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
Please can anyone advise on what the regulated +15V supply on the main lift-up board (PCB5) on Beogram CD 5500 is used for?
The reason for asking is that the CD tray on my CD5500 has become erratic, shooting in or out, or going very slowly, or jamming in the out position, but it works fine when PCB5 is lifted up into service mode. In the fault condition, when the CD tray is not responding to the Open button, the +15 volt supply (and hence the +12 volt supply from the zener diode) are almost zero. So although the pulses from the opto-coupler get to the connector on the PCB, they are not able to get to the TRAY POSITION input at Pin 12 of IC4 on PCB5 and the tray goes out of control.
Something must be shorting out the +15 volt supply (and hence the +12 volt supply to IC4) when I lower the board, but I can’t see what it is . The scanned manual (‘BGCD5500_service-eng.pdf’) downloaded from Beoworld is a major help but some of the bits on page 5 are out of focus and I’m wondering if the clue might be there.
Problem solved
Eventually I realised that the +15 volt supply goes to the two audio output amplifiers, IC11 and IC12. (I’d not realised that the PCB5 circuitry is split between two pages in the service manual!).
When no CD is playing the + and – 15 volt lines go to zero by design, so the problem was not that the +15 volt line was shorting out as I’d assumed; it was that the DC feed to the+15 volt stabiliser and to the 12 volt zener diode (D2) was intermittent.
Eventually I found that the slightest movement of the wires going to connector P1 on PCB5 made the voltage across C3 go on or off and it turned out that there was a break in the soldered joint between one of the pins and the track on the PCB. The break was invisible, but reflowing the solder on the pins of P1 has cured the fault .
See also "Beogram CD 5500 – erratic behaviour of CD drawer", https://archivedforum2.beoworld.org/forums/p/49274/347403.aspx#347403.