Phoenix Gold Phorum

is this part

a possible reason for the thermal light to remain on?

any way to find a replacement?

....ok what is not showing on the picture is the fact that one of it's legs is cut right at the "base" of the part....

The part is here on the board. A thermistor i believe but can not find the specs for a replacement. I'm believing that this is the reason that amp is not working (severed leg from base).
If anybody can help i would greatly appreciate it.....

I am not sure either. Maybe Eric will know but he is not on that often. There is a facebook page called PG classifieds that has some people on that might be able to help as well.

Yes, it's a thermistor. If you can still get a meter across the leads, measure resistance at 0c and 100c, then you can probably find a match. If I get it to the shop this week I'll check one for you.

Good luck,
Jason

OK, I'm not 100%sure on this, but it looks like it is 2.2k, curve 2, type ntc. Vishay makes these exact ones still, but they are just the bare thermistor, you might have to epoxy it to a small tab with thermal epoxy. I'll see if I can find the exact replacement later, but have company atm.

Oh, and to your other question, yes, a broken lead will absolutely keep the amp in thermal.

WOW..... much thanks to both ttocs and Jacampb2 for their answers. Seems like i will finally maybe get somewhere on trying to resurrect this awesome amp. Would greatly appreciate if you guys find a store/source so i could purchase the part.

....could it be a ptc instead of ntc? searching online i didn't find any "ring type" ntc but found "ring type" ptc....
...supplied link
https://gr.mouser.com/ProductDetail/Mur ... VN4g%3D%3D

Hey bro, sorry for the delayed replies. I don't spend as much time on the forums as I used to. It is possible that it is PTC, but most thermal protection circuits use NTC. You won't always be able to find the same package the factory uses. Many of these parts are fairly specific to the car audio industry and as such do not have widespread availability, especially in low quantity. I have seen the style that PG uses, but many, many times you see the thermistor thermal epoxied into a little ring type mount, it's perfectly adequate to do this if need be.

The only way to know for sure is to hook a meter to the thing, and apply heat, see if it is NTC or PTC. I do know for certain that it is 2.2K at "room temp" You could swap it for a 2.2K resistor and see if the amp fires up. If it does, you could replace with say a 10K linear potentiometer, set it at 2.2K, fire the amp up and then increase resistance slowly and see if it goes into protect. If it does, it was likely PTC. If not, try going the other way.

If you can't get a meter on your leads now, LMK and I will pull one from a good amp and test it for you. I am currently laid up with a bad back, so things are going slowly around here, but I will get back to you eventually!

Good Luck,
Jason

Jacampb2 wrote:Hey bro, sorry for the delayed replies. I don't spend as much time on the forums as I used to. It is possible that it is PTC, but most thermal protection circuits use NTC. You won't always be able to find the same package the factory uses. Many of these parts are fairly specific to the car audio industry and as such do not have widespread availability, especially in low quantity. I have seen the style that PG uses, but many, many times you see the thermistor thermal epoxied into a little ring type mount, it's perfectly adequate to do this if need be.

The only way to know for sure is to hook a meter to the thing, and apply heat, see if it is NTC or PTC. I do know for certain that it is 2.2K at "room temp" You could swap it for a 2.2K resistor and see if the amp fires up. If it does, you could replace with say a 10K linear potentiometer, set it at 2.2K, fire the amp up and then increase resistance slowly and see if it goes into protect. If it does, it was likely PTC. If not, try going the other way.

If you can't get a meter on your leads now, LMK and I will pull one from a good amp and test it for you. I am currently laid up with a bad back, so things are going slowly around here, but I will get back to you eventually!

Good Luck,
Jason

truthfully any and all answers given at any time are at least god given and extremely highly praised by me cause i had given up hope on getting it repaired locally.(locally=greece). So whenever and whatever information you can supply i will be forever thankful and regretful that i cannot at least "buy you a beer" for your help.

I also want to wish you a speedy recovery with your bad back.
trying to get a reading is a no go as pin was cut off at the root...tried to dremel away some material away without any luck. I will try the 2.2 resistor and 10k linear potentiometer route as you suggest and will let you know.

I'll get out to the shop today or tomorrow and I'll pull and check one.

No need for thanks, I do appreciate it, keeping these pieces alive is reward enough in my book.

I'll post back later.
Jason

oh hell man sorry to hear about the back.

ttocs wrote:oh hell man sorry to hear about the back.

Thanks, but it has been a long term thing for me. Last 14 years or so, I am pretty used to it...

Back to the thermistor, this has been more complex than I imagined. The schematic clearly shows it as 2.2K, but it is not marked as a normal thermistor would be. I have pulled and checked them from three different TI series amps, and I was at a loss for what I was seeing. They measure about 80 ohms at 0° C, and they measure 100 ohms in 100° C water. That is not enough resistance change to effectively do this job. Also, these things oddly went down it resistance at first when heat was applied. I did some more research, and I believe I know what they are. I think that they are made by a company called Murata under the trade name of "posistor". They are an odd duck known as a switching PTC thermistor. They have a very non linear temp<-->resistance relationship and they also typically drop in resistance at first and then start to increase. The trick is that at a predetermined temperature known as the "curie temperature" the resistance increases very rapidly, most likely up to 2.2K as the schematic shows.

