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Beomaster 6500 slight overhaul

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Egomon
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Egomon replied on Fri, Feb 5 2016 4:39 PM

Little bit more about the 5500. I don't know  if this is common fault in 5500 series but RCA sockets in this amplifier were lose from the soldering points. I had to solder them back to the board.

It sure looked like no external damage just poor soldering job from beginning. I discovered it when plugin in my phone via tape 2 RCA sockets. Lucky for me that was very easy soldering job and didn't even have to take off the cover.

tournedos
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tournedos replied on Sun, Feb 14 2016 6:18 PM

I just (hopefully) repaired another 6500. This Beomaster worked fine for a couple of hours, but if you then put it into standby, after an hour or two the standby dot would vanish and the Beomaster seemed dead. Leaving it unplugged from mains for some time usually gave another try.

I replaced the usual caps - see the first pages - and it seemed to work fine. I then disconnected it from mains to remove the probes I used for idle current adjustment (I don't do that "my probe slipped and I fried the device" stuff) , but it was dead again when I connected it back to mains. Not even the usual relay click (which actually means the amps are powered on - the Beomaster energizes the main relay when it goes to standby).

Some measuring around revealed missing standby power, just a little over a volt at the emitter of TR12. So no power to the CPU either. Turned out to be an intermittent standby power rectifier (D3). I replaced it and all seems fine again.

I'm posting this because my BM5500 had an intermittent D3 as well when I bought it years ago. Seems like a common fault.

--mika

JPM88
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JPM88 replied on Tue, Mar 1 2016 12:34 PM

Does anyone have parts to this card available, (processor, rom )? I have one with no life. Only some curious level pulse between processor and rom data line. Chrystal, voltages etc are ok.  Card is identical as yours only S/W is 1.4

tournedos
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The processor is a generic 8032 which should still be available; if not new, then NOS on some popular auction site (avoid the later "downward compatible" derivatives which have additional features, as they may not work properly with the B&O firmware). I guess the ROM could be easily replaced with a regular 27512 EPROM chip, but of course you would need to get the firmware from somewhere. I would be suprised to have a faulty ROM, but the CPU is a bit susceptible to ESD and overvoltage hazards from the external Datalink lines.

But first check carefully the reset circuitry, as the processor won't start up correctly if the RESET signal isn't driven properly when the power comes up. The PSEN and ALE lines should have a lot of clean logic level traffic at ~1 MHz when the CPU is running.

--mika

BeoMedia
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BeoMedia replied on Sun, Jun 17 2018 4:32 PM

Hello all!

I have decided to replace some capacitors in my BeoMaster 7000 (module 9, the front circuit board with the display) as described in this thread.

I have measure the three of them with my ESR meter and one was dead, one had 5 times the resistance and the third was ok. I will be replacing all three.

Question 1:

The values I read from the components are:
C15:  1uF/100v (Question, I cannot find 100v anywhere, only 63v, will this be okay???) When i look at the service manual I am not sure how to read it. Is it mean that the voltage is 40v? Please see picture from service manual I have attached.

C20:  10uF/63v

C19:  2u2/63v 

Question 2:

Will I need to tune the IR receiver once I have replaced the capacitors as per this quote or was this due to a more complex issue being investigated?

Look at page 7 from the below service manual, that is where I took the clip from:

BeoMaster 7000 service manual

Many thanks all, I will report once I have completed the repair.

BeoMedia

tournedos
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tournedos replied on Tue, Jun 19 2018 2:23 PM

63V should be enough for C15. It sits on the unregulated 40V power supply line, and the filter cap for that line (in the power supply) is actually specified as 50V. 100V was probably just a convenient choice when the Beomaster was designed.

Don't touch the adjustments (I probably wouldn't have needed to either).

--mika

BeoMedia
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BeoMedia replied on Tue, Jun 19 2018 10:14 PM
Hi Mika thank you so much, I will now replace these capacitors as soon as I can Smile

Will report back if it was a success. Hoping it will be.
BeoMedia
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BeoMedia replied on Mon, Jun 25 2018 7:59 PM

All three capacitors are now replaced and the system started up effortlessly from standby (so far so good). The repair went very easy and I have some pictures I can upload later if there is any interest.

However, trying to start it up from standby at a later time (i.e. after it has been connected to the mains for some time) it is again not very sensitive at all to receive an ir command like RADIO or similar. (I have even disconnected the aerial but it is the same issue.) Once it is turned on it is very sensitive to new ir commands and works as it should. The problem is only when trying to wake it from standby.

Are there other capacitors on a different circuit board I should be looking at as well? Should be likely as they are all equally old.

Any pointers would be much appreciated.

villeke
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villeke replied on Mon, Jul 16 2018 8:37 PM

BeoMedia:

However, trying to start it up from standby at a later time (i.e. after it has been connected to the mains for some time) it is again not very sensitive at all to receive an ir command like RADIO or similar. (I have even disconnected the aerial but it is the same issue.) Once it is turned on it is very sensitive to new ir commands and works as it should. The problem is only when trying to wake it from standby.

I have the same problem with Beomaster 6500. If I disconnect it from mains and replug it, it will work fine again - for some time. I would also be delighted if someone has clues where to look for...

BeoMedia
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Hello Mika and all on this thread,

I thought I would need to continue my work on my BeoMaster 7000. The issue I have had for some time now is that the BeoMaster 7000 is not very sensitive at all to an ir command when it is in stand by and has been connected to the mains for some time. (If it has just been connected to mains it is fine. Once it is powered up and playing it is also fine.)
I have looked at the capacitors on the power supply and power amp board as per Mika's brilliant tutorial on the first page of this thread and I will be looking at replacing these. I measured them with my ESR meter and all but one gave an acceptable value.

