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 all, I've just completed my first complete overhaul of my beomaster 8000, complete recap on every board except the one under the can, idle and volume trimmers, new switches , LEDs and Martin kindly overhauled the displays with new LEDs , all went really well, today was my first day of sitting back and simply enjoying listening to it, wanted one for ages but was still taken back by its incredible performance paired with my ms150s
This evening I lost sound from the right channel whilst playing radio, tape play fine through both channels , don't really want to lug this beast back up to my workshop tonight, any ideas ?
Thanks in advance Jason
I'm sure this is unrelated but I came back in and the radio was on , I dismissed it thinking I had forgot to turn it off when I left, then again last night I was woken up by AC-DC playing on planet rock , great tune but still a shock to be woken up by the amp turning itself on, it will be hard to find if it only happens every few days, I guess I shall leave it in standby with the keyboard unplugged for a few days and maybe look at replacing the 2 relays, does that seen sensible ?
jason
Hi Jason,
Sorry to hear that!
I guess you will have to re-open the beast and check your solders on the tuner board, as well as the connectors.
Replacing the relays, why?
There's could a fault within the processor board. You say you haven't replaced the cap inside. Sometimes, after a power cut (even the fraction of a second) the Beomaster can behave strangely. Just switch it off, wait 20 seconds (this is important not to damage speakers), then unplug it.
A founding member and only seven posts?
Jacques
My Beomaster 8000 was giving me some fits with a channel dropping out. One difference in my case though, is that I would get the dropout on any of my input sources (not just the FM). I tried a couple of different preamp boards and both experienced a dropout in different channels at some point. By that I mean the receiver would play for a while, then lose a channel. I was thinking the problem was a transistor on the preamp output, then an analog switch. In the end the problem was a board connector issue. I had resoldered all of the board connectors so it wasn't the board itself. My problem went away when I switched out the P21 and P15 board connectors.
-sonavor
Yes I don't know why it only shows 7 posts, I used to have a few hundred, granted I hadn't really been on beoworld much the last couple years since we had major building work going on
ive hard wired the 2 tuners boards and the cpu with the display board to eliminate the intermittent connections, a little time consuming but sorted the occasional flickering display.
yes tryed powering down a few times, I'm in the habit now of switching speaker switches off before unplugging .
its quite funny really having an amp turn itself on instead of stutting itself down, proof after years of storage that this baby wants to live!!
Further investigation has proved helpful, only just finishing the cdx I found the same right channel is also missing there as before I had only finished the beocord 8004 which worked in both so I was concentrating on it been the timer board been at fault, so I checked the phono briefly and again no right channel, yippee I'm getting closer!!
from the service manual it seems ic202 on the preamp board pcb3 has all 3 inputs in common on the right channel
Sorry tuner board not timer board
Check the input level preset potentiometers. They are rarely used so will often oxidize.
Martin
Hi Martin,
thankyou, yes I'm heading home now all excited and hopeful to give that a try, much better than trying to locate that chip and the presets on the pre-amp board are something I hadn't cleaned or looked at yet, strange thing when I first opened it and I'm pretty sure I was the first I noticed one of them was missing the rod (for lack of the correct name) so was going to look out for one just to make it complete.
ive also noticed the volume and station presets occasionally have changed , could that be related?
do you recommend unsoldering them and taking them apart somehow to clean them properly ?
Kind regards Jason
Soaked with contact cleaner and turned 50ish times each, I couldn't take them apart without breaking them but they did feel a little better afterwards, it was a good thing to do due to them probably just sitting unturned for most of thier lives but unfortunately it didn't restore sound to the right channel through any of the 3 affected inputs
does anyone have a AD10-278 chip for sale?
Sorry please ignore my request for the ad10-278 chip , I switched ic202 and ic201 in the hope I would lose tape1 and gain the other sources but nothing changed so I was wrong
who said restoring one of these was easy? Oh yes.... no-one !!😂
Jason bannister: ive also noticed the volume and station presets occasionally have changed , could that be related?
This will be related to the processor board. They are known to have troublesome vias, depending on what version you have.
Hi Jacques,
thanks for that, I do need to get in there and make some bridges but havnt as yet found a clear enough list of recommend bridges as well as any needed at the time, also change the cap, did I read somewhere to add a 100nf somewhere to help protect the microprocessor ?
jay
The 100 nF is for the processor 5V PSU - the regulator on the small heatsink, on the right side of the receiver - between ground and +V. Tim Jarman insists on the mandatory aspect of this mod.
Here are the links, if your processor is the early version.
Thanks for that, mine already had a 10uf 63v which I had replaced for a new 105c as part of the full recap, should I still swap this out for the 100nf ?
