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
Hello i am new to this forum,
I came in possession of a complete B&O system.
Sudden the Beomaster 5500 lost control with the remote control.
Also the front buttons did not function anymore.
Found the cause deep inside in the CPU unit a blown 1A F1 on-board fuse
D1 zener diode caused short circuit.
After replacing the 5V6 zener it worked again.
I noted Relay1 switching the 30V power for the output amplifier have some sparking.
Strange that this power is not soft switching
some other weak point:
The response to the master control panel commands is slow although the IR level seems okay.
Another problem exists in the BEOGRAM 6500
Starting to play a record the arm moves normal to the first position and moves down.
But the sound was weak and distorted and the stylus does not move it jumps back to the same groove
I inspected the arm the tracking system seems to function the arm can move freely in its bearing
A very delicate system
The linear tracking motor does move when i carefully push the arm forward.
So the tracking system does work.
The needle looked okay but i think maybe transport damage.
When i moved the 3 transport screws where fixed but the heavy disk plate was not removed i did not know it was loose
I have not seen the Beogram 6500 working in very long time it was just standing there since the owner died.
Those original cartridges are extreme expensive for just having it repaired an not much use.
I wonder if someone knows an alternative for the BEOGRAM elements ?
Elements cartridges are also provided by:
https://www.tonabnehmerservice.de/B-O-MMC-Systeme/
https://sound-smith.com/rebuilding-your-bo-cartridge
BeoMaster 5500 has RIAA pre amp inside for the turntable
BeoMaster 6500 and 7000 not.
BeoGram 6500 and 7000 have RIAA pre amp inside
thanks for reply
yes i saw the Riaa correction circuit in the diagram
Another repair i did
The Amplifier got very hot at high volume and also hot just by the bias.
The bias power:
44V 0.2A per Power transistor total 0.8A x 45V about 35W bias power , measured 45mV over the 0.22
The cooling fan circuit 6 did not run due broken PCB traces
Checked the NTC R50 >200k at room temperature drops when heated but the fan did not run at 40C
so i paralleled 100k with it to have the fan always running at low speed
that keeps the heathsink cool
still the remote has a very slow response and sometimes the Beomaster starts up with max volume... good that i have no neighbors...
Jaap van Oosten: thanks for reply yes i saw the Riaa correction circuit in the diagram Another repair i did The Amplifier got very hot at high volume and also hot just by the bias. The bias power: 44V 0.2A per Power transistor total 0.8A x 45V about 35W bias power , measured 45mV over the 0.22 The cooling fan circuit 6 did not run due broken PCB traces Checked the NTC R50 >200k at room temperature drops when heated but the fan did not run at 40C so i paralleled 100k with it to have the fan always running at low speed that keeps the heathsink cool still the remote has a very slow response and sometimes the Beomaster starts up with max volume... good that i have no neighbors...
Check - or replace - the backup battery.
Martin