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
Hi guys,
this Beomaster was given to me, it is in pristine condition. But it is also dead in the water. On power up, all I get is the relay clicking several times and a display that says [P]. That's it.
So I suspect the power supply immediately. Caps were all OK (although ripe for replacement). Then it hit me, there was no power at all. I can see no AC voltage flowing into the circuit, so nothing happens at the higher voltage point. There is simply no power; all fuses are fine.
The smaller transformer appears to work, somewhat. If I disconnect the connector to the power board it will give me between 8 - 10v. When I connect it the output immediately drops to less than half of this, which is odd.
I have a sinking feeling that this Beomaster has had a failure in either the large transformer or both the larger and the smaller one. What do you think? Or is it the relay that is bumming the system?
Regards,
BB
It is difficult to tell when we can't see what you see but it sounds like you are getting power if you see lights and hear relays clicking.To me that would indicate that the Beomaster is getting power to the microcomputer board but there is a fault that is keeping the amplifier circuit from powering up, so the protection relays are kicking in.By pristine condition I am assuming you mean cosmetically. If the Beomaster is running with its original parts inside then you will likely have a bunch of faults with its age due to capacitors being out of tolerance. Specifically, the electrolytic type capacitors. Once they start drifting beyond the limits the circuits are designed for the circuits no longer perform correctly.
Replace the electrolytic capacitors, check board to board connectors (inspect and even reflow those connector solder joints). That will likely solve a bunch of the problems. There still could be some other issues but the first step is replacing the electrolytic capacitors.
-sonavor
I agree with John. Electrolytics first, and connectors.
I very much doubt that the main transformer should be defective. I think that what you are experiencing is the amp's protection doing its work;
Don't underestimate the amp board trimmers. They are often found to be defective, not being potted.
This amp is really straightforward mind you. Nothing exotic.
Do bear in mind that you will also possibly have to clean the volume pot, and possibly replace its belt.
May I suggest that you upgrade your membership to silver or gold and download the service manual?
(The manuals you find elsewhere were just unashamedly taken from here!)
Jacques
It is in pristine condition based on the cosmetics, but inside it is also completely clean.
This is not my first project by far, it is my first BM-6000 though (just never got around to them). I know that there are many crappy caps in there but that is very unlikely to be the issue I suspect. I have done older Beomasters with the same caps and they are problematic but not that problematic.
What is the sequence in this machine? What is the expected chain of events? My machine is doing either:
- Nothing (meaning: absolutely nothing)- Starting without a relay click (just displays a garbled number)- Starting with a relay click, displays [ P ]- Starting with a relay click, displays [ TP ]- Starts with a load of relay clicks and then nothing (no display)
That would tell me the issue is somewhere else. And in none of the situations above does the main power transformer have any actual power. Which is odd, the relay clicks so there should be power.
I have tested the components on the power board but they are all fine. Tested out of circuit. There is nothing on there that would cause this problem.
Thank you for the suggestion but I already own a large amount of original B&O service manuals (amongst them for the BM6000).
I need to find the actual fault before i start messing around in the machine. What is the sequence of events. I am more worried about the processor pcb than then amplifier. I have already resoldered most of the connectors but that did not help. The soldering is fine, that is not the issue. Machine is in much better condition than I have seen most B&O amps. So the suggestion is a good one but this machine is fine solder wise.
Generally I would like to understand what is wrong before I start messing with pcb's. Sure the amp is easy but I would rather trace the issue first. I might have a machine here with a dead microprocessor or other busted IC's.
So I am trying to wrap my head around the issue: where to start the fault finding?
Check that the processor is powered and that its power is clean (no ripple).Check its reset signal.Check that it's running with a scope.Check for cracked solder joints at the connectors at the front edge (lower edge when opened) of the processor board.
Martin
I resoldered all connections, no change; basic procedure on these Beo's as they are prone to solder issues. But the solder is actually fine for a change.
As a matter of curiosity I removed the power amplifier and bench tested it with a external power supply. Magic smoke appeared at half the required rail voltage. It seems the darlingtons in the right channel are toast. Reason is most likely a set of open caps as tested. All other components are fine. Other low voltage caps are, of course, degraded severely but the high voltage caps are still OK. Oddly enough there was no cascade as all other diodes, transistors and resistors appear to be OK, which I find really odd.
