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,
Maybe you have been following my other thread about my Beolab Penta 3 restoration. They came as part of a package which included a non-working Beocenter 9500. The lady who sold it thought it had blown a fuse during a party. The lower glass panel is cracked across.
I decided to make a quick investigation and opened up the small cover on the back of the mains transformer. The fuses checked out for continuity and negligble resistance. But one was 0.2 Ohm. I figure that could be normal but I will replace it anyway once I buy some fuses.
Hooking up 220v makes a small hum from the transformer. The connectors on the #64 pcb does not show in the service manual so it is hard to see if the voltages check out but something is fishy here. I read 10v Ac on some points but no 12v as in the diagram. I don't really trust my multimeter and will get another one.
Next is opening up the unit more and measuring the rectifier PCB and stabilizers. Any thoughts?
Beocenter Overture | Beolink passive | CX100 | CX50
Ok, so I'm back from measuring the voltages coming out from the PCB #60 (Power supply and output amps). The relay clicks as it should and all voltages seem to check out in comparison. There is a relay on the rectifier board #62 also clicks so this leads me to believe it is trying to get out of stand by mode. Since the relay on the rectifier board seem to also click as it should (and output some of the mixed voltages to the #60 board to be stabilized) I'm thinking that the power supply of the unit should be ok.
The problem is that the 9500 is dead in every other way. No lights on the upper panel or the lower panel is lit. The only sign of life is the CD mech that do a sort of startup move with the laser and stops when powering up the unit.
This leads me to suspect that there is something wrong with the controller board #40. I've seen some post on the archived forum that states that the standby mode cannot be exited if the backup lithium battery is dead. But would that give the effect that I see (no lights no nothing)?
I've tried to short circuit the TEST MODE connector with no change. Just to be sure, I tried to send some IR traffic with a beolink 1000 remote without any luck.
Next up is checking the voltages on the upper and low display (keyboard) board.
Since there is very little feedback from the community I will continue this thread as part of my therapy
Anyway I seem to have found the source of the problem! While investigating if the controller PCB #40 was alive I noticed that the !RESET signal is always low on connector P50 pin 4. This signal is generated from the transistor circuit seen below on the power supply PCB #60. If disconnect the connector P50 on the PCB #40 and manually short pin 4 to ground briefly, then the unit goes to stand by and lights the standby indicator diode. Shorting the TEST MODE connector under the glass panel enters the testing routines. I also get the CD door to open (though it needs some TLC, it doesn't move smooth) and the cassette door.
So I'm going out tomorrow to get some new BC577B (TR15 & TR16) transistors and the C12 (2.2uF). Hopefully that will allow me to fix the problem.
Stay tuned!
Sounds like a good place to start.What kind of voltage do you have around TR15 ?
Martin
Hi Martin,
I have done some measurements:
Conditions: connector P85 (containing pin 8 !RESET signal to MCU PCB #40) connected
Measurements:
TR15:
Base 6,75V
Collector 4,97V
Emitter 1,3V (RESET)
IC4:
Pin V1 11,5V
TR16:
Base 158mV
Collector 15,5mV (!RESET)
I assume that the circuit should work normally so that while the system voltage is on the rise the TR16 allows current to pass until TR15 becomes saturated? So would you say that the TR16 is the problem (always energized)? I'm a bit rusty in the analogue domain.
Since the MCU board comes alive when I disconnect the connector from the PSU board and manually ground the !RESET pin briefly I'm thinking the problem should not be there?
Mikael
Mikael: TR16: Base 158mV Collector 15,5mV (!RESET)
Sounds like either TR16 or C12 is shorted.
--mika
Hi,
I'm not so sure it is shorted. There is approx 150kOhm across TR16 collector and emitter when !RESET is connected to the MCU pcb #40. If open connector then i read several MOhms on the same spot.
/Mikael
Hi Mikael,
as mika said check TR16 and / or C12. The collector of TR16 should be around 0V only for a short while after power on. Then it should rise to nearly 5 Volts. You said that you get 15,5 mV at the collector that's logical a '0'. The RESET line is low-active due to the line above RESET. and a logical '0' is low. so your processor gets a constant reset signal and cann't start working it's propgramm. If you disconnect the reset line as you done before and connect the RESET line briefly to ground the µP can start as you stated.
Ralph-Marcus
I'm leaning towards replacing TR16 and maybe the C12 while at it.
The TR15 emitter should be held at a constant 5V by the voltage supply.I suggest you check this.
