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
I bought this off ebay a couple of months ago very cheaply, postage was as expensive as the piece if I remember rightly, my thinking was I may need to cannibalize it to complete Mr Roast's BM6000. However as that has not been the case I felt compelled to open the box and have a look, It looked a bit sorry in the ebay picture and when opened up the picture proved to be quite accurate.....looks like it has been in the wars.
I know.....I probably need a good kicking for taking this on, and its probably getting a bit boring.....but I don't care ;¬)
Close inspection suggests someone has attempted to open her up and I suspect they failed, looks like an attempt has been made to remove the tuning dial that has resulted in the machined disc being detached, and some of the casing screws have been replaced in the wrong places, the cheese head allen screws normally holding the selector switches in place have been replaced with slotted screws and an allen screw is located to the rear.
The ebay seller advised that the unit was completely dead and therefore had removed the plug from the power cord, fair enough.
Removed the securing nut from the tuning spindle and following the application of some servisol and a couple of quite firm taps was able to draw out the damaged tuning wheel and dismantle the casing.
To my astonishment the internals look very nice indeed, I can see no footprints left by any previous repair technician, there did drop out a small pushbutton spiggot that has clearly come adrift from one of the keys which suggests a broken saddle somewhere within, but otherwise there are no signs of damage, burning or anything else.
The seller advised that the problem may be a blown internal fuse, wonder why he thought this, flipping the unit over and removing the fuse cover revealed one of the two 4A slow blow fuses was indeed blasted, the screws showed signs of removal. These fuses feed the primary windings of the transformer...if they are shorted out I fear the transformer may be goosed, could a high current in the secondary windings blow these fuses? I suspect not but some advice from Martin would be well recieved before I dive into this.............
A drastic short on a (powerful) secondary would cause a high primary current as well (that's where the power comes from).Fit a new fuse.Isolate the secondaries, gIve the transformer a creeping slow spin up on the variac and watch the primary current.If it goes through the roof the transformer has shorted.If the transformer alone uses close to no power, check its secondary AC voltages.If all is fine - check the loads with an ohmmeter - or fit them one by one and watch the current again as the mains is turned up slowly.
Martin
By the time you've done this one I recon you'll be able to do them in your sleep! You might even have to change your username to Craig6000
I think I may need counselling...........
Thanks for that Martin......had quite a time finding my way around the transformer, was a devil of a job removing the cover to get a good look at it all, it looks in really good shape actually, disconnected both 27v and 42v transformer outputs, dropped in two 3A slow blow (tried to err on the safe side) and with gritted teeth (don't have a variac, told my partner to put it on my Christmas list) powered up.....no load pops or sudden smell of burning shellac. with a heave of relief hooked up my fluke and measured 27v and 44v respectively......I think that puts the transformer in the clear.
Next I will pull out each bridge rectifier and measure up, I'm hoping for a short across one of them.
Discovered this little fellow to be shorted across its A/C terminals in both directions, looks like the culprit, printed on the side it says ITT B80 C7500/5000 so will check out RS for a compatible replacement and get it on order.
I think counselling is far too late - clearly need sectioning! To repair one BM6000 is a challenge, a second is possibly a little strange but three! When you restore a 3 head Beocord 5000, then I'll send the boys round! Have you tried a VX5000? I probably have one lying around!
Peter
Peter.....i'm flattered, that's probably the nicest thing anyone has said to me ;¬)
I've ordered up a replacement rectifier single phase 100v 4a, will be a lot smaller than the one I'm replacing so will need a little modification to the mounting, I know this is a long shot but does anyone have anything to go on here?
If not I'm considering a piece of fir burr veneer I have out in the garage, cant leave it as it is.............
Would it be an idea to machine a very thin layer off?
A 4A rectifier will not be powerful enough to replace a 7,5A/5A
I really do appreciate the watchful eye provided by yourself, its priceless.....I will see what alternatives are provided by RS, anyone who needs a 4A full wave rectifier please let me know.......;¬)
Craig
Ok....lets try again, I have selected a Vishay KBU8B-E4/51, Bridge Rectifier, 8A 100V, 4-Pin KBU. This shouldn't see 100v and its above the 7.5a current requirement.....so I'm thinking this should be a good replacement?
persuaded Debbie to leave this under the christmas tree for me, wont cope with a beomaster at full output, but I wont be testing at raised volumes so it will be fine, and a lot better than gritting my teeth.
Absolutely better than nothing. Though a current monitor would be nice to have.Keep an eye out for a B&O RT12.
Very nice looking piece of kit.....and very hard to come by I would have thought, I can buy a combination digital volts and amp meter which could be fixed to the front plate using a piece of DIN rail with just a little modification to wire it in.......I will evaluate the possibilities when it arrives, If I'm allowed to open it before the 25th ;¬)
Fitted the replacement rectifier and measured 60vdc coming out, however all is not well......the selector lamps illuminate when pressed but no lamps illuminate on the volume/bass/treble or balance assembly, the main relay clicks in, the control servos drive up and down and the red LED illuminates.
checked across the 3300uf Cap and measured 36vdc.......cant measure any quiet current millivolts.......and time has run out, will resume tomorrow, oh joy!
Refreshed I have had a measure around with a multimeter and found everything around the power supply outputs as they should be. I was getting a good 59vdc at the + term of OC5 the big 10,000uf cap, removed the relay RL....2 screws in the front and out it comes, the relay operated fine when power was switched on and off and 59vdc was present at input terminals 10 & 16 but nothing coming out at 9 & 15 (these terminals are connected together with one cable out. took the relay out and removed the cover....it looked in very good condition to be fair.
