Bush DAC90A can't get tuning knob off
 

Hello; decided to start a "new" hobby, well since 1964 and the school radio society. Friend gave me a Bush DAC90a which I plugged in (know now I shouldn't have) and it worked, sort of for a bit with distant Radio 4. Seems to be an older restoration judging by the dust inside.

Problem is, the band change and volume knobs are secured by grub screws as per advice in this site, but the tuning knob (which looks original, with felt disc and broken perspex collar) doesn't have a screw securing it but what seems like an oddly shaped metal bush on the shaft as seen from the inspection hole underneath. I can't work out what this is or how to get it off to get at the chassis. Can anyone help? Otherwise my new hobby seems to be dead in the water.

Thanks

Re: Bush DAC90a can't get tuning knob off
 

That doesn't sound original. The tuning and volume knobs should be the same.

The collar is a retaining clip on a push on knob from somewhere else. Judicious application of Plus Gas, gentle heat and brute force is likely to be needed. The knob's not right anyway, so.....

Re: Bush DAC90a can't get tuning knob off
 

It looks to me like a 'Horseshoe' spring, made from spring steel. Others will hopefully confirm but I think you just have to prise it open at the gap shown in the second picture until the gap is wide enough to let the spring come off the shaft.

Of course it may be rusted onto the shaft, which could complicate things a bit.

Re: Bush DAC90a can't get tuning knob off
 

The knob would normally just pull off complete with the "D" clip.

Lawrence.

Re: Bush DAC90A can't get tuning knob off
 

As Lawrence said the knob should just pull off.
See if you can carefully ease the clip off the back of the knob using a long screwdriver through the hole. Then as suggested apply some release agent to the back of the knob you may be able to get it to run down the control shaft and into the back of the knob.
Once it has had time to soak in wriggle the knob carefully and push and pull at the same time. It should give in. The clip is easily refitted once the knob is off.
Before you refit the knobs apply a little grease or Petroleum Jelly to the control shafts this will make refitting and future removal easier.
If you have one front knob held with a screw and one with a clip one of the knobs is wrong for the set. Only the later versions had knobs held with clips, earlier had screws. A picture of the set and knobs would help identify which knob is the wrong one for the set if that is the case.
Rich.

Re: Bush DAC90A can't get tuning knob off
 

Many thanks to all, will have a go if I understand the advice correctly. Yes the two knobs are different, different sizes, the tuning one looks original. Will let you know how I get on

Re: Bush DAC90A can't get tuning knob off
 

Yeah it does look like its on the wrong way round try using flat head screw driver through the hole push in a sliding motion (with the screwdriver still straight) against the area marked by the red arrow try not to use the hole as leverage as you will damage that area of the case if your not sure/confident put cardboard around the hole but a touch of force and a bit of technique will get it off take your time and think it through

Re: Bush DAC90A can't get tuning knob off
 

Plus gas on the shaft and leave radio face down so it soaks in - always worked for me. I also find a lever each side of the knob helps once the plus gas has had some time.

Re: Bush DAC90A can't get tuning knob off
 

Thanks all especially DJ Keet, I used the plus gas and flathead screwdriver approach and it came off - turns out it was not a metal bush but part of the bakelite knob. Still I now have a chassis free and ready to replace the caps, living and learning in this great hobby.

Re: Bush DAC90A can't get tuning knob off
 

Surely the two knobs must have looked different, you even mention a Perspex collar on the wrong one.

Re: Bush DAC90A can't get tuning knob off
 

Hi Steve glad you got this set please be aware that this set has no mains transformer and depending which way the mains lead is connected the chassis becomes live and have you got the service sheet ? you can buy it on this forum for £1.99 kind regards Bob

Re: Bush DAC90A can't get tuning knob off
 

Yes thanks to all I have got the service sheet and am aware of live chassis (potentially). Will be very careful when it comes to testing.

Re: Bush DAC90A can't get tuning knob off
 

Hi Steve please post some pictures of the set before & during replacing capacitors kind regards Bob

Re: Bush DAC90A can't get tuning knob off
 

Steve

If you want electrolytics you can get them from Jellyfish Audio at very reasonable prices

Ken

Re: Bush DAC90A can't get tuning knob off
 

Does it need new electrolytics? My DAC10 is working fine on the original from 1952!

Re: Bush DAC90A can't get tuning knob off
 

Indeed.

Electrolytics in Bush DAC90A's seem to be a cut above the rest. I've never had to replace a smoothing can in one.

Re: Bush DAC90A can't get tuning knob off
 

Yes I second that I have not had to replace a smoothing can on a DAC90A or DAC90. Kind regards, Bob.

Re: Bush DAC90A can't get tuning knob off
 

After about 3 years of use, my restored DAC90 electrolytic caps failed. I wish I had changed it when I restored the radio, it would have saved a run around thinking it was an intermittent valve fault.

John.

Re: Bush DAC90A can't get tuning knob off
 

Hi John was it the main ht capacitor that had failed ? & what was the make kind regards Bob

Re: Bush DAC90A can't get tuning knob off
 

Hi Bob, I will check tomorrow.

John.