[TenTec] Hercules II fault

[Gary J FollettDukes HiFi]

On the Bias Board is the Fan Driver. This provides an adjustable drive voltage for the fan.

The op amp that acts as the control is U3A feeding U3B to Q1.

U3A receives signals from either of the two power amp boards via the Fan Diode inputs from each power amp.

The schematic for the power amp(s) appears to me to be incorrectly drawn. D1 and D3 are shown as being thermally connected to Q2 and Q4 respectively. However, while the Bias Board schematic shows inputs for two Fan Diodes, the Power Amp schematic designates one of the thermally linked diodes as a Bias 1Diode while he other amplifier designates the same respective diode D3 as a Fan Diode. This seems to be an error.

Their job is to sense the temperatures of those transistors and then turn the fan on (or up) to cool the devices.

The manual states that the only things that activate the FAULT light are overdrive and excessive drive (transient) and over voltage, overcorrect, amplifier unbalance and disabled band selected (latching).

There is no mention of overtemp as a FAULT condition.

It is not likely that overtemp is your issue at turn-on anyway.

I am not certain if the fan is suppose to run all of the time, I assume it should and that the Fan Diodes only serve to increase airflow at overtime.

In your experience using this amp, does the fan stay on all of the time that it is powered under normal conditions?

With zero drive, does it still key when your transceiver goes into transmit?

Most likely you have a transient power up problem, likely on the power Distribution Board, but I need to know the answers to the questions to go any further.

he fact that the FAULT light goes out suggests that you are no longer in FAULT condition but we need to be sure.

UNDER NO CIRCUMSTANCES SHOULD YOU APPLY ANY DRIVE TO THIS AMP UNTIL ITS PROBLEM IS RESOLED!

Gary
W0DVN


> On Jan 18, 2016, at 5:29 PM, Zivney, Terry <00tlzivney at bsu.edu> wrote:
> 
> 
> My Hercules II  was working but now..
> 
> 
> 
> 
> On power up (with matching TenTec power supply) the front
> 
> panel fault light comes on as does the fan.  Waiting a few
> 
> seconds, the red led fault light dims out and the fan stops,
> 
> but the meter lights still have full brightness.  The amp
> 
> does not switch over to XMT (a good thing, without the blower!)
> 
> 
> 
> 
> Any ideas what to check first?
> 
> 
> 
> 
> Terry N4TZ
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