Grundig Yacht Boy stuck tuning knob - UK Vintage Radio Repair and Restoration Discussion Forum

leaky_cap · 17th Jan 2016, 11:55 pm

I did this job today so thought I'd share the story of this overhaul before it fades from my memory.

I came across one of my Grundig Yacht Boy's (209/210) on the shelf and the tuning knob was seized solid. It was stiff a couple of years ago but I did nothing about it and this is the result. I took the radio apart and found that the grease had gone rock hard in the tuning spindle bearing. The same way grease goes rock hard in old record decks that seize the turntable and the automatic mechanism.

First I needed to get to the spindle and this meant removing the drive cord pulley. I didn't want the aggro of the drive cord unravelling so I put some scotch tape around it to prevent it coming undone. The last thing I wanted was to spend a whole day fiddling with the drive cord. I pulled off the pulley and then carefully removed the grease at the top of the shaft. This was all I could get to as there is no easy way to dismantle the bearing. I used the smallest jeweller's screwdriver to carefully remove the flaky grease from around the top of the bearing. Before I did this, I made a hole in a piece of paper and slipped it over the spindle so the crumbs of hard grease didn't fall into the radio. Once the grease was removed the top of the bearing looked clean. There may have been a black spring clip at the top of the bearing but it was too small for me to make out even with a magnifying glass. All I could think of doing was to use 3in1 oil to free the bearing. So I put a tiny amount of a Qtip and tried to soak it into the top of bearing. I only used tiny amounts just enough to let some oil sit on the top of the bearing. I put the tuning knob back on to help and after a few minutes I could feel it start to move, but was still very very stiff. I very gently rocked it back and forth not wanting to put too much pressure on it. Patience is the key here. After about 15 minutes it was moving from one end of the dial to the other, but still stiff. I carried on rocking it and occasionally going from end to end of the dial and gradually over an hour the oil worked into the bearing. I didn't add any more oil after the initial application at the start. Just enough to see a pool of oil sitting at the top of the shaft.

Then when it was free enough to spin the tuning knob with one finger on its outer rim, I replaced the drive cord pulley. This added a fair amount of load the the spindle and I now needed a finger and thumb to turn the knob. I also had a creaking sound from the drive cord. I decided to try some silicone polish on a Qtip and rubbed it on the drive cord guides. Black crud came off the drive cord. It helped but still had the creaking noise. After about 3 applications of the silicone polish including rubbing it along the drive cord the creaking disappeared and the the force needed to tune the radio was normal.

Then carefully got some Servisol into the bottom of the press button switches with the radio upside down so it ran into the switch from the bottom. They were not that bad, but are now crackle free. Then replaced the blown dial lamp and was ready to reassemble.

The power on/off press button feels rough and sometimes needs extra pressure to get the latching mechanism to release. Servisol didn't help at all, so I turned my attention to the copper colour tab at the top of the switch that flaps slightly when operated. I carefully dabbed some oil on it, but confess I have never understood how those switches work and wish I could get my head around what makes them rough or not latch - any ideas/experience very welcome.

After this I replaced all the electrolytics in the audio amplifier. Probably wasn't needed but the old ones are over 40 years old.

I guess the moral of this story would be to occasionally twiddle the tuning knob of these old radio's. I know I will be from now on.

crackle · 18th Jan 2016, 7:31 am

Its great that you have managed to get it working again, they are a great radio.
I have done this sort of thing to about 4 Grundig radios now, but I use sewing machine oil as I have heard that 3 in 1 oil can go hard in time. To speed the process of getting the spindle to start turning I put the tip of my 30w soldering iron on the spindle to warm it.
I then work in penetrating oil to loosen and dissolve the old grease, then I work in a drop of sewing machine oil.
If the on/off button has a nylon shaft they normally rely on being clean and dry as nylon is self lubricating. It may be that 3 in 1 oil, which is not that thin, will gum up the latching mechanism. It could simply be worn out and replacement needed.