Seeing that I don't stock these darlingtons I will source them, might take a week or so to get them. Same for the 47uf bipolar cap, don't stock these. Will let you know what the status is afterwards.
I think this machine is knackered beyond repair. Even with the power amp removed nothing happens beside what is described above. Mostly now it just randomly does 'stuffs'. Either just display a P, sometimes with (half) of a digit. Or plain Jane nothing at all. It never responds to any key.
There is no voltage to speak of anywhere. The small transformer should deliver 10 - 20 VAC, it does not. That voltage should be there irrespective of the relay click. The large transformer should give me 36,7v after the relay clicks, but there is no voltage there as well. Never do I get any voltage even close to the ranges I would need, not even by a milestone. Not with everything connected and not while disconnecting the hell out of boards. I do see that disconnecting the small transformer from the power board gives me 10VAC; connecting it drops the voltage to 3VAC or less on the transformer outputs.
So something is seriously wrong; generally I would have suspected the power amplifier seeing it creates the magic smoke. But with the power amp removed the machine should at least start and give me power. So something or most likely a lot of things died and went to heaven.
I think this machine might be better used as a spare parts item. I will do some poking around but without power that is going to be a rather short poke session with the scope.
Did you pull the transformers and check their secondaries stand-alone?
I am isolating the two transformers as we speak, let me see what is the result of this.
I have also pulled IC1 and IC2 from the power supply. IC1 tests well but the HFE is only 4. Seeing that this is a darlington transistor, that is no good. It should be around 750 - 1000 beta. I suspect that it is knackered as well, but these don't fail often. Must be fatigue.
I isolated the transformers and drove them directly. Both outside and inside the circuit. To make sure that the large caps aren't boinking the results I changed C1 and C10. C1 was jumpered because it is using two negative points. C10 wasn't jumpered as it appears to be using only 1 negative point (even though the pcb marking and schema say otherwise).
IC1 was removed from the circuit but for this test only the rectifiers are important.
Driven directly the large transformer only generates a small voltage. But in circuit it pulls the correct voltages (36vac). Output of the rectifier is 56v. This is higher than the schema says but it is likely due to running on 230v. So the big transformer is OK.
Driven directly the small transformer will give me a rather small output voltage but consistent (around 5vac - 10vac). In circuit it drops down to just about nothing. Depending on what I connect it might give me 4v (highest output measured). I believe this transformer to actually be OK but that the circuit is impeding it; something is causing it to drop its load (or that no load is asked for).
So. We have two transformers that both appear to be OK. But when in circuit neither is giving us the correct voltages. Seeing that the big transformer is loaded through the relay and works fine driven directly the issue seems to come from the circuit of the small transformer. IC1 was already confirmed as a bad component. IC2 might be bad as well, it is a cheap voltage regulator so it can be changed easily. If these are working perhaps there will be a load from the circuit and the voltages will pan out again. Might drop in a replacement relay as well.
But for sure, nothing is chooching in there right now.
I had a bit of spare time and decided to jury rig the power supply. IC1 was replaced with TIP147G darlington, TO247 custom modded to fit the TO220 spacing. Ludicrous, but if it works then it works, easy as that. Can always replace it later. IC2 was replaced by a "modern" 15v voltage regulator (L7815CV).
Now when we power up, stuff happens that I would expect. System starts in standby mode. I can activate the system by pressing buttons and the system responds to buttons pressed. Tuner activates. Segments in the display appear to be missing, must be dead LEDs.
Volume control is down / invisible. This might be due to the power amplifier not being present, I haven't read the schema that far. Might also be dead lamps or something like that. Need to investigate.
So. First steps taken; some success but need to rebuild the power amplifier to see if it actually dances.
Will report back when the spare parts arrive.
