting of the trimpot before biasing?

Use 1/3~1/2 to start with. And trim slowly.
Start with 1.5A bias at room temperature.

5)The labelling (circled as 'A' & 'B') on the regulator board correspond with the schematic and where does the J2(D)goes to?

D is the relay connection driven by the protection board.


Patrick