Location: Liverpool
Posts: 766
I'm Sandro.
Looks very interesting Sandro, I’ll be watching this thread with interest
Location: Liverpool
Posts: 766
I'm Sandro.
DSCF2533[1].jpg
First draft of the Power boards
This is the N channel
Only difference whit the P channel is the diode connection at the bottom
I may not use the turbo depending on how much Bias/power dissipation the heat sink can take
Bias whit the diodes is limited at around 350 mA across the 1 homes resistors. If the turbos (diodes) are not used it could go a fair bit up
On my old F5 is set at about 1.3 A
The difference between the turbo and the "normal" is More power out at hi volume or more class A power at low volumes from what I do understand
Location: Liverpool
Posts: 766
I'm Sandro.
There is going to be same delay on getting the boards made in China
Location: Liverpool
Posts: 766
I'm Sandro.
DSCF2384.jpgtest rig
DSCF2536.jpg fan controller circuit
I have 100 each of the Fairchild FQA19N20 and FQA12P20as in the 2012 F5 Turbo article those are both obsolete components and duringthe year’s alternatives have been IrF
240 and 9240
http://www.firstwatt.com/pdf/art_f5_turbo.pdf
on my now 12 years old F5 I have used the TO220 versionFQP19N20 as I could not get hold of the TO3P version
To make things simple and keep the engine analogy thePositive and negative Mossfet work as the pistons on a boxer engine one pullwhile the other push around a central point, 0 volts, the class A operation ofthe amplifier, which gives no cross over distortion, is limited by the Biascurrent.
How much current depends on how good the interfacebetween Mossfet and heat sink is and how much heat the heat sink can sink.
One can get rid of 120 W of heat on a 300X170X80 heatsink whit same help by fan cooling
Or about 770 mA bias on 4 Mossfet
I do not know at present how much I can get on the new400x220x83 sinks I got, I hope not to use fans on this project, but the morebias the better.
I am using the best interface I can get kerafoll red as Iam finding quite difficult to get same CVD diamond pads
The bias circuit is quite simple more about it on thearticle
www.firstwatt.com/pdf/art_mos_test.pdf ·
The originalF5 was rated at 25 W whit 2 devices I am going to use 8, 4 FQA12P20 and 4FQA19N20 I may not use the Turbo diodes but space for those is on the boardsthat will not be made for same time now
The use of 4devices on each supply rail calls for matching, lacking the founds for a curvetracer, I am going to use my Atlas DCA Pro for a first sorting and then my hotplate.
Each Mossfetwill be tested for Voltage between source and gate at various points, as the parameterschange whit the temperature of the devices the testing will be done as much aspractical at a constant temperature of around 50C
3 repetitionof the same circuit are in use
A) Plate heater is a Mossfet used as heat sourcefor the copper plate, 1 A current at 35 Volts = 35 Watts
B) Fan controller again a Mossfet used to drive aCPU cooling fan the speed of which is adjusted whit a thermistor, the CPUcoolers are rated at 150W, so that the temperature is as constant as possible and does not change whit the total current dissipated
C) DUT circuit The VGS of the Mossfet under testwill be measured at different currents allowing time for the plate temperatureto remain at 50 C
If one is remembering Homes Lawit is quite easy to measure current whit pretty good precision by measuring thevolt drop across a known resistor 1 V / 1 Homes = 1 A
I will record for each of the 200or so Mossfet the VGS at the point at which it starts conducting and then 100300 350 400 600 800 1000 mA, any small error caused by EG the tolerance of theresistor will be common to all devices the resultant component matching shouldbe a few orders of magnitude better than what is in the article
I am popping out for a while Imay be same time
Location: Liverpool
Posts: 766
I'm Sandro.
I have been working on the speaker protection
the boards on Martin amplifier's use standard relays , First year birthday BTW
There is much better on the market. The Amplimo LR-24
they have 2 set of contacts one designed for hi power and one for low level signal that open and close whit a tiny delay I have been using those on MYF5 for the past 12 years or so the design has changed over the years but Amplimo told me that the specks are exactly the same
DSCF2542.jpg First draft of the boards
DSCF2537.jpg
The diagram is the classic for the UPC 1237
I have added a Led Blinking circuit, as in my experience a blinking Led draw much more attention than a steady one
May not be very elegant, my knowledge of electronics is not that god
It is nothing more than an astable multy vibrator giga magic whit 2 PNP BC 556 and a BC 337 to break the charge / discharge cycle of the 10uF capacitors
the control voltage for this is taken from pin 6 of the UPC 1237
When the relays are open there is full voltage on this pin the BC 337 is closed Led is on off on off, as pin 6 sinks the relays the voltage go down and the BC 337 stay open charge discharge of the capacitors stop and the LED is steady on
DSCF2539.jpg
So far is all working on the bread board
Location: Liverpool
Posts: 766
I'm Sandro.
DSCF2543.jpg
Space for the Speakers terminal's and board size
this work well whit a stereo build The UPC 1237 can sink 80mA at pin 6.
a 10 v drop across R1 (10/330) =sink 30 mA whit supply rail at 32 voltage across the coils 22v
the speaker terminal's are spaced at 60mm
Location: Liverpool
Posts: 766
I'm Sandro.
DSCF2549[1].jpg
spades or bare wire 45
the boards fitted directly to the speakers terminals
M6 holes
Location: Liverpool
Posts: 766
I'm Sandro.
Just had most interesting conversation about connecting 2 pairs of speakers on the same channel
Dude : hi I got bla bla bla 16 channels AV amp bla bla bla
Ok grab red speaker 1 terminal and put on the red amp then spk1 black to spk2 red and spk2 black goes to amplifier black
Dude: ok simple enough
yes 5 minute job really but then again … you got manweb phone number handy
Dude :
after all you can do like last time Just tell them that the light went off it would not be the first time you blow up a 400A fuse at the substation by mistake
Location: Liverpool
Posts: 766
I'm Sandro.
DSCF2550.jpg
Home brew boards
Yes Ebay ones look pretty and cost less
But can you do this ?
DSCF2551.jpgDSCF2553.jpgDSCF2555.jpg