Beocenter 8500 -Losing settings - Page 1
Forum section: electronics / repair

author: Miles Teg
author_rank: Regular Contributor
timestamp: December 11, 2022, 08:53:04 pm
content: Hello,I'm currently on a heavy refurb of a B&O Beocenter 8500. Lot of cap change, resolder joints. Cleaning. CD Player is now working properly.For me that's a massive equipement with some challenge to get access to the boards. That's a big mess of tight harnesses.My last problem is that the mother board doesn't store correctly settings after switch OFF.Volume is not recorded and more specific to this issue, Balance setting is bugged. Must have a wrong value out of scale making the Balance page display acting really weird with flickering.It happends also when device remains connected to main (with a standby led still on), that's maybe more a problem of reading previous settings at startup more than a data storage issue.I replaced the coin cell battery, No change.I replaces all electrolytic caps on this board, no change.I will push forward on a real study on the chips and how there power and resets should be timed. And check if supplies have correct shapes.If you have any advice, it would be welcome. Thank you.Some schematic and more PCB pictures coming.

author: Miles Teg
author_rank: Regular Contributor
timestamp: December 11, 2022, 09:01:42 pm
content: Here picture of the PCB. And its schematic.Full PDF are available.

author: FIXITNOW2003
author_rank: Regular Contributor
timestamp: December 12, 2022, 07:30:07 am
content: i wonder if the pcf8583 is starting to forget its setting eeproms only have so many write cycles , ,not sure if you can get away with fitting a new blank device , or if you will need to copy the contains across

author: cozza
author_rank: Regular Contributor
timestamp: December 14, 2022, 12:33:05 am
content: BC 8500 and 9500 have a sequence of key presses to initialise the Battery backed up memory.The 8500 is a 9500 chassis with a few features removed.If it is required the unit will display CODE in the numeric displays.From beoworld.org website :This usually happens if you have replaced the S/W or the lithium battery has been replaced or needs replacing.Fix the battery or RAM and then:Using a Beolink 1000 press:1271After 3 seconds, disconnect the 9500 from the mains and then reconnect. - Done!Perhaps try disconnecting your new battery, and with the power off, short out the battery connections on the PCB for a minute or so to reduce the standby battery rail to 0V. This should trigger the code reset process in software. (Assuming you have a working Beolink 1000 remote to perform the reset procedure)

author: cozza
author_rank: Regular Contributor
timestamp: December 14, 2022, 12:34:29 am
content: I think from memory, you may need to press play after the 1271 entry.

author: cozza
author_rank: Regular Contributor
timestamp: December 14, 2022, 12:37:12 am
content: Note there are two SRAM chips, PCF8583 stores tone and volume settings and radio presets and the other is a display memory which does other timer related I/O functions like reading keyboards and IR processing - if the 8155 is defective, or not being reset at power up it may cause the issue with the display you are describing. It is also possible that the MM5450N running the LEDS is the issue on the display board.The 8155 display SRAM / timer needs to be reset at power up by the circuitry around TR14.The PCF8583 is a real time clock with SRAM, it's not a problem to replace with a new blank one if you can source it.

author: cozza
author_rank: Regular Contributor
timestamp: December 14, 2022, 12:49:54 am
content: One more thing : check the wiring harness all the way to the display board with the balance indicator. The header plugs are an IDC type header and the wire connections can become intermittent if disturbed. If a select ,clock or data line to the MM5450 display chip is high impedance it will behave very erratically.

author: Miles Teg
author_rank: Regular Contributor
timestamp: December 14, 2022, 09:26:29 am
content: Quote from: cozza on December 14, 2022, 12:49:54 amThank you, that's a lot of good informations thereSo i've some work to do these days.Will keep the topic udpated following my advance.I asked the owner if he has the Remot control.See you!

author: cozza
author_rank: Regular Contributor
timestamp: December 14, 2022, 07:17:14 pm
content: While you're inside the processor module, it's a good practice to replace the two gold Roederstein axial capacitors and the blue radial electrolytic as these have been known to fail. You can use good quality radial (single ended) parts here and sleeve the exposed lead with heatshrink as axial electros are getting hard to find and its not critical.Definitely remove the rectifier and filter cap board next to the transformer and tidy up any bad solder joints - this area is prone to them, especially the large caps. Check around the PCB header plug pins and bridges as well.

author: Miles Teg
author_rank: Regular Contributor
timestamp: January 03, 2023, 10:31:49 pm
content: Thank you Cozza!So i've listed your recommandation. And here I am:Processor module: the 3 electrolytic capacitors were already replaced.Power board: All caps (poly film) included were replaced. All joints were already resoldered.Harness to display board: Will check later maybe, but diagnostic indicates more a memory problem than a display problem.Memory chips: I'm putting more effort to understand the block diagram.But yes seems logic that IC6 (PCF 8583) the only one connected to battery is storing the settings. Will check its availability (I think this was ok) and solder a DIL8 support to exchange this chip if necessary.I received the remote control from the owner. But seems not working.Under investigation.Other problem: Belts kit I received for the tape reader seems not corresponding. It indicates Beocenter 8500, but the biggest belt of the set is half the size of the belt to be replaced.Certainly will need to find another kit.See you! I keep you updated.

