Help with Braun MT99R - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

Edward Huggins · 5th Mar 2018, 9:40 pm

The Acos GP67 should not be used, it is a mono type only and will damage stereo records. The Acos GP91-3C has too high an output and may overload the AF stage. The ceramic cartridges you cite will be suitable. but these all have a slightly lower output than the original medium output crystal cartridges that would have been used in the day.

muttley1984 · 7th Mar 2018, 1:57 pm

Thank you for your help, much appreciated

Audio1950 · 7th Mar 2018, 3:30 pm

Whichever cartridge you choose, make sure it comes complete with the mounting clip. Some don't, and without it you will be unable to mount the cartridge in the arm.

muttley1984 · 24th Apr 2018, 9:05 am

Just a quick update on my project and another question I am hoping someone can help me with

I have spent the last few weeks tinkering with my Pye Black Box donor unit which houses the BSR UA8 which I eventually intend to transfer into my grandmas MT99R. I picked up the Pye black box pretty cheap and it said it was all working but in need of some TLC (understatement of the century!). Once I had replaced the old mono cartridge and rewired the new stereo cartridge (which was an extremely fiddly and frustrating job) I was really pleased and pleasantly surprised to finally hear my first ever sound from a vinyl record! On closer inspection the deck was in a pretty bad way. The motor was not correctly supported, the turntable was slipping, the speed selector was ery stiff and both control knobs were broken resulting in 12" records fouling on the speed selector knob! I started by taking it all apart cleaning and lubricating it as per the service data guidelines. The more I learned about the BSR UA8 and how it works the more fascinated and impressed I have become with this technology. Initially I was content that I had replaced the cartidge and was getting some sound but having seen the autochanger working on Youtube videos I was determined to get mine working perfectly. In summary I have cleaned and lubricated all areas suggested in the manual, replaced the motor grommets, replaced both control knobs, replaced the over extended stop pawl spring (with a spring from a stapler!) and adjusted the bend on the reset linkage. Eventually I had the unit recognising the correct size of the record, the pick up moving in to the correct position at the right pressure and playing the record. The autochanger was working perfectly and once the final record had dropped and finished the pick up moved back to its rest and the unit switched off. I was so happy that all the frustrating hours had paid off and pleased that I could now look to get the working deck into the MT99R. The next day I rewarded myself by playing my very limited viynl collection at a decent volume. Happily listening away it suddenly went BANG! I can only assume a capacitor has failed?!? Although pretty gutted with this development I have had to remind myself that the Pye black box was only ever a donor unit to get the BSR UA8 fully functional so to a certain extent it has served a purpose for me.
I am now going to turn my attention back to the MT99R and particularly to trying to make sure it doesnt fail in operation! Boater Sam mentioned the grid coupling capacitor as being C69 on the circuit diagram. This is shown as a 25nF capacitor. Can someone please advise other details (voltage etc.) of this capacitor so I can purchase it ahead of my next visit to my grandmas so I can look to replace it when I wire the BSR UA8 into the MT99R? Hope you can help, cheers

p.s If its easy enough to diagnose and replace the failed capacitor on the Pye black box I would be up for giving this a go but would probably need some clear guidance to attempt a repair

Thanks.

ms660 · 24th Apr 2018, 9:37 am

https://www.cricklewoodelectronics.com/CFH22NH.html

Amongst other suppliers.

Lawrence.

Edward Huggins · 24th Apr 2018, 10:07 am

There is quite a lot of info on repairing these Black Boxes on this site and elsewhere. If your version used the BSR UA8 deck, then it is likely that the amplifier will be a 4 valve unit. You should see 2 x EL42 valves in it. The "BANG" suggests maybe the main smoother capacitor may have failed. If you inspect the chassis you may possible see some damage. Reading your update you have made excellent progress with the UA8 autochanger. Even so, it still comes as quite as quite a shock to me to learn that this is the first time you have ever heard music from a Vinyl record!

5th Mar 2018, 9:40 pm	#21
Edward Huggins Dekatron Join Date: Sep 2015 Location: Southwold, Suffolk, UK. Posts: 8,327	Re: Help with Braun MT99R The Acos GP67 should not be used, it is a mono type only and will damage stereo records. The Acos GP91-3C has too high an output and may overload the AF stage. The ceramic cartridges you cite will be suitable. but these all have a slightly lower output than the original medium output crystal cartridges that would have been used in the day. __________________ Edward.

