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I was in a bit of a rush yesterday, so I took a few moments to re-examine the differences between the PCB9 from the 5500 and the 6500. It turns out there are a few changes, which compensate for the now-missing IR circuitry on the 6500 PCB4. R2 is changed from 22K to 33K; R6 from 8ohm to 2ohm, and in-line C6 is deleted.
BM6500 PCB9 (Top) and BM5500 (Bot):
It’s possible that the 6500 CPU and the 5500 display combination worked anyways simply because I was right up next to it. Perhaps if I had been across the room, the receiver would have difficulty picking up the signal.
The 6500 PCB9 has a sticker over the board number, labelling it as 001283A.
Before reinstalling the display board, I always wipe down the inside of the red plastic cover, sometimes with a swab, and sometimes with a soft cloth. I’ve used IPA on this surface before with mixed results – sometimes I’ve noted that the red coloring comes off with the use of liquid, so I more frequently have resorted to a dry cloth.
With that, I swapped the BM6500 PCB4 into an otherwise unmodified BM5500 with stock PCB9, took a deep breath, and plugged it in. Whew, no smoke. So . . . did it work?Yes. The BM5500 responded to BL7000 commands, and sent status data back to the BL7000, enabling 2-way communications, as far as my 3-minute bench test showed. I’ll have to hook this up to BeoBabble to verify that all the Datalink data was identical to what the 6500/7000 was sending, but it appears to be functioning as expected. More testing will need to be done later to verify everything is working normally.
The BM6500 PCB4/9 that I have appear almost identical to the BM5500 boards I’ve been working on, with some noted exceptions – the afformentioned missing external IR logic, and a bigger battery, as well as a larger ROM/memory access package. Importantly, the 5 caps I’ve circled in red have identical values. Of the 12 boards I’ve worked on (6 of each type) in the last 2 days, only a SINGLE board out of the 12 had all of its capacitors reading within spec! Many, MANY tested open-circuit, and others with incredibly high ESRs in the double digits. If you have one of these older units, I highly recommend replacing all of these caps, and while you’re at it, the battery too.
The yellow circles show the Send/Receive diodes. I cleaned off about four decades of accumulated dust with IPA and tested for reliability. The four sending diodes should test in the 1.24V range with a continuity test. I’ve only measured a reading of about 8V on the receiving unit, so I’ll assume thats within tolerance, because they all worked fine after reinstall. There was some discussion in an earlier thread about how to dial in this receiving component, but I’d have to stop what I was doing to learn how to measure it properly, and my impatience led me to skip this maintenance step. Also, I didn’t have the correct spare battery, so I will need to order some up to replace it. The installed one still tested 3V, but I might as well change it out soon, for the next 40 years of service.
As mentinoed, the 6500 contains a new memory access chip on the back of the board, which allows the board to address the larger memory space provided for the 6500 EPROM. This is a key component on today’s PCB-swap, because it enables the CPU to respond properly to a BL7000, with the enhanced Datalink protocol. If I’m going to have a true BM5500 to 6500 upgrade path, I may want to consider this retrofit (which appears to be “hand-made”, if I do say so myself) as part of the upgrade path.
I’ve spent the last few days doing some cleanup work on several BM5500s that have been waiting for a little TLC, focusing only on refreshing PCB4 (Controller/CPU) and PCB9 (Display). I was reminded of a thread posted months ago by @martin-lundholm. He attempted to use a BM6500 PCB4 in a BM5500 chassis, and reported mixed success with getting it working, with some issues getting the MCP to wake up the system. I decided to take a stab myself and duplicate his experiment, since I was already swapping out the PCB4/9s.
First things first, an analysis of PCB9 Display boards shows that there were small changes around the time the BM7000 came into being, but the BM6500 Display I had must have been an earlier unit, because the board layout and component values appeared identical to my BM5500 boards. That being said, I decided to forge ahead and do a refreshtoration on the BM6500 boards, and then do some board swapping to see what would happen.
