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Old 4th April 2010, 04:09 AM   #7641
jackies is offline jackies  United States
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Originally Posted by wingman65 View Post
Been reading this loooong thread, only to page 564 Is there a consensus for heat sinks here in the US? Those seem to be the hardest parts to source at reasonable expense.

I read this thread in it's entirety several times back and forth. Trying to make shure no single bit of useful info slipped away...
As for heatsinks, barredboss on ebay has some good ones, he also now has a store:
HeatsinkUSA, llc
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Old 4th April 2010, 04:27 AM   #7642
flg is offline flg  United States
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Like Jackies says
"It was the perfect high end audio product: Exotic, inefficient, expensive, unavailable, and toxic." N.P.
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Old 4th April 2010, 04:41 AM   #7643
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Thanks Jackies, reading this thread and all the links is paramount to an education in electronics. It's been 25 years for me so a lot of cobwebs getting cleared out

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Old 4th April 2010, 05:40 AM   #7644
stroob is offline stroob  United States
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Looking for some suggestions. Finished my F5 build and it looked to come up without any issue and played music and the sound was pleasing. I used 1ohm resistors for r11/r12 and set the bias current to 900mA. The barred boss heatsinks were warm, but not anywhere close to being a concern. The setup is dual mono and the two 250VA transformers were extremely hot. Blistering hot. What would you check?

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Old 4th April 2010, 07:20 AM   #7645
RKH is offline RKH  United States
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Default Hot transformers

Just a thought... no guarantees. If there is any DC offset (even a few millivolts) on your mains, you could be saturating the core of your toroidal transformer. There is a little circuit to prevent that DC from getting though:

2 diodes + 2 diodes (opposite polarity, in parallel) and a lot of capacitance across both (observing diode polarity). Essentially, the diodes prevent DC from getting into your transformer core and saturating it.

Hope that helps.

Lighten up while you still can ...
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Old 4th April 2010, 07:55 AM   #7646
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Originally Posted by RKH View Post
Essentially, the diodes prevent DC from getting into your transformer core and saturating it.

No. The capacitors stop dc.
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Old 4th April 2010, 07:56 AM   #7647
sangram is offline sangram  India
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I had some puny 180VA units and when running at stock bias, they would get very toasty to the touch.

Now on 440VA units (one/channel) and it's all cool as a cucumber.
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Old 4th April 2010, 09:35 AM   #7648
jazz is offline jazz  Netherlands
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Location: leiden, physically that is...
@ Renron,

Ok sorry, I stand corrected. I only remember the first version of arctic silver and believe to remember that that version was/could be conductive. Maybe bad memory, maybe things have changed.

oh, what a beautifull day
I wanna go out and play!
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Old 4th April 2010, 11:14 AM   #7649
AndrewT is offline AndrewT  Scotland
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Question artic silver or not?

I have this silvery looking heatsink compound.
How can I test it to ensure it is either conductive or non-conductive during all operational conditions?
regards Andrew T.
Sent from my desktop computer using a keyboard
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Old 4th April 2010, 11:29 AM   #7650
Mooly is offline Mooly  United Kingdom
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Ways and means.
Put a blob of the stuff on the plastic front of an old power transistor, then connect to PSU and use a pot on the base to vary bias (heat). Hold a scope probe or DVM to one side of the blob and connect hold a voltage source to the other and see what passes through.
If you want to be really sure and do detailed measurements, first epoxy a couple of wires to the transistor to make pads with which to bridge with the compound.

Were you snowed in ?
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