An expert who has achieved level 3 by getting 1000 points
An expert that got 20 achievements.
An expert that got 10 achievements.
An expert that got 5 achievements.
Re: Failed power transformer
With out make and model, I can not supply parts information. Please update this with that info. Also, depending upon the age of the unit, parts may not be available. Are you sure that the problem is the transformer? This part is rare to fail.
- 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.
This is a wonderfull idea, a great way to learn about electronics. Open the top of the amplifier, check for any internal fuses, if they check out, the power transformer may be open at the primary, [ too wires ] If you have a digital meter set it on ohms and touch the probes on the too wires going into the transformer, if no reading the power transformer is open.
You will need to open out the set and check from the fuses. If ok check on the secondary supply, if the small transformer has failed, unless this powerrs the microprocesor the main transformer and circuit will not be powered. so use a multimeter to check this voltage to the micro-+5, if there is no supply then you will have to check on this power supply. If the supply is present then check on the mP , the crystal osc. for working. clean any dirt or moisture if present.If not there is a possiblity that this section if faulty. Check this out carefully with a voltage reading on the stages. get help if you are not competent. Hope this helps. Good day
Oh yes... I have repaired several of these supplies.
For the IGBT's use APT28GA60BD15 which are pricey at $9.28 from Digikey.com (still lower than alternative sources. Getting the heatsinks off, one of which has a thermal sensor as well is a real pain! Transformers don't fail...
The C2655's are really 2SC2655-Y and those I get from Allied. The mating 2SA1020-Y I believe is available either at Digikey.com or Mouser.com.
You will LIKELY find the IR2153 chip is blown and that I had to get from Allied. Usually one of the PL4148 surface mount gate drive speed up diodes is blown either short or open (D24 and D25).
Often transistor T9 is gonzo (BC856MTTCT).
Often the 10 or 22 ohm wirewound charging resistors are blown open. I use TWW10J20RE as replacemens for those. Be sure and use silicone to help support them.
Now when you are done with that, you need to find WHY the supply failed. It is either because a ceramic cap across the 85 volts failed OR one of the power amps arced out. If the unit has the HCA2400 amp in it I will tell you what happens: In the vicinity of the SPF9640 MOSFET and a big surface mounted cap will be an arc between layers of the multi-layer circuit board. This shorts and fries the IRFP250 MOSFET and BOTH SFP9640 MOSFETS. The repair of this is major involving carving out the "cancer" and reinsulating with epoxy and replacing blown carved out traces with hookup wire. The proceedure I can't document here, but failure to correct this will result in power supply failing again.
FOR YOUR SAFETY ONLY work on the supply using an isolation transformer. Use a 150 Watt lamp in series for testing to act as a fuse so you don't pop the supply again. DISCHARGE the 85 volt outputs BEFORE plugging the amps back on the power supply.
These units don't have a separate "power suppy" per se. There is a power transformer and a separate board that contains the standby power supply components. The main power supply components are on the main board.
Rather than looking for a "power supply", what is the problem with the unit? Is there a standby light?
Quick check... If the amp still stays in safety mode with the vol turned down and the speakers disconnected, it will have failed in some way. Since you have the safety operation light ON, you can expect that the power transformer is OK. I would expect that you have a DC offset condition on one channel. The most common problems you may have are
dry solder joints about the power stages such as regulators, and output/driver transistors/IC's.
blown output transistors/output IC with possible fusible resistor failures, and or sometimes burnt up printed circuit tracks.
a voltage rail failure from a burnt fusible or power supply component.
If you are up with electronic fault finding, soldering and have the tools, have a go yourself, I could talk you through it. If not, I would suggest you contact you local HiFi specialist and find who can repair it or at least check to see what has failed for you. Good Luck. If you cannot find someone, hit me back and I will try to find someone for you. Cheers
Hi Hansjo. You may find that if one capacitor has failed, then there may be more. If you see any signs of bulging, leaking, or pushing the bottom out of any caps, then It is a good idea to just change them all. For the small expense, it is worthwhile knowing that your power supply has fresh caps. Try the amp and then see how it goes. If you still have problems, get back to me here and we can talk about it more.