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
This Beogram 8002 was a recent find. I picked it up as a learning unit because one of my primary, everyday turntables is a Beogram 8002 I bought way back in 1983. That original 8002 is still working well. I had a B&O technician look at it about eight years ago and he made some adjustments. That was before I took on this vintage audio hobby. When this recent aquisition became available I decided the price was too good for me to pass up.
In the picture you can see the lid assembly is off. The main spring and lid attachement came apart. I am going to fix that first.
Electrically, this new 8002 powers on and the turntable starts spinning as soon as it is plugged in. None of the pushbutton controls work. So this could be a real troublesome repair.
Here is a picture of the re-attached lid/spring assembly.
Another picture of the re-attached lid.
Service position
01 and 02 modules from under the control panel
01 (PCB1 - Control Circuits and Power Supply) and 02 (PCB2 - Microcomputer) Modules removed. With this Beogram 8002 starting up turning at 33 RPM when the unit is plugged in ... does that point to a problem with the microcomputer?
A mechanical question - The picture below shows the cover panel (the one that is under the tone arm when it is at rest). The underside of the panel has a smaller metal panel that appeared to be glued to the cover panel. That glue has become dry and crumbly. In repairing that piece, do you scrape off all of the old adhesive and apply a new adhesive like epoxy or something less permanent like tacky glue?
The crumbly adhesive is also in small squares on the under side of the aluminum top plate. What is the function of that adhesive and what should be used to replace it?
It is the remains of the foam double sided tape that was originally used to hold the parts together.
Regards Graham
Dom
2x BeoSystem 3, BeoSystem 5000, BeoSystem 6500, 2x BeoMaster 7000, 2 pair of BeoLab Penta mk2, AV 7000, Beolab 4000, BeoSound 4000, Playmaker, BeoLab 2500, S-45, S-45.2, RL-140, CX-50, C-75, 3x CX-100, 3x MCL2 link rooms, 3x Beolab 2000, M3, P2, Earset, A8 earphones, A3, 2x 4001 relay, H3, H3 ANC, H6, 2014 Audi S5 with B&O sound, and ambio
I see. So the square tape remains on the underside of the aluminum top plate and the corresponding remains on the deck (see pictured) means the aluminum top plate isn't supposed to come off.
sonavor: I see. So the square tape remains on the underside of the aluminum top plate and the corresponding remains on the deck (see pictured) means the aluminum top plate isn't supposed to come off.
Here are a couple of more detailed pictures of PCB1
...and here are a couple detailed pictures of PCB2
There are two more electrolytic capacitors on the chassis - OC1 and OC2
I contacted Beoworld member auric about a Beogram 8002 repair post he created back in 2008 (now in the Beoworld Workbench archive forum). His 8002 was having some electrical stability issues due to problems with the electrolytic caps and some solder joints. He was able to get his 8002 back in good working order. This morning I made a quick run over to my local Mouser electronics warehouse and picked up replacement electrolytic caps for my 8002. Pulling off the existing ones, there were several that were out of tolerance. In particular, C24 (2200uF, 16V) measures 818uF ! My plan is to replace the electrolytics, then recheck the state of the 8002...and proceed trouble-shooting from there. I will also check solder joints. Auric advised me to concentrate on the PCB connector solder points so I will definately check those.
-sonavor
On PCB1, the 2200uF C27 electrolytic capacitor is a different kind of mount than typically seen (typical being a single positive and negative lead). The original C27 cap has a single, center lead that is the positive lead. It has three negative leads. The PCB1 then has four holes for mounting that C27 cap. I am replacing the C27 capacitor with a two terminal, snap-in device. To make it fit in the same area I had to solder on some extension leads. I used some tacky glue to help secure the replacement to the PCB since it is a little wobbly with my extension pieces. Once the glue dries I will jumper the negative terminal to the other two mounting holes where the original, four lead cap was soldered to. I'll post a picture of the C27 cap after it is soldered in place.
sonavor: I contacted Beoworld member auric about a Beogram 8002 repair post he created back in 2008 (now in the Beoworld Workbench archive forum). His 8002 was having some electrical stability issues due to problems with the electrolytic caps and some solder joints. He was able to get his 8002 back in good working order. This morning I made a quick run over to my local Mouser electronics warehouse and picked up replacement electrolytic caps for my 8002. Pulling off the existing ones, there were several that were out of tolerance. In particular, C24 (2200uF, 16V) measures 818uF ! My plan is to replace the electrolytics, then recheck the state of the 8002...and proceed trouble-shooting from there. I will also check solder joints. Auric advised me to concentrate on the PCB connector solder points so I will definately check those. -sonavor
OMG You lucky lucky lucky person being able to 'pop' round to mouser arghhhhhhh! That is THE number 1 electronics supplier IMO, no UK company touches it, or at least non that I have found, and it is the only place I can get capacitors of the same type across all the value range!That capacitor checker is great, hehe, I can 'pop' in to Peak anytime as they are down the road from me, but would rather have Mouser any day!!!Hope things go a bit more smoothly for you this time :-)
Olly
Yes, I can tell you that Mouser warehouse is a huge place. It is really handy. I still have to order some parts from other places but the majority of what I need I can get from Mouser. I like those little Peak testers.Today, I have made pretty good progress on the Beogram 8002. It is kind of working now.
