Fender 59 Bassman Burnt Resistors...Can Anyone Help with Issue?

Sp8ctre

Sp8ctre

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I have a chance to pick up a 59 Bassman reissue for a decent price, but it has an issue. There are a couple burnt resistors.

Can anyone tell by looking what the issue may be?

If no ideas and assuming it could be something as expensive as a transformer, what would a good price be?

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Have you looked at the underside of the board yet? If you can, try following the chain with a Volt OHM meter, there might be a bad capacitor in the link that's throwing out too much Voltage, or it could be just a bad resistor.
 
guitarweasel said:
Have you looked at the underside of the board yet? If you can, try following the chain with a Volt OHM meter, there might be a bad capacitor in the link that's throwing out too much Voltage, or it could be just a bad resistor.
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It's not in my possession...I have a chance to buy it as is...
 
if it was cheap enough & the amp fit in the lineup..off it would go to my amp guy for an analysis. if its too fried out would have custom made into Marshall treble side fender other,on a turret board . Got a Super RI & thought that it would need to be done..but it was darn good just the way it was, needed a few things gone over better(loose tube socket, some touch up on circuit, but we did not mod it)....so he went over it for $100 & its close to my fav amp..
I tend to look for stuff like that..knowing it needs to be worked on...with some work & mods..is it worth it in the long run is the gauge. Every one of mine started out with an issue of some sort but solid and need some things to make em them better. No way could i do it if i didnt have a tech friend.
 
eSGEe said:
wow looks clean otherwise
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Yea. The guy said he sold it and the buyer returned it "Not Working" but it was working fine when he sold it. Looks like the buyer screwed the pooch
and then screwed the seller by demanding a return. Not sure what could have happened?
 
Sp8ctre said:
Guy is asking $525 which I think is too high...they do go for $800 to $1000 in excellent condition and full working order.
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that is tricky,,,the speakers are good for that amp..the amp in stock form is a good sounding amp. Have played a few & the RI is better than most think. MY factor would be...is something beyond a board cooked? Cause if you had to turret it..you would have a very reliable amp for the price of a reissue that can have a circuit tweak anytime you want....those amps can be made quite aggressive or be classic fender or a blend of both. I was experimenting in the bassman-jtm range for a year..it could of gone either way for my main amp..but the Super showed up..but that bassman....love em. Most of my amps end up between 750-900 when done,,but have to be bought right to come in at that range..but my tech is prob cheaper than most & thats the only way i could do it. you have a great platform there if the money is right !
 
Sp8ctre said:
I should be able to repair it for $200 or so...I hope!
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Well, checking the amp and changig a few parts should not be too difficult if You have accress to the schematics.

But there may be a serious source of danger in the future: the burnt part of the board might have become conductive or become conductive in the future. And thats possibly dangerous if the resistor is on high voltage, e.g. if the resistor is part of the filter chain or if it is a screen resistor.

If You are strict on safety You should abandon that motherboard. (which i did on a board with a burning spot in the vicinity of 750V).
 
Ok, I've been looking at a few pics of 59 reissues online trying to find this exact board (unsuccessfully so far), but what I have noticed is that the power tube "screen grid resistors" are mounted on the board in this area, so I'm thinking the two burnt resistors are these screen grid resistors. These are fitted to prevent the screen grids from over-dissipating & take the brunt in the event of this type of power tube failure. They would be 470 ohm, 1 watt resistors & of the "metal oxide" type like it appears these are. It appears kinda like one has burnt up & cooked the other beside it & this also makes sense.
Now if these are the screen resistors, a repair would entail replacing the two 470 ohm/1 watt resistors. Possibly replacing the screen supply filter cap (but maybe not). Replacing & biasing power tubes. Hope this helps. Cheers
 
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ivan H said:
Ok, I've been looking at a few pics of 59 reissues online trying to find this exact board (unsuccessfully so far), but what I have noticed is that the power tube "screen grid resistors" are mounted on the board in this area, so I'm thinking the two burnt resistors are these screen grid resistors. These are fitted to prevent the screen grids from over-dissipating & take the brunt in the event of this type of power tube failure. They would be 470 ohm, 1 watt resistors & of the "metal oxide" type like it appears these are. It appears kinda like one has burnt up & cooked the other beside it & this also makes sense.
Now if these are the screen resistors, a repair would entail replacing the two 470 ohm/1 watt resistors. Possibly replacing the screen supply filter cap (but maybe not). Replacing & biasing power tubes. Hope this helps. Cheers
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Yeah, but if any of those tracks are damaged, then you're going to have to do jumper wires. But like @bea said: The board might be too compromised. Then what? Buy a new complete board? Gut it and then convert it to point to point?

Could a bad power tube have taken out that screen resistor?
 
syscokid said:
Yeah, but if any of those tracks are damaged, then you're going to have to do jumper wires. But like @bea said: The board might be too compromised. Then what? Buy a new complete board? Gut it and then convert it to point to point?

Could a bad power tube have taken out that screen resistor?
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Yes, a power tube failure often takes out the screen grid resistor.
I would convert it to point to point, as I'm sure you would. Cheers
 
syscokid said:
Yeah, but if any of those tracks are damaged, then you're going to have to do jumper wires. But like @bea said: The board might be too compromised. Then what? Buy a new complete board? Gut it and then convert it to point to point?

Could a bad power tube have taken out that screen resistor?
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if you go PTP & you can set that thing up exactly how you want it,,for 400 i would be on it ..ready to dump 3-500 more & have cheap road ready Bassman more customized & reliable than anything you buy at that price...prob my fav way to get an amp done up..you rebuild it to your specs & then can tweak as you go...no PCB to to mess with..,
 
BFT Gibson said:
if you go PTP & you can set that thing up exactly how you want it,,for 400 i would be on it ..ready to dump 3-500 more & have cheap road ready Bassman more customized & reliable than anything you buy at that price...prob my fav way to get an amp done up..you rebuild it to your specs & then can tweak as you go...no PCB to to mess with..,
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Oooooh... I like it when you talk like that... :love:
 
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