Mark-sf
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First focus on it not finding the record. The lamp+Photocell handles this at the end of the fixed arm. Do you see the B&O logo at the end lit up? If not that bulb needs replacing. If you are, then the lamp’s and photocell’s alignment may be off. The black insert pulls out of the arm enough to allow it to drop down in most cases or you can remove the arm screws under the cover.
How are you connecting it? Type of cable – DIN or RCAs? Phono Input on what component?
That could be multiple adjustments. Go through the adjustments detailed in the above service manual.
Not sure which adjustment you are seeking. Take a look at this service manual for all. https://beomanuals.com/manuals/Beogram/Beogram%202400/Bang-Olufsen-Beogram_2400-Service-Manual.pdf
The fact that you got both channels working albeit at a low level into the Sonos points to the Beomaster phono inputs. You stated you have the RCA DIN adapter. I would try that as it allows you to switch channels to see if the bad channel follows. If it does not then it’s a Beomaster problem.
When muted all pins are connected. That’s where the 0,2-0,3 Ohms come in. When unmuted, the L- and R- are still connected (signal ground), so when measuring between L+ and R+ you are measuring the two coils in series. Their common center connection to ground doesn’t matter, seeing as you are not measuring with respect to ground.
Martin, I was not commenting on the first diagram. It’s the second that is wrong. It should read
* 1480 *
740. 740
*. .0.2 *Those do not look right. Measure the cartridge pins when it’s not installed. The pins are looking from the back: L+. R+ L- R- The 740 ohms should exist between L+ to L- and R+ to R-. There should be no resistance between R+ and L+.
Unmuted; When the cartridge is fitted to the arm, the two coils have their respective negative ends connected to signal ground. This means that if you measure from L+ to R+, you measure the two coils in series (2x 740 = 1480). All fine. Muted; All cartridge pins are connected to signal ground. All fine. Martin
Martin, I agree but the diagram is still wrong as a single pin cannot have 1480 and .2 ohms. It would be 1480 and 740 ohms.
Those do not look right. Measure the cartridge pins when it’s not installed. The pins are looking from the back:
L+. R+
L- R-
The 740 ohms should exist between L+ to L- and R+ to R-. There should be no resistance between R+ and L+.
The muting switch shorts the signal to so your ohm readings are correct. What you need to measure is when the cartridge is plugged into the arm and the switch unmuted you should see around 800 ohms on both channels.
I’ve not worked on one but I believe from the manual that there is a snap on LED cover that you remove to release it and the wire stays attached to the LED.
To narrow down where the fault lies try all sources to see if the channel is missing from all or just one or more. If all, then I would look at the preamp area prior to the mono switch and check for bad solder joints especially a the board connectors.
I addition to Guy’s excellent tips, if you have a multimeter you can measure the resistance between the top and bottom pins of each side of the cartridge. The readings should be a within 2% of each.
As long as the cartridge body (coils) is fine you can simply replace the stylus. The SP-9 was the elliptical version of your SP-7 and is available on the web such as https://www.lpgear.com/product/BOSSP09.html.
The ring is just an indicator. You rotate the weight which is the cylinder behind.
That appears to be Figure 142 and part 257022 Arm, Speed in the manual.
You need one which is “NO” for Normally Open and is DPST with the correct pin-out.
If they spliced the cable, then you can connect the ground wire to the braided shield of the DIN cable. As to replacement cartridges, your SP-6 has a conical stylus. An SP-12 would be better; however, I do not know why you’d have an issue with the tracking weight of an SP-10. Do you have a stylus gauge? What range are you able to set?
