• TalkBass has been independent since 1998. Add your voice.
    Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
    Join free Log in
    Want zero display ads or expanded classifieds tools? Compare plans.

Is my amp dead for good?

#61
agedhorse said:
They ARE more difficult to troubleshoot, there are a lot of things going on operating in a non-linear mode... and they are potentially more dangerous due to the primary rectifier and bulk storage being located on the primary side of the isolation barrier.
Click to expand...
They reminded me of the TV flyback/driver loop. The kinda similar loop in a switcher goes dead if any one component goes dead. I worked on a few in old CRT displays when they were expensive, just for internal customers. Cost prohibitive to do guess work for paying customers, not to mention repair reliability. At that time, $125/hr., $250 min., and displays were $250ish. Most were under our warranty and a few under service contract, so they got a new one. Dummies on hourly rate got a $250 display for $500. Smarties went elsewhere for their new display.
 
#62
BadExample said:
They reminded me of the TV flyback/driver loop. The kinda similar loop in a switcher goes dead if any one component goes dead.
Click to expand...
Very much like these supplies actually, some (many) SMPS are in fact flyback types.
 
  • Like
Reactions: BadExample
#65
agedhorse said:
They do not fail from the voltage but the excessive current combined with the voltage. Lightning strike by itself isn't the cause of the damage, it's the current that flows... which also damages other components. Often, you will find additional damage beyond the thermistor which must be addressed. Otherwise, upon power up, additional components )such as the primary bulk storage caps) can explode if they are compromised. This is a dangerous and messy event.



There are different kinds of limited current AC supplies, depending on the type of power supply. As this involves primary voltages, and a lack of understanding of the (real) dangers involved, I'm not comfortable going into detail that's likely to be misunderstood.

(Please note that I'm not being a jerk here, but it's quite possible to get injured. I have a special test bench/equipment that I use when working on switchmode power supplies for exactly this reason. I don't want to get hurt.)
Click to expand...
Let me second all of that.
My sense is that the OP has very limited skills in this area.
Even just the soldering job of replacing the Thermistor can be problematic for the uninitiated.
Hence my question about soldering skills.
 
#68
Hard telling what the best approach is for you personally. If it were me, I'd get a bright light on it and a magnifier and do a close inspection of the copper traces and all the components. Go for it 10 or 15 minutes at a time. At least covering the area around the burnt thermistador (I'm now into changing "or" or "er" suffixes into "ador" just sounds badassed), and the area of the power supply and the traces from the supply. It's time consuming, and you can't see everything, much less failures that don't display themselves visually. I there are some tanned spots on the board that don't seem to be on a visible copper trace, it might have a multi-layer board with power and/or ground internal. Something like that can be jumpered around. Semiconductadors might have cracks or sometimes discoloration... hard to spot since most are black. Then I'd do my best guess replacements, jumpers around burnt traces, etc., and power it up COVER ON with at least a few screws in and tightened. If fail, go to the TV shop...

If it's like the Philippines, they may or may not be great bench techs, but they have what most of us don't, time and ultimate perseverance. They actually fix cell phones there. Working without a schematic and knowledge of the type of circuit is a bit like a backyard mechanic rebuilding your engine... drunk. But if it's all you got...

I hope you get it to go. Just be very careful, powered on or not. I've revived a few things shooting in the dark, some lasted, some didn't.
 
#72
BadExample said:
Hard telling what the best approach is for you personally. If it were me, I'd get a bright light on it and a magnifier and do a close inspection of the copper traces and all the components. Go for it 10 or 15 minutes at a time. At least covering the area around the burnt thermistador (I'm now into changing "or" or "er" suffixes into "ador" just sounds badassed), and the area of the power supply and the traces from the supply. It's time consuming, and you can't see everything, much less failures that don't display themselves visually. I there are some tanned spots on the board that don't seem to be on a visible copper trace, it might have a multi-layer board with power and/or ground internal. Something like that can be jumpered around. Semiconductadors might have cracks or sometimes discoloration... hard to spot since most are black. Then I'd do my best guess replacements, jumpers around burnt traces, etc., and power it up COVER ON with at least a few screws in and tightened. If fail, go to the TV shop...

If it's like the Philippines, they may or may not be great bench techs, but they have what most of us don't, time and ultimate perseverance. They actually fix cell phones there. Working without a schematic and knowledge of the type of circuit is a bit like a backyard mechanic rebuilding your engine... drunk. But if it's all you got...

I hope you get it to go. Just be very careful, powered on or not. I've revived a few things shooting in the dark, some lasted, some didn't.
Click to expand...
Sir Badexampleador, you are awesomeador.
 
  • Like
Reactions: BadExample
#74
DrummerwStrings said:
Hopefully it's just that part that's blown.

Mods can weigh in if this is Off topic - does home/renter's insurance cover the fried lighting & appliances?
Click to expand...


I don't know about in Kenya but here where I live in the US, when the power company blows up your stuff you send the bill to them. We had an issue here at the shop where they put 208 volts down our nominally 120 volt lines while replacing utility poles out back. We fixed most of the stuff ourselves because that's what we do. For the couple of things that were beyond repair, we submitted claims and got reimbursed.

We also handled the preparation of claims for other people when the Dept. of Water and Power blowed up other people's stuff.

Mugre
 
#76
This is why I used to just flip off our main breaker when the local power distributor had brownouts.
We'd do w/o power until we saw that the other homes were doing fine & then finally power back up.

At the time I had this handy little battery-powered fan + light, so it could keep you cool & light up the room at the same time.
 
  • Like
Reactions: Dieboy

Latest posts

Top Bottom
Back