Mike

paulsherwin · 18th Jan 2016, 11:34 am

They do seem prone to this. I use Plus-gas to free everything up, followed by some automotive engine oil a few days later. A complete stripdown is desirable but is a lot of work.

3 in 1 shouldn't dry up but the extra additives it contains offer no benefit, and many people do like to steer clear of these proprietary witch's brew concoctions.

mhennessy · 18th Jan 2016, 2:52 pm

Contact cleaner/lubricant can work well for this. I use Electrolube EML. Perhaps there are good reasons to use something else, but it does seem to do the business, and a full strip-down, clean and re-grease doesn't viable in these sets.

For the really bad ones, a bit of IPA works well to break up the solidified grease, but obviously that doesn't have any long-term lubrication effect, so you do need something else afterwards.

The tip about applying heat is a good one

emeritus · 18th Jan 2016, 3:04 pm

I well remember my late father, who worked in a chemical works, singing the praises of Plus Gas for freeing seized fasteners and pipes more than 50 years ago. I just hope the EC don't decide to ban it! If you don't have any Plus Gas handy, petrol lighter fluid (preferably Ronsonol) works quite well.

I remember seeing an advert for 3 in 1 oil in a pre-war tools catalogue. It said that it was a mixture of three different types of oil: mineral, vegetable, and animal, AFAIR. Goodness knows what goes in it nowadays.

paulsherwin · 18th Jan 2016, 4:32 pm

It's basically mineral oil plus a bit of white spirit. Household oil was mostly castor oil before the 1950s, so that may be where the reputation for gumming up comes from.

17th Jan 2016, 11:55 pm	#1
leaky_cap Diode Join Date: Jan 2016 Location: Newmarket, Suffolk, UK. Posts: 2	Grundig Yacht Boy stuck tuning knob I did this job today so thought I'd share the story of this overhaul before it fades from my memory. I came across one of my Grundig Yacht Boy's (209/210) on the shelf and the tuning knob was seized solid. It was stiff a couple of years ago but I did nothing about it and this is the result. I took the radio apart and found that the grease had gone rock hard in the tuning spindle bearing. The same way grease goes rock hard in old record decks that seize the turntable and the automatic mechanism. First I needed to get to the spindle and this meant removing the drive cord pulley. I didn't want the aggro of the drive cord unravelling so I put some scotch tape around it to prevent it coming undone. The last thing I wanted was to spend a whole day fiddling with the drive cord. I pulled off the pulley and then carefully removed the grease at the top of the shaft. This was all I could get to as there is no easy way to dismantle the bearing. I used the smallest jeweller's screwdriver to carefully remove the flaky grease from around the top of the bearing. Before I did this, I made a hole in a piece of paper and slipped it over the spindle so the crumbs of hard grease didn't fall into the radio. Once the grease was removed the top of the bearing looked clean. There may have been a black spring clip at the top of the bearing but it was too small for me to make out even with a magnifying glass. All I could think of doing was to use 3in1 oil to free the bearing. So I put a tiny amount of a Qtip and tried to soak it into the top of bearing. I only used tiny amounts just enough to let some oil sit on the top of the bearing. I put the tuning knob back on to help and after a few minutes I could feel it start to move, but was still very very stiff. I very gently rocked it back and forth not wanting to put too much pressure on it. Patience is the key here. After about 15 minutes it was moving from one end of the dial to the other, but still stiff. I carried on rocking it and occasionally going from end to end of the dial and gradually over an hour the oil worked into the bearing. I didn't add any more oil after the initial application at the start. Just enough to see a pool of oil sitting at the top of the shaft. Then when it was free enough to spin the tuning knob with one finger on its outer rim, I replaced the drive cord pulley. This added a fair amount of load the the spindle and I now needed a finger and thumb to turn the knob. I also had a creaking sound from the drive cord. I decided to try some silicone polish on a Qtip and rubbed it on the drive cord guides. Black crud came off the drive cord. It helped but still had the creaking noise. After about 3 applications of the silicone polish including rubbing it along the drive cord the creaking disappeared and the the force needed to tune the radio was normal. Then carefully got some Servisol into the bottom of the press button switches with the radio upside down so it ran into the switch from the bottom. They were not that bad, but are now crackle free. Then replaced the blown dial lamp and was ready to reassemble. The power on/off press button feels rough and sometimes needs extra pressure to get the latching mechanism to release. Servisol didn't help at all, so I turned my attention to the copper colour tab at the top of the switch that flaps slightly when operated. I carefully dabbed some oil on it, but confess I have never understood how those switches work and wish I could get my head around what makes them rough or not latch - any ideas/experience very welcome. After this I replaced all the electrolytics in the audio amplifier. Probably wasn't needed but the old ones are over 40 years old. I guess the moral of this story would be to occasionally twiddle the tuning knob of these old radio's. I know I will be from now on.

