Question about Technics SA-AX720 Receiver
I know this post is pretty old, but I just came across it. I have a GTP-750 that I have fixed. They do run extremely hot which causes the rectifiers in the power supply to fail. I have the rectifier part numbers to fix it as well as cooling method. I have been running mine now for about a year after fixing it sometimes at high levels for extended amounts of time and the case is now barely warm. If you need advice or pictures of my setup send me an e-mail
Posted on Apr 26, 2007
Fan? If there is a cooling fan in the SV454 then they forgot to install them in the ones I've worked on. These use special 2sc5242's and 2sa1962's for the final outputs (transistors) they are manufactured by Toshiba, special because they were a special or unique house brand type of transistor made for the SV454. The specs for these really seem to to push the envelope for the case style/size. Most of similar types of transistors are rated about 33% to almost 50% but not quite, lower then these. What I speculate in the SV454 is a condition where a final output transistor is working its little guts out. Things like caps drying up shouldn't be near an issue with this model because it's not all that old yet. Who knows? It could have been a cost cutting move, it could have been an experiment with a unique transistor designed for a specific circuit and amp, or something I'm not even thinking in terms of. Electronics in practice is a theory based science so when something is designed it should work, as we all know after a number years it either holds up or it has problems many of us term as "overheating" or just "blowing up". In theory the application should work, hold up, and maintain within tolerance. In practice, years of service and/or use, the theory is blown away. I point to the final output transistors, but it could be a number of many things like diodes, caps, or ? that cause final outputs like these, that are running on the fringe, to actually overheat or blow. The finals are the most frequent component that require replacement in this model, specifically the main amp or front channel if you prefer. Some people may think that replacing all the caps, whichever those may be, helps because I see this suggestion almost all the time and it's getting way to common, but the truth is I see more heat related stress in the prestage area of the circuits then anywhere. So in that respect where a thermal condition could cause these very small transistors to overheat and oversaturate due to this condition, excess current could very well effect the finals which are running on the edge to begin with. With that said then it would make more sense to replace the prestage amps/transistors then almost anything else. In my opinion, I don't believe that DC, DC offset, DC leakage is related to the common failure issue and the trouble is a thermal condition effecting the prestages that ultimately fries the finals. The electrolytic caps are coupling filters bewteen the stages, designed to prevent DC from being passed on and amplified to the next stage. The AC caps are filters in the power supply to prevent AC from interfering with the DC supply voltages to things like the rail voltage or b+ and neither of these seems to be the culprit. It never hurts to replace inexpensive electrolytic caps, but I don't think it's necessary in solving the real issue with this model mainly because these are not that old and secondly because I've rarely ever seen one bad if at all. If you really wanted to service this right, I'd replace the prestage transistors and monitor the zener diodes for thermal responses and not worry a whole lot about any caps unless you had specific reasons like DC offset, higher or imbalanced levels would be a sure sign.
Posted on Jan 05, 2007
Buy a new one...
Posted on Jun 23, 2008
Hello, I had same problem, unit heat up real bad and loosing sound quality, but I solved it!
Old days, high power units used to have built in fan, I just add small fan in to cabinet and as soon as it detects heat, fan turns on automatically and cools off the unit no matter how long or how much the volume is up. Everything and the unit is back to normal.
Posted on Feb 12, 2008
I have the same problem with a Onkyo tr sx600 and with a Pioneer VSX 307.
These are pieces of junks.
Only solution is trow them in the garbage and avoid buying any produckt of those brands again, and SPREAD THE WORD, so these false "good receivers" factories go BANKRUPT and stop stealing our money.
Posted on Feb 11, 2008
I'm sorry for the double post but I forgot some information and being an impatient newbie at this forum I didn't see the edit option.
I realize that not everyone has a table hockey fan laying around but I just wanted to open up the possibility of using a better fan. It doesn't have to be the right brand or size if you're good at rigging things up. I know it sounds primitive but it fixed the problem without any money spent. I powered it separately with a separate outlet plug, meaning to keep the unit running AND cool, it required two outlets to be used. It was a bit less convenient (fan doesn't turn on with the unit's remote - I used the power button on the surge protector to turn it all on), but it worked.
Posted on Jan 06, 2008
I have one of these units (SA-DA8), given to me FOR FREE only because it was so hot during normal low volume use that the original owner thought it would start a fire. The top of the casing was so hot that one would have to be masochistic to leave a finger on it for more than one full second. Although there are vents up there, the heat was literally burning hot.
I tend to be a champagne taste on a beer budget kind of guy, and often stumble upon good stuff for low prices or free.
