Fan modification for the SPE Expert 1K-FA solid state 1KW linear amplifier

The Expert SPE 1K-FA is a fantastic 1 Kwatt solid state linear amplifier. Two inputs and four outputs, automatic tuner, automatic band switching and cat controlling for almost every radio on the market. The revision 3 (Thirth series Dec-2009 or later) is the latest production model. SPE's design powers one of the seven fans all the time. The idea behind this is to create a small air flow to retract heat from the power transformer. At startup the inside temperature is 24° Celsius or lower but the fan already runs at full throttle making a bit to much noise to my liking. When the deck temperature reaches 40° Celsius, the six other fans kick in to retract the heat from the PA deck. Further increase of the inside temperature is compensated by increasing the speed of the six fans in three traps. The first fan that runs from the start always keeps running at the same speed.

The goal of this modification is to silence the first fan in order to obtain a quiet amplifier only when used in stand-by or while listening on the bands. From the moment the inside temperature increases due to transmission, the fan should run.

Testing resulted in startup temperatures of 24° Celsius rising very slow to 30-31° Celsius and stabelizing at that point. This is with or without the first fan running. It takes about 60 minutes to reach 30° Celsius. After a transmission periode, the deck temperature returns slowly to 31° Celsius thanks to the first fan running solo between 40 and 31° Celsius. After reading the DC5WW 1K-FA fan modification I was temped to do this modification myself.

Parts needed for a revision 3 model:

- 1 x ELV fan controller board.
- 2 x Extention fan power cable
- 1 x 5KOhm 0,5 watt multi turn potentiometer

If you like to control more fans or want to do the DC5WW mod for a series 1 or 2 model you need also:

- 1 x Multi fan board
- 3 x additional Extention fan power cable
- 1 x Darlington BDX53 transistor

After finishing this modification, I now have a complete quiet amplifier when powering up. The first fan only kicks in when the deck temperature reaches 30° Celsius. If I start to transmit and the temperature rises above the stand-by temperature of 30° Celsius, the fan starts to run, like it should. The rest of the Expert's own temperature controlling with the six remaining fans works as designed and is not changed at all. For additional info on building and completing the modification I refer to the DC5WW page from the original author. Altering the SPE design removes waranty and note that you can not claim issues to my address.

fig.01: Installation of the multi fan board

fig.02: View on the ELV fan controller and Darlington transistor

fig.03: Finished project - in stand-by the fan on the rear remains quiet when deck temp is 24-30° Celsius

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