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
Next thing is to install Martin's tach disc. Here is the disassembled inner platter ready for the new disc.
It is a little tricky getting the snap ring put back on but here is the re-installed tach disc.
Now it is re-installed in the Beogram and I am ready to see if the turntable functions. The small snap rings for the speed sensor assembly were actually harder to put back on that the large, tach disc snap ring.
I connected up the main board, transformer, keypad and gave the Beogram a try. At first the power did not appear to be on. There was not red dot on the display. I measured the power supply voltages though and they were there. It turned out that the main board 800mA fuse was blown. That was before I got the turntable and this one should be good to go so I replaced the fuse with a new one and power was restored.
All of the control panel buttons work. The only problem I see is the Beogram downs start up correctly or stop correctly. In both cases, the arm moves close to where it should, then stops. I will have to look into that next but it is nice that the turntable has life.
I added the top platter and my speed test record to check the turntable speeds. They were pretty good. I saw a upper measurement of 33.6 RPM and a lower measurement of 31.5 RPM. For 45 RPM I measures 44.9 to 45.3 RPM.
sonavor: Now it is re-installed in the Beogram and I am ready to see if the turntable functions. The small snap rings for the speed sensor assembly were actually harder to put back on that the large, tach disc snap ring.
Nice work indeed !I noticed you took off the opto from the swinging bracket and had "fun" getting the spires ("snap locks") back on.I take it, you are aware that the opto swings aside if you losen the screw at the end of its bracket (as mentioned in the tachodisc instructions) ?This is also used to adjust the opto for best pattern reading results using the original tachodisc. (The new disc is not remotely as sensitive tothe positioning of the opto, it merely needs to sit over the pattern. )
Martin
Dillen:I noticed you took off the opto from the swinging bracket and had "fun" getting the spires ("snap locks") back on.I take it, you are aware that the opto swings aside if you losen the screw at the end of its bracket (as mentioned in the tachodisc instructions) ?This is also used to adjust the opto for best pattern reading results using the original tachodisc. (The new disc is not remotely as sensitive tothe positioning of the opto, it merely needs to sit over the pattern. ) Martin
The service manual also shows how to move the opto yoke out of the way of the turntable hub on page 8-1.
-sonavor
The only problem with turntable electronics right now is the operation of the tonearm. It is not moving correctly at the start of play or on stop of play. The reason is because I turned those photoresistor control screws down when I was cleaning earlier and so they need calibrating per the service manual.
Here is my adjustment of the photoresistors. After this adjustment the Beogram tonearm movement started working correctly.
The next step is to start going through the rest of the service manual adjustments. This project is going pretty smoothly for me. I usually run into some crazy problem to fix but so far no surprises (I hope I didn't just jinx it )
sonavor: (I hope I didn't just jinx it ) -sonavor
I started looking at what Beogram 8000 cabinet pieces I will use on this first one. None of my samples have pristine dust covers so I will have to just pick the one with the least scratches. On the cabinet base, it turns out that the later model serial number is slightly different than the two earlier serial number cabinets. The newer serial number has the static discharge spring for the metal deck that the Beogram 8002 models have. So I will use that base cabinet for this first turntable.
The Beogram pieces are ready to start reassembling back into the chassis. I closed up the processor module and made sure the lid with the heatsink is touching the processor chip.
The board assembly reinstalled in the chassis.
Now all the necessary components for a function check are installed.
A quick function check to verify nothing changed from when I tested the electronic components outside the chassis. Everything still looks good so I will try to get the final adjustments done this weekend...unless I can sneak some more time in before then.
Be mindful of the black cartridge holder on the end of the tonearm when fitting the cartridge, I've seen two broken now in as many months, one I did myself from simply removing the cartridge gently, I wonder if a wipe of liquid silicone may help it's longevity ?
other members may have different thoughts on this?
jason
All very interesting John.
I'm looking forward to the moment when you tackle the sudden arm descent problem. I haven't been able to solve that so far.
Jacques
Jason : Be mindful of the black cartridge holder on the end of the tonearm when fitting the cartridge, I've seen two broken now in as many months, one I did myself from simply removing the cartridge gently, I wonder if a wipe of liquid silicone may help it's longevity ? other members may have different thoughts on this? jason
I don't know if you saw my repair of the broken tonearm cartridge tab on a Beogram 4000 (here), but I initially pulled the cartridge mount out of a Beogram 8000 tonearm to use before I switched to using one out of a spare Beogram 4004. I have sent that BG8000 cartridge mount to Beolover to investigate the possibility of producing a 3D printed replacement. It sounds like the plastic clamshell could be done but finding/manufacturing the contacts are difficult. In the case of repairing a broken Beogram 8000 cartridge mount, maybe if the original contacts can be salvaged, they could be reused in the new, 3D plastic part. john
chartz: All very interesting John. I'm looking forward to the moment when you tackle the sudden arm descent problem. I haven't been able to solve that so far.
