Well, I managed to get the amp upstairs tonight, finally! Commitments mean't it just hasn't happened until now which has been a little frustrating! So last update was that I had plugged in with no life. Found the 4A fuse had blown rather abruptly so just for the heck of it put another fuse in (smaller value) and switched on. Not long before magic smoke appeared and that is where I left it over a week ago!

So, to the bunker - A little cramped, but I can always tidy the bench up a little!!

After expecting the thing to open in a similar manner to other Beocenters, I was initially a little stumped with this one! A quick glance at the service manual helped me realise the strange way this thing comes apart.... Lots of screws and no nifty car bonnet contraptions here!

First bit of relief I got when inside was that I noticed the damper was disconnected from the panel arm. Moving the damper with my hand revealed a good bit of resistance so now I know that the door will open nice and smoothly when I get the thing back together! That, despite being irrelevant until I get the amp fully operational cheered me up a little. No sign of any leaks either!

Anyway, I start looking at why the fuse died as it did. To be honest it did not take long to track down the first fault. 30C1, the main reservoir capacitor for the left channel positive supply is very low resistance, about 4 ohm! This will explain the blackened fuse then!

I have non of these in stock atm so will pop over to RS tomorrow for a temporary replacement, while I decide on a more permanent, but reasonably priced alternative! Man these large capacitors get real expensive!!!

In an attempt to get the amp going with this problem unresolved, I decide to disconnect everything after the rectifier (easier and a little safer than disconecting the secondary wires) on the left hand channel, and plug in to see what happened.

And what happened? Well, I got a standby light! Tentatively, I pressed the standby button and the Beomaster came to life, sort of! I expected to see frequency and to hear something in the right channel but nothing as yet.

Tested the output of the large transformer and this revealed nothing in the way of a voltage. Checking the supply to the primary side revealed no voltage at all, which led me to check the dropper resistors R1 & R2 on board 7. Now I found out where magic smoke came from

One of the resistors is open circuit. Now I have no 5.5W 5.whatever ohm in stock but happened to have one 12R 10W so I figured that would be ok for a temporary basis. That's another overpriced component I will have to buy from RS tomorrow!!

Put the resistor in...

and...

BINGO

So intial tests seem to reveal most systems are actually working ok with nice radio reception and clear audio in the right hand channel. Just need a replacement capacitor for the left channel to make sure no further faults then I will be good to continue with the restoration (read as new electrolytics / presets and strip clean linear pots check dry's etc etc...) and a good cleanup then hook her up to my S120's and see how she performs! Can't wait :)

Stay tuned, hopefully will have an update tomorrow...

Keep em coming Olly, we are watching

ok spent a bit more time earlier. I robbed a capacitor out of a spare beomaster as my RS order is not arriving until tomorrow. Can't wait for that! After fitting, I proceeded to check the left channel, which is fine!

Couple of faults I have realised - the tuning can be a little eratic, sometimes the display flashes and frequency is reluctant to move up. There is hiss in the right hand channel which is such a common problem with this family of B&O coupled amps I am more surprised if I don't find at least one channel noisey! Nearly always the same culprits too! Only noticable when volume near max with no source but it can only get worse so will be sorted.

Also on power off the signal meter seems to go crazy and MPX light flickers eratically. Not sure why so will need to investigate this...

I have compiled a list of electrolytics and tantalums to replace so I will need to order them. Not sure what to go for atm, I suspect most folks would say this amp deserves something special so will need to have a look at what's on offer!

Anyway that is all I can do today as I am off out tonight!

Nice work.

" .. Also on power off the signal meter seems to go crazy and MPX light flickers eratically. Not sure why so will need to investigate this..."

This is normal.
As the voltages are bled down, the circuit will become unstable and produce erratic readouts.
The signal meter pointer will swing up and down and the MPX light will flash a couple of times.
Strange, but all perfectly normal.

