I think if I had a microwave that could operate with its door opened I would get rid of it immediately!Time for a new one.Another interesting use for the Panasonic invertor power supply-HV supply for "ham" radio RF power amp.Guess gone are the days of using surplus power company pole pigs for that!And sometimes those pole pigs were used as 3 ph power supplies in commercial transmitters where the station owner was too cheap to get the proper replacement transmformer or it just wasn't no longer available.Our GE transmittters have HV rectifier transformers that are in pole pig enclosures.4160V primary-8kv sec.Used in our GE 250Kw transmitters-one bank of transformers for the 12Kv RF power amp supply another for the 15Kv modulator supply.and a pole mount transformer that has 4160V primary-230V sec-115Kva.This is for the LV supplies and pump,blower motors.All these transformers sit on the vault floor.
New microwave: inverter?
- Thread starter jeffg
- Start date
Help Support :
davetranter
Well-known member
Hydraulique
My most profound apologies.... I have just re-read your post, and also my own. I did not think for a minute that you would deliberately disable the door interlock, I suspected that it was a mechanical repair which had -eventually- jammed in the 'door closed' position, I inadvertently omitted that word from my post. You make it clear, however, that the interlock failure was a completely separate event.
My own 'daily driver' is an old Samsung RE570D, which I picked up about 15 or more years ago from where it had been placed beside (not in) one of the dumpsters at our local tip/recycling site. I took the fact that it's previous owner had placed it outside the skip/dumpster to mean that he had considered it to be reuseable/repairable, so took it home. (I am actually gently heating a can of Baked Beans in it as I type this). The repair was simplicity itself. The timer motor was a 100-120V model with a series resistor for 220/240V operation. The series resistor had gone open circuit, resulting in it operating at 'Full Power' for as long as you left the door closed. Within an hour of bringing it home I had a working Microwave. Back then, Microwave ovens were still quite expensive and considered 'exotic' on this side of the 'pond', and it was not an appliance which I would have considered buying at the time. I now have a couple of 'spare' ovens, including a 900W Microwave / fan oven combination, which I use for the fan oven. The low (500W??) power of the old Samsung means that I avoid the intermittent boil/spatter problems that I see friends dealing with from their newer, higher powered, devices.
All best
Dave T
P.S. Beans on Toast is a very much underrated meal... As is Cheese on Toast..
P.P.S. In my book, 'bodging' is GOOD. It's how I keep most of my appliances going... ;-)
My most profound apologies.... I have just re-read your post, and also my own. I did not think for a minute that you would deliberately disable the door interlock, I suspected that it was a mechanical repair which had -eventually- jammed in the 'door closed' position, I inadvertently omitted that word from my post. You make it clear, however, that the interlock failure was a completely separate event.
My own 'daily driver' is an old Samsung RE570D, which I picked up about 15 or more years ago from where it had been placed beside (not in) one of the dumpsters at our local tip/recycling site. I took the fact that it's previous owner had placed it outside the skip/dumpster to mean that he had considered it to be reuseable/repairable, so took it home. (I am actually gently heating a can of Baked Beans in it as I type this). The repair was simplicity itself. The timer motor was a 100-120V model with a series resistor for 220/240V operation. The series resistor had gone open circuit, resulting in it operating at 'Full Power' for as long as you left the door closed. Within an hour of bringing it home I had a working Microwave. Back then, Microwave ovens were still quite expensive and considered 'exotic' on this side of the 'pond', and it was not an appliance which I would have considered buying at the time. I now have a couple of 'spare' ovens, including a 900W Microwave / fan oven combination, which I use for the fan oven. The low (500W??) power of the old Samsung means that I avoid the intermittent boil/spatter problems that I see friends dealing with from their newer, higher powered, devices.
All best
Dave T
P.S. Beans on Toast is a very much underrated meal... As is Cheese on Toast..
P.P.S. In my book, 'bodging' is GOOD. It's how I keep most of my appliances going... ;-)
davetranter
Well-known member
Tolivac
My 100KV laboratory supply (and also a smaller 15KV unit) was made by the (now defunct) U.K. based company of Brandenburg High Voltage. They are similar in all respects to the series of high voltage laboratory supplies manufactured in the U.S. by Messrs. Glassman Inc., Information on which I am sure will be available Online.