Jay
Jason bannister:Thanks for that, mine already had a 10uf 63v which I had replaced for a new 105c as part of the full recap, should I still swap this out for the 100nf ? Jay
That's really helped thanks
youve left me with no excuses left for not getting into the processor board 😉
Well I'm at a complete loss, what should have been a relatively straightforward fault finding mission on the preamp board to restore sound on the right channel on all sources except tape1 has sent me round in circles .
does anyone have a spare preamp board ?
les is 'bout to bin some BM8000shttp://archivedforum2.beoworld.org/forums/t/6928.aspx?PageIndex=15im sure you can have those boards for nothing
Swapping out a spare preamp board is the quickest and easiest but if you don't have a spare available...Have you traced the Left and Right signals at various points in the preamp board? The easiest point to check first is the External Filters jumpers on the side of the BM8000. Do you have a dual channel oscilloscope you can use? If you're missing a channel there then you can pull the jumpers and recheck. Or you can just check connector P21. If it is still missing then go back to the board inputs (P20 for the Tape 1 & 2). I would also reflow the solder on the connector joints of the preamp board if you haven't reflowed those yet.
Hi Sonavor , thanks for your assistance ,
yes I've re flowed virtually the entire board, swapped over all the ic lf353n both ad10-278 , all transistors between right and left also recapped and cleaned all the preset pots thoroughly , it was initially working fine now only works properly on mono with stereo only on tape1
at present I'm only able to check with a meter so a little limited
thanks jay
Jason bannister: it was initially working fine now only works properly on mono with stereo only on tape1
it was initially working fine now only works properly on mono with stereo only on tape1
Since you're getting sound from both channels with the Mono switch engaged, that means the last stage of the preamp board must be okay. At least that is how I read the schematic. That means the problem is before the Ext. Filter jumpers. Tape 1 is different from the other inputs as it goes through 3IC4 via pins 9, 14 while all the other inputs (Tape 2, FM, Phono) go through 3IC4 via pins 11, 12. You switched AD10-279 (3IC102/3IC202), which is the path the other sources go through but I'm wondering if 3IC4 (AD10/192) is the problem. There is only one of those on the preamp board though. There is another AD10/192 on the Filter and Tone Controls board (4IC4) but I wouldn't recommend disturbing that board right now. Any nearby Beoworld techs with a scope you can borrow? You can check that the AD10/192 (3IC4) is getting proper voltages and grounds with your volt meter in the meantime.
Hi Sonavor ,
thanks so much, you steered me in the right direction , it would seem that ic4 ad10-192 is possibly always switched to pin 9 and 14 and not switching to 11
Bridging 10 and 11 give me stereo on everything
it looks like the issue is not the ic4 but the control circuit before it as I can't find a 5v signal sent from board 9
ill let you know how I get on
really appreiated your input thankyou
Well I have a good working solution , I think the chip ic4 may well be faulty afterall , and no longer available in that pin out at least
so bridging pin 11and 10 works extremely well in this paticular case and allows every function to work as normal.
cant explain how happy I am right now and thankyou to everyone who offered advise
jason 🔊🔊😍
Back in September, BO worked a similar issue on his Beomaster 8000 here. He found a substitute for the original 3IC4 analog switch (AD10/192) in : AD7512DI. There are a number of places to order those and range in price by quite a bit. BO got his supply off Ebay and they worked out. You can check with him and see if that repair is still working good. I believe he uses his Beomaster 8000 pretty frequently (as I do with mine).
Here is a picture
Thanks for that,
although the work around I've used has worked in my case , there is no crosstalk from tape 1 due to datalink switching that off whenever another source is selected and I get normal channel separation throughout on all sources, unless I'm missing something obvious everthing is working as it should with the bridge in my case, but defiantly something I would look into if the ic4 fails in another way
Jason
Fortunately there are some AD7512DI chips available for the 3IC4 replacements. I have yet to find a replacement for the 3IC102 and 3IC202 (AD 10/278) analog switches. They appear to be a 3:1 or 4:1 switch in a 16 pin package. Luckily I haven't needed to replace those but should they go out, does anyone know what a suitable replacement is? The repair might require some sort of custom solution that maps a replacement switch to the existing circuit.
My repair is working perfectly and I'm using my BM8000 daily as my main system.
//Bo.A long list...
I like your thinking, it would be nice to know if they ever failed we have a replacement between us to keep these monsters running , do you guys run your machines on surge protectors?
to celebrate the success on my bm8000, last night I picked up my first 1971 beolab/beomaster 5000 , a little extravagant for my workshop stereo but as I spend most of my time in there it was easy to justify yo myself 😄