However, I am now also struggling with poor signal reception on the radio. I can hardly get a channel. So, I also looked at the caps Mika mentioned on his post concerning the radio circuit board. Here I also had poor caps according to my ESR.

Then I went on to measure other caps on the same radio circuit board and many of these were also out of spec!

Question: It seems to me that most caps on these systems are ripe for replacement. How should an amateur go about this? Shall I try to replace all caps that measure out of spec or only take one step at the time (for me it would probably be replace the caps on the power circuit board, then later move on to the caps Mika mentioned on the radio board).

Shall I leave the other out of spec caps be for the time being?

In theory it should not hurt to replace them all but I understand that the circuit boards are rather fragile and traces can easily lift from the board. 

Question: How do you guys repair a lifted trace? Are there any pens that can carry this sort of current or how do you save your boards once a trace has lifted? What is the best temperature to desolder caps with to avoid lifting traces perhaps 400 celcius?

Many thanks all! I really want my system back to full glory and I will happily be posting pictures and comments from what I have learnt along the way once I am done.

BeoMedia

tournedos
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tournedos replied on Sat, Apr 13 2019 4:17 PM

BeoMedia:
Question: It seems to me that most caps on these systems are ripe for replacement. How should an amateur go about this? Shall I try to replace all caps that measure out of spec or only take one step at the time (for me it would probably be replace the caps on the power circuit board, then later move on to the caps Mika mentioned on the radio board).

Do the mandatory caps first - these are the small electrolytics in the power supply and the CPU board (maybe the front panel as well). No need to even measure them.

The rest is optional... the tuner problem is probably something else than caps, and it is easy to get back to that later anyway because the board is the first to come off.

BeoMedia:
Question: How do you guys repair a lifted trace? Are there any pens that can carry this sort of current or how do you save your boards once a trace has lifted? What is the best temperature to desolder caps with to avoid lifting traces perhaps 400 celcius?

The old soldering alloys that contain lead (and these were definitely used at the factory at that time) melt at about 180°C. Current lead-free solders melt/cure at about 220°C. The right temperature depends on your soldering iron. If it is slow to react to the cooling of the tip of the tip (so to speak) or the tip has poor heat transfer to the object, you may need a bit more to compensate. But 400°C is probably the upper limit, you shouldn't need that much - with a too hot iron, the resin evaporates off the solder making soldering difficult, and you will overheat the components and the PCB.

But don't use too low temp either, because then you will also overheat the components because (de)soldering takes so long. The "usual" tip temperature for lead-free solders is 350°C.

To help save the traces, don't start wiggling the components until the solder has actually melted through. With two-legged upright components such as most caps in this case, try to avoid pushing the opposite leg in while trying to pull the other out through the PCB. If the component is to be replaced anyway, you can cut the legs off first if there's space, and then easily remove them one by one.

And when the accident happens, I usually solder in a jumper wire if the next solder spot is very close (1 cm or so). For longer distances, it may be more sensible to scratch off the insulation on the trace and solder a short wire on top of that.

 

--mika

BeoMedia
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BeoMedia replied on Mon, Apr 15 2019 3:28 PM
Hi Mika,

Great explanations and advice!

Okay, I have already replaced the caps in the front panel but not on the CPU board or the power supply so will start with these. Perhaps the power supply caps can explain the tuner issues? We will see.

With regards to the caps on the CPU board I am not sure what specifications I need. They read (please refer to the pictures taken of the CPU circuit board (C35 and C57). What specification are these? They read 100µM and 47µT but I can’t find that when I want to order. What does the “M” and “T” mean please?

In the service manual I only see 47µ and 100µ (please see attached picture from service manual).

Many thanks BeoMedia

tournedos
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tournedos replied on Mon, Apr 15 2019 5:27 PM

Just match the capacitance and voltage and you’ll be fine. If you cannot find the exact voltage rating, replace with the next higher value (10V -> 16V and so on).

The T and M are probably tolerance ranges, you can ignore them in these applications.

--mika

toptip
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toptip replied on Tue, Apr 16 2019 4:16 AM

I was reading this and wanted to mention something a bit similar that I did. 

I live in NYC and I bought a BM and a BC6500 from France. I converted them from 220 to 120V (actually on the BM6500, 120 is not an option. They seem to have had separate transformers for the US and Japan of 120 and 100V, respectively. The two coils on the 220/240V models have taps at 110 and 130V only, not 120).

I decided to go with the 130V taps. Now these are normally connected in parallel and in phase, to have the same power at 110/130. But I will not be using the power amp on the BM. Then why waste electricity on a larger trafo? So I only connected one of the two 130V coils to power, leaving the other idle. I should have tried it both ways to see if in fact it draws fewer milliamperes that way in standby but that is a project for another day.

BeoMedia
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BeoMedia replied on Tue, Apr 16 2019 11:48 AM
Thanks again Mika,

One last question before I order the parts. I have noticed in your thread that for certain parts of the job you have opted for MKS capacitors rather than aluminium electrolytic caps.

What is the reasoning behind this and which would you recommend me to use for the following:

Output and and power supply:

C8, C9, C11 and C14

CPU circuit board:

C57 and C35

Tuner circuit board:

C201, C401, C207, C407 and C35

Can the MKS ones better withstand exposure to the heat inside the BeoMaster or how does it work please?

PS: I assume they are all meant to be polarized?

Thanks again and sorry to keep asking questions I just want to be sure I’m adding the best parts as it is fragile and would like to avoid replacing these again in the near future.

Regards BeoMedia
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