author: cozza
author_rank: Regular Contributor
timestamp: January 04, 2023, 02:37:43 am
content: There were two different tape mechanisms used in these during the production run. Looks like you've got the V1 tape mechanism and a V2 belt kit.Also check that there are no tracks which relied on the 3 outer pins of the filter caps to connect - they sometimes use the outer shell pins to connect pad to pad on these. You can bridge them with wire links if needed.I wouldn't have bother changing the film caps - they're pretty reliable. The main filter caps are rarely problematic as well. I'd normally test them for ESR / capacitance value and replace if needed.

author: Miles Teg
author_rank: Regular Contributor
timestamp: January 04, 2023, 08:38:47 am
content: Belt Kit:Ho I see. Found it on Thakker.euPower boardYes, got the good advices about bridges on a youtube video and beworld(I feel a little )sorry to post here instead of beoworld)RAM ChipGot everything on Farnell. Trying my best with a SOIC to DIP8 adaptor. Cross fingersThank you!

author: Miles Teg
author_rank: Regular Contributor
timestamp: January 07, 2023, 06:14:30 pm
content: Hello!I prepared the new RAM chip. Needed to adapt the SOIC on the DIP adapter as the size didn't fitsmy fault not checking package size.Anyway after hot air gun, that's done.But before removing the memory brain of this beast, I made some look on the logic 16 I had already plugged on the I2C.Got easily some results.Get exchange with RAM on address 0x50Code:write to 0x50 ack data: 0x38 0x06 0x00and also saw exchange with CD player on address 0X1CI see every minute an exchange certainly related to time:write to 0x50 ack data: 0x3A 0x02 0x30write to 0x50 ack data: 0x3A 0x02 0x310x50 is the RAM chip Address0x02 is the memory address to "seconds" value of the RAM clock.0X30 and 0x31 are the value result from RAM.But what is 0x3A?Anyway, generally I don't see any coming to the RAM chip when I modify any setting like volume, balance.Seems strange to me.How it is considered to recall these values?Other case, search function on radio:Click search rightCode:write to 0x50 ack data: 0x38 0x06 0x00write to 0x50 ack data: 0x08 0x9B 0x59write to 0x50 ack data: 0x08 0x9B 0x61write to 0x50 ack data: 0x08 0x9B 0x69write to 0x50 ack data: 0x08 0x9B 0x71write to 0x50 ack data: 0x08 0x9B 0x79write to 0x50 ack data: 0x38 0x06 0x00write to 0x50 ack data: 0x08 0x9B 0x81write to 0x50 ack data: 0x38 0x06 0x00write to 0x50 ack data: 0x38 0x06 0x00Reach station 88.0 FMSwitching from AM to FM:Code:write to 0x50 ack data: 0x38 0x06 0x00write to 0x50 ack data: 0x08 0x80 0x7Bwrite to 0x50 ack data: 0x08 0x80 0x7Bwrite to 0x50 ack data: 0x38 0x06 0x00

author: cozza
author_rank: Regular Contributor
timestamp: January 09, 2023, 12:10:48 am
content: It doesn't write the volume and tone settings to ram when they are changed. To update them to memory, you need to press <sound> then <store>

author: Miles Teg
author_rank: Regular Contributor
timestamp: January 09, 2023, 07:45:26 am
content: Quote from: cozza on January 09, 2023, 12:10:48 amHo my... ho mymymy!!!It works!So yeah this Beocenter needed a battery change. But yes, if you don't know you need to manually store the settings...And for the detail tha buttons actions needed is: <programming> then <sound> then <store>But why?!Why needing this manual action to store the volume or other settings???RTFM strike again!Anyway, thank you very much. Love you Cozza!Comme back soon with I2C log of settings storage, just for fun.

author: cozza
author_rank: Regular Contributor
timestamp: January 10, 2023, 07:19:29 pm
content: It does seem a little strange when you're not used to the B&O antics but powering on to a preset volume and tone setting level is useful, especially when you've got one of these connected to speakers all over the house via the silly speaker level distribution system know as Master Control link..

author: cozza
author_rank: Regular Contributor
timestamp: January 10, 2023, 07:24:42 pm
content: PS - well done! Rather you than me these days!Sorry I should have picked up on this much sooner, but the description of flickering indication on the balance indicator threw me off - there's a precedent of another unit with failed preset SRAM which popped into my head.

author: Miles Teg
author_rank: Regular Contributor
timestamp: January 12, 2023, 09:41:02 pm
content: Quote from: cozza on January 10, 2023, 07:19:29 pmI really don't want to knowQuoteNo problem, I'm really glad to have post my case here after 1-2 months struggling with it and your konwledges were very welcome.Thank you again and see you!