If it keeps me awake at night, I don't do it.
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Strange and Lazy repair !!!
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Originally posted by Chuck H View PostI've never seen fuses replaced with aluminum rod. I've seen plenty that were wrapped in aluminum foil (sometimes from a cigarette pack).
What about lazy repairs that WE do. C'mon!?! I know there are some shortcuts we've all taken that are less than ideal but known to be "good enough". Is anyone here willing to fess up? I'll go first...
On a few occasions where board removal was a real PITA I've replaced "through hole" PCB components by snipping the leads and soldering the new component/s to the old leads. Likewise, when making value changes on such boards I've also just piggybacked components on existing ones rather than pull the board to change the existing value. I'm not proud of this, but I don't expect it to cause any real problems either.
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Originally posted by MarkusBass View PostI hate to disappoint, but this is not the case (double fuses) in SVT-2 Pro. The first fuse is for the whole amp (including power transformer) and the second is for the filament transformer only. The second fuse is 1.5A and the value on the schematic is correct.
Or schematics that are just mazes of terminals & connectors, Marshall being especially bad. It wouldn't be so annoying if they included a road map of the connectors/terminals, but they never do.Originally posted by EnzoI have a sign in my shop that says, "Never think up reasons not to check something."
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Originally posted by Jazz P Bass View PostSo what exactly happened to the IC pins themselves?
Must have laid the IC & heatsink over & snapped them.
"Here's your amp back. Fresh as a daisy.""I took a photo of my ohm meter... It didn't help." Enzo 8/20/22
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Originally posted by Chuck H View PostI've never seen fuses replaced with aluminum rod. I've seen plenty that were wrapped in aluminum foil (sometimes from a cigarette pack).
What about lazy repairs that WE do. C'mon!?! I know there are some shortcuts we've all taken that are less than ideal but known to be "good enough". Is anyone here willing to fess up? I'll go first...
On a few occasions where board removal was a real PITA I've replaced "through hole" PCB components by snipping the leads and soldering the new component/s to the old leads. Likewise, when making value changes on such boards I've also just piggybacked components on existing ones rather than pull the board to change the existing value. I'm not proud of this, but I don't expect it to cause any real problems either."I took a photo of my ohm meter... It didn't help." Enzo 8/20/22
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Originally posted by Chuck H View PostOn a few occasions where board removal was a real PITA I've replaced "through hole" PCB components by snipping the leads and soldering the new component/s to the old leads.
My occasional method:
On a few occasions where board removal was a real PITA I've replaced "through hole" PCB components by snipping the component leads and then removing the old lead remnants, then using chem-wik to clean the thru-hole, and then soldering the new components in where the old component was.
The only thing with this method is, you have to be extra careful not to flow too much solder so that you don't accidentally make a bridge on the bottom, otherwise you end up having to pull the whole damn board anyways, negating the 'cheat' in the first place. lolStart simple...then go deep!
"EL84's are the bitches of guitar amp design." Chuck H
"How could they know back in 1980-whatever that there'd come a time when it was easier to find the wreck of the Titanic than find another SAD1024?" -Mark Hammer
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The problem that I've seen with soldering in components to the cut off leads of the old parts is that the solder joint on the underside of the board reheats and will become a cold joint if you are not careful.
The worst thing I can remember doing is drilling a hole through the chassis of a cheap Gorilla practice amp to resolder a loose input jack. To get the board out you had to remove the power transformer as well as the heatsink, the knobs, the controls, etc.
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Originally posted by 52 Bill View PostThe problem that I've seen with soldering in components to the cut off leads of the old parts is that the solder joint on the underside of the board reheats and will become a cold joint if you are not careful.
The worst thing I can remember doing is drilling a hole through the chassis of a cheap Gorilla practice amp to resolder a loose input jack. To get the board out you had to remove the power transformer as well as the heatsink, the knobs, the controls, etc.
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I should rename this thread 'Strange, Lazy and Russian roulette'
I have just bought a 40year old Sound City 120 guitar amp. It was cheap, in good cosmetic condition and came with a free 4x12 matching cabinet. The previous owner admitted that he'd had it for about 20 years without as much as even cleaning let alone servicing. The only thing he told me was that for those 20 years there had always been a strange crackle but putting it down to a 'feature' rather than a problem.
Having stripped the amp from the case and giving it a good clean I noticed that one of the power caps has some insulating tape around the bottom. I powered the amp up and sure enough a crackle and buzz. I metered between the top of the 'taped' cap and the chassis to find a 'healthy' 121 vdc flowing like a river. Out of intrest I plugged a guitar into the input and metered between the strings and this cap - 121vdc.
I contacted the previous owner to find out if anyone had at all looked at the amp during his ownership, just to check if maybe he'd forgotten. But no. So for 20 years this guy was a microphone away from a good frying.
I suggested he give me 6 numbers for the lottery !!!
Anyway, remaining with this sound city amp, the caps in question are 200uF @ 350vdc. I have looked around for replacements without success. Can anyone recommend suitable value replacements ?In life there are no problems, only challenges but in my present situation I may have a problem
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I'm afraid that there is nothing wrong with the cap. If you look at the schematic: http://soundcitysite.com/sc_120_2.jpg , you'll see that there are two capacitors in the power supply, one stacked on top of the other. It's due to the fact that the power supply voltage of the power amp is higher that the voltage allowed for the cap. That's why there is isolation tape on the cap. Problems with the amp are caused by something else - you may create a new thread for this amp.
Mark
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The reason the module was not wired the same is because it was not the original, which has been out of production for years. There are newer modules available with higher power but they are not plug-in compatible and one pin difference in count, different mounting screw spacing etc. Be wary of modules on eBay unless you know the supplier because a lot of those from China are remarked as higher power versions or just are not original.
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Originally posted by MarkusBass View PostI'm afraid that there is nothing wrong with the cap. If you look at the schematic: http://soundcitysite.com/sc_120_2.jpg , you'll see that there are two capacitors in the power supply, one stacked on top of the other. It's due to the fact that the power supply voltage of the power amp is higher that the voltage allowed for the cap. That's why there is isolation tape on the cap. Problems with the amp are caused by something else - you may create a new thread for this amp.
Mark
Originally posted by km6xz View PostThe reason the module was not wired the same is because it was not the original, which has been out of production for years. There are newer modules available with higher power but they are not plug-in compatible and one pin difference in count, different mounting screw spacing etc. Be wary of modules on eBay unless you know the supplier because a lot of those from China are remarked as higher power versions or just are not original.Originally posted by EnzoI have a sign in my shop that says, "Never think up reasons not to check something."
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