Bush PB12 Basic Checklist - UK Vintage Radio Repair and Restoration Discussion Forum

BrianAllen · 9th Jun 2020, 6:37 pm

Good evening all,

I have just completed replacing all of the low value caps and 3 electrolytics.

The good news is that with the aid of my lamp limiter (obviously built with the help of this site) no damage was done on powering up.

All valves seem to be working ok and can hear a hum from the secondary transformer/speaker but no radio stations.

What I am looking for is a basic checklist, of which I am sure I have seen somewhere on here.

Does anybody have the link to the page or another basic checklist page?

Thank you.

OldTechFan96 · 9th Jun 2020, 8:28 pm

What bulb are you using in your limiter? The amount of voltage restriction could be enough to make the radio seem inoperative.

Bypass the limiter and see if things change. I had a similar issue with a radio last year. Once the bulb was bypassed the radio came to life!

If things do not change, start with measuring HT from the smoothing capacitors and valve anode voltages.

BrianAllen · 9th Jun 2020, 8:34 pm

I have already bypassed the limiter and looking promising; I will do as you recommend.

I am assuming that the multimeter should be set to DC voltage to test?

OldTechFan96 · 9th Jun 2020, 8:39 pm

Set your DMM to VDC. What DMM are you using?

Is your DMM auto-ranging or is it manual? If your DMM is manual you should use the highest DC range.

BrianAllen · 9th Jun 2020, 8:41 pm

Yes, auto-ranging.

OldTechFan96 · 9th Jun 2020, 8:48 pm

That's good. I find they make measurements much easier.

I've just found the Bush service manual. It looks a nice set.

When you have the limiting on, how bright is the bulb?

BrianAllen · 9th Jun 2020, 8:55 pm

Yes, a very nice set but had to do a lot of work on the cabinet as the base was full of woodworm; now replaced.

When limiter on there is no glow from the 100 watt bulb.

OldTechFan96 · 9th Jun 2020, 9:04 pm

When you say 'no glow' do you mean that the bulb is not lit at all? If the radio is drawing a normal amount of current the bulb should glowing slightly, but not too bright.

When you switch on the set the bulb should glow brightly, then settle at a lower brightness as the valves start to conduct.

BrianAllen · 9th Jun 2020, 9:08 pm

Switching the radio on with the limiter in operation, the bulb flickers a little and then goes out completely.

I have tested on another radio and the limiter is working ok.

McMurdo · 9th Jun 2020, 9:10 pm

are the valves all lit up?

BrianAllen · 9th Jun 2020, 9:12 pm

Yes, apart from one that I can't see as it is completely covered in the Mullard red coating.

OldTechFan96 · 9th Jun 2020, 9:13 pm

I get the impression that the set is not drawing excessive current. That's good!

What DC voltage do you measure at the cathode of V5, pin 8. It should be about 260V with the limiter off.

BrianAllen · 9th Jun 2020, 9:17 pm

I won't be able to look until tomorrow as lighting here is very poor and prefer daylight.

Should I be checking from underneath the chassis or with the valve removed from the top of chassis?

cathoderay57 · 9th Jun 2020, 10:30 pm

Hi Brian, is this the link you were looking for in Post #1? https://www.vintage-radio.com/repair...and-tests.html

OldTechFan96 · 9th Jun 2020, 10:52 pm

Quote:

Originally Posted by BrianAllen

I won't be able to look until tomorrow as lighting here is very poor and prefer daylight.

Should I be checking from underneath the chassis or with the valve removed from the top of chassis?

You should take the measurement with the chassis safely propped up towards you. Carefully experiment to find out what is most comfortable. All valves in.

Have you cleaned valve pins and bases etc.?

sortedradio · 10th Jun 2020, 1:56 pm

You don't say what you are using as an aerial. 10' of wire in the aerial socket should do.

BrianAllen · 10th Jun 2020, 4:03 pm

Good afternoon, all of the above has been noted, thank you.

I powered up the radio last night and will all house lights off, I can now see that all valves are glowing.

Yes, that was the link I was looking for, thank you.

