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The Dynahi Construction Related Questions Thread

post #1 of 630
Thread Starter 
I thought would be a good idea to start a thread that will compile all or most Dynahi construction related questions. There are and will be many such questions along the way. Some people are posting some already in the Elma Attenuator Groupbuy Thread, and some others are posting questions in the Dynahi Boards Groupbuy Thread.

I have one question myself. Related to populating the Elma attenuator. How do I know what's best for me, whether a 25k vs 50k configuration??? Is that more or less equivalent to fixing the attenuator to a Hi-gain (25k) vs a Low-gain (50k)?
post #2 of 630

Tranistor pinouts

on the boards the SK389 show as two seperate (DQ 2) transistors yet it is a dual J-Fet with 7 pins also the 2SJ209 is a dual (DQ 3) how are these being used ?
post #3 of 630
On the fets you don't connect the middle pin, either bend it up
or cut it off.
post #4 of 630
Post some pr0n when you can, guys.

post #5 of 630
How are you guys going to deal with the power supply?
post #6 of 630
Was there ever a group buy for the heatsink(s)? Also, I am unable to find the OP27 opamp. Does a substitution exist? Will any opamp do?
post #7 of 630
Trevor, the op-amp I'm going to try out first for this amp is the OP177GP, which someone had mentioned in a previous thread.

Just to be thorough, I'm going to repost my board propagation quasi-guide in this thread (I had posted it in the Dynahi pics board earlier today)...

On the right in this picture on top and bottom are spaces for resistors -- these can be recognized by the long rectangular shapes with leads coming out each end. Resistor orientation isn't really specific, but for continuity you should orient it so that the letters on the board and resistor are going in the same direction. Pull the leads in from each side of the resistor so that it is close to the board itself.

To the left on top and bottom are transistor slots -- the transistors themselves have three leads that all eventually bend inward. You want to push the leads through until you reach those bends. You should feel resistance when you get there. Orient the transistor so that the curved side lines up with the curved image on the board.

Here we have a transistor slot with a heat sink attached, as shown in the image. Again, line the heat sink (the silver part of this type of transistor) up as it is shown on the board.

Here you can see a slot for a capacitor -- note the + next to one of the holes. This indicates that the capacitor is a polarised one, and the positive lead goes in the plus side. You should be able to identify the positive lead because it should be longer than the negative lead.

Here is an image of the op-amp slot on the board. Again, the indent seen on the left side of the op amp should line up with the indent (or sometimes simply a mark or small hole) on the op-amp. You might want to first install a socket for the op amp so that you can easily replace it if it goes dead or you want to do some op-rolling. ^_^

This is a picture of the rectangular capacitor that's near the bottom towards the middle-left of the board. This is a non-polarised capacitor, but you may as well orient it so that the text on the cap sits the same way as the text on the board.
post #8 of 630

output transistor package

I haven't gotten the transistors yet and was wondering if the package on the 2SC3421 and 2SA1358 is all plastic or metal backed? Will they need to be electrically isolated from the heatsink?
post #9 of 630
if i remember from my brief look at the transistors i have, they are all plastic, although i seem to remember kevin saying that silicon washers are needed to insulate them from their mounting screws. i could be wrong, though.
i am also wondering about the heatsink group buy. kevin posted what heatsinks he used and said they were relatively cheap if purchased in bulk. i would imagine that somebody could start to organize the group buy relatively soon. i would volunteer, but i am too busy with school and i am afraid i dont have the patience or resources that raul does. if someone searches through one of the threads related to the dynahi, they can find a link to the heatsinks.

post #10 of 630
I got my heatsinks from here: http://www.surplussales.com/Heatsinks/HeatSink1.html

TrevorNetwork, try looking for the OPA27, the OPA177 will work as well. The latter is cheaper with slightly better offset and drift specs, though a bit noisier.
post #11 of 630
which one did you get? do you have any specs to know it will work for the dynahi?
post #12 of 630
The HS-TWS will work fine. In fact i just ordered a dozen.
Much easier than the $72 i paid for the first 2.

The silicon wafers are to make sure there is real good contact
between the transistors and the heatsink. No electrical isolation
is needed.

I'm getting too old to deal with messy thermal glue. Peel and stick.
mouser part number 532-53-77-9ac
post #13 of 630

Regarding the heatsinks; how many of the HS-TWS are needed? Has anyone purchased more than a few, that is willing to sell me what's needed?

post #14 of 630
1 heatsink per audio channel. Plus an angled piece of aluminum cut
to shape and punched or drilled per channel.

You could use a 3rd heatsink for the pass transistors for the
(yet to be designed) power supply.

There just aren't enough hours in the day...
post #15 of 630
Thanks Kevin!

So does anyone have a couple of HS-TWS and the appropriate angled aluminum to spare?

/has PayPal
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