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Old 5th Jul 2018, 9:58 pm   #1
GreatHollands
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Default Bush AC11 Advice

Hi everyone, I have bought a Bush AC11 to replace my Grandad's old one, which was pretty much destroyed in a flood (veneer came off and curled up, chassis rusting away, cabinet coming apart at joins etc). The valves were probably OK but unfortunately the remains were dumped.

I bought it from a radio restorer as one he had not got around to doing. He recommended this website. He said he had powered it up on a variac and it had worked, but was very quiet and would probably need replacement capacitors and an IF tune.

I should say I am OK with mechanical things. I fixed up some old GPO telephones, record players, tape, CED and laserdisc players etc when I was younger, but that was mostly cleaning and re greasing, changing motors and drive belts, gears etc. When it came to actual circuits all I did was swap out whole boards from other scrap items.

I've never owned anything with a valve in it, and did not really know anything about them, other than that they glowed. I spent the evenings of the last 3 weeks watching black and white US Army videos on YouTube about valves, what they do, how they work and even a video of them being made in the Mullard factory. I read up on capacitors and what they do in a circuit and I think I've pretty much got the basics.

I did a few searches on the AC11 and found a series of videos by a guitar amp technician who was restoring a DAC90A. The videos were very good as he did each capacitor step by step and said each value and the C number on the trader sheet. I have the trader sheets for both radios. I thought this was something I could do so I bought a DAC90A on ebay very cheap to practice on before I tackled the AC11.

The seller had bought it in 2010 for a 1950's vintage tea party. it had not worked very well and had not been turned on since. I bought it and also a set of pre packed capacitors for it. I recapped it over the last two evenings, doing it step by step with the bloke in the video and am happy to say it has been on for the last 20 minutes on a lamp limiter and is picking up Virgin loud and clear. I have not changed the 16/32 electrolytic capacitor, but the radio is not buzzing. It is stinking my flat out though, not a burning smell but more of a bad curry smell. The green voltage dropper and valves 4 and 5 are giving off a lot of heat, but I believe this is normal. I'm a little uncomfortable with the heat and high voltages these operate at, but understand now why this is so. I'll leave it on until I go to bed, and try full voltage (current?) tomorrow.

Anyway, I ramble. I have a few queries about the AC11 which I have not been able to find answers to. Firstly, I cannot find a pre packed set of capacitors for the AC11, so I will buy them from RS, and the 16/32 and the 50 uf C22 electrolytics from Tube Amp Doctor in Germany. They don't do a 50 but they do a 47 which I read is OK. Is this the right way to go?

Also, am I right in thinking I need to replace all the uf capacitors but the pf ones will be OK? When I did the DAC90A I replaced the 0.003 C17 tone corrector with a 0.001, apparently to improve the tone. Should I do this with the AC11? I see a part tone control and two part tone corrector capacitors, C30, C31 and C32. Should I change these values?

I read I should lubricate the dial pointer string, is this true? I have WD40 or some expensive clock oil I use for turntable bearings, which should I use? Or something else?

Another thing, I can see dust between the fins of the tuner. I have tried to hoover it which has helped but there is still dust there. Can I spray contact cleaner down there?

With regards to the cabinet, it is in a not too bad state. I have zero woodwork experience, so may leave it (it depends a bit on how the recap goes). If I do restore it, I have read about two ways. One is to use paint stripper, a metal paint scraper to remove the old varnish, rub down with 1000 grit wire wool and re varnish. Another said not to use paint stripper as it will damage the veneer. Instead rub down with sandpaper, it didn't say what grit, and then re varnish. Can anyone recommend a way for an amateur to get good results?

I am going to my Auntie's in France for 2 weeks. It is in a tiny village in the middle of nowhere so I'm going to take the radio to give me something to do while I'm there. Therefore I need to take everything I will need with me. Is there anything I've missed which will need doing? maybe some common failing resistors? I have not had to change any in the DAC90A, which by the way has been on for an hour now (I'm a slow typer and EastEnders is on) and the smell is fading a bit.

