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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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15th Jun 2021, 7:40 pm | #21 |
Octode
Join Date: Oct 2019
Location: Stockport, Greater Manchester, UK.
Posts: 1,612
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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
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20th Jun 2021, 3:05 pm | #22 |
Octode
Join Date: Oct 2019
Location: Stockport, Greater Manchester, UK.
Posts: 1,612
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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... |
20th Jun 2021, 3:43 pm | #23 |
Octode
Join Date: Oct 2019
Location: Stockport, Greater Manchester, UK.
Posts: 1,612
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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 |
20th Jun 2021, 8:31 pm | #24 |
Dekatron
Join Date: May 2010
Location: Greater Manchester, UK.
Posts: 18,676
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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.
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20th Jun 2021, 9:57 pm | #25 |
Rest in Peace
Join Date: Mar 2011
Location: Basildon, Essex, UK.
Posts: 4,100
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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 |
21st Jun 2021, 1:58 pm | #26 | |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,548
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Re: KB MR10 sudden fault, help needed
Quote:
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.
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21st Jun 2021, 2:10 pm | #27 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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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. |
21st Jun 2021, 2:22 pm | #28 |
Dekatron
Join Date: Nov 2009
Location: Lincolnshire, UK.
Posts: 4,985
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Re: KB MR10 sudden fault, help needed
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.
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21st Jun 2021, 2:32 pm | #29 |
Octode
Join Date: Oct 2019
Location: Stockport, Greater Manchester, UK.
Posts: 1,612
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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. |
21st Jun 2021, 3:00 pm | #30 |
Dekatron
Join Date: Nov 2009
Location: Lincolnshire, UK.
Posts: 4,985
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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.
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