UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Other Vintage Household Electrical or Electromechanical Items

Notices

Other Vintage Household Electrical or Electromechanical Items For discussions about other vintage (over 25 years old) electrical and electromechanical household items. See the sticky thread for details.

Closed Thread
 
Thread Tools
Old 1st May 2018, 9:31 pm   #1
Colourstar
Octode
 
Colourstar's Avatar
 
Join Date: Feb 2006
Location: Ilkeston, Derbyshire, UK.
Posts: 1,397
Default 1980's Pansonic microwave - repairable?

Warning
Microwave ovens are, for all their deceptive simplicity, extremely dangerous. If you don't understand the risks, you really shouldn't attempt any work on one. If you do understand, it is possible to effect some repairs with care. It should not be necessary to work on one live, and always ensure that the capacitor is discharged first, as advised in this, and other threads.
----------------------------------------------------------------------------------------
This microwave, from the 'beige and brown' period, was purchased by my parents sometime around 1986 and has performed absolutely faultlessly for an impressive 32 years of use. That must equate to hundreds of meals, jacket spuds and puddings etc etc. Last week however I had a call to say that it had finally thrown in the towel. It still lights up and the turntable rotates, but there is no heating whatsoever.

I realise it's almost certainly the end of the line for this family friend, but before it goes down to the recycling centre, I thought I'd ask whether anyone had any dealings with these models. I guess it's the magnetron itself that has failed (don't worry I have absolutely no intention of delving inside as I'm aware of the dangers within). I think the meal heating became a bit luke-warm before finally going altogether.

The great thing about this microwave is it's size- you can stack two dinner plates and heat both meals in one go. Most modern microwaves lack the height to do this. It also has a stainless steel interior rather than the painted ones you tend to get now, which seem prone to rust quite rapidly. My parents are both well into their 80s, so finding a replacement that's easy for them to use and of decent capacity could be a challenge, assuming the trusty Panasonic really has bleeped its last....

Steve
Attached Thumbnails
Click image for larger version

Name:	microwave.jpg
Views:	2306
Size:	64.9 KB
ID:	162122  

Last edited by AC/HL; 7th May 2018 at 4:17 pm. Reason: Warning added
Colourstar is offline  
Old 1st May 2018, 9:58 pm   #2
Boater Sam
Banned
 
Join Date: Dec 2013
Location: Middlewich, Cheshire, UK. & Winter in the Philippines.
Posts: 3,897
Default Re: 1980s Pansonic microwave - repairable?

Most 'quiet' failures are simple fixes, high voltage fuse, diode, capacitor. Magnetrons are valves and as such are very reliable with ovens of this age.
Noisy failures are more likely to be major parts.
Boater Sam is offline  
Old 1st May 2018, 10:01 pm   #3
julie_m
Dekatron
 
Join Date: May 2008
Location: Derby, UK.
Posts: 7,735
Default Re: 1980s Pansonic microwave - repairable?

If the magnetron has had it, the oven has had it. But the rectifier diode could have failed, or the capacitor. A microwave oven of that age is unlikely to have a fuse in the EHT.

Remember there are no second chances with microwave ovens. Be sure the capacitor is discharged! It should have an internal bleed resistor, but don't trust that after all this time.
__________________
If I have seen further than others, it is because I was standing on a pile of failed experiments.
julie_m is offline  
Old 2nd May 2018, 10:26 am   #4
broadgage
Nonode
 
Join Date: Jan 2010
Location: North Somerset, UK.
Posts: 2,129
Default Re: 1980s Pansonic microwave - repairable?

Microwave ovens are, internally, one of the most hazardous domestic appliances, due to the presence of thousands of volts at dangerous currents.
No reason why a suitably experienced person should not investigate but do please be very cautious.

The risks are arguably at least as great as some early TV sets in which the EHT is mains derived.

Though dangerous, microwave ovens are not that complex and spares are fairly readily available on line, so repair can be worthwhile.
If the step up transformer or the magnetron have failed, the oven is BER, most other components are worth replacing.
broadgage is online now  
Old 2nd May 2018, 10:47 am   #5
vinrads
Dekatron
 
Join Date: Feb 2009
Location: Chesterfield, Derbyshire, UK.
Posts: 3,738
Default Re: 1980s Pansonic microwave - repairable?

Note ! if the touch pad is faulty , you won't get a replacement I speak from experience, as far as I know you can get the capacitor /diode and the magnetron. Mick.
vinrads is offline  
Old 2nd May 2018, 11:49 am   #6
bikelectro
Pentode
 
Join Date: Jun 2008
Location: London, UK.
Posts: 157
Default Re: 1980s Pansonic microwave - repairable?

