Beogram 5500 LH channel not working

18 replies
HE
herrit
Bronze
26 posts
Posted May 5, 2023 at 02:29 GMT
#1642256
I have just had my ~1989 MMC4 re-worked / re-furbished, but having installed it no sound comes out of the LH channel. Except ...
  • When the needle drops I get _some_ sound on the LH channel for a _very_ brief moment, then silence.
  • When I lift the needle, I get _some_ sound on the LH channel for, again, a _very_ short period, then silence (as the needle is no longer on the record).
Is this likely to be the turntable, the amp (Beomaster 5500), the DIN connections, or perhaps even the stylus? As I have only recently dug the system out of a box after years of storage, I didn't check the stylus before I sent it off for repair. The rest of the system works fine on both channels. TIA   EDITED TO ADD - according to this old thread it might be the muting relay. https://archivedforum.beoworld.org/forums/t/7055.aspx I have just changed the muting relay in the Beomaster 5500. Does anyone know if it is the same component, as I did order a "spare" relay last week.  
HE
herrit
Bronze
26 posts
Posted May 5, 2023 at 15:45 GMT
#1656209
There are four terminals coming out of the back of the muting "switch" - just below the "11" on the board; the lower pair show OL when the switch is "out", and 0.2 Ω when in. The top pair show OL & 0.4-0.5 Ω. The leads themselves measure 0.2 Ω, so does that suggest that it is the top pair that are not making "perfect" contact (ie 0.2 - 0.2 = perfect, but 0.5-.02 isn't)? Forgive me, but I am very new to all of this. If I check the left hand (vertical) pair of contacts then the readings are OL & 0.3 Ω, and the right hand pair are OL & 0.2 Ω In the other thread it suggests shorting the muting switch; how do I determine which contacts need shorting?  
Mark-sf
Mark-sf
Bronze
596 posts
Posted May 5, 2023 at 17:06 GMT
#1656210
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.
HE
herrit
Bronze
26 posts
Posted May 6, 2023 at 15:07 GMT
#1656232
Thanks; with the MMC4 back in, I get the following resistances ... but am not sure how to interpret them. Might I have some assistance? I'm still not sure whether the channels are vertical or horizontal. TIA  
DI
Dillen
BronzeModerator
12777 posts
Posted May 6, 2023 at 16:52 GMT
#1656234
All fine so far. The fact that you actually have sound from the affected channel, even if only briefly, suggests that the wiring is fine. The problem could be with the cartridge itself. I have seen cases where sound is lost when the needle is on a record. Perhaps a dying cantilever suspension. Do you have access to another cartridge for testing? Martin
Mark-sf
Mark-sf
Bronze
596 posts
Posted May 6, 2023 at 23:05 GMT
#1656240
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+.
DI
Dillen
BronzeModerator
12777 posts
Posted May 7, 2023 at 07:02 GMT ? Edited May 7, 2023 at 07:04 GMT
#1656243
HE
herrit
Bronze
26 posts
Posted May 7, 2023 at 10:08 GMT
With the cartridge removed I get ~ 764 Ω on both channels, and OL across the other pin pairs. So combining both of the above two replies I think that a) the cartridge itself, b) the wiring to the mute switch and c) the mute switch itself are all doing what they should be doing. Interestingly, with the power to the turntable removed, but the phono plugged in to the Beomaster, the mute switch _does_ mute / unmute the LH channel when I press on the lever with my fingers. Not sure if this matters or not, but when the mute switch is released (ie unmuted), I do get some additional hum from the LH channel if I touch the metal shielding on the switch body. But with a record on I still only get the briefest of sound out of the LH channel when the stylus is lowered or raised.
DI
Dillen
BronzeModerator
12777 posts
Posted May 7, 2023 at 11:29 GMT
#1656248
Do you have access to another cartridge for testing? Martin
HE
herrit
Bronze
26 posts
Posted May 7, 2023 at 11:35 GMT
#1656250
I don't have another, no. And they are sufficiently expensive that I am hesitant to want to buy one if possible
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