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This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
I have on my Christmas bench a beomaster 8000 for a recap. It had the old trimmers (someone has recapped it before) so I was thinking its a simple job and nice to do now when I have time -not nice at all.
I change the trimmers and right side was simple and easy but when I started to adjust the no load current on the left side and I was almost at 18 mv the Bm vent suddenly to the protection and cut the power. And after that it went to protection as soon beomaster was turned on from stand by.
No worries, I thought -I have a spare unit where one channel is fully working, so I made the swap. The same thing happens. I made the 18 mv adjustments and left it on for a while (20 sec or something) and then the same thing happens- bemaster went into protection and cuts the power.
So I was wondering is this a oversupply problem. Its strange though the beomaster was fully working with no problems prior this. And I only removed the two outputs nothing more was done to it. The power supply has been recapped by someone before.
Wiresnwires
I remembered that I did a recap job on the filter board as well. As all ways I take pictures prior and after the recap just to make sure everything is correct. Could some problem in filter board trigger the fault switch and cut the power. As tested the right channel is working properly when the left channel is disconnected.
The BM was working properly prior cap and trimmer change.
I did a recap on the power supply board and re-flow of the connectors but the problem is the same. As with the first output I had in the bm the idle current was adjustable and I got the 18mv but after a little while apr. 20 seconds it cut the power off and after that it went straight to protection as soon bemaster was turned on from standby. The same scenario was with a donor output from working beomaster. If the channel is not connected to power supply then beomaster works fine. So this lead me to believe that the problem is not the output but somewhere else in the beomaster like in power supply board. I did re flow and recap but yes problem is the same. Next is the microcomputer board one cap and re flow of all the connectors. I use a cap kit from Martin and got channel trimmers from him as well.
Here is the channel after recap and with new trimmers added. I made re flow of the connectors to all so checked the continuity:
Here is the power supply prior re cap, someone has all ready done a recap for this but I wanted to be sure and recapped it anyway and did the reflow of the connectors and checked the trace continuity to:
Here is the power supply after recap:
Next is the micro controller board. And as said the Bm was fully working prior recap of the bought channels and filter board.
Hi,
The Beomaster 8000 Left and Right channel output amplifier assemblies are identical so I would probably swap them as a first test to see if the problem moves with the swap. Then you know whether the problem is with the Left channel output amplifier assembly or with something else.
It is kind of a pain to replace the Left channel output amplifier assembly but here are a couple of posts I made showing how to do it.
Link 1
Link 2
-sonavor
Hi Sanovar and thank you for the reply. I have actually change the output for a working one to test it form another unit. The result was the same.
I now changed the switchers all so wit the same result. The unit goes to protection as soon the unit is turned on from stand by. Here is the whole unit opened up:
And after truing it for couple of times I got a little lovely sparks from this area marked with yellow circle:
It started out as fully working unit-had been in heavy use in my living room for 4 years, it had old trimmers on output what I wanted to change to a new one to prevent a channel blowout.
Now its just a bundle on c...p I think I will use it to make a new barbecue for the summer to grill stuff on it...
..
Don't give up on it. It can be fully functional again. You just have to deduce where the problem is.If I understand correctly you have independently verified that the two output amplifier assemblies are good. With a new left channel output amplifier assembly you now see the unit going to protection immediately when you turn it on. The area you circled is the startup circuit which has the two big relays on it. Something is triggering the protection circuit so that needs to be figured out. Sparks on the startup circuit may mean you have a short somewhere.
With the ±55V power removed from the Left Channel Output Amplifier does the Beomaster still go into protection shut down?
Just a caution...The Beomaster 8000 has a complicated set of connections and wires. When messing with everything it is very easy to get some things messed up. Carefully review all of the wires. Also measure all of the main power outputs (+5V, ±15V, ±55V) to verify all of those. Be careful probing for measurements. I always unplug the Beomaster whenever I move measurement probes. It is safer that way. It avoids accidentally short circuiting something.
Cracked solder joints at the relays.- And what John just said.This is not an easy beast to service. It is known to give even trained tech guys a good run for their money.
Martin
Dillen: Cracked solder joints at the relays. Martin
Cracked solder joints at the relays.
Oh yes....It is very possible that in moving things during the recap exercise some problem solder joints failed. It is a good idea to re-flow the solder connections on ground vias, board connectors and large components mounted to the boards like the relays Martin mentioned.
Hi and thank you for the helpful tips, I totally disregarded the startup circuit as a possible culprit for this BM.
I did the re flow of the start up circuit. Following thing happens when plugged in.
The unit comes to standby. When the unit was powered up a huge amount of smoke came out of this area and the power was cut off. I think this is the RL1:
And the 30R2, 180 ohm resistor on the rectifier blow out here:
And unit cut the power. the more frustrating is that the unit was fully working but as you bought said the units are delicate and who know what could happen when removing one or bought outputs... As im out of the 180 resistors I have to go get them next week on monday.
Oh dear. To regroup...you know that for the resistor to burn up like that something is causing too much current to take that path. I would disconnect as much of the Beomaster you can that isn't required for power on before replacing the burned components and retrying. It is likely the cause is still present. Perhaps some component or wire got pushed into something it shouldn't when inserting the output amplifier assemblies. There must be some short circuit to somewhere it shouldn't to cause a resistor to burn up.
Hi, I think what happened was that the C1 - the 330nF/275V cap went up in smoke its not nice to look at :
If I now remember correctly it was bad looking prior the recap but not as bad as this. Is it possible that this cap was the problem from the start...just in the brink of failing?
Here is the other side of the startup board with burnt out resistor on the left there:
So Now to order new parts, I think in this thread is the same problem:
https://archivedforum2.beoworld.org/forums/t/36661.aspx
Now off to order some parts
That capacitor is a Class X or X2 component. It sits right across mains and must be replaced ONLY with one of a similar type.
The same goes for the resistor that burned. It's a safety component, it MUST be a flameproof type (and you know why now).The suppression capacitor is not the reason the resistor burned. The reason for that will have to be investigated.
Hi. Thanks for all the advice. I did the right thing and took the Beomaster to the repair man. It is working now.
But there is the fault of left channel 2.9 volume cut out. Beolover addressed this in hes forum but Its not clear for me is the left channel AD7110KN upper or lower chip. I managed to order some of chips online and want to do the swap.
Regards
E.
Here it is with picture. I took the picture from Beolover sblog.
Is the left channel volume chip the A or the B?
Thank you for the reply and help. The right channel is chip A and left channel is chip B!