Toaster FB10 elusive fault - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

crackle · 15th Dec 2017, 6:07 pm

I may still have a spare ferrite rod aerial for one of these, but I dont think it will be better than the frame aerial, frame aerials are quite efficient. You could test the windings for continuety on the frame to see if there is a problem.

Mike

Pete_kaye · 17th Dec 2017, 4:33 pm

The coils are not shorting together as far as I can tell .I will re-examine tonight .It seemed to me that the sudden change in volume , odd whistles and weak interference from MW stations on LW pointed towards an aerial fault , but I am grasping at straws here. I measured 0.1 ohms and 1 ohm with cheap DMM for the L1 and L2.
The original 6BA6 (45% on test )valve was substituted with a new one and no change noticed .

Sideband · 18th Dec 2017, 12:02 am

Next time the fault occurs carefully check the tuning (assuming that altering the tuning doesn't clear the fault....). See if the tuning has changed....i.e is it 'broader' (the tuned station taking up more room on the scale). If so, it could be something subtle like a capacitor going O/C in one of the IF coils. This could certainly cause crackling and a reduction in volume since the IF transformer won't be tuned to the correct IF frequency when the cap is O/C.

Tractionist · 18th Dec 2017, 12:19 am

Sideband's got a point. As previously mentioned ..... if you are concerned about using freezer spray ..... think about some hot air?

Boater Sam · 18th Dec 2017, 3:55 am

As a method for repair, I have never found modifying a set to be the best answer, only a last resort solution.
Changing to a ferrite rod seems to be a lot of work with little guarantee that it will solve the problem, a defect in a frame aerial should be obvious and repairable.

Sideband · 18th Dec 2017, 12:17 pm

Agreed... and it's very unlikely that there will be a fault with the frame aerial anyway... certainly nothing to cause burn marks (there is nowhere near enough current anywhere to do that) although of course it could have been damaged by careless handling or a soldering iron at some time.

All I can say is that my FB10 works very acceptably on it's frame aerial.

Boater Sam · 18th Dec 2017, 1:09 pm

Quote:

Originally Posted by Pete_kaye

It seemed to me that the sudden change in volume , odd whistles and weak interference from MW stations on LW pointed towards an aerial fault

This sounds more like an IF transformer detuning or an oscillator fault than aerial.
Its not loose cores in an IF trany is it?

Sideband · 18th Dec 2017, 10:33 pm

Quote:

Originally Posted by Boater Sam

This sounds more like an IF transformer detuning

...as I alluded to a few posts back. The problem (if it is an internal tuning cap failing) is deciding which one. Usually if the internal cap fails, the tuning slug has little or no effect or it has to be screwed fully in or out.

As far as I am aware they are just standard ferrite tuning cores so not likely to be a detached core.

Pete_kaye · 21st Dec 2017, 2:27 pm

The burning on aerial was caused by the very close rectifier and output valves. For now , it is going back in its box. Thanks for all the advice.

15th Dec 2017, 6:07 pm	#21
crackle Rest in Peace Join Date: Mar 2011 Location: Basildon, Essex, UK. Posts: 4,100	Re: Toaster FB10 elusive fault I may still have a spare ferrite rod aerial for one of these, but I dont think it will be better than the frame aerial, frame aerials are quite efficient. You could test the windings for continuety on the frame to see if there is a problem. Mike

17th Dec 2017, 4:33 pm	#22
Pete_kaye Octode Join Date: Jun 2005 Location: Sheffield, South Yorkshire, UK. Posts: 1,227	Re: Toaster FB10 elusive fault The coils are not shorting together as far as I can tell .I will re-examine tonight .It seemed to me that the sudden change in volume , odd whistles and weak interference from MW stations on LW pointed towards an aerial fault , but I am grasping at straws here. I measured 0.1 ohms and 1 ohm with cheap DMM for the L1 and L2. The original 6BA6 (45% on test )valve was substituted with a new one and no change noticed .

18th Dec 2017, 12:02 am	#23
Sideband Dekatron Join Date: Oct 2003 Location: Croydon, Surrey, UK. Posts: 7,567	Re: Toaster FB10 elusive fault Next time the fault occurs carefully check the tuning (assuming that altering the tuning doesn't clear the fault....). See if the tuning has changed....i.e is it 'broader' (the tuned station taking up more room on the scale). If so, it could be something subtle like a capacitor going O/C in one of the IF coils. This could certainly cause crackling and a reduction in volume since the IF transformer won't be tuned to the correct IF frequency when the cap is O/C. __________________ There are lots of brilliant keyboard players and then there is Rick Wakeman.....

18th Dec 2017, 12:19 am	#24
Tractionist Heptode Join Date: Apr 2016 Location: Cheltenham, Gloucestershire, UK. Posts: 875	Re: Toaster FB10 elusive fault Sideband's got a point. As previously mentioned ..... if you are concerned about using freezer spray ..... think about some hot air? __________________ Red to red, black to black. Throw the switch and stand well back!

18th Dec 2017, 3:55 am	#25
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Toaster FB10 elusive fault As a method for repair, I have never found modifying a set to be the best answer, only a last resort solution. Changing to a ferrite rod seems to be a lot of work with little guarantee that it will solve the problem, a defect in a frame aerial should be obvious and repairable.

18th Dec 2017, 12:17 pm	#26
Sideband Dekatron Join Date: Oct 2003 Location: Croydon, Surrey, UK. Posts: 7,567	Re: Toaster FB10 elusive fault Agreed... and it's very unlikely that there will be a fault with the frame aerial anyway... certainly nothing to cause burn marks (there is nowhere near enough current anywhere to do that) although of course it could have been damaged by careless handling or a soldering iron at some time. All I can say is that my FB10 works very acceptably on it's frame aerial. __________________ There are lots of brilliant keyboard players and then there is Rick Wakeman.....

21st Dec 2017, 2:27 pm	#29
Pete_kaye Octode Join Date: Jun 2005 Location: Sheffield, South Yorkshire, UK. Posts: 1,227	Re: Toaster FB10 elusive fault The burning on aerial was caused by the very close rectifier and output valves. For now , it is going back in its box. Thanks for all the advice.