Slant face K150-1 thernal shutdown [message #5260] |
Sun, 02 January 2005 15:49 ![Go to next message Go to next message](/FUDforum/theme/vk30/images/down.png) |
jbreher
Messages: 11 Registered: January 2005
|
Junior Member |
|
|
I am repairing a friend's K150-1. The thermal switch on the output Q heatsink is shutting the AC down after a couple minutes playing time. Kicks back in a minute later, only to shut down again a couple minutes after that (ad nauseum).
I put a meat thermometer on one of the mounting screws for the thermal swich. It cuts out at 120 F, and back in at 119 F. This seems like a low trip point. Anyone know what temp this should kick in at?
The bias diode is clipped to the heatsink with what looks like a 3AG style fuse holder clip. Is this the normal means of thermal transfer from the heatsink to the bias diode?
Anything else I should be considering for the source of this problem?
Lastly, I have schematics and layouts for the two preamp boards, and the layout for the driver board. I could really use the schematic for the driver board and power supply sections. Does anyone know where I can get a copy?
TIA, Joe
|
|
|
Re: Slant face K150-1 thernal shutdown [message #5266 is a reply to message #5260] |
Mon, 03 January 2005 15:27 ![Go to previous message Go to previous message](/FUDforum/theme/vk30/images/up.png) ![Go to next message Go to next message](/FUDforum/theme/vk30/images/down.png) |
stevem
Messages: 4755 Registered: June 2004 Location: NY
|
Senior Member |
|
|
Hi, the 2n3055 output transistors are the norm for kustoms,they are rated for a max temp of 200 degrees C, or about 390 degrees F according to the specs for the transistor that I found, and the temp conversion chart I used. That termal cut out swt is bad. If you go to thre mouser site with the part number off it they have a cross ref to use and determin what brand and part number they stock a replacement in. That bias diode in the clip is the stock set up, just make sure the diode fits good in the clip and it has some white thermal compound still on it.If this is a metal face 150 I have a schematic for the output and driver board of a 250, it is most likey the same as the 150, but for the extra transistors and resistors that you do not have. If you need a copy, send me a self adressed stamped legal size envelpoe to steve magnotti p o box 1160 yorktown n y 10598. If you need to replace both outputs order NTE 130MP ( I think thats the part number) from the mouser site, these are a matched pair of them.
|
|
|
|
|
|
|
Re: Slant face K150-1 thernal shutdown [message #5280 is a reply to message #5279] |
Tue, 04 January 2005 12:08 ![Go to previous message Go to previous message](/FUDforum/theme/vk30/images/up.png) ![Go to next message Go to next message](/FUDforum/theme/vk30/images/down.png) |
chicagobill
Messages: 2005 Registered: April 2003
|
Senior Member |
|
|
Joe:
How hard were you were running the amp before it shuts down? I've never worked on a 150, but all of the 200's and 250's I've seen, rarely get hot under normal playing conditions.
As for power output, the story goes that the model number is the peak power rating (double the RMS). So a model 150 should be somewhere around 75 watts. I'd be interested to here to hear what your results are.
Bill
|
|
|
|
|
|
|
|
Re: Slant face K150-1 thernal shutdown [message #5300 is a reply to message #5293] |
Thu, 06 January 2005 12:46 ![Go to previous message Go to previous message](/FUDforum/theme/vk30/images/up.png) ![Go to next message Go to next message](/FUDforum/theme/vk30/images/down.png) |
chicagobill
Messages: 2005 Registered: April 2003
|
Senior Member |
|
|
Joe:
I was only offering what I have seen in my personal experience to be true. I agree with you, that multiple independent component failures are rare, but they can happen.
Not knowing where or how (or if) the amp was used during its past life, it would truly be impossible to state anything as definitive, but in a 30 year old piece of equipment I would guess that the two problems could have developed at completely different times. If I had to defend this position, I would think that the thermal cutoff probably fell out of spec a long time ago, but was never noticed until the overheating problem arose.
Just my point of view, Bill.
|
|
|
|
|
|
|