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
The replacement caps actually arrived yesterday (Tues). I don't think I will have time to install and test until the weekend but here is what they look like.The 12000uF replacement for C17 measures 11000uF.The 2700uF replacement for C12 measures around 2400uF.The two 8200uF replacements for C5 and C6 measure around 7400uF.I pulled of one snap ring (from the original C17) to use in mounting the new caps to the rectifier board. I test fitted the caps in the plastic mount and they fit good. I won't have to add any additional filler.
I prepared the replacement for C17. Tomorrow I will check the power on the BC 9500 with just this C17 change and see where I am at with this unit.
I tried out the Beocenter power tonight...the 13V is still dead. The new C17 capacitor is fine (11000uF). However, the fuse (F4 - 2.5A) is blown. This Beocenter is a type 2506 and the fuses are a small black can with leads that plug into the board. Is this type of fuse from Mouser a suitable replacement?
That link to the fuse in my previous post was for a fast blow fuse. Looking at the service manual again, it specifies a 2.5A T so that must mean time delay/slow blow fuse, right? So I think I need this type of fuse.
correct
//Bo.A long list...
What a wonderful thread. Fantastic people that help.Perfect slow saturday noon reading with a cup of coffee. Thanks to all
My re-capped M75 are my precious diamonds.
It is a great thread and in case you need parts just let me know, got about 25 of those machines :-)
Brengen & Ophalen
Thanks Leslie
My BC9000 have a dead CD, I might need a new transport to it soon, when I get to it in a couple of weeks, I will soon open it and document the version of the transport, and do simple error tracking.Todays work will to dive back into my BC7700 :)
Christian Christensen: What a wonderful thread. Fantastic people that help.
What a wonderful thread. Fantastic people that help.
I agree. I can attribute all of my successful B&O restorations to help I have received from this forum over the last couple of years. It has been really great.
Thanks,Sonavor
...I have ordered the replacement fuse (and some spares) but since Mouser is closed on the weekend it will be Tuesday before they arrive.
The Beocenter came back to life today with the new F4 fuse in place. So far I have just replaced C17 with a value that measures 11,000uF, 35V and the related F4 fuse. The Beocenter powers on in standby mode as expected and I observed it come on when I pushed some of the button pads (I have the glass panels removed because they were loose).
The voltage across C17 measures 17.61 VDC though. The service manual shows 13VDC. I didn't leave the Beocenter plugged in as I am wondering about that voltage level. Is that typical or is there something wrong?
sonavor: The voltage across C17 measures 17.61 VDC though. The service manual shows 13VDC. I didn't leave the Beocenter plugged in as I am wondering about that voltage level. Is that typical or is there something wrong?
Did that power rail have any load when you made the measurement? If it didn't, the DC voltage over the filter cap climbs to the peak value of the output from the rectifier, which incidentally will be around 17V from a 12VAC winding.
If you have the full service manual, it probably specifies somewhere the operation conditions that are needed for the announced test point voltages.
--mika
Here is the schematic of the area I am testing (highlighted in yellow). I re-measured the voltage across C17 using my scope this time. It measures around 18.7V. With the Beocenter power plugged in I took it out of standby mode and exercised some buttons while monitoring the C17 voltage. It is a steady DC signal at the level (18.7V) the whole time. I went through my service manual again but I am not finding anything regarding testing this voltage. I just see the 13V reference on the diagram. I'll sleep on it and see what else I can measure tomorrow (actually later today now).
If you look on page 1-6 under "Measuring Conditions" you'll see that the voltages on Diagram C are measured with a 1W output level. That might be significant, as Mika pointed out.
/ Johan
Thats right, "free running" voltage is higher that loaded, so I would check with load. If you are worried, maybe you could plug wires off and try with dummyload.
blah-blah and photographs as needed
I see that section in 1-6. I was thinking that since C-17 was for the processor, it ought to see its typical load when the Beocenter comes out of standby. It shouldn't be affected by the power amplifier driving some speakers, right? I can connect some speakers to the Beocenter tonight and re-measure though.
If you look furher on line, there is regulator IC4 for 5V, TR19 for 7V and other stuff, not all going to prosessor, so there is probably other current consumers also for that.
