Dealing with crackling tuning gangs. - UK Vintage Radio Repair and Restoration Discussion Forum

ray@roberts · 15th Sep 2006, 1:32 pm

I have repaired a Bush MB60 and it is now working well except when tuning it, there is one point on both MW and LW where the radio emits loud crackles. I have cleaned the vanes of the tuning capacitor (in situ) as thoroughly as I can (with a dry paintbrush and toothbrush) so I suppose that the vanes are slightly out of alignment.

I have a spare tuning capacitor that comes from one of the transistor Bush radios in that body style. It appears to be very similar internally though the body/chassis of the capacitors are slightly different in construction but not in size. What I would like to know is:

1. Would replacing the original from the mains/battery radio with one from a transistor radio be possible and would it work?

2. Is there anything else I can do to the original to make it work better? As stated above, I have not removed it from the radio.

3. Should I leave well (or almost well) alone? My Valve Radio Repair book says whatever you do, don't remove or tinker around with these tuning capacitors!

Thanks for any help that anyone can give.
Ray

howard · 15th Sep 2006, 1:59 pm

Hello Ray,

There is an adjuster on the end of the tuning capacitor, have you tried loosening the locknut and gently turning that to get rid of the noise ? It has always worked for me on TR82s. Incidentally, sometimes I take those adjusters right out and repack the ball bearings with some LM grease cos it can dry out a bit. Careful you don't drop any ball bearings !

Howard

Biggles · 15th Sep 2006, 3:28 pm

I would agree with Howard, replacing tuning capacitors is something I would avoid if at all possible. Even with a near identical unit, there are bound to be minor differences which could necessitate a re-alignment. In the past I have managed to slightly adjust the troublesome vane which was shorting and causing noise, but it needs a steady hand and plenty of patience!

Biggles.

G0PKH - Pete · 15th Sep 2006, 5:37 pm

You could try gently rubbing a peice of folded paper through each if the vanes in turn, with the capacitor open (minimum capacitance)

Rather time consuming, but may work.
I have got rid of minute whiskers this way.

Pete

PWH · 16th Sep 2006, 7:37 am

You have probably got dirt in the contacts between the moving shaft and the 'brushes' it sits on or the bearings. try a small amount of switch cleaner or WD40 at each end of the shaft where the bearings are.

If the above fails, dismount the cap and spray it with Jif* or other foam cleaner . leave for 15 mins then rinse in hot water. leave to dry thoroughly in a hot place (sun, radiator, cooker etc) Works every time for me.

*Now known as Cif, apparently.

Mike Phelan · 16th Sep 2006, 8:36 am

A trip in the dishwasher cleans up the ally vanes nicely, as well. Distraction techniques need to be perfected!

If you do this or use PWH's method, do not forget the bearings need lubrication afterwards.

PJL · 16th Sep 2006, 3:49 pm

Recently spent 30 minutes fixing a transistors tuning capacitor that had been tinkered with. Original fault was probably machine marks and dents on the top edge of the vanes. Ended up using fine sandpaper and lots of patience to realign them all. These were never precision parts so I wouldn't unduly worry about messing it up but you may need to re-align the set afterwards.

I assume the fixed vanes are soldered in place and do not have any means to adjust the spacing?

ray@roberts · 19th Sep 2006, 8:06 am

Thanks to you all that suggested ways to get rid of the crackling from the tuning capacitor. I have followed your advice and the set now tunes in with no crackles at all. As I don't possess a dishwasher, I didn't go down that route but maybe that's just as well!
Many thanks
Ray

15th Sep 2006, 1:32 pm	#1
ray@roberts Retired Dormant Member Join Date: Sep 2005 Location: Cambridge, Cambs. UK. Posts: 31	Dealing with crackling tuning gangs. I have repaired a Bush MB60 and it is now working well except when tuning it, there is one point on both MW and LW where the radio emits loud crackles. I have cleaned the vanes of the tuning capacitor (in situ) as thoroughly as I can (with a dry paintbrush and toothbrush) so I suppose that the vanes are slightly out of alignment. I have a spare tuning capacitor that comes from one of the transistor Bush radios in that body style. It appears to be very similar internally though the body/chassis of the capacitors are slightly different in construction but not in size. What I would like to know is: 1. Would replacing the original from the mains/battery radio with one from a transistor radio be possible and would it work? 2. Is there anything else I can do to the original to make it work better? As stated above, I have not removed it from the radio. 3. Should I leave well (or almost well) alone? My Valve Radio Repair book says whatever you do, don't remove or tinker around with these tuning capacitors! Thanks for any help that anyone can give. Ray Last edited by Darren-UK; 30th Jul 2007 at 10:29 pm. Reason: General tidying.