Cleaned the contacts with very fine sand paper, spot of servisol and replaced it......powered up and was rewarded with 59vdc on 9 & 15. Checked the quiet current and that was present at each output pair of darlingtons.....was a little high at around 17 to 18 mV so tweaked them down to 14.
so far I'm happy.....further investigation revealed 17vdc & -5vdc on the volume slider lamp connections of PC12, as I was on a roll I decided to try the obvious and replace the bulbs.......4 of these proved to be burned out, they are in a sort of series parallel config so as it turned out 4 was enough to put them all out.....sorry Mr Roast....the bulbs I was intending to give you back have been commandeered ;¬)
Sandpaper destroys the ultra-thin layer of platinum on relay contacts.
Obviously, the best thing to do is replace the relay but if that is not an option cleaning could be done
using a piece of paper soaked in contact cleaner pulled between the contacts.
You can prod the contacts together a bit to add a little tension as you pull.
The papers abrasive effect is usually adequate. If this doesn't help, the contacts are really burned and scarred (as you would
be able to see in a microscope) and must be replaced.
Sanding the contacts will only make it work for a short time as scars will build up (contact material moves from one contact part to
the other when breaking the circuit, because of the current flow) incredibly fast without the platinum layer.
Nice work as always!
Martin...your correct, during my day job I occasionally specify control relays for logic sequence control, this is getting less frequent these days with the increase in PLC controllers over relay logic control panels, we always specify that the relays are to be supplied with contacts coated with "noble metal" which is often gold and as you say very thin (vendors give nothing away). I'm thinking this relay could be replaced with a DPDT (double pole double throw) relay with a 24vdc coil, couple of mods to the base to connect some of the terminals together. Space would be the issue, getting one small enough to fit in the gap left by the original....Omron do a good minature relay range complete with solder base that would be close, something to bear in mind for the future I suppose. Meantime I need to see if I can get any sound out of this.....will try this evening.
Hooked up my Ipad to AUX2 and a couple of speakers to the front L&R outputs, selected some music and pressed AUX2...nothing at all coming through, a little deflated I played with the volume and balance for a moment then remembered to select FRONT on the bank of selector switches and out came the sound. Swapped the speakers over to the rear L&R and tried again.....all good. However (there is always an however) when selecting FM the tuning bar lights come on and the tuning meter lights up along with the FM indication lamp above the keypad...the radio static comes out of the speakers too, but as soon as the FM button is let go the lights all go out and the sound drops out too.....so I have a latching issue somewhere, had to be something I suppose.
Seems my power supply woe's are not yet over.....discovered I'm missing both my 20vdc and 21.5vdc supplies to the electronic switch board, this explains the P1-P5 and FM lamps coming on and dropping straight back out, half of each network is not powered.
After a good deal of searching finally found the supply rails source from the IF section....I'm sure there must be a very good reason for putting it there?
Ok......little guidance required at this point, looking at the above circuit I require some replacement parts. I have a couple of 1N4448 to replace 2D8 & 2D10, done this and found one open circuit and one short in both directions, replaced them both however not getting anything at the collector of 2TR8 so didn't make any difference. 2TR8 is available online so no worries there however the regulating diodes are a little less clear can I use the following:
0D2 ZPD20 (can I use BZX79C20V as an equivalent)
2D9 ZPD9.1v (can I use BZX79C10V as an equivalent)
Martin....... ;¬)
Don't fit a 10V zener instead of a 9,1V.
What are the voltage readings on the three pins of the transistor?
Martin.....ok I have sourced some 9,1v zeners now so that's good, thank you. I have also removed 0D2 and tested it, strapped to the shield of the front end to keep it cool, it reads short circuit in both directions. With this diode removed the voltages at 2TR8 are as follows:
B = 44,2v
E = 45.4v
C = 19.78v
Looks like 0D2 was dragging down the collector voltage?
Regards Craig
Hi Craig.
i am almost sure i have found a tuner wheel for you,i contacted the guy i bought my 6000 system from and he is absolutely sure that he has one,i get an answer from him next week.Are you still interested?
Henrik.
That looks like an Arial......and with a name like square 4 it has to be, yes Henrik I would be very interested in acquiring your friends tuner wheel.
I let you know as soon as i hear from him.
Yes it is an Ariel Square Four.
Henrik
very nice....I always wanted one of those when I was a young man, they said the two rear cylinders suffered from overheating...is it true?
Always enjoy your restoration posts Craig. Quick question, have you ever heard the Pink Floyd Dark Side Of The Moon quad recording played on a proper quad system? It was famous back in the day but sadly I never got to hear it to know what it was like.
Good luck with the resurrection.
Jeff
I'm afraid I'm recovering from the BeoVirus.
Hi Jeff
I have had a listen to some of the tracks posted on youtube that are said to be mixed in quad sound, some of the tracks do sound very effective and some sound a little ropey.......I suspect the real deal would be via a BG6000 and a vinyl copy.
The mrk 1 could have some trouble with overheating but not the mrk 2 as mine.
You should be sorry that you never bought one.it is the absolute best motorcykle i ever owned.It won 4 first prices here in denmark ,i am sorry that i sold it,but with the summer we had this year in denmark i would not being riding it anyway.
I hope some day i will find Dark Side of the Moon as a sq record,but they are very rare.
https://www.ebay.co.uk/i/253287484307?chn=ps&adgroupid=43920634520&rlsatarget=pla-359427365517&abcId=1063846&adtype=pla&merchantid=113532435&poi=&googleloc=9046778&device=c&campaignid=797602469&crdt=0
I have had the full 6000 system - have to confess not that impressed! CD4 records are the best but have to be pristine and only played on a Beogram as the rear channels are destroyed by high down force styli. SQ/QS records do not have the separation of the CD4 and sound a bit odd if truth be known. I think I gave the records away but will have a look! SQ do have the advantage of playing on any deck with a stereo cartridge and the Beomaster then unscrambles the matrix.