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K100-1 Question [message #11666] Fri, 21 August 2009 17:02   pleat Messages: 1452 Registered: June 2004 Location: Belding, Mi Senior Member Here a question I have for the tech's. I have a K100-1 amp. Transistors Q113 and Q116 are the 1/4 diameter metal transistors. They run quite hot and I would guess if you left your finger in the top of either one, it would burn your finger. Is that normal operating temp for that amp? The amp has had some repairs done to it years ago and works great. There are two other transistors Q121 and Q122 the same size that have finned heat sinks around them. I would like to add the heat sinks to them just to be on the safe side or am I concerned for no reason. I noticed the hot transistors when I was adding the newer 3 pin grounded power cord. Thanks, Don Report message to a moderator

Re: K100-1 Question [message #11667 is a reply to message #11666] Fri, 21 August 2009 18:15 chicagobill Messages: 2005 Registered: April 2003 Senior Member Don: Which PC board are you talking about? Tonight when I get home, I'll dig up my K100 schematics. The two transistors with the heat sinks are the power amp drivers. The heat sinks are built-in and come welded to the transistors. I think that the two transistors that you are refering may be part of the low voltage power supply, as these transistors would be the only ones that would normally get hot. Are these original or are they part of what was repaired earlier? I ask this because I think that the originals in the power supply were all plastic cased ones and not metal TO-5's. Maybe they are marked with a part number? In any case, heat and transistors are usually not a good sign. It may mean that there is too much current being drawn through the circuit causing the transistor to heat up. Adding a heat sink will help save the transistors, but it may not cure the problem (if there is one). There are any number of push on heatsinks out there, if you want some, I'll see if I can dig up a few for you. Report message to a moderator

Re: K100-1 Question [message #11668 is a reply to message #11667] Fri, 21 August 2009 18:23   pleat Messages: 1452 Registered: June 2004 Location: Belding, Mi Senior Member PC103 is the circuit board number. I have the schematic's if you need copy's of it. Don Report message to a moderator

Re: K100-1 Question [message #11672 is a reply to message #11668] Sat, 22 August 2009 14:58 chicagobill Messages: 2005 Registered: April 2003 Senior Member Ok, I was wrong on the plastic case theory, the pass transistors on the 100 heads are in fact small TO-5 metal cased transistors. The transistors in question, Q113 and Q116 are in fact the voltage regulator output transistors. Q113 is Kustom part #38735 which is an RCA 40408. Q116 is Kustom part #38734 which is an RCA 40406. Each transistor is rated -65 to +200 C, so they should be able to withstand the heat. Adding a small heatsink would probably add to the component longevity. Report message to a moderator

Re: K100-1 Question [message #11678 is a reply to message #11667] Sun, 23 August 2009 18:21   pleat Messages: 1452 Registered: June 2004 Location: Belding, Mi Senior Member Bill, that would be great if you had a couple of push on heat sinks or let me know who may have them and I can order a few. I just got the amp back from the repair guy and it works great but I've never ran across any kustom that the transistors seemed that hot under normal operating conditions. I just got a K200B1 in the mail wednesday and it was dirty, cleaned all the controls and bright switches, and the right channel came to life, and sounds great. The left channel was not so good. No sound but when you move the volume control, it makes all kinds of noise. I don't think my control cleaner will bring that channel back to life. I think that one, I'll take to my tech and have him go through it. Thanks, Don Report message to a moderator

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