Lastly, should I earth the chassis? I have read some pieces which say yes and others which say it will cause interference. I'm going to order a braided mains lead for it, not original I know, but I like the way they look on the 300 series telephones, so need to know whether to get a 2 or 3 core. The two radios use the same valves so I'm going to take the ones out of the DAC90A with me in case any in the AC11 don't work.

I should mention I don't have an oscilloscope or anything like that, so I won't be able to do the IF tuning, but from what I've read it seems it doesn't usually need doing and you can do more damage than good by trying if you don't know what you're doing. Is this true? The DAC90A seems OK.
I think that's everything, any advice would be greatly appreciated. Thanks.
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Old 6th Jul 2018, 7:59 am   #2
stitch1
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Default Re: Bush AC11 Advice

Hi, it seems like you’ve done a good job on the DAC90A so this one should be no problem. Just my personal view and there’s lots of skilled people will help you through the restoration ...

Capacitors: you’re probably correct but I would change the audio coupling cap/s and after doing safety checks power it up on a lamp limiter to get an idea of how it’s working or not. If its not working at all you need to find out why before changing any caps. Clean the wave band switch, check valve continuity and clean pins etc. If it’s working in a fashion I’d change the larger uf one at a time switching on each time and seeing what improvements it makes.
If there are still problems using the service data sheet check valve voltages and check for resistors that have gone very high. Post your results on here for advice.
You should not need to change the tone caps value, better to get it working first then you can experiment if you want.

Pointer: I use silicon grease (not saying this is the best) oil or wd40 would run.

Tuning cap:if it’s just dust then I use aerosol air duster. I would not use switch cleaner on the fins.

Earth: I don’t know this radio but I’m assuming from the model number it’s AC only. Check the service data and if it is and has a proper mains transformer then I would earth the chassis. I doubt it would make any noticible difference to the reception.

Alignment: as you say unlikely you’ll need to do this but it is good fun (well I think so) and you don’t need a scope.

Will you need to change the voltage setting to work correctly in France?

Good luck, post your questions on here with lots of pics and there are many people much more experienced than me that will help.

Good luck.

John
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Old 6th Jul 2018, 10:12 am   #3
Boater Sam
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Default Re: Bush AC11 Advice

You will get a good sound from an AC11 without making changes to cap values.
Leave all the small silver mica caps alone.
You may not need to change the reservoir and smoothing caps, 16/32, they usually reform.
Leave any realignment alone unless it is absolutely vital, you need a signal generator and DMM at least.
Dial cord is best lubed with a wax candle rubbed on the sections that goes past the spindle, fine oil on the pulleys pivots.
Keep WD40 for the garage, it has no uses on radios. Use proper switch cleaner only.
Dry dust in the variable cap is fine, if you spray it the dust will go into balls and muck it up tuning wise.
Unless the cabinet is really bad just clean it and polish. They are cellulose lacquered, Rustins scratch cover works well, wax touch up crayons for deeper scratches.
Do not try sanding at all, the veneers are very thin. you will rub through to the white wood no matter how careful you are.
If you must strip it, paint stripper and a scraper, wash off well, fine wire wool ( keep the speaker and the chassis well away else you will never get rid of the bits ) and 2 or 3 coats of Danish Oil will give a nice finish.
Put a 3 core lead on and earth the chassis, I do with all mine that have a proper transformer like yours, never had any problem and its a lot safer.
AC11 is a good set, restored dozens of them. Are you aware that the glass is designed to be removable by pushing the bottom trim down? Makes it safer to put it somewhere out of the way.
You seem to have done your homework, congratulations, you are on the right track. I wish all were as ready to learn as you obviously are.
Caps, one at a time, slowly slowly.
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Old 6th Jul 2018, 3:07 pm   #4
Tim
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Default Re: Bush AC11 Advice

Ditto all above. I did one of these some years ago.

Don't get any oil on the tuning cord. A DROP of clock/ sewing machine oil applied with a wooden cocktail stick or similar will be fine on the pulleys and shafts etc.
Easy to work on, very similar board arrangement below decks as a DAC90A as I recall.
Hopefully the UL41 will be OK.

http://www.vintage-radio.com/recent-...bush-ac11.html

This set will probably work perfectly well in France .Set to 240
Do check the polarity of the mains over there though. The Gallic electricians don't seem to be very fussy that way!

