Paradise Builders

I have now succesfully mounted the powertrannies on the boards. It was fairly easy after all:) I did the following. First i mounted the heatsinks on the boards with 6 8*3mm screws, then i used a small amount of thermal goof, to glue the silicone pads to the transistors, then stuck them into the board one at a time, steering them in place by their legs from under the board with one hand and placing the clips with the other, then with one hand holding the transistor and clips in place and pressing it in with a little plier.
When all of them in place, turn the board around and solder.
Hope this will serve as inspiration to some of you who havent got to this point of assembly yet:)
 
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I have now succesfully mounted the powertrannies on the boards. It was fairly easy after all:) I did the following. First i mounted the heatsinks on the boards with 6 8*3mm screws, then i used a small amount of thermal goof, to glue the silicone pads to the transistors, then stuck them into the board one at a time, steering them in place by their legs from under the board with one hand and placing the clips with the other, then with one hand holding the transistor and clips in place and pressing it in with a little plier.
When all of them in place, turn the board around and solder.
Hope this will serve as inspiration to some of you who havent got to this point of assembly yet:)

very good
 
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Yes, I did notice (too late for my own build) that the clips come in two version: v1 needs to be pre-assembled, and v2 can be used afterwards like you describe.

GOOD NEWS is that all of you have v2 clips, facilitating the mounting. The assembly guide however kind of refers to v1 - not a problem as that way can be done with v2 clips just as well. So we are good...
 
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transistor matching

Hi all,

it seems that not everybody has a curve tracer or a DMM that can measure the current gain of the transistors. So here is a little circuit that can do that, see attached picture.

It works like this:
The battery has 9V, so the voltage across the 4.2M resistor is 8.3V, giving a base current of 2uA. If the transistor has a current gain of , say, 500, this translates into a collector current of 1mA. That will cause a voltage drop of 510mV at the collector resistor. Using a DMM to measure the voltage across that resistor, it should give you the current gain immediately (and if you would use a 500Ohm resistor, 1mV corresponds to a gain of 1).

As long as you do it quickly, the battery voltage will not change too much over the course of measuring a few hundred transistors, but you may want to check the voltage from time to time, and re-measure "known" transistors so you can compensate.

Best to use some socket or test fixture for the transistors,these are available from your favourite components supplier at little cost (e.g. TF183 from Fischer Elektronik)

Edit: "DUT" is of course the device under test.
Edit: For measuring the PNPs, simply reverse the battery
 

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I have now succesfully mounted the powertrannies on the boards. It was fairly easy after all:) I did the following. First i mounted the heatsinks on the boards with 6 8*3mm screws, then i used a small amount of thermal goof, to glue the silicone pads to the transistors, then stuck them into the board one at a time, steering them in place by their legs from under the board with one hand and placing the clips with the other, then with one hand holding the transistor and clips in place and pressing it in with a little plier.
When all of them in place, turn the board around and solder.
Hope this will serve as inspiration to some of you who havent got to this point of assembly yet:)

Hoping a lot of build pics will start showing up. ;)
 
I have posted a circuit I have found on the intraweb on MPP a while ago
The circuit hesener has posted is perfectly fine (please don't get me wrong)
this is a different just different way...
Transistor_matching

It does look at VBE matching and as the DUT and reference are at same ambient themperature it takes same variables (temperature and suply voltagge) out of the equations.
 

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very nice!

Tankyou
As you know I don't know much about electronics.

looking at the conections and resistor values there are quite a few differencies between the 2 circuits.

The one I have posted does not have a base resistor to start with.

Culd you please modify the circuit I posted.

I like very much the fact that, in your circuit, with the 500 homs resistor a gain of 1 = 1 mV

wuld I be corect in assuming that if I half the base resistor and duble the collector resistor the same will aply gain of 1 = 1 mV
4.2 meg are not in my bin and 1K is much easier to find that 500R

Maybe only thing worth looking at one I posted is litle 7805 those or LM317 are in most peoples bins
so resistor values for say a nice and round 10V suply may be a real bonus.
 
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Hi , your circuit really only serves to compare VBE, not HFE. in order to change it to measure HFE, you would end up with my circuit or something similar.....

on the mods you propose, halving the base resistor would double the base current (and so the collector current), and then putting in a 1k resistor would double the voltage, so you would end up at 4x......

what you could do is supply it from a 78L05 as per attached circuit. The base resistor becomes 2.2M (which you could build from 2x 1M and a 180k), and the collector resistor is simply 2x 1k in parallel... hope you like it
 

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that's true, but don't think you can run it without servo... micro A thermal drift creates huge offsets, as the impedance is high-ish around the RIAA circuit. So while the offsets seems large (if monitored without the serve) he servo actually works very little in terms of injecting currents into the circuit, so the balance and working points is only minutely affected by the servo DC current injections.