BeoMedia wrote:

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 wrote:

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.

 

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

Login to view image

Login to view image

Login to view image

Login to view image

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.

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.

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

tournedos wrote:

...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.

Hello again, I have replaced caps on the BeoMaster and the IR reception is perfect again. I also replaced the backup battery while I was in there and it turned out it was a little sweaty underneath so timing was good.

However - my radio reception does not work. Occasionally when fiddling around with it I may be able to get one channel with sort of okay-wish signal. Then it disappears and I can't get a channel to tune in again. When I start the radio up and try to tune for a radio station it tros for a very little while and gives up. I only hear static.

When I look in the service manual the advice is to replace the entire radio board. What can I do as this is not possible. I have replaced many of the caps to no avail.

I do not have a lot of equipment other than an ESR reader and multimeter (and obviously soldering iron).

 

I would really appreciate help in getting this unit up and running again :-)

Thanks and have a great weekend, BeoMedia

Unfortunately I cannot help much with tuner problems. Major repairs to it would need test equipment even I don't have.

I can only suggest that you redo any dubious looking solder points, and perhaps clean the connector socket/plug on the tuner board that receives the aerial cable from the rear panel. Mine was black inside.

Also check that the wiring looms are all connected with no loose wires.

tournedos wrote:

The preamp board has plenty of electrolytic caps on the signal paths and they could be replaced with fresh caps or upgraded - if you're interested in that, visit Die Bogener's workshop thread on BM6500/7000 in the archived forum.

 

Hi Mika, 

Thanks for all your tips in this thread, I am new in a B&O world. I just bought beosystem 6500 and using it with beolab 8000. Thanks to your tips I changed power to 240V (which reduced heat at work and an electric smell near the device). Now I am thinking to change capacitors in the pream line, the speakers significantly play more open sound when connected directly to the source than through the preamplifier. The link you pasted does not work at the moment, I hope it could help in the selection of new caps. Do you know where I can find this archive?

 

olmaster wrote:

tournedos wrote:

The preamp board has plenty of electrolytic caps on the signal paths and they could be replaced with fresh caps or upgraded - if you're interested in that, visit Die Bogener's workshop thread on BM6500/7000 in the archived forum.

The link you pasted does not work at the moment, I hope it could help in the selection of new caps. Do you know where I can find this archive?

Ah, the link needs to be https to work; like so.

Hi Mika and others reading this thread.

Firstly a quick recap of the tuner problem: It plays static noise and occasionally it will randomly catch on to a signal (after been disconnected from mains for some time) that is not super clear. Changing the frequency (the stored channels) does indeed show a new frequency but plays the same as if it has not changed the frequency though the display suggests this. I cannot tune for a strong signal as tuning (auto or manual) does not find a signal.

Since my last post I have now acquired a second BeoMaster 7000 that didn't look as nice cosmetically but worked fine (including the tuner part). I wanted to move tuner card to my initial BM7000 which looked nicer and to which I have changed caps and updated the SW.

I successfully moved the tuner card that I had confirmed was working in the donor BM7000 (which was same part number) to the initial BM7000. In the beginning it worked fine (few moments while I was trying to store some channels) then after say a minute or two it reverted to the same symptoms as I experienced with the old tuner card.

I then tested the donor BM7000 with the old tuner card (which I thought was the problem) and it worked perfectly.

 

The good news is that the tuner cards (both of them) are perfectly fine which is great as these are very difficult to repair.

The bad news is that I have still not managed to sort out the problem. 

What do you think it sounds like the problem is?
1) is there a bad cap somewhere suppling stable power to some relevant part which could explain this? (I have replaced the caps at the power supply and behind the display to ensure good two-way communication which solved the previous issue that it would not respond to IR signals and turn on). Doesn't it sound like it is a bad cap as it works well the first time for 1-2 minutes after when I connected it after I had swapped the tuner card but then fails again?

2) Could it be the CPU of the BM? Likely not as it does perform all other tasks?

3) If one of the connectors or wires could you please help direct me to which one it could most likely be? They are all rather brittle and fragile after all these years and I would prefer not to pull in all of them too much. Perhaps it is the electronics near the CPU that are at fault as I guess that is where the instructions to the radio card is coming from and where station presets are stored?

 

I am really looking forward for some help on this topic as I hope to get them both alive and working again.

Many thanks, BeoMedia