Ok, back from my little workshop. I've replaced both TR15 and TR16. That gave no improvement at all. More or less the same voltages as before. The TR16 collector is 50mV now so still a logical zero.
Then I replaced C12 as well. That also gave no improvement.
Checking R36 and R37 gives resistance according to the schematic.
Sigh, I am a bit out of ideas right now...
I guess moving on to check the mcu PCB which btw still starts up if I manually reset it.
Did you check the 5V supply to TR15 emitter as I suggested ?
Oh, are you sure, you didn't get the emitter and collector pins mixed up for TR15 ?
You mean the voltage over TR15 collector and emitter or from IC4 pin VO? I will check both.
About mixing the pins, I will double check. I'm pretty sure that the replacement transistors drops right in without any shift in pins from the old ones since I got a bc557b and a bc547b.
Made some more measurements:
TR15
Vce=-3.14v (postive probe on C)
Vbe=1,8V
Ve=4,85v
Vc=1,3V
IC4
Vo to TR15=4,5mv
I was thinking if the Vi voltage of IC4 is only 11,5v compared to the 13v in the schematic. Would that give a too low voltage on the TR15 base?
Sorry but now I think you are looking at the wrong place. Everything seems fine on PCB60
Remove P50 and insert a 100k Resistor from TR16 C to +5V. Measure the voltage on C - it should be more or less 5V.
As this signal isn't RESET of the processor (as I suspected from only lookin' on diagram C) I suspect the error is on schematic G / PCB40 where the -RESET signal continues; probably around TR2/TR3. Measure resistance between -RESET on C25 / R27 to GND and to +5V (P50 unplugged, BC9500 off).
And in the on-state the voltage across C25.
BC9500 is surely worth repairing....
Gunther
Hi Gunter,
I will test your proposal regarding the 100k resistor and TR16.
Regarding measuring the !RESET pin on PCB#40 I have some data. When no P50 connector the resistance to ground is 150k. Should be ok I assume. I havent measured to 5v yet.
Powering up and no p50 connector gives 4,8v on the !RESET pin 4 (on P50 PCB side).
Maybe C25 is leaking?
Those 150k look ok as they are R27+R28. Same 150k should be to +5a through R21+R20 so looks like voltage across C25 should be around 2.5V without P50.
EDIT: just measured it - Pin 4 shows 5V. Don't know why yet - seems I can't read schematics anymore
EDIT2: found out that either schematics is wrong or I have a modified PCB40: My reset circuit is similar but R27 isn't connected to -RESET but to C of TR2 - so it's clear that we have 5V on P50/4 - puh - seems I haven't lost electronic sense R21 IS connected to -RESET
Measuring P50/4 to GND and to +5Va will both show 150k as in terms of low resistance +5V and GND is low resistance (measures some 450R on mine)
Just had to check if any supply comes through P50 to make checks fail - seems it does not.
I have an open BC8500 here so can cross-check. Don't know about its status though, never powered it up before.
Hi and welcome to the thread,
Do you measure +5v with the p50 connector attached or open?
Mikael:Do you measure +5v with the p50 connector attached or open?
open - but plugged as well
With P50 plugged it shows 5V rising slowly within 2-3seconds to +5V.
You might be "chasing your tail" here somewhat sir?
Have you got the 5volt supply to the upc module(P57-1),and is there a 50/60hz ref signal at P55-5?
Basic steps I realise,but it might be usefull to check,as there is a danger of "not seeing the wood for the tree's"!
Nick
Hi Nick,
Not sure about the 5v on p55, I need to check that later. But if I make a manual reset (brief shortcut to ground) on pin 4 p50 then the unit starts up.
Quite so,but check the 5 volt supply before you do anything else,and 4.7v won't do!!!
It's quite common on these units for the 5volt supply resevoir cap to fail or become dry jointed (same effect) Check that the ref signal is present also.
Ditto
The supply signal is 4,85v (that is measured on pin p57-1) For the ref signal I need a scope probably so that will be tricky to verify. Where do you find the reservoir cap, is it the one on the mcu board (C20) or the big boy on the rectifier board?
Today I am one happy camper!
This forum rocks!
If you remember I had som worries about the input voltage to the 5v regulator was low 11v vs 13v in the schematic. So the suggestion above regarding the reservoir capacitors led me to look at the rectifier pcb #62. The 13v is coupled with the C17. Removing first the CD mech allowed me to gain access to pcb #62. upon inspection of the solder side I noticed that C17 had a greyish milky texture on the leg an looked cracked in the joint. So I heated it up and added some more solder. Assuring myself that nothing is shorted when the cd mech and pcb was in service position, I powered up the unit. And it is alive!
