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, Its been raining so much in sweden i finally got around to applying Dillens BM3000 kit to my pretty banged up machine.
All has gone well without any major ***-ups. If you have done this work, the kit is quite comprehensive.
What I cannot figure out is the pictogram for the idle current adjustment in the service manual.... 100mA , right.. trimmers known, right.... but over which component?... at which two points should i measure?
Any help would be welcome, don't want to fry my almost spanking new amp!
BM 2000 *1974, 2x BM 1200, BM 1001, BG 1200, BG CD X, BC9500,BM3300,Bcord 3300, BG CD3300, Beovox Cona, Beovox CX100, Beovox 1200, Beovox RL60.2
You'll notice that the two connectors in the centre at the rear of the amplifier board are push on types,or should be?
Simply disconnect one at a time and connect your meter between the pcb pin and it's disconnected cable.
Set the meter to measure current,initially use a range above 100mA to allow for switch on surge,then set the current using the appropriate preset,which hopefully you have also replaced?
A good idea would be to clean the pin and it's connector with antioxidant to ensure a good connection later too
Regards,
Nick
Thats great, crystal clear!
When you say replace presets, do you mean the whole wheel assembly, or just the tantals behind?
I have a spare wheel ass. just in case.
Tantals where replaced!
many thanks!
No,the preset resistors on the amplifier board that you adjust the idle current with.I imagine that Martin supplied these in his kit,but if not then it would be sensible to replace them too.
Garten: Thats great, crystal clear! When you say replace presets, do you mean the whole wheel assembly, or just the tantals behind? I have a spare wheel ass. just in case. Tantals where replaced! many thanks!
Nick refers to the idle current trimmers.Not the fingerwheel potentiometers for the FM station presets.
Martin
Ahh, many thanks, Yes trimmers ofcourse replaced from the kit.
Left side stable as a rock (red/white cable) but right side (solid red cable) is oscillating wildly in a 50mA span.. adjusting the trimmer only moves the span ..like 70-120 or 80-130
Any idea what is causing the idle current to do this?
Thanks
//g
Hi all,
To update my own post, i had a short on the back of the amp board, had forgot to cut a protruding wire from one of the caps, terrible. all sorted, all is stable and well.
The only thing that seems odd is the stereo lamp.. its always on. It flickers slightly during tuning, but it nevers goes off. I assumed first that it would be TR22 according to the service manual. (seee pic) but then i noticed that even with one or both of the mono buttons depressed it keep being lit. I have actually yet to find a situation where it is not lit.
Ideas?
Hi,
The TR22, TR21 may be faulty. If you disconnect ZF18, same result => TR22
Check both AA119 and TR21.
Ralf
Many thanks, I'll get back tomorrow after checking.. looking at the schema again...
TR21 is a BC113 and TR22 is a BC148
Both seem to be replacebe by BC549B would you agree? seems my closest match.
I also have these in my inventory, but the BC549B seems best replacement for both, any thoughts?
BC559C
BC557B
BC253B
BC547B
HI all...
All was fine and dandy, until suddenly smoke and panic...
TR58 is toast and took 470Ohm Resistor 578 with it.. totally blown... aswell as spanking new cap (553)
As soon as i switch it on the 470hm resistor puffs a little,.. on light is present, and all else seems well.
only way to keep it from burning is to disconnect the "push on" white/red connector front middle of the board, and a white-brown connected wire under the board (point H)
when i meaure and compare to "the working channel" seems the wire underneath to the working left side (solid brown) has 26v while the white-brown of the nonworking side has 54v (I assume its 54 and not 60 as i have it set to 240v in sweden which is approx 230 inreality)
So possibly i have an issue with this wire.
It commes from the bundle of resistors connected to the large filter/reservoid caps.
In this post, they are all changed, i can seem to find what components they are from the schematic/listing, and frankly they are crosscoupled in a way that I have a hard time understaning,
Looks like they are the 56K, 68K and 1,5k.. but there are more than accounted for by that part of the schematic
http://archivedarchivedforum2.beoworld.org/cfs-filesystemfile.ashx/__key/CommunityServer.Components.PostAttachments/00.00.35.78.67/BEO3000_5F00_optres_2D00_2.JPG
http://archivedarchivedforum2.beoworld.org/forums/t/42883.aspx
Any help or hints would be very appreciated.
thanks
Garten,
Assume that the original circuity is not to blame as it worked about 40 years. From the moment you are restoring a system, anything can happen and you must check and re-check every steps you made. From the capacitors polarity, soldering, wiring, selected replacement components, etc...