Did some more tests this morning as it was early days, crowing with the rooster. This machine appears to be somewhat of a headache inducer. Several faults are present (aside from all-dead lamps and missing LED segments):
- Volume control doesn't work. Either the motor is seized or the motor control IC is busted. I reflowed the motor control PCB and replaced a capacitor. When volume controls are pressed there is no response from the motor. From manual inspection it seems as if the motor itself is seized, must take it apart and see what happened.
- Tuner frequency stuck. This appears to be a common fault related to IC8 U264B on the main processor. Of course this is a chip that is pretty damn expensive so I need to figure out if this chip is the actual problem. No need to spend €20 on a specialist chip for no good reason.
- Found three dead transistors. Easy fix as I have all of them in stock.
I am wondering now if this machine is the correct platform to jump from or if I would be smarter to buy a 'working' condition machine and use this one as parts machine to restore the other one. Or merge two into one. Need to think about this for a moment as I have this nagging feeling that this might become one of those projects where you spend countless hours on, only to conclude that was never going to chooch to begin with.
Hi
FOR ME a recap of the powersupply board (board 16) and the motor control board ( board 6) is the first thing to do when working on a Beomaster 6000 because the system relevant voltages for a propper performance are delivered by these PCB's.
There are not a lot of caps to renew.
Measure the voltage at the volume motor when the volume up or down button is pressed. The adjustments, if necessary, are made on PCB 6.
after that controlling the "NO LOAD CURRENT" of the poweramp, most the trimmers are corroded and the adjustment is very sensitive, I always use new spindle trimmers
For the stucked FM display you can use a U664B Prescaler IC instead. Same PIN OUT, only for 1,50 € in the Net. For me it worked always when I needed to exchange the IC.
Check the shielded wire comming from the tuner to the uPC board, sometimes it slipping of the sockets.
Good luck
Best regards
Christian
Hi Christian,
I rebuilt the power supply and the motor control board, they should be fine. I replaced the transistors /IC's where they were blown.
When the volume functions are used, there is no activity on the motor. Nothing at all. This tells me either the driver IC went to see it's maker or the motor is stuck. The driver IC has completely carbonised the pcb so it has been generating a whole load of heat, that is not good at all. My guess would be that the IC is not working, I will check the motor on a separate power supply.
Good catch on the U664B! I did not know this and that will indeed be less costly, might even have some lying around (will check).
Will also check that cable and remove that entire PCB from the casing. Need to change the lamps anyways.
Bert
Hmmm, just did some more tests on board 6. I am getting the wrong voltages by a huge margin surrounding the LM378 chip. Pins 6 / 7 / 8 /9 should all be around 1.7v but in mine it is 14.4v. Pin 13 and 2 should output 2.4v but are outputting 15v. I think this chip is busted which corresponds nicely with the huge amount of carbonisation on the pcb. I think it became very hot and failed; now it is completely cold (should be lukewarm).
The voltage on the motor is 4.8v and rising when the volume up / down is pressed. It should be 2.4v. Possible cascade can be that the motor seized and then burned, causing the chips to fail with a high return load. Difficult to say but that LM378 should not have been so hot that it burned the pcb.
Pfff. Let me see if I have this chip lying around somewhere. I suspect that the MC7445 chip is also busted. Need to check that out further. Up to now I don't think this is entertaining, receiver seems built to fail in multiple places. Very different from the Beomaster 8000 which I have restored 2 of, much better design although the master chip is still the single point of failure.
Ok, adventure continues here.
I exchanged the 7445 chip (presets) for a fresh one. And behold, the LM378 is getting loopy loony hot immediately. That's not right at all. It should be lukewarm at the most. So from experience I would say that the chip is busted but will do a trace to see if anything else has cascaded somehow, but I will say that it is a bad sign.
Have you disconnected the motor for a single test?
If yes and the motor doesn´t spin disassemble the gearbox from the motor, I´ve already had a sized one.
Yes, I took the motor out of the machine but it is seized. I need to take it apart and check if the gears are busted or the motor itself. The motor control board has some serious issues and it could have taken out the motor easily.
The motor control board has voltages that are completely wrong in many parts. I desoldered the IC's to check the voltages (input and output) but they are way off chart. Essentially, the entire circuit that lives for and drives the motor is getting 14.4v - 15v where it should be no more than 1.7v - 2.4v. This is with all connectors enabled or disabled (to other boards besides the power line); it does not make any difference.
