public
join:2002-01-19
Santa Clara, CA
 ·DSL EXTREME
| reply to Dogwood
Re: Cayman 3220-H running hot with stock Power Adapter
said by Dogwood  :
The internal power supply has always been an issue with the 3220-H, and was probably undersized from the beginning.
My solution was to install the fan set you see here.
Let's put an end to this once for all.
Internally the 3220 uses two supplies. 3.3V and 5V. When Cayman designed this unit, they did not have much in house design expertise. The purchased a switching converter module for the 3.3V supply, and when this exceeded cost budget they decided to use a 5V linear regulator with a dinky little heat sink for the 5V supply. This is the hottest part in the whole box.
To minimize heat generated by the 5V regulator use the lowest external supply which will guarantee proper operation. This is about 7Vdc regulated.
Most of the cheap cubes are unregulated, hence they used higher voltage so that the combined ripple and AC variation will stay above 7V.
Therefore if you use external regulated 6.5 to 7V supply you will minimize heat generated inside the box. |
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WB6PWJ
join:2004-05-12
Anaheim, CA | I have been running my 3220H for years on an eight volt switching wall wort intended to power an IBM printer. The unit runs much cooler than with the stock analog one that in my case measured 11V under load. |
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DocWonder
join:2003-01-11
Miami, FL | reply to public
So a 6.5 V 2.0A switching power adapter is the final answer? |
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WB6PWJ
join:2004-05-12
Anaheim, CA
 ·VOIPo
| The voltage must be above the regulater min. As I recall a 7805 for example has a 2.5 to 3v difference. at 5V I would not feed less than eight. Later designs require less but they all must have more input than output. The problem is that that difference is thrown away as heat. With a large heat sink you could run twenty volts into the regulater. All that would do is heat up the cabinet. The reason that switching regulaters are prefeered is that they can run at 90% efficentcy. The 7805 in the above example would be 25% at 20v. 50% at 10V, etc. |
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