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
hi
i have a BeoMaster 5500 that suffered from a short from the power transistors of the right channel.
the fuse on the primary side of the transformer was blown. i have replaced the two transistors, the fuse, the 2 big 10'000uF caps, the 4700 uF cap.
the power amp seams to work fine (i've tested it with a signal generator and a scope).
the problem seams to be the CPU unit.
after connecting the mains, the standby-relay clicks and after a few seconds the standby-dot on the frontpanel turns on.
but i'm not able to power on the amp. the MCP shows "no connect", the button mute or prog step on the front doesn't do anything.
i've checked the cpu. i have a stable 1.4MHz square signal on the ALE pin, also the CPU is talking to the static ram, to the input shift register and to the frontpanel chip. no errors found so far.
i've replaced the caps on the cpu board -> no effect.
i've also checked the voltages and the signals as described in the service manual -> seams all ok.
have anyone a idea what might be wrong?
thanks
alain
Check F2, 40 Volt. Needed to send ir back to MCP. But without that it should react on instructions..
+/- 40V supply is ok, also all other voltages.
the amp also don't react to any button on the frontpanel or from a normal remote.
very strange..
There's a fuse inside the CPU casing too if I remember correctly.
Martin
There is, but in that case there wouldn't be any signal present at the cpu.
I would start with checking for bad solderjoints between the cpu and the mainboard.
Beobuddy: There is, but in that case there wouldn't be any signal present at the cpu.
Of course. Maybe I should have read the whole thing..
thank you all, i've found the fault:
TR1 on board 2 was dead. now the amp turns on normal. everything seams to work as expected except for the tuner.
it's again a bit strange.. the tuner did not detect any stations (i have a type 2331). if i jump manual between the frequencies, occasionally i can hear a radio station, but if i tune in to a known frequency, there is only noise.
it's strange because the tuner worked perfectly before the short on the output transistors. i did not touched any pot on the tuner board.
any idea what might be wrong? is there any way to calibrate the tuner without a FM-test-sender or a sweep generator?
thanks!
Well done on the repair!
My advice is, do not touch anything in the tuner section. Perhaps you forgot a connector or something.
Jacques
chartz: Well done on the repair! My advice is, do not touch anything in the tuner section. Perhaps you forgot a connector or something.
Good advice. Check the easy things first. If that doesn't help, you might need to look for cracked solders - the tuner board is large and flexible.
You might also have disturbed a solder point at the CPU board connectors, or the wiring looms themselves... But whatever the fix is, it most probably does NOT involve rotating the trimpots or varicaps on the tuner board.
--mika
yes, i total agree with that.
as said, i can hear the radio station loud and clear if i scan in manual mode through the frequencies.
for me it looks like there is maybe a offset in the tuning voltage. i will check all connections and solder connections. a cable is definitely not missing.
i had replaced the battery on the cpu module. are there any offsets for the tuner stored in the memory?
alainstucki:i had replaced the battery on the cpu module. are there any offsets for the tuner stored in the memory?
Ah yes, I think there is! At least 6500 has that issue if the NVRAM is wiped completely. Wait a bit before doing anything else, somebody must have more info on that. I believe it's not completely described in the regular service manual.
Chapter 7 in the Beomaster 6500 service manual.I believe this is also valid for Beomaster 5500.Manual available for silver and gold members.