ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
dear all, I've been holding on to a broken MCL2P for quite some time. I bought it about 3 years back at a giveaway price on eBay, despite not having a use for it at the time I thought it was too good to pass up, and I was planning on a larger multi room installation when I moved house. Anyway, about a year ago I tested it out and was disappointed to find it was not working. On closer inspection it was clear the unit had been dropped when it was posted, and the PCB had cracked, taking a number of components out of the circuit as the tracks had sheared. I repaired all of the broken tracks with flying leads from the affected components, tested and reboxed. All worked okay but it's been a bit temperamental since. I'm trying to get it working reliably as I need it to provide a bit of extra 'umph' for some gel audio units (on the back of a plasterboard wall).
I think the issue is the pair of unusual large capacitors, which only appear to have one central 'leg'. One of these had detached itself from the board. I asked my father about these; he's been an electronics engineer since the early 1960s and he has never seen anything like them! It seems there is a ring on the base of the can that engages with a matching ring on the PCB to provide the second point of contact. It's not clear whether these should be soldered to the outside of the can or not, and if so it would be hard to make a good joint due to the metal used (possibly with lots of flux and a good blob of solder, but that doesn't seem like a very sensible way to design the components!) Does anyone have any experience or knowledge of these capacitors and how I can ensure a good connection?
apologies for a long post, many thanks for your help
Pictures please. Oh and I found a diagram on the net - hope it's alright to post it here
These caps were used a lot in the 80ies. Supplier is a german company called "Roederstein" .
Today it is a little bit difficult to get these parts, but these big caps are very durable, quite in contrast to the samller types.
The middle pin is"+", the round ring with 3 pins ground. Soldering was never a problem??? Must be something with your equipment, temperature or wrong solder...
The can be replaced by todays standard material, no problem. Just remember, that B&O used only 1 of the 3 ground pins... so choose the right one.
They can still be supplied...
http://www.ebay.de/sch/i.html?_odkw=roe+nos+hi_end&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.H0.Xroe+4700+nos+hi_end.TRS0&_nkw=roe+4700+nos+hi_end&_sacat=0
Fantastic - thanks very much. I was using a good quality temperature regulated iron and good old fashioned lead based solder (I know, but the new stuff doesn't flow properly). Probably just a case of giving the cans a good clean down.
Thanks again a in for the help
Luke
Die_Bogener: These caps were used a lot in the 80ies. Supplier is a german company called "Roederstein" . Today it is a little bit difficult to get these parts, but these big caps are very durable, ..
Today it is a little bit difficult to get these parts, but these big caps are very durable, ..
These Caps do leak often. I've had BC9500's with shortened caps and BM4500 with the leaked contence on the mainboard. So when I see these "Roederstein" I always measure and look at them carefully.
Die_Bogener: The can be replaced by todays standard material, no problem. Just remember, that B&O used only 1 of the 3 ground pins... so choose the right one.
It is just a mechanical matter. With these 3 (ground) pins the caps could be placed firmly on the board. But be aware that in some B&O designs, the ground pins are used as "Via". As I remember in a BC9500 the outer pins are used as via's. So, when you replace the cap, connect the pins where traces are connected by making a small "bridge" between the pins.
And last thing. When you see these caps, then ALWAYS resolder them. 90% change that the inner pin is loose. Most times hardly visible, but it causes a lot of strange behaviour. Due to the warmth inside the device, the inner pin of the cap, stretches, or shortens it's leg. Causing bad solder joints.
As I understand the OP's post, it seems that the mounting rings have snapped off the capacitor cans. as you can see from the linked auction pictures, they are an integral part of the cap itself and not some separate mounting solution. Don't even bother trying to solder the ring back to the cap - the case of the cap is most likely aluminium.
if you can source another type of caps with the same capacitance and voltage rating that fit physically, they will work just fine (but note what Beobuddy said about interconnects on the circuit board).
--mika
Many thanks for the advice everyone - sounds like it is a case of sourcing some new caps to drop in (noting the issue about the grounding pins). With a bit of luck there's still life in the old amp yet!
all the best