I have about 10 metres of aerial attached to a post in the garden.

I have cleaned all valves and bases but will check again.

I did wonder how to test with the valves in and powered up; will take care propping up.

Is this chassis live?

Thanks for your recommendations.

Brian

OldTechFan96 · 10th Jun 2020, 4:18 pm

I don't think your PB12 has a live chassis. It looks to have a double wound mains transformer.

What results do you get with the external aerial attached? I've noticed that the PB12 includes a internal frame aerial. Is is present?

BrianAllen · 10th Jun 2020, 8:46 pm

Ok thanks.

Have tried an external aerial and no stations coming through.

Yes, the internal aerial is still in place; time to work through the checklist now I think!!

9th Jun 2020, 8:28 pm	#2
OldTechFan96 Octode Join Date: Jul 2017 Location: Newcastle Upon Tyne, Tyne & Wear, UK. Posts: 1,186	Re: Bush PB12 Basic Checklist What bulb are you using in your limiter? The amount of voltage restriction could be enough to make the radio seem inoperative. Bypass the limiter and see if things change. I had a similar issue with a radio last year. Once the bulb was bypassed the radio came to life! If things do not change, start with measuring HT from the smoothing capacitors and valve anode voltages. Last edited by OldTechFan96; 9th Jun 2020 at 8:32 pm. Reason: More info

9th Jun 2020, 8:34 pm	#3
BrianAllen Heptode Join Date: Nov 2018 Location: Staffordshire Moorlands, UK. Posts: 595	Re: Bush PB12 Basic Checklist I have already bypassed the limiter and looking promising; I will do as you recommend. I am assuming that the multimeter should be set to DC voltage to test?

9th Jun 2020, 8:39 pm	#4
OldTechFan96 Octode Join Date: Jul 2017 Location: Newcastle Upon Tyne, Tyne & Wear, UK. Posts: 1,186	Re: Bush PB12 Basic Checklist Set your DMM to VDC. What DMM are you using? Is your DMM auto-ranging or is it manual? If your DMM is manual you should use the highest DC range.

9th Jun 2020, 8:41 pm	#5
BrianAllen Heptode Join Date: Nov 2018 Location: Staffordshire Moorlands, UK. Posts: 595	Re: Bush PB12 Basic Checklist Yes, auto-ranging.

9th Jun 2020, 8:48 pm	#6
OldTechFan96 Octode Join Date: Jul 2017 Location: Newcastle Upon Tyne, Tyne & Wear, UK. Posts: 1,186	Re: Bush PB12 Basic Checklist That's good. I find they make measurements much easier. I've just found the Bush service manual. It looks a nice set. When you have the limiting on, how bright is the bulb? Last edited by OldTechFan96; 9th Jun 2020 at 8:50 pm. Reason: Extra

9th Jun 2020, 6:37 pm	#1
BrianAllen Heptode Join Date: Nov 2018 Location: Staffordshire Moorlands, UK. Posts: 595	Bush PB12 Basic Checklist Good evening all, I have just completed replacing all of the low value caps and 3 electrolytics. The good news is that with the aid of my lamp limiter (obviously built with the help of this site) no damage was done on powering up. All valves seem to be working ok and can hear a hum from the secondary transformer/speaker but no radio stations. What I am looking for is a basic checklist, of which I am sure I have seen somewhere on here. Does anybody have the link to the page or another basic checklist page? Thank you.

9th Jun 2020, 8:55 pm	#7
BrianAllen Heptode Join Date: Nov 2018 Location: Staffordshire Moorlands, UK. Posts: 595	Re: Bush PB12 Basic Checklist Yes, a very nice set but had to do a lot of work on the cabinet as the base was full of woodworm; now replaced. When limiter on there is no glow from the 100 watt bulb.

9th Jun 2020, 9:04 pm	#8
OldTechFan96 Octode Join Date: Jul 2017 Location: Newcastle Upon Tyne, Tyne & Wear, UK. Posts: 1,186	Re: Bush PB12 Basic Checklist When you say 'no glow' do you mean that the bulb is not lit at all? If the radio is drawing a normal amount of current the bulb should glowing slightly, but not too bright. When you switch on the set the bulb should glow brightly, then settle at a lower brightness as the valves start to conduct.