A useful feature of the 15KV unit is that the rectifier block is reversible, so it can supply positive or negative voltage with respect to ground.
All best
Dave T
My 100KV laboratory supply (and also a smaller 15KV unit) was made by the (now defunct) U.K. based company of Brandenburg High Voltage. They are similar in all respects to the series of high voltage laboratory supplies manufactured in the U.S. by Messrs. Glassman Inc., Information on which I am sure will be available Online.
A useful feature of the 15KV unit is that the rectifier block is reversible, so it can supply positive or negative voltage with respect to ground.
All best
Dave T
Dave:Besides the transmitters we have 4 portable HV "power supplies" that are Hi Pot testers.They are used for testing HV components in the transmitters without using the transmitter supply.These units are also used to cook "gas" out of new power tubes and vacuum capacitors.Better to cook the gas from these parts with the current limited Hi Pot tester than the high current supplies in the transmitters.The transmitter and the components will be damaged.We have two Phenix Technologies 0-70kv 10Ma DC high pot testers and two AC high pot testers-0 to 50Kv.They are rated at 30Ma.One is GE the other is Comet-same company that makes Comet vacuum capacitors.All units have 120V primary inputs except the Comet unit-its 208V.Used mainly in the shop since there is a 208V outlet there.AC Hi pots CANNOT be used for testing or cooking tubes-will damage them-they can be used on vacuum capacitors.And the AC Hipots can be used for testing AC HV supply cables.I suppose your HV Lab supply could be somewhat similar to our HiPot testers.What is the current rating of the supplies you use?Our second Phenix unit is used in the tube and capacitor room to cook gas from tubes and vac caps-sometimes you may have to run the unit for a couple days to cook the gas from tubes or caps.Once the gas is cooked out the shelf life of the part is longer.Internal parts of tubes and caps absorb gas from when they were made-and very slight gas "seepage" in the tube or capacitor seals-esp if the tube or capacitor has a ceramic case.The ceramic is slightly porus and gas molecules can slowly seep thru it.
davetranter
Well-known member
Tolivac
Sorry everyone.... Really not trying to 'hijack' the thread....
My 0-15KV supply is only rated to about 3mA or so. Not so sure about the 0-100KV supply. The data plate only rates it to about 100W continuous, but on the odd occasion when I've had a flashover from it, the fatness, sound, and duration of the spark before the protection trips indicates that there is some considerable 'horsepower' under the bonnet. (And also why I say it doesn't give 'second chances') ;-)
Sounds very like your DC Hi-Pot testers (which I have a couple of, rated at 0-15 and 0-20KV), except that the testers seem more robust in construction, being designed to withstand regular shorts due to failure of Devices Under Test. The 'lab' type supplies are designed to provide a few mA of continuous supply to (cathode ray??) equipment in physical laboratories.
All best
Dave T
P.S. All 240V 1ph
Sorry everyone.... Really not trying to 'hijack' the thread....
My 0-15KV supply is only rated to about 3mA or so. Not so sure about the 0-100KV supply. The data plate only rates it to about 100W continuous, but on the odd occasion when I've had a flashover from it, the fatness, sound, and duration of the spark before the protection trips indicates that there is some considerable 'horsepower' under the bonnet. (And also why I say it doesn't give 'second chances') ;-)
Sounds very like your DC Hi-Pot testers (which I have a couple of, rated at 0-15 and 0-20KV), except that the testers seem more robust in construction, being designed to withstand regular shorts due to failure of Devices Under Test. The 'lab' type supplies are designed to provide a few mA of continuous supply to (cathode ray??) equipment in physical laboratories.
