This is the third part of the Bang & Olufsen Beolab Penta restoration. For the original post, see:
Vintage Bang & Olufsen Penta Restoration “Project Twins” – Part 1
Crossovers – All of the electrolytic capacitors were spent as well as numerous resistors and coils that were completely fried. I decided to replace all the capacitors with polypropylene units that will likely outlast the rest of the speaker. They sound great and are durable, but also much larger. As a result, lots of reconfiguring and “capacitor tetris” is necessary to make everything fit.
Removing burned out components from the crossover:
Components removed revealing heat damage to the circuit board:
More cleaning up pictures of the circuit board:
New coil and lots of new polypropylene capacitors installed:
Mostly complete and rebuilt (and overstuffed) crossover:
Showing the two boards that make up the crossover for each Penta speaker:
Boards installed as well as the largest of the capacitors relocated further up in the speaker body:
Next: Vintage Bang & Olufsen Penta Restoration “Project Twins” – Part 4
{ 2 comments… read them below or add one }
Erik,
Unfortunately I don’t have a parts list still, but they were polypropylene units in the same specifications as the B&O service manual. The mix of capacitors was solely due to availability at the time. Certain values were only available in certain brands. Also keep in mind that the higher the voltage rating, the larger that capacitor. These polypropylene capacitors are already quite large so the Daytons at 250V vs. the Jensen 400V units were smaller. In terms of sound, I’d doubt anyone could really tell the difference.
Fitting the polypropylene capacitors was extremely challenging. If I ever restore another pair of Pentas, I’ll likely recap the crossovers with high quality electrolytic capacitors instead.
ICE amps are fantastic, however I found restoring the original amplifier pretty standard. While it’s a bit small on space, it’s a conventional design and any decent repair shop should be able to fix it.
The fabric was called “dance fabric” at a local clothing fabric store. It has a bit of lycra in it which made some of the complex angles much better. This is typically used to make ballet and dance clothing.
Hope that helps!
Cheers,
Eric
Hi Eric
Thank for you help and advice about yours huge Penta Twins project. Respect!
I notice that you use difference capacitors; Dayton and Janzen that both are well known brands. Why ?
Do you still have the part list over capacitors to the crossover?
I think, that many Penta owners want to change them first (next (after new foam on midrange speakers), Its not so difficult to change them either.
Properly will many Penta owners just skip the old intern amp ( they are difficult and very expensive to repair, but keep them a heavy stand. Just remove the large fuse in bottom to the amp. and keep the small fuse, then will display still work as normal) and use a new and better amplifier to power the Penta´s ( I use 2 x 1000 original B&O ICEpower watt, as amplifier to my Penta today
(they don`t play louder, but sound great)
Can you please tell, what fabric and value you have used from C1-C2 ect. on crossover one and two?
I notice, that those capacitors you have used, are much bigger then the originally, but still they seems to fits nearly perfect, with enough ( but very tight) room to place the crossover inside the cabinet.
I don`t think, that there is any reason to order expensive capacitors, that we can`t find room for in the cabinet, and therefore yours capacitors part list will be great to make a order after.
Greetings from Erik, Denmark.
{ 1 trackback }