20 Most Recent Panasonic NN-T990SA Microwave Oven - Page 4 Questions & Answers

Moisture accumulation can sometimes be caused if the cooling fan is not running properly or if the vents in the back are blocked or there is not enough free space around the sides and back of the microwave.

One thing that helps is to keep the door open a few minutes after using it and to wipe down the inside after use.

If the cavity metal of the oven is chipped or charred, it will have to be sanded smooth and clean and dried thoroughly.

Then you can apply some high-temperature appliance paint, available from places like Wal-Mart, Lowe's or Builder's Square.

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

This is usually caused by either a bad door switch, a loose door switch mount (which are pretty simple problems to fix) or occasionally a problem on the control panel.

Even though a door switch clicks, it may still be bad inside.

Door switch or mount trouble can be caused by slamming the door or by opening the door while it's cooking without hitting the Stop pad first.

There are plastic mounts inside the microwave which hold the door switches and onto which the door latches lock when you close the door.

The screws on these mounts may be loose. If they get too loose, the switches will not be activated properly.

Sometimes it's a broken tab on the switch holder, allowing the switch to rotate just out of position. This tab can be hard to see, since it is under the bottom edge of the switch.

If you or someone you know decide to look into it, we have critical information on safety, disassembly and door switches at our site, and our link is at our listing here on FixYa:.

The best place to order parts is Tritronics. You can also call them at 866-779-5835

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

no prende

Without HV test equipment it is quite difficult to determine if it is the magnetron or inverter.

5 years is a little short for magnetron failure but it appears that this is about all you can expect these days from a magnetron - the best I have seen was 11 years. I have not seen an inverter failure as yet (although I am not a full time repair man). The main reason I suspect it is the magnetron is the short time period from start to stop - it is typical of magnetron failure in Panasonic microwaves.

As regards door hinge side, that is one of the great unknowns. I suspect it comes from most people being right handed but even refrigerators could be specified as right/left hand hinged originally and now can be changed by customers.

Usually this indicates failure of the magnetron and/or the inverter. Neither is easy to test without specialised HV equipment. Often the cause is operating the oven without anything in it. If this has happened, it will generally be failure of the magnetron.

Replacement of the magnetron is relatively easy (about 15 minutes) and the inverter a little longer but if you do not have the knowledge/skills please do not do it - there are very dangerous (deadly) voltages associated with magnetrons even after they have been switched off.

Cost of magnetrons ranges upwards from USD25 to USD100 (from Panasonic spare parts) and inverters range upwards from USD125. The cost of parts is often the reason microwave ovens are not repaired.

Doug

yes, get that fixed. it is a danger.

This model uses an inverter to produce high voltage instead of a convential transformer system. While an inverter (switched-mode power supply) is more efficient from a power consumption standpoint, it is more complex, thus more statistically prone to fail. These should only be examined and worked on by someone who has the necessary technical qualifications. Seriously. Often the machine-soldered connections in a microwave inverter are too weak, so they eventually fail, especially if heat is high in the area. They sometimes fail catastrophically. When not catastrophically damaged, you may hear clicking or squealing and may smell an electrical odor, which is sometimes obscured by the cooling fan. Some manufacturers do not encourage or assist technicians to repair microwave inverters. Most offer the inverter as a whole assembly. But sometimes that is actually cheaper than the time and labor required to fix the old one. If a technician is willing and able to troubleshoot and repair the inverter to component level, it will may be expensive, but may be worth it, especially if he or she will resolder and reinforce connections as needed as part of a thorough repair. That could easily make your inverter beter than a new one! You might be able to get some verbal estimates if you call Panasonic-authorized repair shops and ask then specifically about inverter repair and inverter replacement costs for your model number.

well you should problee buy a new one i hope you arent to old

all microwaves have 2 safety switches at least... but these are tied to a set of relays that turn it on, my bet is a sticking or stuck relay because you unplug it right and plug back in its not running?-relay ... if always runs driver transitors.