All best
Dave T
P.S. All 240V 1ph
Our Hipot testers do have adjustable current limit-least the Phenix ones do-so the device under test is not damaged-the supply just trips off.The AC hipot testers do not have this-the Comet one does have a current limiting resistor on the HV secondary side to limit current.The older GE one does not.These don't get much use here.Unlike the hipot testers the lab supplies have lower ripple in their output-and tighter-more precise voltage regulation.The testers here have that sharp arcing sound as well-but when the power supplies in the transmitters arc over it is a very LOUD arc like the ripping of canvas!And things get burned.One time when one of the Continental Electronics 15Kv main power supply arced-it found an old abandoned ground wire imbedded in the concrete block vault wall-burned thru 2 in of concrete to find it!This transmitter supply can develop 15Kv at up to 60A-that hole burned in the wall looked like something done with a plasma torch!The patch on the wall is still there.when a grasshopper fuse blows on one its filter caps-sounds like a rifle shot!And if you are nearby-you jump out of your skin!
davetranter
Well-known member
Microwave Inverter HV Supply
Earlier today I found the Inverter Supply which I mentioned in reply #12. It appears to be identical to the one which Kb0nes repaired some time ago (link in reply#15). Does anyone have any schematics for the Inverter or control panel?? Is it voltage controlled or some kind of PWM?? Any and all help would be appreciated, as this seems as good a time as any to investigate. Yes, I do have a suitable HV probe, and can probably fabricate a capable dummy load.
All best
Dave T
Earlier today I found the Inverter Supply which I mentioned in reply #12. It appears to be identical to the one which Kb0nes repaired some time ago (link in reply#15). Does anyone have any schematics for the Inverter or control panel?? Is it voltage controlled or some kind of PWM?? Any and all help would be appreciated, as this seems as good a time as any to investigate. Yes, I do have a suitable HV probe, and can probably fabricate a capable dummy load.
All best
Dave T
Dave,
If yours is indeed a Panasonic board there isn't a lot of information floating about out there. Panasonic considers them to be "non-serviceable". The link takes you to a .pdf an Australian ham put together on the original version of the inverter circuit.
There is a fairly complete diagram of the actual power circuitry itself. Of course this is easy to reverse engineer anyhow. The mystery is more around the power control board circuit although I think its pretty well known that its a simple duty cycle control from the microprocessor control of the oven. There does appear to be a bit of smarts there for voltage and current monitoring too.
http://www.vk3hz.net/amps/Microwave_Oven_Inverter_HV_Power_Supply.pdf
If yours is indeed a Panasonic board there isn't a lot of information floating about out there. Panasonic considers them to be "non-serviceable". The link takes you to a .pdf an Australian ham put together on the original version of the inverter circuit.
There is a fairly complete diagram of the actual power circuitry itself. Of course this is easy to reverse engineer anyhow. The mystery is more around the power control board circuit although I think its pretty well known that its a simple duty cycle control from the microprocessor control of the oven. There does appear to be a bit of smarts there for voltage and current monitoring too.
http://www.vk3hz.net/amps/Microwave_Oven_Inverter_HV_Power_Supply.pdf
Dont know if they still make or even sell anything in the usa but never buy a samsung unit. I had 1 a few years ago loved it but the thing after 1 week of use became a death trap run with door open start itself and so on. I cut the cord and never will buy anything samsung aging. I even called samsung over this and there reply was a joke we will give you a refund and you must send the old one back to u. I took the lost thing weight as much as a tv so never sent it to them.
This was the one I had new was about $389.00
http://www.amazon.com/SAMSUNG-MT1088SB-Toast-Bake-Microwave/dp/B000083GO8
This was the one I had new was about $389.00
http://www.amazon.com/SAMSUNG-MT1088SB-Toast-Bake-Microwave/dp/B000083GO8
As an Amazon Associate we earn from qualifying purchases.
davetranter
Well-known member
Thanks, Kb0nes
Thanks for the link (reply#27). I have read through the PDF and will consider contacting the author directly, since he seems to have encountered the same problem which I would anticipate... That of modifying the circuit to provide a largely constant voltage.
I'll let you all know how I get on...
All best
Dave T
Thanks for the link (reply#27). I have read through the PDF and will consider contacting the author directly, since he seems to have encountered the same problem which I would anticipate... That of modifying the circuit to provide a largely constant voltage.
I'll let you all know how I get on...
All best
Dave T
