Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: bakerlite on December 18, 2014, 05:41:09 pm
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trying to repair my friends blues junior - caps failed and scortched R47
Small mercy is the carbon damage is limited to a very small area the shape of the resistor. unfortunately i cannot simple clean up and replace though as both the solder pad and almost an inch of the trace has lifted -
These boards are SO fragile,
I am wondering would it be considered bad form to simple run the fresh 2.2k resistor on top of the board from the positive end of the c26 cap to the base of the P2 b+ terminal - this effectively places the resistor accross the positve ends of c25 and c26.
i know its not factory finish but just wondering is there any other advice against it?
thank folks
http://support.fender.com/schematics/guitar_amplifiers/BluesJuniorIII_schematic_Rev-D.pdf (http://support.fender.com/schematics/guitar_amplifiers/BluesJuniorIII_schematic_Rev-D.pdf)
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the only other option (unless i learn the miracle of creating replacement traces) is to put resistor in original place and run a jumper wire along the old line of the trace - This would not be my preferred method but the only other thing i can think of -
to make it worse i have just lost another pad changing out the mid cap, arghhh
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Maybe your iron is too big for pcb work?
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nah, i switched to the slim tip before i went near it.
the amp has seen ALOT of road and spent many nights in the car next to the sea.
gonna chat to him tomorrow and see where we go
one of those nights where the few hours put in seem all for nothing.. ah well
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When you lift a trace, for the most part this (what you said) is the only way, to replace the old with a run of bare jumper wire or insulated wire. Those Fenders seem to be particularly susceptible to trace-lift/pad-lift. As far as I know, the way to lessen the effect is to get your soldering iron temp (way) down AND you can't exert any mechanical pressure on the pad(s) which is where the trouble starts, after all. On most PC boards, you can heat the solder joint and stick a screwdriver under the lead where it it's bent over and pry it up so you extract the component lead by straightening it and pulling up on the component. In most cases on these boards, you have to cut the component lead on the non-solder side of the board, then heat the solder joint and then suck the stub into your solder-sucker to clear the hole. That makes reusing the part a lot less convenient because the lead doesn't reach down to the board any more.
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IMHO these amps are not roadworthy. In fact, put a pedal, even a tuner, permanently in place in front of it, so as not to stress the input jack.
Anyway, for me it's ok to solder components or new lead wires on top of the board, "point to point".
If only a little more damage could somehow happen to this POS board :angel , then one of Doug's new boards might be in order.
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Yes dougs board is definitely an option
But he sure want his reverb and not in front of the pre amp
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I've always had the worst luck with this family of amps. It seems like it doesn't take much for a trace to start lifting and then it's time to do just what your talking about and clean up the trace or go back to the nearest component and put in a jumper. I hate it because it ends up taking more time to do a repair that your not counting on.
Good luck!
Scott...
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I modified circuit boards in a factory for 5 years. We would take an exacto knife and scrape the protective coating off the top of the foil path to expose the foil and then lay the lead or 28awg wire right on top of the path then solder it.