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This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Some of you will probably think I am dumb but, after reading threads and threads about most of you repairing their stuffs, I thought I was ready to, at least, have a look inside my beomaster 700. It works fine but I have some small issues with the volume control (sometimes very loud even at very low level, it seems I have a problem with the knob). As it seems to be more a mechanical problem than an electronic problem, I think I am capable to do it.
So, yesterday, I read an old post from the archived forum and look at an advice from Martin to remove the cabinet (thank you from writing so many detailed posts about repairing almost every vintage B&O stuffs) : “Remove screws at the bottom and, depending on version, the four rotating knobs on the front.”
It seems to be easy but… I do not know why I understand “remove screws at the back…” and I started to remove all the screw at the back (almost 12 screws) and the cabinet did not slide ;) ! My girlfriend was watching TV (I was in the living room (another thread ;)) and she said me : “did you look at the bottom ?” ! Obviously it was the solution ;).
So I slide the cabinet and screw all the 12screws I removed. Nothing complicated at that time.
BUT, when unscrewing the 3 special screws that are at the back (people who know this radio already know the major mistake I made ;)), it loose the FM dial string and I had to put it back L
I took me 3 hours to put this string back !!!! I hated the guy who invented this multiple pulleys and this thin string ;) ! At the end, after hours trying and trying, watching videos, reading posts on beoworld, I realize I can play a little bit with the 3 screws to win the 3 mm I needed to finish the job (to be honest, being an octopus will have help) !
After finishing, I realize I did not improve or repair anything but feel very proud being able to repair MY mistake ;)
This was my first attempt and I probably learned the most important lesson ;) ! Being patient and calm help, thinking before doing is the key, it is much more complicated doing things than reading them.
The only problem is that it gave me the desire to continue ;)
Thank to all of beoworld members that give so many advices and post so much pictures and a special thanks to my friend Leslie who really infected me with this beovirus ;). (sorry for the too long post)
On Friday, episode 2 ;) I will have to fix this volume control, if some of you have wise advices ;).
As I like pictures (even if mine are always poor quality), this is the result with the guilty 3 screws I should NEVER have unscrew (or maybe it was a good lesson for me ;)).
Good job !
There are several, slightly different, versions of the Beomaster 700 and 900.Some have two screws at the bottom, others four.Some have two fairly large screws at the extreme left and right edge of the rear panel.Some have two or four smaller screws at the extreme upper and lower edge of the rear panel.Some will need the four knobs at the front removed.
If the volume control cannot be repaired a replacement potentiometer could be the only way.I have seen them fail occasionally so it would come as no surprise.
Martin
Thank you Martin, mine has 4 screws at the bottom and I had to remove knobs ;).
I will see tomorrow what to do with the volume control (my idea was first : look internally to see if nothing is broken, then maybe add some sewing machine oil...).
Is there any way to easily control that the potentiometer is good or not ? Is it difficult to change it (if it is faulty and if I can find one ?))?.
Thanks again,
Jacques
Finally, I correctly remove the amp from the cabinet, unplugged the antenna, the speaker plug and identify the problem with volume control.
Indeed, the knob has become a little bit loose and when turning, it do not always turn the potentiometer internally (I hope I explain it correctly).
My question is : Is it repairable or should I change the whole potentiometer ? If I have to change it, where can I find one ? and how can I remove it (it does not seem to be screwed....
Thank you in advance,
The potentiometer has a large brass nut.Take off the dial and you can see it.I can probably find a good used original part if yours cannot be repaired.
thank you for the proposition that will probably be usefull.
I removed and opened the potentiometer (very easy, I should have see this washer ;)), then I take a picture, put everything back and tighten the whole things.
One advise for newbieslike me : “each time you open something, be careful, something will probably fall from inside ;). Take a lot of pictures if you want to be able to close it after !
I do not know if this will be better :( . Before trying it, I have to go in the cellar to take my soldering iron (I unsolder one of the leg of the small resistance at the bottom of the potentiometer). If you can see that it is broken, I will not test it ;)
To try it, I will use my Iphone as external source to have a better control of the volume (the idea is not to blow the speaker if I did something bad)... good idea ?
after testing.... it does not work :(
Martin, I will PM you if you can provide me this potentiometer ;)
That's a special beast, a 22K potentiometer with a loudness tag at 5K.Beoworld to the rescue :
Thanks a lot Martin,
Sorry, I am really a beginner, could you explain me what does "loudness tag" mean ?
BR,
Jacques.Things like that happens to me all the time, when using a screwdriverSometimes Service manuals are not clear enough. Sometimes I know which screw to unscrew, and just cant explain even to myself why I unscrewed that screw I KNEW I shouldnt unscrew. Sometimes things fall apart of age. Years later, I just reflext and say "hmmm, things to learn again" The string, ohh yes.. it takes time.If it breaks, I have sucssefully used nylon string that you use for sewing. We called it "bear-thread" here as it is super strong.Christian
My re-capped M75 are my precious diamonds.
Jacquesboo: Thanks a lot Martin, Sorry, I am really a beginner, could you explain me what does "loudness tag" mean ? BR, Jacques
Loudness is a tonecontrol function, adding a little bass and treble at low volumes to compensatefor the humans ears sensitivity for these frequencies at low volumes.In most Beomasters loudness can be switched off if you prefer the true yet thin and a bit canny and sterilesound that results.Beomaster 700K has loudness on permanently. The extra solder tag on the potentiometer is for this function.
I understand better why it sound so warm ;).
I am am eager to change this potentiometer !
thank you,
jacques
Yesterday, I changed the potentiometer (my first real reparation), thank you Martin ! I like the sound of this beomaster 700, warm with a very good radio reception (In my view, mono is always better for old radio). Thanks to Leslie who did the job, I do not have to change any capacitors, so everything now works perfectly ;). Next time, I will do it ;)
Ok, it is a very simple task but I am really proud of me ;).
To be honest, I am a little bit ashamed to put the picture of the result (I did not use a soldering iron since school ;). But I know I will do better next time. The most important is that it works ;)
Thanks to all who helped me, this is just a beginning ;)
Christian Christensen: The string, ohh yes.. it takes time.If it breaks, I have sucssefully used nylon string that you use for sewing. We called it "bear-thread" here as it is super strong.
The string, ohh yes.. it takes time.If it breaks, I have sucssefully used nylon string that you use for sewing. We called it "bear-thread" here as it is super strong.
The beomaster is now closed and I did not break the strings ;) ! Hope it will never happend (but know that it will probably on another machine) ;)
Thank you