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
Hello everyone,
My latest acquisition, my BM5500, has developed a fever. When I say spicy, I mean it is so hot you can't leave your hand on it for more than a few seconds. Strangely, even when it is in standby the heatsinks are hand-scorching hot. I wish I had a thermocouple to measure this heat, it really is that crazy.
The strangest part is that it continues to handle playback without a hitch. Currently, it is performaing vinyl duty in my apartment's dining area. It stays unused and unplugged most of the time for fear of fire.
I searched the forum and couldn't find any similar issues.
Before I assemble my parts order, I wanted to get your input as to what the problem may be so I can go ahead and order replacement parts. Anyone know whats going on here??
Thanks in advance, all.
Beo4 'til I die!
BeoNut since '75
elephant:Is it drawing full power even when in stand by ?
And check you no load current
Collecting Vintage B&O is not a hobby, its a lifestyle.
Reflow the solder joints on the amplifier power relay, particularly those for the coil.Do the solder joints on the driver transistors too, they will also be bad.And repair the idle current circuits as Søren correctly suggested - replace trimmers and adjust to the specs given inthe servicemanual, do one channel at a time and begin with the channel with the highest idle current.
Martin
Not sure - I need to buy a current clamp to make quick measurements.
Søren Mexico: elephant:Is it drawing full power even when in stand by ? And check you no load current
Absolutely, I'll report back once I have it on the bench.
Dillen: Reflow the solder joints on the amplifier power relay, particularly those for the coil.Do the solder joints on the driver transistors too, they will also be bad.And repair the idle current circuits as Søren correctly suggested - replace trimmers and adjust to the specs given inthe servicemanual, do one channel at a time and begin with the channel with the highest idle current. Martin
Boom! Martin for the win!
Thanks guys. I'll post some pics shortly. The Detroit auto show is just around the corner so this project might be a few weeks out!
Good evening Ladies and Gentlemen,
You join me in my new guest bedroom workshop with my Fostii/iPod playing DRP3's Natradio and a feverish BeoMaster 5500!
I'm off to fetch the screwdrivers and the soldering iron!
After getting the BM5.5k opened up, I spent considerable time simply looking at everything. B&O's methodical, meticulous layout and details are extremely interesting. I start to realize how ironic the overheating issue is.. Thermal considerations have been made throughout the unit, one would think that this would never have a cooling issue. There's a thermistor taped to the transformer as well as what look like a few up against the heat sink, not to mention the massive cooling system complete with a fan and duct work! However, my absolute favorite part is the fan - it is an exact copy of a compressor wheel out of a turbocharger!!
Speaking of the cooling fan... I think that may be the primary issue. Just to the right, there is the motor control board and what seems to be an extra-crispy section of PCB.
Upon even closer inspection, TR4 is actually loose! The solder is still there, however it has completely detached from the legs of TR4.
Nice to see you back at work Evan
I think the problems are a) the Beomaster gets hot and b) the fan doesn't work - but in that order, not the other way round. You'll of course need to sort out the fan circuit, but start with the things Martin suggests above.
I have actually never witnessed a pizza box Beomaster fan starting up during normal operation. In your case it apparently should, but the BM shouldn't get that hot in the first place.
The fan controller PCB has been a bit dark in all Beomasters I've looked into. Apparently it gets quite warm even normally.
--mika
My guesses would be:It runs hot because of bad idle current trimmers and/or settings.Amplifiers are powered also in standby because the solder joints for the amplifier power relay coil are bad (the relay is active in standby!).The cooling fan doesn't run because the transistor you found has broken free from it's connections in the board.It's also my experience, that most Beomasters are a little dark in that area.It's not uncommon to see the fan run a bit if playing at a solid livingroom level using f.e. passive Beovox Pentas.
Thanks Mika,
I'll be honest, I completely forgot this unit even had a fan! The moment I took the case off I saw it and wondered if I should go back and see if it spins etc. But then my eyes landed on the well-done section of the motor controller
There are some other seared sections in the amp as well. Would be interesting to hear if those are also normally warm.
Thanks Martin. Last night I did re-solder TR4 so that should be fixed. However, it wouldn't be such a terrible idea to replace some of these components, I'm sure.
What a strange machine! However, knowing that the amp runs in standby explains its excessive standby sizzling. I have some pictures of the relay that I'll post tonight, it looks to have some sort of corrosion inside the casing.
The strange part is that I only use this for its preamp! The only passive speakers I have driven are my replica BeoVox 2500s and those have never given any of my other BeoMasters any problem. I would expect the BM5500 should remain below average temp. in my setup.
The deposits inside the relay plastic housing is normal and NOT a bad sign.A new relay will have the same in no time.The relay is fine if the amp is playing.
The amp should not run in standby. It's just the power relay to the amplifier that is active in standby (so if the coilis not powered, the amplifier is!).
Hi Guys,
I'm embarrassed to say it has taken me so long to get back to this project, but as of last night I have finally ordered all of the parts needed to overhaul this amp. After a year and some months I'm finally ready to get my second listening space back to normal and knock this project out once and for all.
I have no less than 80 parts on their way to me right now! They should be here sometime early next week.
I'll keep you guys posted