The oddity here is that I have removed all transistors for out of circuit testing: they are all fine. All diodes are also fine but replaced by me with better parts anyway: still the voltage offset is huge.
Perhaps I am not seeing something that is clear as ice but for now I can't wrap my head around it. What can throw this off whack so much? The resistors all look just fine, nothing out of the ordinary and clearly it they failed then a whole bunch would have failed, it is not logical at all. Even on the off chance that a current surge was there, the resistors would have been black as coal.
I have removed the motor assembly and disassembled the motor. The basic cogs and wheels are all ok but the motor itself is busted. I can easily turn the motor by hand but when it is connected to a power supply there is just no life in it. It ain't chooching no matter what configuration I put it in. It should run at a low voltage (6.5v) but doesn't. Seeing that a full 15v is somehow dumped into the motor from PCB6 it is not strange that the little bitty motor died.
So i'm calling it a day on this machine. I could try to jimmy rig another motor into it. I could try to find the source of the 15v problem (most likely somewhere on PCB2) and maybe, just maybe it would work. I could fork out €€€ for the chips. But more likely: another problem will arise. I've seen these machines before, they have had some sort of cascade problem, it is just not worth the effort.
Nice machine but essentially built to fail.
Oh dear ;-)
Havn't had such kind of troublr so far with an BM 6000, but stay on the ground keep calm and measure first all necessary voltages from the powwersuply board, check all grounding connections.
For me it was not clear if you had connected the solderpoints from the caps on the powersupply board or not.
The LM 378 getting hot, might be the IC is shot from the sized motor....
Can you confirm the incomming voltages fom PCB 18 Powersupply
PCB 6 P19-5 > 6,5 Volt adjustable with R4 on PSU board
PCB 6 P19-1+3 > 15 Volt
PCB 6 P18-8 > 15 Volt when FM activated
PCB 6 IC3 > 14 Volt in Pin 1
PCB 6 IC 3 > 5 Volt out PIN 3 for the uPC
PCB 6 IC5 > 15 Volt at PIN 14
PCB 6 IC5 > 0 Volt at PIN 3,4,5,10,11,12
PCB 6 IC6 > 5 Volt at PIN 16 comming in from uPC Board
PCB 6 IC6 > 0 Volt at PIN 8
Did you already change the LM 378?
If you need a volumemotor I could help so far needed, but have to check if it runs first.
A PCB 6 would be also in "stock" and I could recap it for you if you like and test it before it goes on the way.
Thank you for your reply, let me check. This is the tenth B&O machine i've done but thus far has been the only one that gives me a royal headache. Even the Beomaster 8000 was much less of a 'look out failure' machine. The PSU was completely rebuilt by me, the caps are in as they should. Jumpered C1.
PCB 6 P19-56,5v is present and R4 is working.
PCB 6 P19-1+3 > 15 Volt is present
PCB 6 P18-8 > 15 Volt is present on P18-9 (red wire)I think this is correct.
PCB 6 IC3 > P114 Volt is present
PCB 6 IC 3 > P35 Volt is present
PCB 6 IC5 > PIN 1415 volt is present
PCB 6 IC5 > PIN 3,4,5,10,11,120 volt accounted for. PCB 6 IC6 > PIN 16 5 volt is present.
PCB 6 IC6 > PIN 8Correct, 0 volt present.
On a hunch I removed the lamps which were all burned out, suspecting that this with the motor malfunction might be one of the reasons the voltages are all off base. ON 6IC5 with the LM378 removed I am now measuring:
P2 = 10vP6 = 1.5vP7 = 10.7vP8 = 1.5vP9 = 10.7vP13 = 1.5v
This is much lower than before. But P2 being high is wrong. As is the high voltage input on the + side of the opamp. This may be because now there are no lamps but I don't know.
On 6IC6 pins 1 - 6 all measure 15v. This is wrong as per service manual. This is based on a new 7445 chip in there. It seems as if the volume system 'thinks' it is on the loudest volume possible. The chip should jump in voltage based on its relative position. But the volume controls are unresponsive of course on account of the motor being removed and readied for ceremonial burial.