Here is the problem though, it does not look like Murata has any coded "C2" as yours and all of mine I checked are labeled. They have them that switch to 2.2K at their currie temperature, specifically one that switches at 110°C, but it's nominal resistance does not match what I measured. Also, mine did not exhibit the dramatically increased resistance while in boiling water. I don't know if that is because their switch temp is that incredibly accurate, or if it just has a higher switching temperature.

There is a second one that is identical to your broken one on the left side under the sinks with the outputs. You could pull that and do some more experimentation. At this point you would need hot oil to go past the 100°C mark, and although I am happy to help, I can't be on my feet that long to set up a detailed experiment.

My other suggestion would be to contact a sales rep at Murata, these may have been run specifically for PG, or they may just be a specially coded label and it isn't in their publicly available information.

Not recommended, but also possible would be to simply bypass it with a 80-100R resistor. It also may be possible to replace it with a self resetting thermal fuse in series with a 80R resitor as long as you find the correct temp that it is supposed to go into thermal. A self resetting thermal fuse is actually almost the same thing as these thermistors. You already know that the connection being open will put it into thermal protection, so I would think a thermal fuse will function ok.

*edit* Another thought I just had, you can find old school bimetallic thermal circuit breakers still as well, in fact, a lot of OS soundstream amps used this for thermals. You could run a thermal CB in series with a 80R fuse and probably have good protection. The hysteresis will not be the same with a CB though, so if it did go into thermal it might cycle repeatedly.

Good luck!
Jason

sounds like you were on quite the quest for info.

Yeah, I kind of went down the rabbit hole with this one. I admit I was perplexed. I wish I could have found the exact part for the op. I pulled some thermistors from some of my parts amps in hope I could send him one, but all my parts amps had actual ntc or ptc thermistors.

Later,
Jason

If the op needs one OEM, I can provide one.

ricky now where have you been this whole time?!

Busy, was working long hours and out of town for the last couple months.

Jacampb2 wrote:

ttocs wrote:oh hell man sorry to hear about the back.

Thanks, but it has been a long term thing for me. Last 14 years or so, I am pretty used to it...

Back to the thermistor, this has been more complex than I imagined. The schematic clearly shows it as 2.2K, but it is not marked as a normal thermistor would be. I have pulled and checked them from three different TI series amps, and I was at a loss for what I was seeing. They measure about 80 ohms at 0° C, and they measure 100 ohms in 100° C water. That is not enough resistance change to effectively do this job. Also, these things oddly went down it resistance at first when heat was applied. I did some more research, and I believe I know what they are. I think that they are made by a company called Murata under the trade name of "posistor". They are an odd duck known as a switching PTC thermistor. They have a very non linear temp<-->resistance relationship and they also typically drop in resistance at first and then start to increase. The trick is that at a predetermined temperature known as the "curie temperature" the resistance increases very rapidly, most likely up to 2.2K as the schematic shows.

Here is the problem though, it does not look like Murata has any coded "C2" as yours and all of mine I checked are labeled. They have them that switch to 2.2K at their currie temperature, specifically one that switches at 110°C, but it's nominal resistance does not match what I measured. Also, mine did not exhibit the dramatically increased resistance while in boiling water. I don't know if that is because their switch temp is that incredibly accurate, or if it just has a higher switching temperature.

There is a second one that is identical to your broken one on the left side under the sinks with the outputs. You could pull that and do some more experimentation. At this point you would need hot oil to go past the 100°C mark, and although I am happy to help, I can't be on my feet that long to set up a detailed experiment.

My other suggestion would be to contact a sales rep at Murata, these may have been run specifically for PG, or they may just be a specially coded label and it isn't in their publicly available information.

Not recommended, but also possible would be to simply bypass it with a 80-100R resistor. It also may be possible to replace it with a self resetting thermal fuse in series with a 80R resitor as long as you find the correct temp that it is supposed to go into thermal. A self resetting thermal fuse is actually almost the same thing as these thermistors. You already know that the connection being open will put it into thermal protection, so I would think a thermal fuse will function ok.

*edit* Another thought I just had, you can find old school bimetallic thermal circuit breakers still as well, in fact, a lot of OS soundstream amps used this for thermals. You could run a thermal CB in series with a 80R fuse and probably have good protection. The hysteresis will not be the same with a CB though, so if it did go into thermal it might cycle repeatedly.

Good luck!
Jason

and again WOW..... encyclopedia of info...!!!
.....I again THANK YOU for your time and effort...!!!!
...will keep these solutions & answers in mind

trickyricky wrote:If the op needs one OEM, I can provide one.

I'm assuming "op" means original poster so that would be me .....and to answer your question ....YES i would definitely want one....!!!
.....just let me know what i got to do....

get a video camera and set it up to record you as you Face east, hop on your left foot with your right hand above your head and repeat "There is no place like home".

ttocs wrote:get a video camera and set it up to record you as you Face east, hop on your left foot with your right hand above your head and repeat "There is no place like home".

laugh all you want....but i'd for the most part gladly would do that to get my baby up and running....!!!

pm me your address and I'll mail you one tomorrow.