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 > Vintage Radio (domestic)

Notices

Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

Reply
 
Thread Tools
Old 15th Jun 2021, 6:40 pm   #21
Gabe001
Heptode
 
Join Date: Oct 2019
Location: Stockport, Greater Manchester, UK.
Posts: 627
Default Re: KB MR10 sudden fault, help needed

A quick picture to show the short caused by a small patch of carbonised paxolin which I scooped out. You can see the cavity marked in purple
Attached Thumbnails
Click image for larger version

Name:	IMG_20210615_160840.jpg
Views:	77
Size:	57.4 KB
ID:	235962  
Gabe001 is online now   Reply With Quote
Old 20th Jun 2021, 2:05 pm   #22
Gabe001
Heptode
 
Join Date: Oct 2019
Location: Stockport, Greater Manchester, UK.
Posts: 627
Default Re: KB MR10 sudden fault, help needed

Back in business, but it took me the whole weekend to sort. I don't know how some of you do this for a living and manage to put food on the table!

The cavity in the paxolin was sealed and filled with milliput. The short is gone.

The set was silent as I disturbed one of the connections on the waveband switch as I was removing the charred area. Resoldering it sorted AM which is working well.

FM was a different story. It transpires that the reason why FM went out of alignment (XS Manchester at 106 appearing at the 100 mark and 2 stations stretched across the whole band) was because a solder joint between c9 and L5 had failed. I think it's OK now but I need to run it for a while and see.

Now I just need to fix the knobs I broke to get the set out...
Gabe001 is online now   Reply With Quote
Old 20th Jun 2021, 2:43 pm   #23
Gabe001
Heptode
 
Join Date: Oct 2019
Location: Stockport, Greater Manchester, UK.
Posts: 627
Default Re: KB MR10 sudden fault, help needed

Thank you to all those who helped, especially for directing me to look for charred paxolin. I don't think I would have sorted this by myself.

The radio is back together now and back in the kitchen and playing radio X without issue.

This experience has highlighted the need for me to invest in a signal generator. Doing the RF alignment by trying to identify the stations from their internet streams was a nightmare.

Gabriel
Gabe001 is online now   Reply With Quote
Old 20th Jun 2021, 7:31 pm   #24
rambo1152
Nonode
 
rambo1152's Avatar
 
Join Date: May 2010
Location: Manchester, UK.
Posts: 2,789
Default Re: KB MR10 sudden fault, help needed

Gabriel, I can't think of a more difficult fault to find than an inaccessible wafer switch tracking to ground. Don't be too modest, you found where the fault was using logical deduction. Well done.
__________________
--
Graham.
G3ZVT
rambo1152 is offline   Reply With Quote
Old 20th Jun 2021, 8:57 pm   #25
crackle
Dekatron
 
crackle's Avatar
 
Join Date: Mar 2011
Location: Basildon, Essex, UK.
Posts: 4,050
Default Re: KB MR10 sudden fault, help needed

Yes this was not a run of the mill fault. So congratulations for finding and rectifying it.
Mike
__________________
BVWS Member, 2E1MJE
The KB Museum

My collection in the Radio Museum
crackle is offline   Reply With Quote
Old 21st Jun 2021, 12:58 pm   #26
Sideband
Dekatron
 
Sideband's Avatar
 
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 6,210
Default Re: KB MR10 sudden fault, help needed

Quote:
Originally Posted by Gabe001 View Post
I don't know how some of you do this for a living and manage to put food on the table!
Most of us don't anymore and those of us that are still in the trade would not be tackling jobs like leaky switches....at least not these kind of switches. Back in 'the day' a replacement switch will have been ordered and fitted or....if the set was more than around 10 years old, it probably would have been scrapped as not economical or just made to work on one waveband if the owner was happy with that.

It would be interesting to know if wavechange switches gave trouble like yours. I suspect very few.....after all it's taken 50 odd years for the switch to fail and that is way beyond the the expected life of the radio.
__________________
On Spike Milligan's headstone......I told you I was ill...
Sideband is offline   Reply With Quote
Old 21st Jun 2021, 1:10 pm   #27
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 11,074
Default Re: KB MR10 sudden fault, help needed

Paxolin tracking used to occur back in the day, I remember some tag strips doing it and some TV system switches.

Lawrence.
ms660 is online now   Reply With Quote
Old 21st Jun 2021, 1:22 pm   #28
Techman
Dekatron
 
Techman's Avatar
 
Join Date: Nov 2009
Location: Lincolnshire, UK.
Posts: 3,764
Default Re: KB MR10 sudden fault, help needed

Quote:
Originally Posted by Gabe001 View Post
back in the kitchen and playing radio X without issue.
That's likely to be why it tracked in the first place. A kitchen with all the moisture in the air from cooking is a common cause for any set using HT voltages to start having tracking problems across switches etc. Either use a battery operated transistor set in the kitchen or turn on the valve set and let it warm up internally well before you start any cooking or you'll have the same thing happen again.
Techman is offline   Reply With Quote
Old 21st Jun 2021, 1:32 pm   #29
Gabe001
Heptode
 
Join Date: Oct 2019
Location: Stockport, Greater Manchester, UK.
Posts: 627
Default Re: KB MR10 sudden fault, help needed

Techman is right. It's next to the kettle
This is almost certainly the cause.
I need to shift things around.
Gabe001 is online now   Reply With Quote
Old 21st Jun 2021, 2:00 pm   #30
Techman
Dekatron
 
Techman's Avatar
 
Join Date: Nov 2009
Location: Lincolnshire, UK.
Posts: 3,764
Default Re: KB MR10 sudden fault, help needed

Yes, I've had valve sets in the kitchen, but kept them as far away as possible from cooking and kettles. I now use a little Ferguson 4 band mains battery transistor set that came in a job lot box of old radios from a junk sale several years ago and guess what, it sits right between the kettle and the cooker, inches away from both of them and works just fine - a valve set wouldn't survive in such a position. I used to run a CRT TV in the kitchen and that used to hiss and crack to the point that it had to be switched off PDQ if cooking had already started before it had been switched on. So long as the set had been switched on and allowed to warm up before the commencement of any cooking, everything was fine with no EHT tracking, which was bad enough when it happened to knock the tuning completely off station.
Techman is offline   Reply With Quote
Reply

Thread Tools



All times are GMT. The time now is 3:50 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 - 2021, vBulletin Solutions, Inc.
Copyright ©2002 - 2021, Paul Stenning.