So. All base voltages seem OK. But the voltages on the chips on PCB6 are decidedly off base. My hunch says it has something to do with either the lamps missing or the motor, or both. But that is guessing ;-).
Oh yeah, there is 15v on the tiny lamps next to the tuner scale. This is certainly enough to burn the little 6v lamps.
Had a bit of early bird time and replaced the volume lamps and re-inserted the LM378. With the motor removed, it is not getting hot anymore. BUT. All of the input and output pins for the actual opAmp (6+7+2 and 8+9+13) now carry 14.4 volt as before. With the opAmp chip removed, the voltages are somewhat lower but still incorrect.
The motor burned because there is 15v dumped into it and it is a really low voltage motor. If I was to put in a replacement motor it would crap out within seconds. I dismantled the motor and I can see where the internals simply snapped because of the high voltage. Too much voltage, too much current and this kind of baby motor will poof out on you easily.
So. If the circuit is running as expected (transistors, diodes, darlingtons are all fine) how the crap is this happening? Both 6IC5 and 6IC6 are fed by the 15v line coming in through P19-1. The 7445 is brand spanking new from my own non-fleabay stock. The LM378 could be dead of course, still doesn't explain the voltages. Because with it removed, input voltage is still incorrect. The 15v inbound voltage should be downgraded to 1.7v on the 6IC5 inputs and then generate 2.4v on the outputs (logical). The 6IC6 chip should not have 14.4v on all preset pins, it is a logical stepping mechanism starting at a low voltage for the lowest selected preset through clamping.
Thus question is if another board is throwing mud into these reading somehow....
Some spare time again, it's Corona hurray. I attached a small 15v motor. It confirms what I was already thinking, it seems volume controls are inoperative. Well, not entirely. I can press the < (lower volume) key and it will trigger the motor (6.5v which is correct). The > (volume up) doesn't work. None of the presets work besides preset 60. But that just activates the motor which never stops (10v over it), it just spins endlessly. I can stop it by pressing the < key. The voltages on the chips are still completely wrong by the way.
I suspect this is not actually a problem with the LM378. It might be dead but the motor control isn't in there. The preset controls and the button inputs are all regulated via the main processor chip. I have the sinking feeling that there is an issue with that chip.
When I reset the system the motor starts spinning like crazy and it never stops (only by pressing < volume). Reset should put the volume back in [0] preset but instead it appears to go haywire.
Does anyone have any in depth intel on that chip?
Hi Bert
The 10,7 Volt at the Pin 6 and 8 of IC 5 are very suspect, of course the IC is an Opamp so it will amplify what comes in, so in my opinion, the IC does what it should do regarding to the incomming voltages.
Please check the connection via D5 to the volume preset and the way down to IC6 PIN 9.
The traces from IC6 PIN 10 and 11 to IC 5 should also being tested,.
It´s quiet a tricky circurit around the IC´s but sometimes it´s working great when everything is OK ;-))
It´s more doing concentric circles around the issue. But the voltages that you confirmed were helpful to sort out a problem wit the PSU.
The preset and volume pots are connected via plugs, would not the first which is not sitting in the right position and making trouble.
So check the plugs and resolder the sockets if ther are any suspect ones.
The volume poti is a three way pot two ways for left and right audio and one way (100k) for the logic circurit.
I´m not shure which IC´s you have renewed.. was it the IC 6 7445 or IC 5?
Trimmer R32, R24, R25 not turned to any endposition?
Let´s dig it
Regards
All connectors and wires were reflowed by me already, standard procedure. PCB6 was completely reflowed and rebuilt, triple check on any solder bridges. Only IC6 was renewed as I did not have an LM378 lying around (that would have been the day).