I've repaired many with no heat. If not anything shorted or blown - CHECK ALL CAPACITOR, MAGNETRON ETC. CONNECTIONS ARE DISCHARGED. Then clean the connections on the capacitor and particularly on the magnetron. Remove each in turn and clean with Brasso, re-tension if necessary and refit. I have had this cure so many! I think continuity to the magnetron's fillament may be lost as it's such low volts. There were never any bounce-backs with the many successes.
bikelectro is offline  
Old 2nd May 2018, 11:51 am   #7
Nickthedentist
Dekatron
 
Nickthedentist's Avatar
 
Join Date: Jan 2005
Location: Oxford, UK.
Posts: 17,820
Default Re: 1980s Pansonic microwave - repairable?

Yes, I'd have a go. Unplug it, ensure the cap's fully discharged (fit a shorting lead for peace of mind), then rely on cold, resistance checks to do your fault finding as far as possible.
Nickthedentist is online now  
Old 2nd May 2018, 12:04 pm   #8
bikelectro
Pentode
 
Join Date: Jun 2008
Location: London, UK.
Posts: 157
Default Re: 1980s Pansonic microwave - repairable?

You can just pull off and re-seat as a quick check - if it this issue, that will get it going, then go back and clean properly. If not that - it's worth doing a visual check on the PCB that there is no dry joint on the relay that switches on the magnetron circuit. Again a warning to discharge! One of the few times the circuit can hold charge is when there is a bad connection and the magnetron doesn't consume the power!
bikelectro is offline  
Old 2nd May 2018, 1:03 pm   #9
Sideband
Dekatron
 
Sideband's Avatar
 
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,550
Default Re: 1980s Pansonic microwave - repairable?

I know someone who had a very lucky escape with an older microwave. It was just a moments distraction and forgetting the HV cap holds a charge......he was thrown against the opposite wall (some 6 feet away) and very luckily didn't smash his head against the wall. He reckons he completely blacked out at the moment of contact with the HV and doesn't remember hitting the wall. He was out completely when we rushed over to him but was conscious a few seconds later. He was dazed and completely disorientated for some minutes during which time someone had called an ambulance. He was still confused when they arrived and he went to the local hospital for observation.

Fortunately there were no lasting effects and he was home the next day. Apart from a large bruise down his arm he was fine. He carried on repairing microwaves but with much more caution and a huge amount of respect for the hidden dangers. He developed a new way of working after that but always joked that at least he'd lived to tell the tale to others so that they didn't do the same thing......

I've changed a few magnetrons but much more common is the door switch or the rectifier. Whatever you do, make sure the capacitor is discharged before doing anything at all.
__________________
There are lots of brilliant keyboard players and then there is Rick Wakeman.....
Sideband is offline  
Old 2nd May 2018, 4:24 pm   #10
bikelectro
Pentode
 
Join Date: Jun 2008
Location: London, UK.
Posts: 157
Default Re: 1980s Pansonic microwave - repairable?

A lot of people must have changed magnetrons when cleaning its connectors was all that was needed. It won't be the door switch in this case I think because it is going through the motions.

Sideband, that's some story! I heard similar and it has made me extra careful. I discharge all connections on the cap and magnetron to the oven casing - seldom see much discharge making me at times doubt the stories - but they are so horrific that I continue the good practice in any case.
bikelectro is offline  
Old 2nd May 2018, 5:05 pm   #11
ex 2 Base
Heptode
 
Join Date: Nov 2009
Location: Scarborough, North Yorkshire, UK.
Posts: 507
Default Re: 1980s Pansonic microwave - repairable?

First discharge the capacitor, incidentally the shock from it is no worse than that from a discharge light fitting *. I think they have a glass type odd amperage fuse. Clean the outlet grill from the wave guide. Piece of burnt food can cause arcing which makes people really afraid, they think it will kill them. If it needs a new transformer or magnetron scrap it as they cost more than the price of cheap new one. CPC used to stock all the spares.

* See post 46
ex 2 Base is offline  
Old 2nd May 2018, 6:54 pm   #12
Richard
Heptode
 
Richard's Avatar
 
Join Date: Feb 2003
Location: Garnant, near Ammanford, South Wales, UK.
Posts: 657
Default Re: 1980s Pansonic microwave - repairable?

Looks like a NE993 or 992, repaired many.

If it goes through the motions most likely a HT fault.
No HT fuse or short protector on machine this old.

All HT components will be available, or a near enough one.

If its making a deep hum there is a HT short, any of the HT components, transformer HT short will be accompanied by smoke.

If no deep hum, either no power to transformer or most likely magnetron filament feed, poor contact to mag tag or where the wire is crimped in the tag.

