One Channel Not Working on Lehmann Black Cube SE
- Thread starter regatron
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- lehman black cube rega
If it works at all, and you can make it work by wiggling the cables, then you know that the actual circuit itself is working OK. Then it becomes an elimination game:
Try some different cables from record player to phonostage, and phonostage to amp (if you can). If doing this eliminates the problem then you know its a cable.
If it persists with other cables, then its likely to be a cracked or "cold" solder joint. These can be hard to spot unless you know what you are looking for.
Do you know anyone locally to you who is handy with a soldering iron?
Some example cold solder joints shown in the attached pics - note that these would be considered really obvious.
Try some different cables from record player to phonostage, and phonostage to amp (if you can). If doing this eliminates the problem then you know its a cable.
If it persists with other cables, then its likely to be a cracked or "cold" solder joint. These can be hard to spot unless you know what you are looking for.
Do you know anyone locally to you who is handy with a soldering iron?
Some example cold solder joints shown in the attached pics - note that these would be considered really obvious.
regatron
Member
The RCA cables from my phono are hard wired so I can't easily replace them. However, I spoke to a local hifi dealer and he suggested I try squeezing the ground (outer conductor) of the RCA cables to bend them slightly inwards in an attempt to get tighter fit and it seems to be working! If it get them really tight then both channels continue to work even if I wiggle the cables slightly. Apparently the outer conductor / female part of the RCA connector is not so consistent across cables/jacks.
I'll continue to test but hopefully this isolates the cables as the source of the problem. I may still bring it to a tech to have a look just in case, I dont see signs of cold solder joints (thanks for the pics @fran) as I dont have the proper magnification and am having trouble fully removing the circuit board from the case - there is a plastic washer attached to the cable that's preventing the cable from moving so there is insufficient slack to maneuver the card out fully.
For my own future reference, could the signal dropping intermittently or "blipping" on and off in rapid succession cause damage to the speakers or any other components? I have been testing at very low volume just in case but it would be good to know if this is an actual concern.
Thanks everyone for jumping in with help and guidance, it's greatly appreciated! I'm happy to be joining this online community!
regatron
Member
That's a great idea!
a.palfreyman
pfm Member
Yes, it only takes a few thousands of an inch to go from f'kin tight to wobbly.... I had exactly the same problem when I build a pre-amp. The new RCA sockets were slightly smaller and all my leads wobbled 
You could either 'nip' the earth connections up as described above, or replace the connectors on the captive leads with locking ones. You then screw the outer to tighten the earth connection. Something like this:
PRO PHONO RCA PLUGS Heavy Duty Locking Connectors - Compass Audio
Nice photos @fran the top one especially, ive seen this a few times with dodgy connections esp on old circuit boards.
You could either 'nip' the earth connections up as described above, or replace the connectors on the captive leads with locking ones. You then screw the outer to tighten the earth connection. Something like this:
PRO PHONO RCA PLUGS Heavy Duty Locking Connectors - Compass Audio
Nice photos @fran the top one especially, ive seen this a few times with dodgy connections esp on old circuit boards.
regatron
Member
Thanks for the tip @a.palfreyman , when I upgrade my turntable hopefully it becomes a non-issue but I'll have this as an option as a backup.