9th Jun 2020, 9:08 pm	#9
BrianAllen Heptode Join Date: Nov 2018 Location: Staffordshire Moorlands, UK. Posts: 595	Re: Bush PB12 Basic Checklist Switching the radio on with the limiter in operation, the bulb flickers a little and then goes out completely. I have tested on another radio and the limiter is working ok.

9th Jun 2020, 9:10 pm	#10
McMurdo Dekatron Join Date: Jun 2009 Location: Staffordshire Moorlands, UK. Posts: 5,273	Re: Bush PB12 Basic Checklist are the valves all lit up? __________________ Kevin

9th Jun 2020, 9:12 pm	#11
BrianAllen Heptode Join Date: Nov 2018 Location: Staffordshire Moorlands, UK. Posts: 595	Re: Bush PB12 Basic Checklist Yes, apart from one that I can't see as it is completely covered in the Mullard red coating.

9th Jun 2020, 9:13 pm	#12
OldTechFan96 Octode Join Date: Jul 2017 Location: Newcastle Upon Tyne, Tyne & Wear, UK. Posts: 1,186	Re: Bush PB12 Basic Checklist I get the impression that the set is not drawing excessive current. That's good! What DC voltage do you measure at the cathode of V5, pin 8. It should be about 260V with the limiter off.

9th Jun 2020, 9:17 pm	#13
BrianAllen Heptode Join Date: Nov 2018 Location: Staffordshire Moorlands, UK. Posts: 595	Re: Bush PB12 Basic Checklist I won't be able to look until tomorrow as lighting here is very poor and prefer daylight. Should I be checking from underneath the chassis or with the valve removed from the top of chassis? Last edited by BrianAllen; 9th Jun 2020 at 9:29 pm.

9th Jun 2020, 10:30 pm	#14
cathoderay57 Nonode Join Date: Oct 2017 Location: Bristol, UK. Posts: 2,386	Re: Bush PB12 Basic Checklist Hi Brian, is this the link you were looking for in Post #1? https://www.vintage-radio.com/repair...and-tests.html

10th Jun 2020, 1:56 pm	#16
sortedradio Heptode Join Date: Jan 2008 Location: Sheffield, South Yorkshire, UK. Posts: 656	Re: Bush PB12 Basic Checklist You don't say what you are using as an aerial. 10' of wire in the aerial socket should do. __________________ Martin BVWS member GQRP Club

10th Jun 2020, 4:03 pm	#17
BrianAllen Heptode Join Date: Nov 2018 Location: Staffordshire Moorlands, UK. Posts: 595	Re: Bush PB12 Basic Checklist Good afternoon, all of the above has been noted, thank you. I powered up the radio last night and will all house lights off, I can now see that all valves are glowing. Yes, that was the link I was looking for, thank you. I have about 10 metres of aerial attached to a post in the garden. I have cleaned all valves and bases but will check again. I did wonder how to test with the valves in and powered up; will take care propping up. Is this chassis live? Thanks for your recommendations. Brian

10th Jun 2020, 4:18 pm	#18
OldTechFan96 Octode Join Date: Jul 2017 Location: Newcastle Upon Tyne, Tyne & Wear, UK. Posts: 1,186	Re: Bush PB12 Basic Checklist I don't think your PB12 has a live chassis. It looks to have a double wound mains transformer. What results do you get with the external aerial attached? I've noticed that the PB12 includes a internal frame aerial. Is is present? Last edited by OldTechFan96; 10th Jun 2020 at 4:21 pm. Reason: Info

10th Jun 2020, 8:46 pm	#19
BrianAllen Heptode Join Date: Nov 2018 Location: Staffordshire Moorlands, UK. Posts: 595	Re: Bush PB12 Basic Checklist Ok thanks. Have tried an external aerial and no stations coming through. Yes, the internal aerial is still in place; time to work through the checklist now I think!!