The first picture is of the recapped PCB1 board. It shows the work around for replacing the four lead C27 2200uF electrolytic cap with a two lead, snap in cap. I used jumpers on the backside of the board to connect up the holes where the original four lead cap went.
Here is another picture of the recapped PCB1
Here is the recapped OC1 and OC2 components on the chassis
On PCB2, I replaced the C28 electrolytic capacitor and put a new layer of thermal grease on the MPU. I remounted the heat sink bar then put the PCB1, PCB2 and control panel back into place in the 8002.
With the Beogram 8002 re-assembled to where I can plug it in and test again - plugging it in results in the turntable starting out correctly in STBY mode (red dot).
Exercising the control buttons, the Turn, 33, 45, <<, >>, Play, Stop, "-" and "+" all work. Here is a picture of the 8002 returning after spinning at 33.33.
Now a problem.After exercising the controls for a bit and taking the 8002 back to Stop/Stby, the Beogram decided to start turning on its own in the opposite (counter clockwise direction). The indicator light still showed the red dot. I could press Play but the platter still turns in the wrong direction. I unplugged the 8002, waited a few seconds, then plugged it back in again. The turntable starts turning counter clockwise again. So I unplugged it a second time, waited about fifteen minutes, then plugged it in again. This time is stayed in the Stop/Stby position and the controls appeared to be working correctly again.
I will test this some more and see if it consistently starts doing bad things on its own again. To start turning by itself and in the wrong direction - would that likely be an MPU signal problem?
Additional information - After the 8002 has been sitting idle (unplugged), when I plug it in and wait for a bit the turntable will start rotating in the counter clockwise direction. Once it starts doing that it seems to be locked into rotating that opposite direction.
When you say you have checked the joints, have you actually reflowed with fresh solder?
Well, this project has taken a turn for the worse. Deciding to start looking at voltages I plugged the 8002 in to make some measurements. To my surprise the Standby light did not illuminate. The turntable is no longer getting proper power. I went ahead and measure voltages going to through the power supply section. I get 5 VDC across C27. It should be 15V. I get -10 VDC across C29. It should be -15 I believe. I don't get anything across C24. If with just the transformer plugged in I do see various voltages (25 Vrms, 40 Vrms, 50 Vrms) on the transormer pins. I don't see or smell anything burnt so maybe there is just a bad connection somewhere.
Step1: When you say you have checked the joints, have you actually reflowed with fresh solder?
I reflowed fresh solder on the transformer connector when I recapped PCB1. I didn't reflow fresh solder on the other connectors. With the power failure I am currently experiencing, I am missing voltages with other connectors (P1, P2, P3 and P4) on or off. So the problem must be between PCB1, PCB2 and the transformer.
You must, at the very least reflow all headers and not stop there either!!! That I suspect, will resolve your current issues.
Step1: You must, at the very least reflow all headers and not stop there either!!! That I suspect, will resolve your current issues.
I agree. I had the weirdest problems and they were all caused by solder joints or broken tracks one could not see without a X8 thread counter.
Jacques
chartz: Step1: You must, at the very least reflow all headers and not stop there either!!! That I suspect, will resolve your current issues. I agree. I had the weirdest problems and they were all caused by solder joints or broken tracks one could not see without a X8 thread counter.
Yes, I think so too. After sleeping on it I am thinking that all of my recent handling of the PCB1/PCB2/Control Panel assembly probably caused extra stress on some weak joints. I try to be careful but the PCB1 board mounts to the chassis in a way that you have to push on it to remove it (and install it). The good news is there has been no smoke smell or any sign of a component burning up so I'm just going to go through the slow process of reflowing solder joints.
Thanks for the suggestions,sonavor
After re-flowing the solder joints on PCB1 and PCB2 today I still have a power problem with the Beogram 8002. So I opened the transformer module and sure enough, the 300ma fuse is blown. Now I know the fuse isn't the source of the problem with this turntable. Working on the problem led to the fuse blowing. I don't know for sure when the fuse went but I think it blew prior to my re-soldering of the boards. I'll have to pick up a replacement fuse tomorrow. I am wondering though if the transformer itself could be a problem. I'll find out when I replace the fuse and see where I'm at. I will make sure to get some spare fuses just in case.
I am having some internet connection problems locally where my upload speed is horrible. So I may not be able to upload any new pictures today. Hopefully that will be resolved tomorrow.