Yes, it will be interesting to check out that circuit in my Beogram. Looking back at the issue, the control of the tonearm lift is electronic and comes from this circuit -
The electronics seem to do their job, the coil moves slowly, but the arm seems to be retained by something (I failed pathetically to locate the issue here ) which makes it drop instead of going down smoothly as it should.
Mine would sometimes hover not dropping then other times after playing fine would bounce back up faster than other.
its been fine since I put a drop of oil to the rod of the coil
also the screw to the side of the tonearm once caught on the black cover and would knock the tonearm slightly to the side
Yes John I'd seen your thread, it happened just after mine, and again since, I've just been over cautious ever since regarding the cartridge holder so wondered about silicone as a precaution .
Have you checked this ?
http://archivedforum2.beoworld.org/forums/p/14182/123992.aspx#123992
Oh, I had missed that one Martin! I'll check it out, thanks!
I had seen that thread (and even responded to it) but the thread creator never followed up if he fixed his tonearm drop problem by removing the Teflon sheet. That is why we ask for pictures
Jason : Yes John I'd seen your thread, it happened just after mine, and again since, I've just been over cautious ever since regarding the cartridge holder so wondered about silicone as a precaution . jason
Taking your advice Jason, I applied some Deoxit Fader F5 to my cartridge mount (top and contacts) before attaching my usual test cartridge (an MMC 20EN). The cartridge went on easily but still felt firmly in place.
Next I wanted to check the arm to platter height and the tonearm tracking force. For that I need the platter not to spin so (with power unplugged) I disconnected P4, then plugged the turntable power plug back in. The Beogram controls will now work, the tonearm will move but the platter will not turn.
I lucked out on the arm height adjustment. The arm to platter deck measures 23mm per the service manual and I didn't have to adjust anything.
My good luck continues with the tracking force (tonearm balance adjustment). I set the tracking force to 1 gram and measured the tonearm before making any adjustments. The result was exactly 1 gram on my scale. I think this is the first time I haven't had to adjust the tonearm balance to calibrate the tracking force slider.I also noticed that the tonearm lowers at a nicely controlled drop speed so nothing to mess with there on this Beogram.
The parallelism checks all look good. This weekend I will see if I can run the Shutter for Photo Control check and the stylus set down position (SO Switch) check on page 5-3 of the service manual. The Beogram 400x series turntables have an adjustment to set the stylus height to rib of the platter but I don't find any adjustment like that in the Beogram 8000 service manual. I guess that isn't something that needs setting on these turntables.
Tonight I performed the Shutter for Photo Control adjustment. When I checked the existing setting I saw the tangential arm motor start turning after about three rotations of the record. That is right at the limit listed in the service manual.
I ended up turning the adjustment screw about a half turn clockwise and measured two rotations for the tangential arm motor to begin turning. This test is also run with the platter motor disabled (P4 disconnected from the main board).
I don't have B&O test record 3621001 but I do have 3621003 so I used it and checked the rotation on several of the tracks.
The set down position of the Beogram was also set perfect so I didn't have to do any SO Switch adjustment. I switched phono cartridges to an MMC-20CL and gave the Beogram a quick listen through my bench Beomaster 4400 and a pair of Beovox S75s. First 33 RPM - sounds nice an even out of each channel. No problems so far.
Same thing for 45RPM. The Beogram played a 12 inch single without any problem. Tomorrow I will start getting the turntable back together completely and run some more tests. These last few bench tests have all been without the chassis suspension in place.
Jacques, the tonearm lowering appears to lower at a nice consistent speed. A couple of times it appeared to be a little faster drop but I will have to run some more tests once I get the Beogram suspension in place.
John
Here is the Beogram 8000 tonearm assembly from my turntable with the broken tonearm. I opened the bottom up to expose the photoresistor, lamp source and shutter that the adjustment screw controls. The adjustment screw moves the shutter to control how much light gets to the photoresistor.
Today I attached the Beogram 8000 floating chassis. It is really helpful to have a small, metal hook tool.