BUSH MB60; valve base/socket faults. - UK Vintage Radio Repair and Restoration Discussion Forum

Mike Noble · 12th May 2007, 1:15 pm

Hello people. This radio is dead so I have taken some voltage readings to try and see whats wrong. What I get is Valve 1 DK96 Mixer anode 82.4V, Osc anode 81.8V and screen volts of 80.5.
V2 DF96 Anode 81.9V, screen 80.2V and V3 DF96 Anode 81.8V and screen 80.2V.
R5 measures 45k and R7 34k. Are all three valves duff? Any suggestions?
Thanks, Mike.

Steve_P · 12th May 2007, 2:29 pm

First, for anyboby who does not know, these battery valves do not visibly glow. If they do, then find out why then buy another valve. Check that the heater volts are still there.

Check on every valve.

Cheers,

Steve P

Mike Noble · 12th May 2007, 3:43 pm

The heater volts are present on all valves at 1.8V and the resistance of the heater on V1 is 15ohms. Other heater resistances are similar.
When probing the input pin on the audio there is a buzz from the speaker so this is working.

Mike Noble · 12th May 2007, 6:49 pm

It appears that the valve bases are not connecting to the valve pins. I have given them all a good clean and now get the correct voltages intermittently but still no output. I suspect that there there are still some bad connections.

yestertech · 13th May 2007, 9:53 pm

Mike, save yourself a lot of aggro and replace the valve bases ! I had one of these which required 2 changing completely before it would work !
The quality of the installed ones is S**T ! - unusually for BUSH
There's also the additional risk that if the heater pins open on one valve it will increase the volts on the others, and may cause damage, due to the way the heaters are fed !

Andy

Mike Phelan · 14th May 2007, 8:53 am

Mike
1.8v on the filaments seems a bit high - are you sure the readings are correct? It will shorten their life if they are. 1.4v is about what you should have.
Are you running it on mains or battery? In the latter case, they cannot be 1.8v !

Mike Noble · 14th May 2007, 8:59 am

Thankyou. Running on mains. The 1.8V was the reading when the heaters were not connecting. Now that at least three are, the voltage has dropped to 1.6V suggesting that there are still contact problems. I think I will have to fit new valve bases!
Mike.

Mike Noble · 17th May 2007, 11:40 pm

FYI. I have now changed the valve bases on the first four valves and at last some life. Not bad and quite sensitive. When I put the back on the audio distorts so I guess the last valve base will have to go. None left so I will have to order some more.
Mike.

Mike Phelan · 18th May 2007, 7:42 am

Good! The bases on these are far short of the usual Bush build quality. The MB60 performs very well indeed with the extra IF stage.

12th May 2007, 1:15 pm	#1
Mike Noble Pentode Join Date: Oct 2005 Location: Harlow, Essex, UK. Posts: 162	BUSH MB60; valve base/socket faults. Hello people. This radio is dead so I have taken some voltage readings to try and see whats wrong. What I get is Valve 1 DK96 Mixer anode 82.4V, Osc anode 81.8V and screen volts of 80.5. V2 DF96 Anode 81.9V, screen 80.2V and V3 DF96 Anode 81.8V and screen 80.2V. R5 measures 45k and R7 34k. Are all three valves duff? Any suggestions? Thanks, Mike.

12th May 2007, 2:29 pm	#2
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: BUSH MB60 problem First, for anyboby who does not know, these battery valves do not visibly glow. If they do, then find out why then buy another valve. Check that the heater volts are still there. Check on every valve. Cheers, Steve P __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

12th May 2007, 3:43 pm	#3
Mike Noble Pentode Join Date: Oct 2005 Location: Harlow, Essex, UK. Posts: 162	Re: BUSH MB60 problem The heater volts are present on all valves at 1.8V and the resistance of the heater on V1 is 15ohms. Other heater resistances are similar. When probing the input pin on the audio there is a buzz from the speaker so this is working.

12th May 2007, 6:49 pm	#4
Mike Noble Pentode Join Date: Oct 2005 Location: Harlow, Essex, UK. Posts: 162	Re: BUSH MB60 problem It appears that the valve bases are not connecting to the valve pins. I have given them all a good clean and now get the correct voltages intermittently but still no output. I suspect that there there are still some bad connections.

13th May 2007, 9:53 pm	#5
yestertech Nonode Join Date: Dec 2002 Location: Coulsdon, Surrey, UK. Posts: 2,135	Re: BUSH MB60 problem Mike, save yourself a lot of aggro and replace the valve bases ! I had one of these which required 2 changing completely before it would work ! The quality of the installed ones is S**T ! - unusually for BUSH There's also the additional risk that if the heater pins open on one valve it will increase the volts on the others, and may cause damage, due to the way the heaters are fed ! Andy

14th May 2007, 8:53 am	#6
Mike Phelan Dekatron Join Date: Nov 2003 Location: Near Leeds, West Yorkshire, UK Posts: 4,609	Re: BUSH MB60 problem Mike 1.8v on the filaments seems a bit high - are you sure the readings are correct? It will shorten their life if they are. 1.4v is about what you should have. Are you running it on mains or battery? In the latter case, they cannot be 1.8v ! __________________ Mike.

14th May 2007, 8:59 am	#7
Mike Noble Pentode Join Date: Oct 2005 Location: Harlow, Essex, UK. Posts: 162	Re: BUSH MB60 problem Thankyou. Running on mains. The 1.8V was the reading when the heaters were not connecting. Now that at least three are, the voltage has dropped to 1.6V suggesting that there are still contact problems. I think I will have to fit new valve bases! Mike.

17th May 2007, 11:40 pm	#8
Mike Noble Pentode Join Date: Oct 2005 Location: Harlow, Essex, UK. Posts: 162	Re: BUSH MB60 problem FYI. I have now changed the valve bases on the first four valves and at last some life. Not bad and quite sensitive. When I put the back on the audio distorts so I guess the last valve base will have to go. None left so I will have to order some more. Mike.

18th May 2007, 7:42 am	#9
Mike Phelan Dekatron Join Date: Nov 2003 Location: Near Leeds, West Yorkshire, UK Posts: 4,609	Re: BUSH MB60 problem Good! The bases on these are far short of the usual Bush build quality. The MB60 performs very well indeed with the extra IF stage. __________________ Mike.