The fix I came up with may not agree with you, but it really does work. I happened to have a very small yet very powerful and quiet fan from an air hockey table. The fan was only slightly larger than the original multi-speed fan, so I cut the fan hole larger with a jigsaw, and used self tapping screws to mount the newer stronger fan.
Since then, the unit's casing does warm up, but not nearly as much as it did before the cheap modification.
Posted on Jan 06, 2008
I have a GTP-740, and I think its heat thats causing it to go bad. It starts making a seriously annoying buzz through the speakers, etc etc. One guy said to email him about his set up but I see no way of emailing him....soo...email me! GroundHoundFive and thats good at Yahoo
Posted on Nov 17, 2007
Check two resistors on the main board nearest the edge twards the the front right these resistors are apart of the volume control IC which is located on the board above the volume knob. this IC over heats and causes these resistors also over heat. the solder under the resistors goes bad. you will also notice burn discoloration under the resistors and the IC. the IC and resistors must be replaced and it is possible that the burn under these resistors may be so severe that the unit can not be repaired.
Posted on Jul 08, 2007
I've owned an Onkyo DS696 receiver for 5+years. Every once in a while (when it was on for a long time?) the receiver would not respond to the remote. At first it could be "fixed" by a simple power cycle. It got worse over the years, and finally the unit would not respond to the remote at all. After reading a post here that made perfect sense, my husband and I opened the unit up, and (even thought the solder at the IR connection LOOKED fine, we resoldered it. (He knows how to do these things expertly). We screwed the unit back together and VOILA! it works perfectly now. Even if you don't know how to solder, if you brought it to a repair shop and told them exactly what the issue was and how to fix it - you can save your sanity and the unit. The solder joint I'm talking about is directly behind the IR on the front daughter board.
Posted on Jun 28, 2007
Have had a very similar problem with the remote control. Sometimes it works at the beginning but then stops or doesn't work at all, more annoying is that the probelm is intermittent. I would agree that potentially it is overheating as the remote sensor is at the front and the heat sink runs straight down the middle front to back. Anyway the solution seems to be to run a soldering iron over the contacts of the devices in the remote receiver circuit - this means taking the whole thing apart and getting to the front panel is more than a bit fiddly. Anyway it seems to have solved the problem - at least for now !
Posted on Jan 16, 2007
Both me and my friend have the same GTP-750 and both have same problem like yours. About a year ago, I sent an email to Adcom and here is the answer from the new Adcom LLC I received: "The GTP-740, 750, 760 & 830 were all manufactured by the old Adcom in NJ. After we purchased the company Feb. 2002 we discovered what we inherited. All of the above mentioned processors are known to have power supply issues. Those units tend to get very hot when in use and require either placed in a very well ventilated area or use a fan to cool it down" ..... "unfortunately I cannot make a recommendation and guess as to what your 750 might need for repairs. It could be a couple of bridge rectifiers or a whole new power supply; I just cannot make that assumption"..... They asked me to upgrade to the GTP-880 but I ended up buy a new Outlaw 990 instead. Have anybody fixed this overheating problem before?
Posted on Oct 07, 2006
If your receiver is a couple of years old, and the fan is volume controlled rather than heat dependent. See this a lot in lower end unis personally I think it is a bad design. You do not drive the unit that hard and it gets hot. So after a couple of years of heating up and cooling the circuit board likes to flex, and can cause a broken solder joint. Hense when it heats up you loose remote, because the circuit to the ir receiver opens when it cools the circuit goes back and you get a connection again. It would be where I would start and if you know anything about circuit repairs it could be an easy fix.
Posted on Aug 03, 2006
Strange Problem. I suspect that your Reciever requires a service. And at that time, please ask the technician to replace all the Power supply Filter Capacitors, as well as the Output Audio amplifiers ICs Capasitors.With time, the Electrolytic capacitors dry up, and the circuits draw more current. This may cause overheating, and overloading of the Power supply as well the Output circuits.
Posted on Jun 29, 2006
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Posted on Jan 02, 2017
SOURCE: Technics SA-GX490 reciever
Disconnect receiver from power and open the unit. Localize fuse that is placed on small PCB between main transformer "big one" and rear panel.Fuse's amperage is 1.6 A .I'm quite confident that fuse is gone.If so, replace it with the one of same amperage and try unit.
My unit has done exactly the same to me with no reason.
Posted on Oct 04, 2008
I went to the HDTV plasma manual. It stated the only way the digital optical audio output would work (from this TV) was to go to the menu, select audio and turn off the TV speakers. Basically, it had nothing to do with the technics receiver.
Posted on Sep 17, 2009
Testimonial: "worked like a champ!"
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