On the PCB1, I started re-flowing the solder joints but decided I would rather de-solder, check components, clean, then re-solder. Starting with the power supply circuit I haven't found any diodes or transistors that test bad (testing them individually off the board). They could still fail in circuit but I'll have to address that once I am at a point to put everything together again.
As for the transformer, testing it by itself, it doesn't seem like the voltages are right. In looking at the service manual, there are five secondary pairs of pins on the transformer P7 connector. There are two additional pins that connect to a capacitor inside the transformer. With the transformer only connected to AC wall power, shouldn't I see a nice sine wave on each pair of secondary pins? Where one pin is 180 degrees out of phase with the other?
You seem to have done everything right, except for resoldering the joints.
I would strongly suggest that you use a "Dim Bulb Tester" (100W incandescent bulb in series with the Live AC line) to connect your projects to AC power, until you have finished troubleshooting. If the bulb lights up, you have a problem. This prevents the fuse blowing each time there is a problem.
Test the voltages across each pair of secondary windings.
Then check the voltages at each of the soldered edges of the flexible ribbon cables - you may have damaged one or two leads - I know that I have done so a few times in my career.
If you are stuck, I have an extra BG8002 (120VAC input) transformer - it belongs to a customer, but I'm sure you can come to an agreement with him.
Menahem
My internet connectivity appears to be good again. I hope it lasts.
While it was down I checked the transformer and power supply circuitry of the 8002. Here is a picture of the transformer opened up (so I could replace the fuse).
After checking the PCB1 components and solder joints I connected up the PCB1 to the transformer again and to the chassis connectors (P1, P2, P3 and P4). I left the MPU (PCB2) disconnected. When I plugged the transformer in the turntable started turning (clockwise). Before I could set up to make measurements it stopped. The transformer fuse had blown again. I decided to replace the fuse and try it again with PCB1 connectors P3 and P4 disconnected as they supply the signals to drive the turntable. Now I can plug the transformer in without blowing the fuse. So my next step was to start verifying the power supply circuit of the 8002.
Here is a picture of that part of the schematic.
The first secondary output (P7-4 and P7-2) go through the chassis circuit 01C1 and supply +5 VDC to the 8002. With PCB1 connected to just the transformer, P1 and P2 (which connect to the chassis 01C1 and 0TR1), I measure +4.98 VDC at P2-2. That voltage is steady so it appears I have a good +5 VDC.
The next two secondary outputs (P7-1, P7-3 and P7-10, P7-7) are used together to supply +-15 VDC to the 8002. P7-1 and P7-7 each go to an input of the rectifier circuit. The AC voltage there measures around 17.5 Vrms with respect to the ground at P7-3 and P7-10. The outputs of the rectifier circuit are about -23 VDC and +23 VDC. The +23 VDC goes through 0TR1 where the collector side connects to C28 (+) and the D25 (+15V zener). Instead of seeing +15 VDC there, I am measuring +20 VDC. That voltage actually starts out close to +15 VDC then creeps up. The zener diode is okay though. The voltage across the zener is around +14.4 VDC. The problem appears to be the anode side of D25 that connects to the TR18 emitter and R79. The DC voltage there jumps around between 3 and 5 VDC. It looks like it should be down close to zero volts. So I need to see why that voltage is unstable. Maybe a problem with TR18 ?
I don't get -15 VDC at the D26 zener's anode. The TR19 (PU01) transistor is not turned on. It looks like the POWER ON/OFF signal from the MPU is required for the -15 V rail.
These are my measured voltages across the pins.
1-3 17.0VAC
2-4 10.7VAC
5-11 30.2VAC
6-12 no volts - it's the 39uF capacitor
7-10 17.0VAC
8-9 5.3VAC
Just disconnect the black Xformer box from the PCB, connect it to AC, and measure the voltages across the pins.
Because you're blowing a fuse, you need to build yourself a "Dim Bulb Tester" with 100W bulb. There's plenty of info on the web.
It will save you blowing fuses, and disconnecting circuits, as you've done.
You should have resoldered everything before reassembly - yes, the circuits are fragile, but for those joints you need a fine-pencil soldering tip. If you already have a high-quality Weller or Hakko solder station, you can buy the suitable tips.
Check the big transistors mounted on the chassis. If you use a dim bulb tester, you can leave the BG8002 powered on for a while, and feel around for hot components - that's the cause.
Another problem area is the pushbutton sensor under the keyboard. Check that both bulbs are working, that you get a circuit change whe pushing the left or right side of the plunger, and that the black wire hasn't come loose.
See the little solder-blobs on that picture, around the line of solder joints? Blobs like that can cause momentary shorts and cause problems like you're having. It comes from resoldering with the wrong solder-iron tip.
Did you change the cap in the CPU box?
Did you put all caps back in the correct polarity?