18th Jan 2016, 7:31 am	#2
crackle Rest in Peace Join Date: Mar 2011 Location: Basildon, Essex, UK. Posts: 4,100	Re: Grundig Yacht Boy stuck tuning knob Its great that you have managed to get it working again, they are a great radio. I have done this sort of thing to about 4 Grundig radios now, but I use sewing machine oil as I have heard that 3 in 1 oil can go hard in time. To speed the process of getting the spindle to start turning I put the tip of my 30w soldering iron on the spindle to warm it. I then work in penetrating oil to loosen and dissolve the old grease, then I work in a drop of sewing machine oil. If the on/off button has a nylon shaft they normally rely on being clean and dry as nylon is self lubricating. It may be that 3 in 1 oil, which is not that thin, will gum up the latching mechanism. It could simply be worn out and replacement needed. Mike

18th Jan 2016, 11:34 am	#3
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,944	Re: Grundig Yacht Boy stuck tuning knob They do seem prone to this. I use Plus-gas to free everything up, followed by some automotive engine oil a few days later. A complete stripdown is desirable but is a lot of work. 3 in 1 shouldn't dry up but the extra additives it contains offer no benefit, and many people do like to steer clear of these proprietary witch's brew concoctions.

18th Jan 2016, 2:52 pm	#4
mhennessy Dekatron Join Date: Jul 2007 Location: Evesham, Worcestershire, UK. Posts: 4,244	Re: Grundig Yacht Boy stuck tuning knob Contact cleaner/lubricant can work well for this. I use Electrolube EML. Perhaps there are good reasons to use something else, but it does seem to do the business, and a full strip-down, clean and re-grease doesn't viable in these sets. For the really bad ones, a bit of IPA works well to break up the solidified grease, but obviously that doesn't have any long-term lubrication effect, so you do need something else afterwards. The tip about applying heat is a good one

18th Jan 2016, 3:04 pm	#5
emeritus Dekatron Join Date: Jan 2012 Location: Brentwood, Essex, UK. Posts: 5,339	Re: Grundig Yacht Boy stuck tuning knob I well remember my late father, who worked in a chemical works, singing the praises of Plus Gas for freeing seized fasteners and pipes more than 50 years ago. I just hope the EC don't decide to ban it! If you don't have any Plus Gas handy, petrol lighter fluid (preferably Ronsonol) works quite well. I remember seeing an advert for 3 in 1 oil in a pre-war tools catalogue. It said that it was a mixture of three different types of oil: mineral, vegetable, and animal, AFAIR. Goodness knows what goes in it nowadays.

18th Jan 2016, 4:32 pm	#6
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,944	Re: Grundig Yacht Boy stuck tuning knob It's basically mineral oil plus a bit of white spirit. Household oil was mostly castor oil before the 1950s, so that may be where the reputation for gumming up comes from.