Threads

Oct 26, 2008

- Sorry if you thought that I was threatening, it was not my intent. But a "Thanks for trying" rating is a bad rating which I felt was not deserved. By rating the solution before I have had an opportunity to communicate back and forth a few times does not give me the opportunity to even earn a FixYa! It is very rare that any equipment can be fully fixed with just one response. In fact, the person who has received credit and is getting paid for your problem is the one you should be getting help from. That person's handle on FixYa! is masterexpert

You should be able to contact him by just clicking on the name above if you would like to make him earn the money you have paid him. I am sorry if you felt I was threatening to not help. But it really is not fair to me, to be the one helping you, when somebody else has been paid already for answering your question. Sometimes FixYa! is not an easy site to get the ratings right and to make sure you are communicating with the person you really want to communicate with. It appears that the instructions for using the site and giving the ratings are not very well explained by FixYa!.

As for your Technics, I have no way of knowing how much experience you or your boyfriend have and just how good your skills are. I must assume at first that you do not know how to identify the problems. Now that I know your boyfriend is an industrial engineer and has good soldering skills, I can assume that he has probably touched up all the questionable solder joints.

Adding a fan may help for a little while, but it will probably still shut off eventually unless the receiver is located in a place that is not getting any ventilation. If you have other units stacked on top of the Technics, it could also be adding to the problem. They do need good ventilation.

The fan is working normal. It is only supposed to come on when the volume level reaches a certain threshold. You can see this in action by watching the fan and turing the volume up very slowly. It will turn on at a certain level and turn off when the level is back under that threshold. The problem know is to determain what is causing it to overheat. It can be one of several things. A single bad speaker can cause it, even if the speaker appears to be fine. If you have any speakers connected to the unit that area below the rated impeadance for the receiver it will cause the amp to overheat. I believe your unit is rated for 8 ohm speakers. If you are using speakers that are below that, it will overheat. Even if the speakers are rated at 8 ohms, you coulod have one or more that are now measuring under what they should be. If you have an ohm meter, you can check them right at the speaker wires. An 8 ohm speaker will normally measure at about 7 ohms, this is still normal. If they measure below that, you may have a bad driver in it and it could be causing the unit to shut off from overheating. It could also be a bad amplifier IC. Technics have some very expensive amplifier IC's and I have seen them cause overheating before. They cost about $100 for each IC, so if this is the problem it would not be a very economical repair.

There is another possibility that I have seen with these receivers over the years as well. The microprocessor may have some cold solder on it. But reflowing the micro requires the very best of soldering skills. It is a flat pack IC with about 80 pins on it and if soldered wrong it will damage it resulting in a dead unit. Unless your boyfriend has some experience soldering flat packs (surface mounted devices) I advise against trying it. It really does take excellent soldering skills. When the micro heats up, if it has bad solder on it it will shut down, or make other very strange symptoms. If this needs to be done, I can help describe how to reflow the solder on it, but I will take no responsibility for any damage caused by somebody with no experience in soldering surface mounted IC's.

Let me know if this helps you at all. Again, soryy if I came across as threatening before, it was not my intent. But if you really consider this situation with your problem you may realize thaqt it is not I who should be helping you fix your unit. It should be the person who was paid for you problem. And for future reference, you should not rate a solution until you are finished with all communication. A bad rating doesn't encourage anybody to continue to help. I was not asking you for a FixYa! before it was fixed. I was asking for the chance for a FixYa! but that is not possible for me now since you have already rated me. Even if I help you fix your problem, I have received a bad rating for helping you. I am hopeful you can understand what I am saying. I am not threatening you with no help, but if I have received a bad rating, what incentive is there to continue helping? Plus, somebody else was paid for the help I am giving you. Certainly, you must see how unfair this is to me. But I am still willing to help anyways, doesn't this say something about me?

Dave

Nov 05, 2008

- Since it is locking up on you after extended use, it could be a problem with the microprocessor or the crystal for the microprocessor. I have seen those as causes of these type of problems. Most of the time with the Technics receivers, the microprocessor is located on the display board. It is normally an 80 pin flat pack surface mounted IC. I do not have the schematic or service manual for this model, so I can not give you precise information. I am working off of memory only. Sometimes the microprocessor can have the solder reflowed and it will fix those problems, sometimes you need to replace the crystal. If you or your boyfriend have an O-scope you can check it to see if it is oscillating at the proper frequency, or at all. The crystal should also have about 2.5 volts DC on each side of it and the frequency is printed on the case, normally in Megahertz. To re-flow the solder on the microprocessor it take exceptional solder skills. Do all of this with the display board off completely. Use solder flux on the pins and put a very small amount of solder on one side at a time, just a tiny little dab (enough to bridge two pins). Then with the soldering iron, melt it and tilt the board, then run the iron along the pins with the board tilted so that gravity can help you roll the melted solder all the way down that side by dragging the iron over the pins very slowly and with very little pressure so as not to bend any pins. You may end up with a solder bridge somewhere on those pins, so make sure you inspect the board closely under a magnifying glass or the like, to be able to see each pin and the spaces in between them. If there are any pins soldered together, just use some solder wick to remove the bridged solder. Then you repeat this method for each of the other three sides of the micro. I normally do not advise anybody to reflow the micro, because if done wrong it can damage the micro and render the unit dead. But your boyfriend is an engineer and must be capable of paying very close attention to detail, which is vital for this procedure. If you do this and it causes damage, please do not blame me for it, I can do this in my sleep, but I have also been doing this for nearly 20 years, and I am now warning you of the potential problems with this procedure if not done very well. So if you are not certain of your soldering skills, please do not try this.

If you have a can of freeze spray, you can also try letting the unit get hot, then when it starts acting up, spray the freeze spray on a suspected bad area. If the freeze spray brings the unit back to normal operation, you may have found your problem. It is either bad solder in that spot, or a bad component breaking down after getting hot.

The problem with your unit is not going to be an easy one to figure out, but I think I have told you all the most likely suspects for it. It would also be wise to inspect your own work again and make sure you did not miss a few solder joints on the main amp board. Even the best technicians who do this work daily can miss something sometimes.

If this unit has a digital board, it could have a problem there as well. Sometimes the memory IC's need the solder re-flowed. I know this may sound crazy or very unlikely, but bad solder is a really common problem with stereo equipment because of the heat they generate. The heating and cooling process, over and over again for year after year really takes a toll on the solder joints.

Thats all for now, I would like to hear what that other expert has to say about helping you. Let's see if he can earn his money!

Dave

Nov 05, 2008

- By the way, the crystal has a reference number on it that starts with an "X" , an example would be "X701" or "X201". something like that, and is located right next to the microprocessor. The reference number should be printed on the board. Most crystals have 3 legs with the center leg being grounded, some have only 2 legs, but it should have that 2.5 volts DC on it as well as the oscillation. It has an A/C signal riding on a DC voltage. I hope this makes sense.