7th Mar 2018, 1:57 pm	#22
muttley1984 Retired Dormant Member Join Date: Jan 2018 Location: Windsor, Berkshire, UK. Posts: 6	Re: Help with Braun MT99R Thank you for your help, much appreciated

7th Mar 2018, 3:30 pm	#23
Audio1950 Dekatron Join Date: Nov 2008 Location: Whittlesey, near Peterborough, Cambridgeshire, UK. Posts: 3,761	Re: Help with Braun MT99R Whichever cartridge you choose, make sure it comes complete with the mounting clip. Some don't, and without it you will be unable to mount the cartridge in the arm.

24th Apr 2018, 9:05 am	#24
muttley1984 Retired Dormant Member Join Date: Jan 2018 Location: Windsor, Berkshire, UK. Posts: 6	Re: Help with Braun MT99R Just a quick update on my project and another question I am hoping someone can help me with I have spent the last few weeks tinkering with my Pye Black Box donor unit which houses the BSR UA8 which I eventually intend to transfer into my grandmas MT99R. I picked up the Pye black box pretty cheap and it said it was all working but in need of some TLC (understatement of the century!). Once I had replaced the old mono cartridge and rewired the new stereo cartridge (which was an extremely fiddly and frustrating job) I was really pleased and pleasantly surprised to finally hear my first ever sound from a vinyl record! On closer inspection the deck was in a pretty bad way. The motor was not correctly supported, the turntable was slipping, the speed selector was ery stiff and both control knobs were broken resulting in 12" records fouling on the speed selector knob! I started by taking it all apart cleaning and lubricating it as per the service data guidelines. The more I learned about the BSR UA8 and how it works the more fascinated and impressed I have become with this technology. Initially I was content that I had replaced the cartidge and was getting some sound but having seen the autochanger working on Youtube videos I was determined to get mine working perfectly. In summary I have cleaned and lubricated all areas suggested in the manual, replaced the motor grommets, replaced both control knobs, replaced the over extended stop pawl spring (with a spring from a stapler!) and adjusted the bend on the reset linkage. Eventually I had the unit recognising the correct size of the record, the pick up moving in to the correct position at the right pressure and playing the record. The autochanger was working perfectly and once the final record had dropped and finished the pick up moved back to its rest and the unit switched off. I was so happy that all the frustrating hours had paid off and pleased that I could now look to get the working deck into the MT99R. The next day I rewarded myself by playing my very limited viynl collection at a decent volume. Happily listening away it suddenly went BANG! I can only assume a capacitor has failed?!? Although pretty gutted with this development I have had to remind myself that the Pye black box was only ever a donor unit to get the BSR UA8 fully functional so to a certain extent it has served a purpose for me. I am now going to turn my attention back to the MT99R and particularly to trying to make sure it doesnt fail in operation! Boater Sam mentioned the grid coupling capacitor as being C69 on the circuit diagram. This is shown as a 25nF capacitor. Can someone please advise other details (voltage etc.) of this capacitor so I can purchase it ahead of my next visit to my grandmas so I can look to replace it when I wire the BSR UA8 into the MT99R? Hope you can help, cheers p.s If its easy enough to diagnose and replace the failed capacitor on the Pye black box I would be up for giving this a go but would probably need some clear guidance to attempt a repair Thanks.

24th Apr 2018, 9:37 am	#25
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Help with Braun MT99R https://www.cricklewoodelectronics.com/CFH22NH.html Amongst other suppliers. Lawrence.

24th Apr 2018, 10:07 am	#26
Edward Huggins Dekatron Join Date: Sep 2015 Location: Southwold, Suffolk, UK. Posts: 8,327	Re: Help with Braun MT99R There is quite a lot of info on repairing these Black Boxes on this site and elsewhere. If your version used the BSR UA8 deck, then it is likely that the amplifier will be a 4 valve unit. You should see 2 x EL42 valves in it. The "BANG" suggests maybe the main smoother capacitor may have failed. If you inspect the chassis you may possible see some damage. Reading your update you have made excellent progress with the UA8 autochanger. Even so, it still comes as quite as quite a shock to me to learn that this is the first time you have ever heard music from a Vinyl record! __________________ Edward.