Bush BS35 - UK Vintage Radio Repair and Restoration Discussion Forum

sexton_mallard · 17th Apr 2017, 7:11 pm

I finally got round to finish off replacing some crumbling wiring and a few hard to reach wax caps. Before boxing up, I did some voltage checks especially around the UL41. The set was obtained in Ireland where mains voltage in the past was 200-220v so the mains TX input voltage selector was moved from the 220V to 250V 'popper' stud. Voltage still seem a little bit on the high side, UL41 anode on 225v (212v on the Trader sheet for the Bush DAC34 which seems to be the closet spec. to the BS35). I have 47v across the UL41 heater as opposed to 45v, 8.2v on the cathode.

I then checked the grid and got nearly +8v

As this set has a mains Tx and U series valves, I measured from the socket pin WRT the chassis. Plug and lead polarity is correct. Not being sure if I was measuring the voltage correctly I decided to measure the current flow on the primary of the output TX. Current is 23-26mA with the transformer getting warm but not hot. All wax caps have been replaced.

The set performs well enough and the UL41 has been swapped with a good spare with no difference. I will carry on checking but is that current value too high?

Boater Sam · 17th Apr 2017, 7:37 pm

No way should you have 8v on the grid.Should be as near to zero as possible with no signal input.

Is pin 4 of the UL41 not connected to anything? it should be blank but Bush often used it as a solder tag, some UL41s have an internal connection to here.

If the valve is OK, the cap on the grid from the previous valve anode is either duff or there is a wrong connection, - somewhere.

Anode voltage is probably about right, you are using a digital meter? Sheet would be with an Avo 8 probably.

sexton_mallard · 15th Jul 2017, 7:07 pm

I finally got to the bottom of this. While tipping the chassis over and clamping in the workmate I noticed bits of solder falling out... I switched on to do more voltage checks and got a angry hum from the speaker and then noticed the rectifier 'red plating'

After switching off and allowing things to cool down I picked up the chassis and gave it a good shake. More bits of loose solder fell out! A very close examination of components took place and another switch on with the lamp limiter gave me...a working radio on all wavebands. The grid voltage was now millivolts. The rectifier seems to have survived this torture and the set works well after bit of fettling on the wavechange switch discs to improve the contacts on MW. The tone control pot gave up the ghost but was revived by opening the case, lots of Servisol and changing the connectons over to use the less worn portion of the track. The action is now reversed turning the tone knob but at least it works.

As a relative newbie these little challenges keep me on my toes. As for the solder. I think it was during a battle trying to get a cap lead to take solder on a waxy terminal and the molten drops dripped and settled in the chassis to cause mayhem later on. I have a NOS UM4 and I don't know yet whether to sacrifice it but I will leave that decision for now and use and enjoy this set to listen on SW (after unplugging all the PLC adaptors in the house which drown out big spectrums of SW with a annoying put-put-put).

Herald1360 · 15th Jul 2017, 8:55 pm

As mentioned elsewhere, if any of your neighbours ever listen on Short Waves, they won't thank you for those hateful PLC sprog boxes either!

sexton_mallard · 15th Jul 2017, 10:07 pm

I was mucking about with a magnet from a tweeter and noticed it deflecting the illumination in the UM4. In fact it got considerably brighter in some areas temporarily as the magnetic field bent and concentrated the electron beam. I'm now going to find some small magnets and place them in the case close to the eye and do some trial and error with the magnet placement.

17th Apr 2017, 7:11 pm	#1
sexton_mallard Heptode Join Date: Sep 2013 Location: Ellesmere, Shropshire, UK & Co. Cork, Ireland. Posts: 502	Bush BS35 I finally got round to finish off replacing some crumbling wiring and a few hard to reach wax caps. Before boxing up, I did some voltage checks especially around the UL41. The set was obtained in Ireland where mains voltage in the past was 200-220v so the mains TX input voltage selector was moved from the 220V to 250V 'popper' stud. Voltage still seem a little bit on the high side, UL41 anode on 225v (212v on the Trader sheet for the Bush DAC34 which seems to be the closet spec. to the BS35). I have 47v across the UL41 heater as opposed to 45v, 8.2v on the cathode. I then checked the grid and got nearly +8v As this set has a mains Tx and U series valves, I measured from the socket pin WRT the chassis. Plug and lead polarity is correct. Not being sure if I was measuring the voltage correctly I decided to measure the current flow on the primary of the output TX. Current is 23-26mA with the transformer getting warm but not hot. All wax caps have been replaced. The set performs well enough and the UL41 has been swapped with a good spare with no difference. I will carry on checking but is that current value too high? __________________ Dom Less snakes...more ladders! Last edited by sexton_mallard; 17th Apr 2017 at 7:17 pm.

17th Apr 2017, 7:37 pm	#2
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Bush BS35 No way should you have 8v on the grid.Should be as near to zero as possible with no signal input. Is pin 4 of the UL41 not connected to anything? it should be blank but Bush often used it as a solder tag, some UL41s have an internal connection to here. If the valve is OK, the cap on the grid from the previous valve anode is either duff or there is a wrong connection, - somewhere. Anode voltage is probably about right, you are using a digital meter? Sheet would be with an Avo 8 probably.

15th Jul 2017, 7:07 pm	#3
sexton_mallard Heptode Join Date: Sep 2013 Location: Ellesmere, Shropshire, UK & Co. Cork, Ireland. Posts: 502	Re: Bush BS35 I finally got to the bottom of this. While tipping the chassis over and clamping in the workmate I noticed bits of solder falling out... I switched on to do more voltage checks and got a angry hum from the speaker and then noticed the rectifier 'red plating' After switching off and allowing things to cool down I picked up the chassis and gave it a good shake. More bits of loose solder fell out! A very close examination of components took place and another switch on with the lamp limiter gave me...a working radio on all wavebands. The grid voltage was now millivolts. The rectifier seems to have survived this torture and the set works well after bit of fettling on the wavechange switch discs to improve the contacts on MW. The tone control pot gave up the ghost but was revived by opening the case, lots of Servisol and changing the connectons over to use the less worn portion of the track. The action is now reversed turning the tone knob but at least it works. As a relative newbie these little challenges keep me on my toes. As for the solder. I think it was during a battle trying to get a cap lead to take solder on a waxy terminal and the molten drops dripped and settled in the chassis to cause mayhem later on. I have a NOS UM4 and I don't know yet whether to sacrifice it but I will leave that decision for now and use and enjoy this set to listen on SW (after unplugging all the PLC adaptors in the house which drown out big spectrums of SW with a annoying put-put-put). __________________ Dom Less snakes...more ladders! Last edited by sexton_mallard; 15th Jul 2017 at 7:14 pm.

15th Jul 2017, 8:55 pm	#4
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,536	Re: Bush BS35 As mentioned elsewhere, if any of your neighbours ever listen on Short Waves, they won't thank you for those hateful PLC sprog boxes either! __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

15th Jul 2017, 10:07 pm	#5
sexton_mallard Heptode Join Date: Sep 2013 Location: Ellesmere, Shropshire, UK & Co. Cork, Ireland. Posts: 502	Re: Bush BS35 I was mucking about with a magnet from a tweeter and noticed it deflecting the illumination in the UM4. In fact it got considerably brighter in some areas temporarily as the magnetic field bent and concentrated the electron beam. I'm now going to find some small magnets and place them in the case close to the eye and do some trial and error with the magnet placement. __________________ Dom Less snakes...more ladders!