I hope you find the write up useful.
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Last edited by Tim; 6th Jul 2018 at 3:12 pm.
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Old 6th Jul 2018, 8:05 pm   #5
GreatHollands
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Default Re: Bush AC11 Advice

Hi everyone, thanks for your responses. As you recommend I will change the AF Coupling capacitor C29 and then power it up through a lamp limiter to see what happens. I read that some people only change one cap at a time between powering up so they know if they've made a mistake, but I also read this will stress the valves and bulbs. Is there a minimum time I should wait between turning it off and on again or is it ok to just crack on?
I will get a can of compressed air for the tuner. The set is AC only, and does have a transformer so i'll earth the chassis. I'm not sure about the voltage in France, I think it's 230v, but ill check it with my multimeter. The voltage choices on the transformer are 110 - 120, 210 - 230 and 231 - 250. Even if the voltage there is as low as 220, I believe it is still better (safer) to leave it on the 231 - 250 setting. Please correct me if i'm wrong.
I will take your advice and not attempt to strip the cabinet, just clean it and polish it. Is white spirit good to use to clean it? And beeswax polish? There is a logo/badge on the top, most of it has worn away but i would still like to keep it for originality.
I did not know about the glass, thanks for that. I see there is a metal plate on the inside which also holds the light bulbs and is held on with 4 screws, I guess I remove the plate to get to the glass, after removing the pointer rail? Or does it come out from the front?
Thanks for the link to the repair by Tim Pullin. I read this when I was first researching the radio, and it went totally over my head. Good to read it again and this time have a bit more understanding, although changing valves for other valves is still way beyond me. I will be wary of the mentioned resistors.
I will check the polarity of the socket I use, as I see on the wiring diagram the on off switch on the AC11 is single pole, not double like the DAC90A. You are right about the Gallic electricians, the sockets there are totally random, some live on the left, some on the right. As far as I know, so called hot chassis items like the DAC90A and some TVs were banned from being sold in Europe, because of this problem. It was all transformers only. Again, please correct me if i'm wrong. I do know all plug in lamp switches, such as switches on the flex, have to be double pole. The problem, certainly at my Auntie's is earth, or lack of it. Only two kitchen sockets actually have an earth wire connected. As my Uncle says, red to red, black to black, anything else, tuck it back.
Thanks again for all your help and encouragement, I'm off on the 23rd. There is a 3g mobile signal so I will let you know how it goes, and no doubt have a load more questions.
I'm off to polish the DAC90A case.
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Old 22nd Aug 2018, 7:18 pm   #6
GreatHollands
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Default Re: Bush AC11 Advice

Hi everyone,
The AC11 was a complete success, I replaced all the wax capacitors but not the electrolytic as it seems ok, cleaned the valve pins and sockets and the volume, tone and waveband change switch with contact cleaner and replaced the flex and it worked better than expected. I ran a 30 metre wire along a line of trees in the garden, north to south, about 8 feet high, and picked up loads of stations. On long wave I got Radio 4, plus an Irish station and a couple of French ones. Lots of French and German sounding stations on medium wave, but it was short wave that amazed me the most. I was expecting to get a couple of stations but it was full of stations all the way along the dial, all just a fraction of a turn apart. Many were foreign, but some were in English including one from Beijing. I had the wire aerial plugged into the Max Sensitivity socket on the back of the radio, but didn't seem to need an earth connection.

There was a weird clicking though, all the way through all wavebands, about one and a half seconds apart, which took us a while to work out. First I thought it was the electrolytic capacitor, which I hadn't changed, but realised that would cause a buzz, not this clicking. Then we thought it was something in the house, so went around unplugging things but still it carried on. A few days later, in the bar in the village, we mentioned it to a local and he said it was the electric fences going round the cow fields, one of which is opposite the house, so my wire aerial was running alongside one of these fences, about 20 feet away.

I definitely enjoyed doing the radio and am probably going to do another one, maybe one with FM next time. I would still like short wave as well though. I have looked online but I have only seen a VHF94 which has all 4 bands. If anyone can recommend any others please do.
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