I simply can't find any fault on PCB6 in the components. The resistors all check out, same for diodes / transistors / etc. So in my experience something else is pushing these voltages. Tracing the schema's the only thing I can find, having removed all other options besides the motor, it the main processor unit. That would correspond with the fact that on 6IC6 all presets are high at 14.4v and not responding to input. Those preset points are a stacked method, so if the unit is in the lowest preset only a low voltage is clamped, the voltage rises with each step. Pins should correspond with those steps. If the main processor is not feeling well then it may tell 6IC6 that it is on the highest volume. This would also explain why the motor is spinning out of control when I boot the machine, it even spins in standby mode.
Other point of interest might be the default volume slider. But that one was desoldered and cleaned and tested by me, it is fine. It also doesn't explain why the > volume up doesn't work (that MIGHT be because the motor is not connected with the motor potentiometer but I still think that would be odd). Nevertheless I would not look there but in the main processor.
Christian, I have literally checked every component on the PCB6 out of circuit, I never do this. There is nothing on the PCB that is broken (well, the LM378 might be). Thus I cannot explain why this is happening or what is causing it, my knowledge of the BM6000 is too small. To me this is a conundrum, it should be working but it does not. Common sense tells me: problem is somewhere else.
The uPC can not give 14 volt, did you measure the inputs on 6IC 6 PIN 12,13,14,15, comming from the uPC board, on 6IC 6?
Is there also 14 volts?
I think the high voltage comes from a not connected grounding or a break in the connection via D5.
Did you check the connections between all components? Not only the desoldered components themselves.
I´ve had already some nice experience with broken traces on the PCB´s, not only in the Beomasters.
If there is no crack in the traces I´m running out of suggestions, maybe some others who are reading with us have a solution where else to search.
I don´t know how the circurit acts if no motor is attached.
BTW you testedt the circurit with motor and a mounted belt? If no belt is mounted te motor will spin as long as you turn the VOL SLAVE pot by hand in a place where it stops the motor. That´s why it is called VOL SLAVE....If the expected value doesn´t come from the pot the motor wont stop.
Maybe you renew the LM378 and the SN7445 at the same time and hook a motor ( maybe a 12volt motor) on, and look what happens. The IC´s are not as expensive and you´ve got nothing to loose exept some more time on this mashine.
The next would be that I´m tacklin´down my working BM 6000 into pices and test what happens when the motor is of.
Maybe I write a little confused but I´m switching always between the manual and the typ-box ;-)) so there are some thoughts comming directly from my head, sorry for that.
Kind rgeards
Sure, I measured the voltages from the main chip. All preset outputs from the main chip are 4.8v (doesn't matter if I connect or disconnect to PCB6). I don't think that they should all be 'high' like that. Voltage also never changes with either the motor or the potentiometer. I did not connect the motor to the pot because it is just a regular motor, there is no way to connect a standard motor to the potentiometer. The broken motor is a bespoke unit, can't be replaced by any odd motor. Without the motor there is no change actually, same readings.
I did trace the parts and all traces are fine. You may be correct with a missing ground plane but I can't find it. There are simply too many variables in here, we could troubleshoot this until hell freezes over. One thing I am sure of is that this machine has it's volume in the loudest position and no matter what I do I can't get it to lower. This is why the 14.4 - 15v is propagated everywhere. 3R4 volume preset is in the lowest position, so 6D5 anode should be clamped to ground (chassis) through 6R27, 6R24 and 6IC6 but it doesn't. I could change the 6R24 pot, it might be a problem but it doesn't measure as such. My experience tells me that sometimes you just can't trace the issue, it might be a pot, it might be the 3R4 potentiometer, it might be the motor potentiometer, so many things that might intervene.
For my 2 cents: better to let this machine rest in peace. The motor is shot, the power amplifier is burned, the motor / volume system itself isn't working, the tuner is dead and the 7 segment display is half dead. Even if we did find the problem in the motor system all the other things would still need fixing. In my humble opinion: this machine is just not worth that effort. It would be smarter to find another machine with a working motor and volume system and merge the two into one; best of two worlds. I will try a new LM378 but I don't think that is the actual problem.
Christian, your help is much appreciated and I actually think you are probably right. I might try some things but i've already put way too many hours into it and I can feel that fuzzy feeling of '*** this machine' in my belly. Thank B&O for developing another loony solution to a simple problem ;-).