Tonight I connected my Beovox S55 speakers to the Beocenter and played a cassette. I kept my scope probe measuring across C17 of the rectifier board. The voltage stays above 18VDC the whole time. In standby it is about 18.7V. While playing music it dropped a little down to around 18.4V. I probably let it play about five minutes. It appears to be working but I would like to know what voltages other BC9500 units are measuring across C17.
I will go ahead and continue cleaning the unit up. I'll try and run the self test mode on it too.
Did you measure the 5V and 7V coming from there?
This BC9500 today is measuring 18.4V across the C17 capacitor on the rectifier board. The 7V supply measures 7.7V.The 5V supply measures 5.14V.
What mains input voltage is the unit set to? And what is your nominal mains voltage?
The mains voltage selector is set to 110. I'll measure the actual value this evening.
My house voltage coming in to the Beocenter mains is 125V, 60Hz. If I use a variac to lower it to 110V, the voltage across C17 goes down to around 15.3VDC. At 125V the C17 voltage is around 18.4VDC. The 5VDC power in the Beocenter stays constant at 5.13VDC.
At quick look, there is not unregulated feed from that line, so no actually danger, only that things get a little hotter than normally, that why I use 240V position as ours mains is around 230V.
That's exactly what I was thinking. Try setting it to 130V and if it works, then I'd leave it.
Setting the mains selection to 130 does bring the C17 voltage down to a better value than 18.4V. The voltage dropped to just over 15V. I will leave it there.So that about does it on this unit for this thread. From Mikael's start of this thread it looked like this unit had the same symptoms. That turned out to be the case and rectifier board C17 was defective. The related F4 fuse on U64 was blown so that was replaced. I don't know yet if the owner of this unit wants me to do anything else. I have the glass panels and frames all cleaned off (of the old double-sided tape). So I will re-assemble the Beocenter and check out the remaining functionality this weekend.
Thanks to all that helped me out on this.
Great thread. Reminds me of my efforts a long while ago when I did a BC9500.
B&O did issue a bulletin a long time ago about setting 130V for 120V areas, and 240V for 230V areas.
The only place where I have seen an issue develop is on the BG4000, where if the AC mains is around 118-119VAC, and the selector is set to 130V, then the orange fluorescent stroboscope lamp does not illuminate.
But that is a very special exception to a good rule-of-thumb, simply because the BG4000 is a very special (if quirky) machine.
I just desoldered all of those big cans, my good god, what a epic battle, traces lifting, having to switch to highpower iron just to liquify the massive blobs, bending the ring legs while heating..sucking, and braid feeding...
The traces on these PCB lift extreamly easy.. i changed a few caps on PCB 53 and i've never seen traces detatch so easy... nerv wrecking!
my old 70:ies BM's never gave me this much grief....
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
Before trying to desolder, ALWAYS melt new (poisonous) leaded solder onto the old joint.
You should never have to apply heat to any smaller joint more than 2 seconds.
Appreciate the tip! It did work! Also reusing the old rinbgs from the gold ROE worked nice! Really a boost in technique....
Ive been doing some work on PCB 54 and PCB 53 changing and upgrading caps.
But taking it slowly and testing intermittently to identify if i induce any problems..
I noticed today that Selecting to TV/AUX from any other source, induced 1-2 second silence before sound comes in.
Changing to TAPE2 from any source is instant.
Was it like that before, or have I induced a deviating behaviour?
thanks
//g
Marcus
Before going any further, confirm that you have already overhauled PCB60 - the vertical PSU PCB at the rear.
There is no point in attempting any overhauls of any other PCB's, until the PowerSupply voltages are confirmed as spec.
The Incorrect procedure is to overhaul the small PCB's first, because they're "quick"
Always do the PSU first - it eliminates many doubts afterwards.
Hi Menahem, many thanks for you reply...PCB 60 and output board all done, and after each board, partial startuptest .and voltage check, at 240v setting (house gets 227 approx) .everything was dandy, not a single glitch or mistake.. everything and every part was 100%.. (a few tracelifts by my above substandard technique..but that was worked on :=) ) so it was actually the last two boards (and some tape lube) that i had left... thats why im pretty certain this "delay" was introduced by me.. if it wasn't there before, which is hard for me to gauge now...
I will measure around and see if anything stand out, got a new UNI-T 139c last week, so might give it a few rounds...
OK, go back and check all the electrolytic capacitors which you replaced, that you installed them at the correct polarity.
Also, check that you installed all the correct values of ALL the capacitors in their correct positions.
This looks like a charging time issue of capacitors.