| 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値l 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痴 been 25 years since Tech school; so I知 a bit rusty. This site has helped me restore several MM amps. I知 replacing the bias transistors do to a run away bias issue. I知 trying to avoid a cap job at this point (not sure if I知 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 |