Regarding the large alu can capacitors, my advice would be be to replace all four.
They are a bit costly, I know, but if one is bad there's a good chance that the other three are
marginal. Try to get 100V types.

The reason for the flickering displays could be as simple as bad solder joints at the board interconnecting
plugs/sockets and sometimes even at the diplays themselves where they are soldered to the board.

Martin

Hi Martin thanks for the info - just so you know the belts arrived so thanks for that.

Interesting regards the meter and MPX lamp being unstable on power off - not really very B&O is it! It is begging for a modification IMO!

Regards the electros yes I intend to replace all 4 of them with 100V types, I think the margin between 55v to 65v is very small considering the work they might be expected to do! I guess technology back then was at its greatest to get such a large value in a small space like that!

One thing I have also noticed, the filter switching is intermittent and works only by moving the upper board slightly, so I am sure to find lots of drys around the plugs etc! Hopefully the dodgy frequency display will be related!

I was surprised to see tip141/147's spec'd in the manual for the output transistors when the 6000 and 5000 etc. use the higher current BDV64/65's... I assume the increase in power just comes from the slightly higher voltage and seperate power supply arrangment while more appropriate heatsinks mean the higher rated transistors are not required...?

I am struggling to understand the exact role of the extra output darlingtons in series and how this configuration helps..?

The extra darlingtons (the upper-most and lower-most in the stack) is for soft-clipping.
They round off the sharp edges that would otherwise be produced when a transistor clips.
This will protect your speakers (and ears), the tweeters in particular, since a square wave contains a huge
amount of higher harmonics.
Distortion from small amplifiers kills more tweeters than too high output power.

The intermittent Filter button is a clear sign of problems with the interconnecting plugs/sockets.
Solder joints will crack, copper traces can break where they meet with solder pads (difficult to spot).
The plugs pins has a kind of metallic surface treatment that can flake off, causing bad connections and
in that case, the plugs will have to be replaced.
In severe cases, it will be necessary to fit short pieces of soft leads to permanently connect the two boards
and use the plugs for the mechanical connection only.

BDV64/65 is occasionally found also in Beomaster 1900 (!).

Martin

Nice thread so far Olly.

Very interesting. I should receiving my BM 8000 shortly...so this is very interesting :)

Thanks folks. Martin interesting regards the soft clipping I will look at this when I come to scope the output and compare with the amp in the 6000!

ok tonight I have mostly done some little things here and there...

I started with the processor and display boards. Yep there were drys alright, quite a few actually... These were the obvious ones!

Also on the display board, I will order new bulbs to replace the original ones. Might try some LEDs yet not sure...

I also checked board 4 (tone volume etc.) while it was exposed nothing serious but went over some bits mainly plugs.

ok so as I need to get other bits on the bench to compile an order list but before I do this I figured there were a couple more jobs I could do now so saving time.

I decided to clean the two tone control pots. As most know these get quite dirty to the point where it becomes audible. We all hear Martin suggesting the only way to clean these is by pulling them apart. I don't think you fully appreciate the truth of this until you actually do that!

Here is a before and after shot, switch cleaner doesn't really do a great deal tbh!

Next the speaker switches also get quite tarnished internally and IMO are worth stripping and cleaning. Sometimes it is so bad that they stop working altogether!

Quite an easy job just a little fiddly to get back together! You can see that I have cleaned one half of the contacts below, this includes the fine edges as shown with the pieces stuck in the platerceine.

The trickiest job is to solder the switch back some helping hands are useful here!

ok so jobs to do now are recap (there is a heavy ripple on the 10V line nearly 2v I might relocate the replacement capacitor away from the rather warm rectifier, as I have done in the Beomaster 6000) replace the pots I am able to setup properly afterwards, this means some in the radio section will stay put!) and sort out the noisy transistor in the right hand channel, but will wait until I recap as I might as well do the job of removing the board once!

