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Offline Paul Birkeland

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Reply #15 on: June 07, 2014, 06:46:44 AM
Generally, it's just easier to replace everything if you are going to replace one thing.

I would also highly recommend not using those ceramic insulators.  It would be hard to say if they would conduct enough heat to effectively cool the TIP50. 

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline mcandmar

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Reply #16 on: June 07, 2014, 12:05:19 PM
Most multimeters will have a diode test function which you can use to compare the reading to a known good one, they should also light up during test.

M.McCandless

Offline NightFlight

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Reply #17 on: June 07, 2014, 04:06:06 PM
The ceramic  insulators are supposed to contain aluminum oxide to overcome the heat conduction issue. The working channel actually got the heatsink very hot very quickly. On par if not better than the pads that come with the kit.  If they insulate the transistor too much - I'll learn the hard way.  ::)

I have to look for a unique angled standoff to get one of the smaller boards installed and stable. Currently its just floating in there and its not good at all.  So I may just order a few Fairchild TIP50 from mouser while I'm at it.  If that doesn't work then I'll ring up the queen and order the whole board.

Paul, can I mix and match with this part?
http://ca.mouser.com/Search/ProductDetail.aspx?R=TIP50virtualkey51210000virtualkey512-TIP50

Not certain where you guys source your parts. Its funny how many other Crack/Speedball parts come up as suggested by others who shop at mouser.

Re LEDs:
I found my meter did not provide enough current/volage to light them up enough to see with the light on. Getting it dark enough in the room prevented probes to be used....

Eventually I figured out I can just use a 9V battery with a 220ohm resistor in series with test leads to light them up properly. Found a bad LED on the bad channel side.  Curiously was an issue with one of the smaller plate boards early on and triggered similar crackling... followed by a gigantic SNAP in the one channel. I have a feeling its the root cause here because its so similar to the previous crackling issue. 



Offline Paul Birkeland

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Reply #18 on: June 08, 2014, 09:19:43 AM
Yes, I believe those are the TIP50's we use.

If aluminum oxide is used in those ceramic parts, are they themselves conductive?

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline NightFlight

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Reply #19 on: June 13, 2014, 11:57:33 AM
I just tested first hand with a meter and my skin is more conductive, which initially threw me off.  I took a spare one and wet both sides with a little water to get good conductivity with the part.  It still insulated enough beyond what the meter can pick up.

The datasheet lists the dielectric strength.  The mouser part is 532-4170. And here is the datasheet: http://www.aavid.com/product-group/interface/insulators (TO-220 form factor).




Offline NightFlight

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Reply #20 on: June 13, 2014, 07:52:21 PM
Back up and running.  So far so good.  No fan for extra cooling.

Thanks for your direction Paul, it was the push in the right direction I needed. 

Going without the one regular board has really opened up my eyes to just how much they clean up the performance. Night and day. I was really going through withdrawal for a bit. :)  In fact with warm up, it sounds better. Could be placebo, but that's good enough for me. LOL


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