15th Sep 2006, 1:59 pm	#2
howard Nonode Join Date: May 2005 Location: Godalming, Surrey, UK. Posts: 2,593	Re: Replacing tuning capacitor on Bush MB60 Hello Ray, There is an adjuster on the end of the tuning capacitor, have you tried loosening the locknut and gently turning that to get rid of the noise ? It has always worked for me on TR82s. Incidentally, sometimes I take those adjusters right out and repack the ball bearings with some LM grease cos it can dry out a bit. Careful you don't drop any ball bearings ! Howard

15th Sep 2006, 3:28 pm	#3
Biggles Rest in Peace Join Date: Feb 2004 Location: Hexham, Northumberland, UK. Posts: 2,234	Re: Replacing tuning capacitor on Bush MB60 I would agree with Howard, replacing tuning capacitors is something I would avoid if at all possible. Even with a near identical unit, there are bound to be minor differences which could necessitate a re-alignment. In the past I have managed to slightly adjust the troublesome vane which was shorting and causing noise, but it needs a steady hand and plenty of patience! Biggles.

15th Sep 2006, 5:37 pm	#4
G0PKH - Pete Retired Dormant Member Join Date: Aug 2003 Location: Stansted Essex Posts: 263	Re: Replacing tuning capacitor on Bush MB60 You could try gently rubbing a peice of folded paper through each if the vanes in turn, with the capacitor open (minimum capacitance) Rather time consuming, but may work. I have got rid of minute whiskers this way. Pete

16th Sep 2006, 7:37 am	#5
PWH Heptode Join Date: Mar 2003 Location: Waiheke Island, New Zealand Posts: 503	You have probably got dirt in the contacts between the moving shaft and the 'brushes' it sits on or the bearings. try a small amount of switch cleaner or WD40 at each end of the shaft where the bearings are. If the above fails, dismount the cap and spray it with Jif* or other foam cleaner . leave for 15 mins then rinse in hot water. leave to dry thoroughly in a hot place (sun, radiator, cooker etc) Works every time for me. Now known as Cif, apparently. Last edited by Darren-UK; 30th Jul 2007 at 10:26 pm. Reason: Consecutive posts by same author on same subject.*

16th Sep 2006, 8:36 am	#6
Mike Phelan Dekatron Join Date: Nov 2003 Location: Near Leeds, West Yorkshire, UK Posts: 4,609	Re: Replacing tuning capacitor on Bush MB60 A trip in the dishwasher cleans up the ally vanes nicely, as well. Distraction techniques need to be perfected! If you do this or use PWH's method, do not forget the bearings need lubrication afterwards. __________________ Mike.

16th Sep 2006, 3:49 pm	#7
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Replacing tuning capacitor on Bush MB60 Recently spent 30 minutes fixing a transistors tuning capacitor that had been tinkered with. Original fault was probably machine marks and dents on the top edge of the vanes. Ended up using fine sandpaper and lots of patience to realign them all. These were never precision parts so I wouldn't unduly worry about messing it up but you may need to re-align the set afterwards. I assume the fixed vanes are soldered in place and do not have any means to adjust the spacing?

19th Sep 2006, 8:06 am	#8
ray@roberts Retired Dormant Member Join Date: Sep 2005 Location: Cambridge, Cambs. UK. Posts: 31	Re: Replacing tuning capacitor on Bush MB60 Thanks to you all that suggested ways to get rid of the crackling from the tuning capacitor. I have followed your advice and the set now tunes in with no crackles at all. As I don't possess a dishwasher, I didn't go down that route but maybe that's just as well! Many thanks Ray