Adcom GFA-4402 fan circuit problem ? - Page 2 - diyAudio
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Old 9th March 2012, 12:39 AM   #11
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The TIP29C should be OK.
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Old 9th March 2012, 08:39 AM   #12
azvrt is offline azvrt  Netherlands
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Thanks Perry, I'll get it today.

Cecil, we were not able to locate that extra PCB you mentioned.
Could it be our amplifiers don't have it, or are we missing something ?

What we could do is put our multimeter in series with the remote wire that goes from the power supply to the amplifier's remote terminal, and measure current. If the fans are directly on the remote turn on, then there should be over 100 mA as the fans are 0.25A and they are supplied approx 4 volt by the amplifier's fan circuit.
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Old 9th March 2012, 04:53 PM   #13
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Sounds like your Adcom's are not modded with the turn on boards. I will try to find the schematic and mail it to you. It was a common problem and a simple mod is to use a Bosch turn on relay that is not current limited. This may be part of the fan problem and it may not. I will direct mail you about this...C
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Old 9th March 2012, 07:47 PM   #14
azvrt is offline azvrt  Netherlands
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Thank you.
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Old 9th March 2012, 08:56 PM   #15
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See page 8 of the 4402 document you sent me. It has the turn board diagram and parts list and such.
Also in that same document the fan does get its 12 volts form the turn on lead so you V drop issues could be related to the lack of the turn on board mod....
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Old 9th March 2012, 09:37 PM   #16
azvrt is offline azvrt  Netherlands
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Our amps don't seem to have this extra circuitry.
I will swap TIP61, if that doesn't fix the problem then I'll bypass the fan's circuitry and use a relay to start the fan as soon as the amplifier gets the 'go' from the head-unit.

It won't be temperature controlled so I'll have it run a little faster than they normally do on these amps, just in case.

Also, I will build am external relay for the person who will be buying 4 Adcoms from me, don't want 4 fans to be running of his head-unit's remote wire, he'd be looking at approx 400 mA, it could damage his HU.

The fans on the other amps run fine so no need to do anything about them, I am just reducing R336 a little bit so they run a tiny bit faster so I am sure they start up. As you said older fans can be harder to start spinning, increasing the voltage a little bit avoids problems, keeps the amp cooler and they are still pretty silent.

So I need to find two relays, one for inside the malfunctioning amp and one for outside for the 4 amps. Are there 'quiet' relays ? I don't want them to make clicking sounds as this person might do SQ competitions, I don't know. I personally like the clicking sound of my relay in my car when I power on the HU, but I don't do SQ competitions. I think they take off points for clicking sounds.
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Old 10th March 2012, 06:36 AM   #17
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I have and use a PG Tidd10 to control all turn on's and turn off's and time delays and what not for all my gear after the HU. If you have ever seen one, you will see why I use it. It does everything you could ever want to do to control all your gear off your HU.
Unfortunately they don't make them anymore and have not for more then three years now. Google search the model number and you should be able to see some lit about it. Tidd10 and Tidd5
Each output is fused, LED indicated, Delayed or instant on, or delay or instant turn off. Variable timers on all outputs etc... Its a great way to kill turn on and turn off thump in un-muted systems of past designs. I was lucky enough to grab one of the last ones PG had in stock when they stopped making and selling them just after the Xenon line stopped.

The two transistor turn on circuit for the Adcom is a easy build on breadboard. No rare or un-available parts and what not. It is so small it was screwed right on top of the lug for the turn on signal inside the amp. If you need to do a quick fix I suggest a simple Bosch relay with its coil activated by the HU, and its output being fused properly to all your external gear, Cheap, simple, and it works forever. If turn on clicking is a worry wrap it in soft foam insulation, and or mount it in the trunk of the ride.... I used this same setup years before I purchased a Tidd10....
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Old 10th March 2012, 06:40 AM   #18
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Oh by your last post I am sure there is something pulling the 12 down by 9 volts this is not the way it was meant to work. There is some defective component in the power supply and fan circuitry causing this issue, of this I am sure...Let me know what you find broken as its a first for my files...thanks ...
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Old 10th March 2012, 08:06 AM   #19
azvrt is offline azvrt  Netherlands
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Thanks for everything.
We are guessing (and hoping) it's the TIP61, if it isn't we haven't got a clue.
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