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February 23, 2020, 07:01:40 AM

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Author Topic: Fender Frontman 65 distortion  (Read 6885 times)

hefty

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Re: Fender Frontman 65 distortion
« Reply #15 on: December 24, 2016, 01:54:57 PM »
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

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Re: Fender Frontman 65 distortion
« Reply #16 on: December 24, 2016, 02:25:32 PM »
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.  ;)  :lmao:

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!
Fear leads to Anger, Anger leads to Hate, Hate leads to Suffering.

hefty

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Re: Fender Frontman 65 distortion
« Reply #17 on: December 24, 2016, 04:28:11 PM »
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.  :dbtu: I appreciate your reply.

Harry

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Re: Fender Frontman 65 distortion
« Reply #18 on: February 06, 2020, 04:23:59 AM »
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 !