Braun LV1020 restoration and noise issues

[TellMeWhy]

Hi Braun fans!
I have a wonderful pair of LV1020 active trips-amped monitors that have had a full professional recap and also most of the transistors replaced....

Since the restoration both units suffer from intermittent, scratchy noises (not volume dependent), particularly when the amps are on idle or playing quietly. There also occasional pops and crackles. These noises were much worse after the first revision, but following extensive cleaning of all the various internal connections it is now much better (but still there).

I have a suspicion that it can either be due to bad connections in the main multi connector, or otherwise bad thermal contact between power transistor and heatsink.

Most of the other suspect connections have been remade, and to be honest, my tech has spent many hours on these amps...

I would like to get ride of the noises as the sound from the speakers is truly first class...

Anyone out there with experience of these active speaker amps?

Cheers from Berlin,
Jon

 

[baco99]

Those boards will benefit from a full recap and re-solder of the multi-pin connector that's located in the middle of the board.

 

[TellMeWhy]

Those boards will benefit from a full recap and re-solder of the multi-pin connector that's located in the middle of the board.

Hi! Yes, both boards have had a completely full recap, and many of the transistors also replaced. The multi connector between pre and power boards was removed and the wired hard soldered into place. Only the multi pin connector on the speaker unit itself has not been looked at (my tech had only the amps, not the speaker chassis...)...
What do you think?

 

[TellMeWhy]

If anyone is interested, I found the solution! The issue was caused by the thermal paste and mica insulators between power transistors and heatsink! New mica and paste and they work like a dream! This will always go onto the fixing list for all vintage amps from now on...

 

[baco99]

If anyone is interested, I found the solution! The issue was caused by the thermal paste and mica insulators between power transistors and heatsink! New mica and paste and they work like a dream! This will always go onto the fixing list for all vintage amps from now on...

ah! I had just assumed that was done with the recap. Yes, highly recommended.

 

[pashka]

I had this, as if a mouse was scratching the speaker. It may be due to a number of reasons, either somewhere on the board there is bad soldering on some element, or the main capacitors in the power supply. The second set of amplifiers has the same nonsense, but I haven't gotten around to it yet and everything original is still there, sometimes I compare what was and how it became.