This will be review for some, but here is how I got the two boards out. The red circles show the 5 clips and screws which must be removed, and the yellow circles show the 5 connectors which need to be disconnected. The orange circle indicates where the external IR port is attached to the BM5500 PCB4. The holes for the external IR are present on the BM6500, but the traces are missing, so it would take a bit of work to add an external IR to this CPU in a backwards-compatible way (but not impossible). Once the display is unscrewed, you can simply lean it forward from the top, and it will hinge downward and pull out. Then you can disconnect the black connector easily.
If you choose, you can use an 8mm socket to free the entire display from the BM, but I opt instead to simply unscrew the single set screw in the middle of PCB9, and carefully slide the entire board abput 4-5mm in the direction of the arrow to free it from its retaining clips. It’s finicky work, but with gentle prodding, it will come out. At this point, sometimes the red filter for the 2-segment display will fall off, and sometimes it stays attached to the board. If it falls off, just make a note of its position, and remember to put it back prior to re-inserting the board.
Just for kicks, I spent an hour today tracing some of the signals for Pin 1 (PL On/Off) and Pin 4 (Speaker Relay). Pin 1 piggybacks off a pre-existing +12v power-on and a 390 ohm resistor. Pin 4 connects to the SP On/Off logic via a 470 ohm resistor. I’m still thinking that I could use the 5500 Sensor Pin 1 (which has a 470 ohm resistor) as the input for Powerlink pin 1, as the voltage drop difference between the two resistor values is probably negligible. I don’t think there is an externally accessible speaker on/off relay available via an external pin, so that is still a work in progress.
[EDIT] Just thinking this morning that the sensor 12V output may not be switched with power up, as it also needs to power sensor circuitry. I should do a bit of testing.
Pulled these white pieces off of a nonfunctional Beosystem 5500 in prep for packing them in my suitcase for the trip home to USA. On the whole, they are not in the prettiest condition, but I’m confident I can make them look decent. Im planning on retrofitting a silver 5500 system for personal use. I’ll still need to paint the Beocord tray white, but apart from that, the color change should hopefully be fairly straightforward.
Yeah, yeah, I know – the stickers on the back will reveal my slight-of-hand. That being said, I’ve never come across a white 120v 5500 for sale stateside, so this was the next best thing I could think of.
Possibly sounds like you are hearing the datalink signals that are sent via the powerlink cables to alter the display on a datalink-enabled speaker. How about when you change the source input – does that also create a “buzz-buzz” sound?
Just to geek out a bit – The electrical pulses (representing the inverse binary of the number) are picked up by the music signal in cheap wiring. Interesting that “8” is louder than “1” – probably has to do with the signal pattern. In the actual signal, “8” would be a bitstream of “0111” and “1” would be represented as “1000”. I’ve read that buying higher quality shielded cables helps with the problem, but it could also be a fun project to alter the datalink transmission protocol via a series of dongles so the datalink signal is sent via some other means, perhaps over WiFi.
I have a black Beosystem 7000 which lacked a turntable, and instead of spending $1000+ to find a matching Beogram 7000, I set about retrofitting a old BG 3000 to match the look, using available parts I could buy online.
The original 3000 lid was cracked, so I opted for a clear replacement from DK Sound Parts, along with a black metal decorative top plate. In the end, IMHO it’s an ‘ok’ match with the BM7000, but not perfect – I give it a 7/10. Perhaps if I had selected the dark grey lid option, it would bland a bit better, especially since the platter is not black.
Here are my costs, including delivery:Beogram 3000 – $75RIAA card – $1254500 lid – $120Top Plate – $20Misc parts – $40———————-Total: $380I think I got a bit fortunate on the purchase price of the BG 3000, so I’d venture to say that a more typical budget would be in the $450-500 range. In the end, I’m pleased with the results, although I’m not sure I’m really saving all that much in comparison to buying a good-condition stock 4500. All that being said, I’m a bit of a purist, so if a black Beogram 7000 comes up for less than $1000 delivered, I’ll probably still look to acquire it.Here’s a solution that no one really was asking a question about. The tiny tab that holds the thread ends which move the tone arm sled tends to snap when things bind up. This morning I took a stab at a remedy.