As other have said beware the HT running, or charged capacitor.
__________________
BVWS member.
Richard is offline  
Old 2nd May 2018, 7:22 pm   #13
Colourstar
Octode
 
Colourstar's Avatar
 
Join Date: Feb 2006
Location: Ilkeston, Derbyshire, UK.
Posts: 1,397
Default Re: 1980s Pansonic microwave - repairable?

Thanks everyone for the replies, I really wasn't expecting any interest. Really fascinating reading and I do heed all warnings of extra respect for the voltages within.

There's no abnormal deep hum when it's on, which is hopeful. It sounds just as it always does. And thanks Richard for suggesting model numbers, as the label on the back is illegible.

I know for a fact the thing will be absolutely full of fluff judging by the back vent. I'll blow it out and take an internal photo. Cleaning up any push-on tag connections is about as far as I'll be able to go with it, but it's worth a try.

Steve
Colourstar is offline  
Old 2nd May 2018, 8:15 pm   #14
Ambientnoise
Heptode
 
Join Date: Feb 2006
Location: Marlborough, Wiltshire, UK.
Posts: 915
Default Re: 1980s Pansonic microwave - repairable?

I had this exact model where the hv capacitor went short circuit. Straightforward repair but heed the warnings !

Ken
Ambientnoise is offline  
Old 2nd May 2018, 8:24 pm   #15
Mike Fulton
Pentode
 
Mike Fulton's Avatar
 
Join Date: Apr 2006
Location: 7 Miles North of Durham, UK.
Posts: 130
Default Re: 1980s Pansonic microwave - repairable?

Looks like a NE-665 circa 2001 to me...
Mike Fulton is offline  
Old 2nd May 2018, 8:28 pm   #16
Colourstar
Octode
 
Colourstar's Avatar
 
Join Date: Feb 2006
Location: Ilkeston, Derbyshire, UK.
Posts: 1,397
Default Re: 1980s Pansonic microwave - repairable?

Yes it was full of fluff! I've cleaned up the connections all of which looked dull. This microwave does in fact include several fuses and I may have located the problem: The fuse arrowed on the circuit diagram has failed. The other fuse off the HV cap to the magentron is intact.
Steve
Attached Thumbnails
Click image for larger version

Name:	Pana1.jpg
Views:	385
Size:	92.8 KB
ID:	162178   Click image for larger version

Name:	Pana2.jpg
Views:	377
Size:	91.6 KB
ID:	162179   Click image for larger version

Name:	Pana3.jpg
Views:	470
Size:	77.7 KB
ID:	162180   Click image for larger version

Name:	Pana4.jpg
Views:	295
Size:	63.4 KB
ID:	162181   Click image for larger version

Name:	Pana5.jpg
Views:	259
Size:	48.0 KB
ID:	162182  


Last edited by Colourstar; 2nd May 2018 at 8:35 pm.
Colourstar is offline  
Old 2nd May 2018, 8:52 pm   #17
Boater Sam
Banned
 
Join Date: Dec 2013
Location: Middlewich, Cheshire, UK. & Winter in the Philippines.
Posts: 3,897
Default Re: 1980s Pansonic microwave - repairable?

There is no need to ever work on a microwave that is powered up.
I used to train engineers and they were instructed how to fault find without power.

That fuse will stop it working, hopefully if replaced the oven will work. It has probably failed with a surge or flash over due to the fluff and grease.
Boater Sam is offline  
Old 2nd May 2018, 8:59 pm   #18
Station X
Moderator
 
Station X's Avatar
 
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,192
Default Re: 1980s Pansonic microwave - repairable?

Wow!

I'm not used to seeing 2400 VAC on a diagram!
__________________
Graham. Forum Moderator

Reach for your meter before you reach for your soldering iron.
Station X is online now  
Old 2nd May 2018, 9:08 pm   #19
Boater Sam
Banned
 
Join Date: Dec 2013
Location: Middlewich, Cheshire, UK. & Winter in the Philippines.
Posts: 3,897
Default Re: 1980s Pansonic microwave - repairable?

4000 VDC after the voltage doubler, more if the mag is O/C !
Boater Sam is offline  
Old 3rd May 2018, 10:13 pm   #20
Colourstar
Octode
 
Colourstar's Avatar
 
Join Date: Feb 2006
Location: Ilkeston, Derbyshire, UK.
Posts: 1,397
Default Re: 1980s Pansonic microwave - repairable?

Before I replace the blown 500ma fuse, Im wondering about the condition of the diode in series with it. Presumably a short in that would cause the fuse to pop, although I can't get any reading either way from the diode on a meter....

Steve

Last edited by Colourstar; 3rd May 2018 at 10:18 pm.
Colourstar is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 12:27 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.