When you are asking for advices, we assume no mistakes were made but we are getting into a tough calls...
Before starting a project, I'm hoping you are taking lots a pictures of the original components where you refer to them afterwards, if not, your in troubles. Also check all the soldering you made with a magnifier making sure you have not bridged components accidentally.
Good luck!
Point taken, rechecked and remeasured anything I touched, and it all checks out.
That the amp sounded perfect for several minutes untill poof in my mind attests to a correct pre-amp job, else in my mind it would have sounded crap.
I left it on long enough also to mkae the idle current measurments. No fuses blow or anything like that.
And when I now measure the two pieces of what is left of that 470ohm resistor I have 54 volts over it. It leads me to suspect those largish resistors and that point-2-point network next to the large caps.
The caps themselves checkout, and that the rightside is getting correct voltages and is fine seems to indicate correct rectification and supplyvoltages exist. So my only though left is where the supply of power separates to the left and to the right side. and thats those jumbles of resistors.
Is that a sound deduction?
So two points:
1. I have a little issue with seeing certain colours , so decoding the values thereby deducing which resistor is which is hard
2. As I can't deduce which resistor is which i have a hard time applying the schematic to reality to understand how its all connected the way it is in reality.
From each terminal of the reservoir cap goes a wire to a point which is connected to another terminal with a resistor. This point is also connected witha resistor the the terminal point of the other polarity.
So from each point with a cable leading to the underside of the pre amp (one per side) each point is connected to both polarities of the reservior cap
...just with two different kinds resistors.Unsoldering them, they are off their spec (if I assume they are the resistors i belive they are , circled in yellow)
But not in such a way to cause 26 volt to become 54..
I have studied these posts, ven though my issues are slightly different
http://archivedforum2.beoworld.org/forums/t/11332.aspx?PageIndex=2
But Can't realy find deviations in the Ohms.
Thanks.
OK,
Do you you have pictures of that board section? If you can't read with accuracy the resistor values and we can't trust the schematic, can you at least read them from the pictures you have?
The resistors you circled in yellow seem to me drop down voltage resistors and you have them on both channels.
Are the resistors burned on both sides? If yes then we must check the common power supply for problem.
Here are a few pictures, I will dismantle and measure each component.. trying to figure something out...
Using Dillen's questions from the older BM3000 posts i linked to, i verified that the 3055's of the busted channel were toast.
If those became toast because the preamp blew or if the pre-amp blew because the 3055 blew is my question.... and what started it all in anycase..
Measuring Also measuring from the power pins (front center across back corner) on the preamp board gives 50K on the working channel and 15k on the busted one.
But that is basically measuring the bustedness of the pre-amp , possibly not the cause of the cascade in the firstplace.
so im getting new 3055's and replacing the copopnents on the pre-amp.. but im realy cautions of the fact that i might not have found the root cause yet...
Im back with some news.
Replaced the 3055, but still nada... so i gathred that more of the pre-amp had blown... replaced TR59 and TR60 with temporary lover voltage transistors, just to see if I can get anything through headphones..
Voila!, the channel is now alive!
Two strange things though. On the previously dead channel I have 50Hz hum... on the other channel perfect silence when volume is "0"
I read somewhere that it might be a decoupling cap thats gone open circuit... any other thoughts?
Also when trying to set the idle current i can't measure anything on any channel.. nada , zero?
FM radio now working through headphones on both channels, 50hz hum in one, and no idle current what so ever on either channel... Rather not connect speakers until i understand whats going on with the idle current...
replace the two 1N4148 as well, disconnect the preamp and connect a sinus generator for testing the preamp.
Most 50Hz hum is caused by faulty caps in the powersupply. Does the 3000 have 2 separated power supplys?
Do you have 50Hz on every source?
Hi Ralf,
Will replace the diodes tonight, lucky break i actually have a few.
Yes, the 50Hz is on every source. The filter/reservoir caps all changed.
And no, the 3000 doesn't have separated powersupplies, The hum is produced from the one channel only and no difference is heard regardless of 220 or 240 setting.
I unfortunately do not have a sinus generator.
thanks!