One more thing - I investigated the jumping display when tuning. I noticed the auto / manual tuning switch didn't seem to be making any difference, despite the manual light coming on. Investigating the diagram, and checking the processor outputs on Plug 85 I noticed there was no change on pin 5 (aft on) when I a switched between Manual and auto.

Studying the diagram more closely made me realise what had happened! When I pulled the front panel off pcb 4 (tone controls etc.) I didn't worry about the four buttons (store x2 monitor filter) as I figured I could test without for the time being, I knew they all worked and filter at least could be accessed via remote. I hadn't realised the controlling half of the man / auto switch was actually part of that matrix (phase 3) for the other four switches, so of course it was able to control the manual lamp, but the processor never got the signal! - silly me Anyway there's a warning for future repairers!

I think that is it until I order the bits required. Decided to go for Panasonic electros nothing special FM FC and Vishay for the axials. There does not seem to be a supplier that has the full range in a particular type in the UK so finding what you want is a bit of a hunt! If anyone knows another supplier other than the usual RS / Farnell etc let me know! Not interested in Boutique tbh I do not want to change the sound, just increase longevity.

SO the amp will go back together for now until I get the replacement parts, I might take it downstairs and try my S120's out and see how it sounds!

I have a few other little jobs to do now I recieved some belts and bits off Martin so might not update this thread with anything exciting until next week.

I forgot to mention something! I decided to get access to the processor board, despite the warning label to return to dealer for service! I guess this amp and the Beocenter 4000 was to be the start of module replacement repair culture seen so much today!!!

Anyway, I was shocked with the lack of care when the thermal paste was originally applied!

Quite messy and I honestly cannot see how that paste can be doing any good like that! Doesn't cover one of the processors over its entirety and I am pretty sure the IC's are not flush with the heat sink (a metal bar riveted to the case). The smaller IC is actually lower than the two main processors but B&O obviously wanted this to be cooled more affectively than ambient. I think I want to do something about this but not sure what yet! If these were PC processors they would either be dead by now or would constantly shut down the PC!

I am enjoying this thread - very informative.

Please let me know which caps you finally source to replace the four 10000uF cans.  I did find some electrical equivalents a while back but they were not able to fit inside the space available.

Regards

Geoff

Hi Geoff, thanks for the interest. TBH I have found just the opposite!  Most modern equivalents are actually quite a bit smaller! I will be choosing at least 80V electros for the main amp PSU. Still not ordered anything yet but want to be sure I have covered quite a few items I have to work through and also waiting for an email off a supplier atm!

I am looking at Panasonics for most of the PSU caps / decoupling etc, some the larger of which I will source from Digikey I think, more choice and quite a saving over our providers in the UK! Signal path caps looks like I am using Nichicon (thanks Eugene for good source) although I am ording some Vishay 515's to try out in my 6000, as I would like to find something with similar specs to the original capacitors.

On a side note I will hopefully update this thread with some Beocord 9000 photos later on..

sorry about the text not sure what I have done here! what is default font on these forums?

I agree that most of the modern caps are much smaller, but the ones that I was looking at were shorter and fatter.  I will still be very interested to see what type of cans you finally install and how well they can be tailored to the limited space.  It would be even better if they didn't break the bank at the same time!!!!

Regards

Geoff

I pulled my 9000 apart last night, the deck was as you would expect, not used for a long time and a little tired looking, was lots of the gooey stuff!

The goo...

So I stripped the mech and started cleaning everything up, including my fingers!

Some more cleanup pics here...

Takeup tensioners

...After

rubber parts like brakes etc.. cleaned up ok and were still supple.

New belts go on..

And the tape path is cleaned up..

Would like to find a new donar for the capston so if anyone has any ideas. There must be a suitable replacement out there somewhere!

I might do some more work on it yet but everything works fine.

Oh I need to sort out cracks in the clutch shaft but they are not as bad as the examples seen in Geoff's thread so they can wait for a while!

