Fender Frontman 65 distortion

[hefty]

Ok that is a great point but don't have access to a scope, when I check all all the voltages they all look good as per the schematic. I chopped stick, pushed and pulled the board, looked for bad traces/connections. The only thing that would stop it was touching the same joint with the meter probe. Without a scope I thought maybe try a change out of those two transistors. I also wondered way he chose the transistors he did instead of what was used in the circuit.This was just as much for the logic behind his suggestion to use the transistor he did instead of the ones called out in the schematic I was just trying to learn something besides the issues with my own amp.

[galaxiex]

Roly was a wizard when it comes to electronics in general, and guitar amps in particular. 

If he used those transistors, then a few possibilities come to mind...

1. He realized that "transistors are transistors" and as long as the new ones meet or exceed the specs for the circuit, then it will likely work ok.
It's just a guitar amp...
Granted.... *some* circuits and or specialized pieces of equipment "need" a specific device and will not work correctly with any other.
That is not likely the case here.

2. He may have had those particular transistors on hand, and popped them in, knowing they meet or exceed the specs.

3. Comedy >>> He had some esoteric reason for choosing those transistors.
They are full of secret MOJO having been pissed on by Unicorns or maybe made from Unicorn tears.   

Seriously, I wouldn't worry about it.
Replace them with the same as Roly did, or find some original part# devices,
or read some data sheets on the originals and find some suitable others to pop in there.

It's all good.
Cheers!

[hefty]

Thank you. This is along the lines I was thinking, having looked up the specs on both pairs. I think your #1 and #2 answers are right on the mark.  I appreciate your reply.

[Harry]

Hi ..I havent been here for few years. Just stumbled back looking for something else and saw my old post Re the Fender frontman 65 distortion problem. If Hefty or anyone else is reading this  i'd just like to make couple quick comments. Roly and i spen tweeks on the problem. It wasn't till i by chance got a  scope photo of the horrible waveform that progress was made. Roly suggested replacing the bad transistors with BD139/140 as he felt they were much better ,  better specs and he knew they were reliable. I bought the BD139/140 from Jaycar, nice and handy as well . Took bit of fiddling  and care to replace both but ......let me tell you to this day the amp  is still going strong, not a problem at all.
Roly was a great friend - mentor and i'm sure lot of people not just me , miss him. A great man and great talent.
I now take a 50 watt valve amp to gigs  as the Fender DSP 90 i have has also sh...t itself 8 times or so in 10 years . Do i like Fender amps ? silly question !

[stedutts]

Sorry to also revive such an old thread, I also have a Fender FM65r which suddenly developed a really unbearable crackling & distortion intermittently every couple of minutes, if I messed around with on off button it stopped but then started again after a few mins and drove me up the wall!!!! I changed on/off switch but no resolve, viewed internally on pcb and found capacitor 50 had leaked, replaced with a new one but amp still did the same, after lots of investigation and searching internet after nearly giving up I stumbled upon this thread, amazingly I found a few others had had same issue and I’d after reading Roly & Enzo smart advice I decided to change transistors Q10 & Q11 to BD139 & BD140 transistors, also cleaned all pots and everything else internally and stunned the amp runs like a dream crystal clear like new and no dirty crackling pots as well. So I needed to say a huge thank you to Roly who unfortunately I hear has passed, a traffic loss to guys like us who totally appreciate his knowledge and his sharing this to help others, big thanks to Enzo and any others who participated in this thread over the years. These threads are a massive help to people like us who are stuck and don’t know what to do next. I was going to give up on the repair till I fell upon this, so a massive thanks again guys you saved me at least £100 trying to get repaired which I doubt anywhere would with it being a non repairable amp by Fender, and such little repair information available anywhere to aid us in repairing, in total the parts cost me about £3 to fix amp and that’s expensive as I only bought couple of each parts needed.
I’ll definitely try here again when I have more issues with any gear. Many thanks all. Steve Dutton, vocals, guitars & production in Manchester band The Dead Xtra’s