Thermistor problem in amp

i have a problamatic thermistor in my linn powertek amp!
the amp is fine and sounds fine! BUT when its been on all day or cranked for a bit it shuts off
(not power just sound)
i called linn usa and they said it would cost $250 to get repaired----i asked how much the part is they said $15---
would you advise me to put it in my self--is this an easy job??i am sensible and carefull-----i'll be bugger'd if i'm paying $250
what would you do?????????????
its annoying having ya amp shut down every once in a while--u can turn it off and on again and itll play but in 10 mins its off again--and off till it cools down for a few hrs----
thanx joolz
Probably the hardest part will be opening the enclosure to get at the location. Thermistors are generally small solid state devices that look like a black match head with 2 small wires coming out side-by-side. Get the part form Linn as all are not the same. You will probably have to solder it in. There's no polarity. Just make sure it is exactly in the same position as the one taken out with regard to the transistor or whatever device it is measuring. It acts like a thermometer whose resistance changes with temp. Position is important if it is to operate properly. Of course, it is possible that it IS working properly and the amp is not adequately ventilated or is being worked too hard over a long time period, or both. Good luck.
Take the cover off and try to locate the thermistor. It should be close to the power switch. If it looks like something you can do, then decide for yourself.
Most thermistors are mounted directly on top of a transistor or to the heat sink. It might not be a problem to replace, but there could be multiple different thermistors within the circuit. As such, you would have to narrow down which one(s) are defective. Once you've done that, it's simply a matter of properly mounting and soldering it in place.

Sounds simple enough, but if you're working blindly, it might turn into a task. Obviously, Linn seems to think that this is a common problem. As such, they might be willing to point you in the right direction. Sean
All of the responses are good in this thread.

As a chemist who used to produce thermistors a long time ago, I can say that $250 is definitely out of line. As a matter of fact, I consider Linn wanting $15 for the replacement to also be unreasonable. The materials involved(combined oxides of various metals such as cobalt, copper, iron, manganese, nickel, etc. pressed into a disk using a lubricant to hold it together, and calcined) are extremely low in cost. Usually, the most important thing is the attachment of leads(which could be your problem); trying to achieve an ohmic contact. However, I do understand the desire to use an OEM replacement...

Thermistors may be NTC(resistance drops as temperature increases, like a typical metal oxide), or PTC(resistance rises as temperature increases, like a typical metal). The two characteristic values of note for a thermistor are TCR(Temperature Coefficient of Resistance - positive for PTC, negative for NTC) and Beta(which is derived from TCR). These would be two things you should try to match(they are a function of the thermistor material), in addition to physical size, etc.
u cats are awsome--thanx a million for responding
yeah linn are out of line $250---thats what they charge period to look at ya kit----they told me that and a few dealers told me that on the phone so its straight up....
so i'm gonna have to do it my self---
yes my amp is well ventalated.....