So I put everything back together and switched the unit on. And wow, I am blown away by the playback quality of this deck! Absolutely amazing for something so old :) So much so I spent the next hour with my headphones on listening to some old-school tunes :)

It then occured to me to try the very thing that excited and intrigued me about this deck - the calibration and recording features!!!

This is were the news isn't so good. I connected to the BM6000, comms fine, got a good strong signal from the radio and tried recording. When I played back the tape, it appeared nothing had happened! In fact the original material remained unchanged! Damn.

Tried calibration. Seemed to go through the actions, and at least this time on playback I heard a few noises and a tone, but this was on top of the original music so it is clear there is a problem related to both recording of signals and the erase circuit.

That is where I am atm. Will investigate further tonight.

BTW anyone experience with digi-key customer service? I sent an exmail to enquire about postage for a number of caps and there has thus far been no reply I hate it when this sort of thing happens, doesn't exactly fill me with confidence! I will have to try again I suppose.

Nice clean up job on the tape deck Olly.  Why do you need a new capstan? I assume that you are referring to the flywheel assembly.

Regards

Geoff

Olly

Just a quick thought

I have never had a single problem with the record circuits on these machines (9000 and 8002) so I will be interested to know what was wrong with yours.  Since both channels are being affected in exactly the same way, it should be something very basic.  I seem to remember that there was a relay in the record circuit and if so, that might be stuck!! 

Regards

Geoff

Check plugs and connectors everywhere.
In some Beocord's plugs can go on offset a pin or two unnoticed.
Check also the solder joints at the connectors.

A replacement capstan (flywheel), why ?
I take it that if it was bent, you wouldn't have enjoyed listening to it for an hour.

Martin

Martin of course I meant the pinch roller No the capston is fine! It has been a looooong time since I did any work on a cassette deck!

I probed around a bit last night and I am spending time actually working out how things work, for the large picture, then I can go into a bit more detail when I have got my head round what is or isn't happening. Quite a complicated beast isn't it I might need your guidence yet Martin but would like to work things out for myself!

Yes there is a relay Geoff that grounds the heads this appears to move just fine but I need to test this properly!

Step1:

 might need your guidence yet Martin but would like to work things out for myself!

Fine Olly, I'll just sit around.

Martin

Seems you were quite correct Martin, Couldn't find any dry joints or obvious breaks to the tracks but as you had suggested with the 8000 the header pins were not in the best of conductive states! I have replaced the headers with some gold plated jobbies, and allowed solder to run over a slightly larger track area by removing some of the laquer. Will do the same to the playback header then I might replaced the sprung terminals inside the sockets. I will polish the other headers not connected with audio and visually check once done.

So far, I am pleased to announce everything seems to be working correctly! The level sliders need stripping as with the 8000, at the moment there are places where it is not always easy to set recording level accurately! Also you can hear the scraping noise.. Looks like I might have to invest in some serious test tapes to get the best out of this machine though! Not sure what to do about that just yet. Any pointers folks?

Recording very good as expected but have not conducted any serious listening tests!

I think I will order caps for this along with the 8000.  Seems I have a different Dolby board which is not featured in this sites copy of the manual, and there are component lists missing etc.. Had to go through every board manually to double check values etc!

If anyone has complete original service manuals they would like me to scan for this site, that could better what is already available please let me know so we can make the collection more complete!

The cassette mechanism looks eerily similar to the ones used in the Beocenter 7000 and 7700. I am still finding belt goop in and around my work area - months later.

Eugene I am sure they are all mostly identical but for a few small changes here and there... I am pretty sure the Beocord 5000 and Beocenter 4000 (the good one!) had the same mechs, different to these!

Olly,

I've got a better-looking-than-yours pinch roller if you want! Not new, but relatively flat and grippy.

Or there: http://cgi.ebay.fr/Bang-Olufsen-2804041-cassette-deck-pinch-roller-rare-/150219226601?pt=Vintage_Electronics_R2&hash=item22f9c37de9#ht_500wt_918

Thanks Jacques, how much would you want for it? let me know...