Hello. I have a punch 551 4 channel amp. The power is blown and found 3 transistors blown. Can this amps be repairable at a reasonable cost? I was told that all 6 transistors have to be replaced because it is all one bank. Thanks, Al
An expert who has achieved level 3 by getting 1000 points
An expert that got 10 achievements.
An expert that got 5 achievements.
An expert whose answer got voted for 100 times.
Re: Hello. I have a punch 551 4 channel amp. The
The cost of the replacement parts is minimal if there is no damage to the audio circuit. If there are shorted output transistors, the cost of replacement parts won't be significantly higher but it may be more difficult to repair. If you're going to try to repair it yourself, read through the following page: http://www.bcae1.com/repairbasicsforbcae1/repairbasics.htm
- If you need clarification, ask it in the comment box above.
- Better answers use proper spelling and grammar.
- Provide details, support with references or personal experience.
Tell us some more! Your answer needs to include more details to help people.You can't post answers that contain an email address.Please enter a valid email address.The email address entered is already associated to an account.Login to postPlease use English characters only.
Tip: The max point reward for answering a question is 15.
maybe because your amp is overload, try to load 8 ohms single speaker per channel, then try to playing loud, if blown your amp again, the power transistors bias maybe excess to 0.6V ' if transistorized, if IC power amp, check cooling fan.
if you unhooked the wire from the amp while the amp was on, you may have possibly blown a fuse, or mayb a transistor or compacitor inside the amp! easy fix, just find new transistors and compacitors and soilder them on after removing old ones!
Short inside one of the transistors. This requires very good soldring skills and electrical know-how, and some thermal paste to go between the heat-sink and the transistor. Unfortunatly this is not a cheap repair, probably cost around 100 dollars.
Hi again! Been thinking about this and you might not need to wait for someone to answer. I assume the transistor in question has blown apart or burnt up so you can't read the number?
However does it come off the heatsink as part of the main amp? If it does then it might have a brother around it. For if it is say the left or right channel transistor, then the other channel will have the same type transistor. Remember the left and right channels are copies of one another. If you see 4 transistors on the heat sink then it's a push-pull amp. They work in pairs, one pair for each channel. By the way it's best to replace the pair, even if only one is blown.
If on the other hand the blown transistor is from the power supply section, then you will have to wait for someone to help, or get the service manual.
If you didn't find any burned parts that would mean one of the buffer amplifiers before the power amp could have died. They could either be transistor based or opamp based. They are fairly low power so they will not explode like the output transistors like to do. Contact rockford, they should be able to send you a schematic. Let me know I will try to help you through it.
Remove the output transistors and measure each of the sets of 3 pads and report the voltage readings here. I suspect that you have either a blown driver circuit or output transistors. The voltage readings will give me an idea on where to start looking for specifics.
The problem is not the transformer. You now have shorted output transistors at the very least. By corssing the wires you presented a zero(0) ohm impedence load to the output section. It quickly went into overload. Before the fuses had a chance to open up, the outputs fried. This unit will require new output transistors and perhaps the previous driver circuit will require parts as well. Figure on $20-$50 in parts plus hte local labor rate for the repair.
Units dc protect mode is probably activating due to Blown channel (shorted output transistors) I work for a Denon Authorized repair Center in Michigan If shipping to Michigan is economical let me know email@example.com
This can be caused by too low of an impedance from the way the speakers are wired, bad speakers, crossed/shorted speaker wires, and sometimes even a poor charging system (if the amp goes into protect when the volume is turned up) and is usually what the problem is 95% of the time. As you said, very possible to be shorted output devices or shorted power supply rectifiers. Beyond that, it could be a shorted filter cap, some sort of short across the power rails, some sort of short across the output, shorts across the primary. And of course loose hardware - any missing screws or nuts? A loose one under a pc board can short out most anything.