Thank you guys!
Now I can start to see what else is the problem. The door belts are looking tired for instance. And there is cleaning to do.
I will keep you posted.
Mikael:Today I am one happy camper!
Such a nice feeling, My wife tells me that I get a funny smile on my face, when this happens, And we love pics
Collecting Vintage B&O is not a hobby, its a lifestyle.
Yes that really made my day
I think that I will leave this thread as is and start a new one regarding the actual restoration job on the unit. There I plan to post a lot of pictures. It's a pity that we cannot post pictures directly from an iPhone or iPad. Pulling out the Macbook takes more effort. Pics makes the threads so much more interesting.
Mikael: This forum rocks! /Mikael
Ditto...and here is another reason why -
Yesterday a friend of mine finally gave me his Beocenter 9500 (just to look at, not to keep). He had told me a while back that it stopped working (would not power on) so I said I would at least look at it. I have a copy of the original service manual so I felt I could look at some things. When I opened it up and first applied power I could detect the transformer coming to life and I observed a slight movement on CD mechanism. Sound familiar? Before I went any further I decided to do a quick search on this forum for Beocenter 9500 repairs. I could hardly believe it when I read the symptoms of Mikael's post here. It sounded like the same problem. So I jumped ahead and made my first checks on the BC9500 Rectifiers Board (62), reservoir cap C17 (10,000uF, 25V). Sure enough, it measures bad. Now, I can't declare this Beocenter problem solved but it is certainly a great start. I will need to order a replacement cap for C17 now but I am wondering about the other large electrolytic caps on the rectifier board. They measure okay but should I replace all of them while I have the board out? Or is C17 the only one I should deal with now?Thanks, for posting this solution Mikael (and the other Beoworld members that had inputs).-sonavor
I thought these pictures of the problem area would be a good reference for this thread.The first picture is of the Beocenter 9500 - removing the CD assembly so the rectifier board (62) could be accessed. I haven't done any cleaning of this unit yet and it has quite a bit of dust.
Next is the rectifier module. You are supposed to only need to remove the two screws shown in the picture. I actually removed the bolts holding the wire harness in place to give more room.
Rectifier board [62] removed
Rectifier board [U62] disassembled to get to electrolytic capacitor C17
Rectifier board [62] C17 measurements - My meters are unable to measure the capacitance of C17. I also tried my DMM but it also could not get a reading. The other rectifier board caps measure okay. I believe C17 is dead and gone.
Any recommendations for replacements for the four big caps on the rectifier board (C6 - 6800uF, 40V, C5 - 6800uF, 40V, C12 - 2200uF, 40V and C17 - 10000uF, 25V) ? They all have a length of 40mm. C5, C6 and C17 are about 30mm in diameter. C12 has a smaller diameter - 20mm.
Great pictures Sonavor!
Brengen & Ophalen
I found some Nichicon LS series capacitors that will fit into the existing space. The original Roederstein caps have a center positive lead and three negative posts for mounting. Whether I go with snap in or radial lead replacements I will have to rig up jumpers to one other negative mount points (on each capacitor). Here is information on the Nichicon LS series.
Since the capacitors on that board are listed as -10% and +50% I decided to order a 2700uF, two 8200uF and one 12,000uF replacement caps (20% tolerance). For some reason those have been on the low side so those should end up within the tolerance of the 2200uF, 6800uF and 10,000uF values in the service manual. I don't have time to drive over to Mouser so I ordered them. It is late in the afternoon so they probably won't get here until Wednesday.To get sizes that fit the Beocenter 9500 rectifier board plastic cap holder, I ordered a Panasonic ECO-S1HP272BA 2700uF, 50V for C12. It is 22mm diameter, 25mm length. The original ROE is 20mm diameter and 40mm length but there is room in the plastic mount for the 22mm diameter. The ROE 2200uF is rated at 40V.I ordered two Nichicon LGU1H822MELB 8200uF,50V caps for C5 and C6. The current ROE caps measure around 8400uF and are rated at 40V. The Nichicon cap is the same size - 30mm diameter, 40mm length.For the C17, 10,000uF, 25V cap, I ordered a United Chemi-Con ESMH350VSN123MR35T 12,000uF, 35V capacitor. It measures 30mm diameter, 35mm length to replace the original 30mm diameter, 40mm length cap.
I did snap ring from old cap and solder it to board to make a bridge.
blah-blah and photographs as needed
Orava: I did snap ring from old cap and solder it to board to make a bridge.
That's a great solution, thanks !