Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: allaboutone on October 15, 2010, 01:39:40 pm
-
New here and see there is a lot of valuable information so hope to visit often.I have a homebuild 5E3 that is about 10 years old.Always worked perfect until loaning it to a friend.He had a couple years and recently brought it back.He forgot to shut his tailgate and it took a spill out of the truck.It is a head and bottom.The only visible damage was a few scratches to the walnut head.It now has about 1/3 of the output that it should and is distorted.I have repalced all of the tubes with no change.Checked every solder joint and component in the amp with a DMM.I just can't see the problem.
Especially after checking the voltages .Pin 3 on the power tubes measures 343VDC.I have 357 on the first filter cap,354 on the second and 258 on the third.V1 pin 1 is 130VDC and pin 6 is 141.V2 voltages are 206 on 1 and 190 on 6.These don't seem far out of line with the exception of 206 VDC on pin one of V2 being high.The amp is basically the stock Fender circuit with the exception of having a choke.Any help tracking down this issue would be much appreciated.
-
Check cathode resistors and caps, one or more could have been damaged. If a cap bypass is dead, gain will be much lower and sound will be distorted.
Check the screen resistors.
-
Thanks for the reply.I have checked the screen resistors.The cathode resistor measures 247.5 so is ok and I've checked all of the bypass caps and filters with a capacitance meter and esr meter and the all check good..I have also inspected all of the grounds.I first thought it would be a bad ground bleeding off signal.Could it be the OT and still getting correct voltages.
-
Have you also checked the RC cathode networks for the small tubes?
-
Not to leave any stones unturned - did you try different speakers? and have you checked the speaker output jack?
206vdc on v2 pin one is around 40vdc too high isn't it? IN addition to what FYL mentioned ,for V2a check the plate load resistor and the interstage coupling cap; is it a .022uf ?