| Author | Message | ||
| Phil G |
I have a question on replacing Je1692 transistors. I ordered replacement 2n6488 transistors. The new transistors are 75w 80v and are much larger (will not fit in the sockets) the old transistors are part # sf 61176 604 (not sure what type). This is for a 112 65 combo. Are these the correct transistors? if so, I'll trim them down to fit. I posted this in another area of this site (I�ll wait for advice before I proceed) Thanks in advance | ||
| Terry |
Were did you get the parts? Mouser has the right ones part #511-2N6488 | ||
| Phil G |
I ordered the part 511-2N6488 from mouser. The 2N6488 is larger and flat (with a hole at the top to screw mount). Looking inside the amp and checking the schematic I see 2 small (half moon looking from the top) transistors in sockets. I believe they are the bias transistors unless I'm missing something. I do not see anything that looks like the part I have. Is the 511-2N6488 square and flat? The marking say 2n6488. Thanks for your help, Phil | ||
| terry |
Phil I think we are not looking at the same thing . What amp do you have? The parts that you want to replace has Je1692 on it? How do you know that they need replaced? | ||
| PhilG |
Terry, Thanks for your help. It�s been 25 years since Tech school; so I�m a bit rusty. This site has helped me restore several MM amps. I�m replacing the bias transistors do to a run away bias issue. I�m trying to avoid a cap job at this point (not sure if I�m going to keep the amp). Other postings had good success replacing the bias transistors to fix this type of problem. My amp is a 2275-65 (112) the only transistors I see are small transistors that plug in a socket. Looking at the schematic (the correct one) I was probably looking at the 2n3391 and 2n4091 (poorly marked). I combed through the amp trying to find the JE1692 bias transistors(no luck). Pin 8 on the tube socket should go to the collector of the je1692, instead a wire goes to pin 8 on the second tube socket. The bias resistor on pin 8 ties to pin 1. I Opened up my 410 65 (2275-65) and it looks the same (unable to find the je1692 transistors). I remember seeing these mounted to the chassis when I biased my 130 212 HD a few months ago. Is it possible that the older amps did not use them, or are they that hidden? I took everything apart and can shine a light to see through the main board where the bias pot is (still no luck). Any suggestions. Phil | ||
| Terry |
Hi If you have the 12AX7 tube you do not have the JE1692. | ||
| PhilG |
Terry, Yes, I have a 12AX7 in there. I have replaced all tubes in the system. I guess a cap job would be the next step. Any other suggestions are appreciated. Thanks again for your help, Phil |
Tue, 03/25/2014 - 09:28
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