It sounds like a probemI with the inverter.

Due to the lethal voltages used and produced, I do not recommend that an inexperienced person work on these.

I would recommend that you contact your nearest Panasonic-authorized servicer. You can find one here:

http://www2.panasonic.com/webapp/wcs/stores/servlet/vServiceLocator?storeId=15001

sir,

Try this link for the manual to repair it.

http://www.eserviceinfo.com/browse.php?id=36

www.yinyanghome.com/Products/Icebox/Microwave.pdf

In most cases, this is a problem with the inverter or a bad magnetron.

Due to the lethal voltages used and produced, I do not recommend that an inexperienced person work on these.

I would recommend that you contact your nearest Panasonic-authorized servicer. You can find one here:

http://www2.panasonic.com/webapp/wcs/stores/servlet/vServiceLocator?storeId=15001

We're happy to help and we appreciate your thoughtful rating of our answer.

the buzzing is the magnatron tube juicing too thousands of volts before emmitting the micro-wave radiation to what your cooking that turns molecules 180 degrees around... guess that friction is what really heats it.
radar ovens is what they use to call em and even people would stand in front of big ones to warm up long ago...lol canibles will love that.

In most cases, this is a problem with the inverter or a bad magnetron.

Due to the lethal voltages used and produced, I do not recommend that an inexperienced person work on these.

I would recommend that you contact your nearest Panasonic-authorized servicer. You can find one here:

http://www2.panasonic.com/webapp/wcs/stores/servlet/vServiceLocator?storeId=15001

We're happy to help and we appreciate your thoughtful rating of our answer.

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This problem may have already been dealt with, but others can benefit from an accurate, thoughtful reply to this problem.

This is usually caused by either a bad door switch, a loose door switch mount, or a problem on the control panel.

Even though a door switch clicks, it may still be bad inside.

If you or a friend decide to look into it, we have critical information on safety, disassembly and door switches at our site, linked here on Fixya: http://tinyurl.com/yzjozk

I would say this one was just a bad door switch.

Yes these are torx safety bits could be a t-10,t-15, or t-20.  Replace the fuse and see what you get.

In this one, the most likely causes are the inverter or magnetron, but it really will need an experienced troubleshooter. Due to the lethal voltages involved, I do not recommend that a person without training and experience ever work on these models. You should be able to locate a Panasonic-authorized servicer here: http://www.pasc.panasonic.com/WhereTo/FindServicer.asp?Pass=1 I would mention the exact symptom when you call so the technician can bring a new inverter with him when he comes out to repair it. Might save you having it pulled into the shop.

You're on the right track. That panel is the waveguide cover.

This is usually due to grease or food particles stuck to the inside of the oven or stuck on or behind the waveguide cover in the waveguide just out of sight.

It can be fragile, and the metal edges behind it can be sharp, so be careful!

The cover and the metal behind it should be cleaned with a mild, non-ammonia cleaner.

If the cavity metal of the oven is chipped or charred, it will have to be sanded smmoth and clean.

Then you can apply some high-temperature appliance paint, available from places like Wal-Mart or Lowe's.

If your waveguide cover is burned, it will need to be replaced.

To order Panasonic parts see http://www.pasc.panasonic.com/epartr

They do this to avoid liability from your exposure to the instantly lethal voltages present in and generated by your microwave oven. For important safety and disassembly tips, search on Yahoo.com (not Google) for all this at once (copy & paste): microwave disassembly.txt safety.txt The oven must first be disconnected from the power line. The outer cover is held in place by several screws on the back and sides, then you lift up and back from the rear to remove it. You need to avoid the sharp metal edges on thge cover and inside the oven. Note there are also catches built into the top & sides of the cover which must be re-engaged upon reassembly, or the cooling efficiency will be compromised. Once the cover's off, if there's any chance you might come into contact with any of the high voltage connections, the high voltage capacitor should be discharged for safety's sake. Once the bulb is located, it can be unscrewed and replaced.