For starters, the bottom of the sled appears to contain an extra tab that does not appear to be used for anything, so my first thought was to carefully slice this off and find a way to graft it in place of the missing one.
I decided to forego that option, and opted instead to head to the hardware store to purchase a few 1.6mm bolts with nuts. This would provide a bit more holding surface and friction. The idea is to place the string and spring in place, and thread the nut onto the rod as a “keeper”, which would prevent the string from falling off. This new plan of action involved generously epoxying over the holes, and drilling a pilot hole I could thread with the bolt, which I thought would be stiff enough to provide a robust holding point to the thread. Alas, laziness prevailed- I went with super glue, and simply positioned the bolts during the curing phase.
We’ll see if this provides enough durability to create a lasting solution to the problem.I’ve got a Sony CDX-A55 inbound that I bought for $30 off eBay which has the same pinout at the A20 – a slightly newer configuration to the original setup. I’d like to definitively know how easy it would be to add a 10-disc CD changer to an 80’s – 90’s Beosystem. Controllers tend to run $60 or so on eBay, so for under $120, you can add a 10-disc changer to your pizza box system for parties.
Clearly it would not have the panache of a 9000, but it would retain most of the function. On that note, I can report that the system works just fine on a Beomaster 5500 Tape or Tape 2 input with fully functional control via a Beo4 or MCP 5500, as I had expected. I have not attempted it yet, but I’d expect it to work with a 5000/MCP5000 as well, as the Datalink ’80 commands required to make it respond should be identical.
The Sony packaging is basically a metal endo-skeleton surrounded by a molded-plastic shell, with large rubber suspension bushings to deal with rough roads – something unnecessary when installed in the home. Unfortunate that B&O didn’t really bother to repackage everything in something a bit more B&O-ish. There’s absolutely no reason why the system & controller together could not fit in a form factor similar to the pizza boxes (it would admittedly need to be slightly taller) with a metal sliding door to cover the carousel – even the eject button in the usual left corner location would be compatible, and require nothing more than a wire extension to function.
Add a switch to choose between Aux and Tape 2 communication – a trivial addition for a competent programmer, and the system would have been quite versatile. Shoulda coulda woulda.
I’ve spent the last few days pulling my hair out trying to figure out all of the mechanical switches and levers on this thing. After several “one step forward, two steps back” moments (I had to disassemble the carousel twice because the elevator kept trying to shove CDs into already occupied spots) I finally got to the point where it could reliably once again cycle through a tray of CDs – loading and unloading, but failing to play anything – even failing to play with my prior hack of “upright position”. So with nothing playing, I was consigned to spending a few hours looking at ribbon cables, cleaning any mechanical switch I could find, and scouring the Sony service manual for clues as to why it wont accept a CD as “Loaded”. I finally zeroed in on this board, which handles the elevator mechanism.
Perhaps a bad seating or broken trace was the issue. Among other things, the board has 2 photo sensors – one to determine if a CD is in the player, and one to determine whether the CD is fully seated in the player tray.
I concluded that one or the other of these sensors was likely intermittent, causing the controller to determine that there was a CD jammed in the system. The readings for the “CD inserted” was indeed reading a medium short. And yet, it appeared to always be working for a specific dark-gold-colored CD, no matter where it was placed in the carousel. Odd!
… and then it hit me. These photosensors are designed to operate in total blackness. And here I was – for days – trying to poke and prod and shine my 3000 lumen desk light inside the internals to try and discern why the darn thing was not working, all the while causing the “CD Inserted” photoreceptor to constantly report a CD jam.
Ugh – I’m an idiot! I switched off my desk light, and everything began to function properly. For now – I have a hunch there are still a few gremlins left to be discovered. And they don’t like bright lights either.
