CS800x - DDT light blink, almost no output

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DaleMurray
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CS800x - DDT light blink, almost no output

Post by DaleMurray » Wed Jan 20, 2021 10:59 pm

I use the amp to power subs on my stereo. Tonight I noticed very little bass, about half as much. Looked at the amp and DDT light on Channel B is blinking like mad but nearly zero output. Channel A is working perfectly, only B has an issue.

I will likely tear into it tomorrow or Friday.

Any chronic issues I should look for first?

The amp is in great shape and was well maintained by the previous owner.

Dookie
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Re: CS800x - DDT light blink, almost no output

Post by Dookie » Thu Jan 21, 2021 4:39 am

First and foremost make sure it is the amp that has a issue not the speaker. If there is a short in the speaker, a blown woofer or damaged crossover then the DDT will come on to protect the amp from the short. The first thing to do is unhook the speaker and try the amp with no load and see if the DDT still comes on. There could even be a shorted Speaker Wire going to the speaker.

Doug

DaleMurray
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Re: CS800x - DDT light blink, almost no output

Post by DaleMurray » Fri Jan 22, 2021 3:44 pm

Channel B is the issue.
Changing speakers or input signals made no difference, DDT lit.

If I power on with nothing plugged in (speakers or source) nothing aside from the power lights are lit.
As soon as a connect anything to the input, just connecting a 1/4" jack, ddt light comes on and stays on until I power cycle the amp.
But this is not always the case, sometimes I can connect a wire and it does not engage DDT; maybe 10-15% of the time.
If I get lucky and DDT does not engage, I will connect other end of wire to powered off function generator, DDT light comes on. Will stay on until I power cycle the amp.
Now with powered off function generator connected to the input of the amp, I power on amp - no DDT light. If I unplug the wire from the powered off function generator, the DDT light comes on and stays on until I power cycle the amp.
But this is not always the case, sometimes I can unplug and DDT light comes on for a few seconds then shuts off. If I then plug that wire back in, DDT light comes on and stays on until I power cycle the amp.

Dookie
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Re: CS800x - DDT light blink, almost no output

Post by Dookie » Sat Jan 23, 2021 8:31 pm

DaleMurray wrote:
Fri Jan 22, 2021 3:44 pm
Channel B is the issue.
Changing speakers or input signals made no difference, DDT lit.

If I power on with nothing plugged in (speakers or source) nothing aside from the power lights are lit.
As soon as a connect anything to the input, just connecting a 1/4" jack, ddt light comes on and stays on until I power cycle the amp.
But this is not always the case, sometimes I can connect a wire and it does not engage DDT; maybe 10-15% of the time.
If I get lucky and DDT does not engage, I will connect other end of wire to powered off function generator, DDT light comes on. Will stay on until I power cycle the amp.
Now with powered off function generator connected to the input of the amp, I power on amp - no DDT light. If I unplug the wire from the powered off function generator, the DDT light comes on and stays on until I power cycle the amp.
But this is not always the case, sometimes I can unplug and DDT light comes on for a few seconds then shuts off. If I then plug that wire back in, DDT light comes on and stays on until I power cycle the amp.
First I wouldn't use the amp on any "good" speaker until the fault is found. Use an old test speaker. When the DDT light is on did you check for DC voltage on the output? Should be in the microvolt range.
I wonder if there is a intermittent DC voltage problem and the Crowbar protection is kicking in. Depends on the age of the amp if this is installed in the amp. The newer ones don't have this and use a different type of protection.

Doug

noelmem1
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Re: CS800x - DDT light blink, almost no output

Post by noelmem1 » Sun Feb 21, 2021 5:59 am

The cs800 cs800X has a DDT defeat switch and Bridge switch you might like to cycle them 50 times . There is also a PL2 engage switch when a Lo-Z input is used or canned crossover-not directly related but you might like to cycle that switch too 50 times. Could be a hanged ground connection
and hi freq oscillation since you did not mention any buzzing sound just before DDT light . Spray oil type contact cleaner to the PL55 plug and plug it in and out into the Hi Z inputs hoping to clean the barrel and TIP contacts . I sent you a PM .

noelmem1

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