| Author | Message | ||
| Tom Siegel (2tone10) Username: 2tone10 Registered: 06-2008 |
Help - It made smoke this time!!! The reverb was a bit scetchy on the old 112 RD 50, it would sound really lush then dry up. If I tipped the amp forward or back the reverb would start working again. Long story short after poking at the tank a bit I got the reverb back but noticed that the amp was breaking up (no headroom) at lower volumes. I swapped out the tubes and fired her back up. I got a loud hum then smoke.I have it appart and found some fried resistors but for the life of me I can't find them on the schematic. I have pictures that I can email, maybe somone can help me track these resistors down? Also there is a green wire hanging loose by the input jack, I am assuming that it goes along with the orange one on the tip but would like confirmation if possible. Thanks, Tom | ||
| Tom Siegel (2tone10) Username: 2tone10 Registered: 06-2008 |
Here is a picture of the damaged area  Any help would be greatly appreciated | ||
| Tom Siegel (2tone10) Username: 2tone10 Registered: 06-2008 |
So the two brown resistors appear to be 2w 27 ohm. From close examination of a previous picture of my board and the resistors, the small one on the left appears to be 680 ohms and the one on the right 39k. I have been over the schematic and can't find any 2w 27 ohm resistors..... | ||
| Tom Siegel (2tone10) Username: 2tone10 Registered: 06-2008 |
Oh - I am also assuming the green wire should be connected back where the orange one is, on the tip of the input jack...  | ||
| Tom Siegel (2tone10) Username: 2tone10 Registered: 06-2008 |
Got it figured out with the help of my friendly amp tech who has a scope. The resistors, 1 transistor and an op-amp were taken out by a bad tube. I also had a headroom problem. This one is embarrassing. I had replaced the grid resistors at one point. They are 470 ohm, the supplier didn't have them, and I was in a hurry so I grabbed 47k. If you ever want to cut the power of your RD 50 down to 15 watts - this mod's for you.... | ||
| Mike Kaus (mm210) Username: mm210 Registered: 05-2006 |
That board looks pretty crisp. I think I'd probably fix the board traces with some tag wire before I went too much further. THose traces are awful thin. | ||
| Tom Siegel (2tone10) Username: 2tone10 Registered: 06-2008 |
Thanks Mike - I actually got the amp up and sounding awesome. The board looks fine from the backside and I always test the traces with my meter after I replace a component, I hope it holds together. Thanks for all of you input on this and other topics. You guys are great |
Tue, 03/25/2014 - 09:32
#1