Crest CKS & CKV input panels


At my university, our Recital Hall and Theatre were built about 8 years ago. Between the two rooms we have 21 Crest CKS amps(anywhere from a 200 to a 1200-2) and 1 CKV 800 amp. Since the begining of the calendar year we have lost four different input panels and about 10 more are on their way to the land on non-functioning parts. It costs about $80 a panel to replace, just in parts from Crest (we have only replaced 2 to date). This would explain the extra hum and hiss in our sound system then, if these panels were burning out one by one.

Here is the sequence of events involved in the death of the board:
1: the resistors R15 & R16 become really hot
2: R15 & R16 blacken the circuit board around them
3: R15 & R16 become no longer a blueish color but a white and all of the color code bands are no longer visable
4: one end of one resistor separates from the board (only happened on our last two burnouts)
5: the amp then no longer works

I can tell which ones are next because of the heat put off by the input panels but I don't know that they are gone until there is no input recieved by the amp.

The people that services my first two amps said that when Crest origionally manufacured these amps they put two little of a resister in the R15 & R16 location. I was just wondering if anyone else had heard this or if they had any other suggestions? One thought that came to my mind was on some of the panels that are almost ready to go, replace the existing resistors with larger ones. Would this work? I have pictures of some of the boards if anyone wants to see them.

Why not just have someone come in and replace the resistors with largers ones on all of them so that you don't lose an amp in the middle of a show. That would be disatrous.
It is really hard to help with this sort of problem as there could be lots of variables that could be causing this to happen.

If you can, talk to Crest or a registered service department. If this is a know fault, then you should be able to get some advice on what to do.

I am assuming that you have checked that you are not exceeding the input and output parameters of the amp? and they are not overheating because of poor ventilation or are dirty inside? (a lot of people do not realise that when you get dust on a circuit board and then add a little moisture (from smoke juice or humidity) you have a really nice conductor).

Putting in larger rated resistors (in wattage rating, not ohms) may stop them from burning out but I would imagine that they are burning out due to a problem, and that they are not the actual problem.

I would seriously consider getting someone out to look at the way in which these have been set up and are being used.

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