My Lingo PS for Linn Sondek LP12 stopped playing 45rpm!
This is my first attempt at fixing something without any evident signs of mechanical or electrical damage. And it is Not going well... There is always an option of a 10-min drive to my Linn dealer but it does not sound like Fun, so here I am...
Lingo regenerates perfect sinewaves to feed the motor: 50Hz for 33rpm and 67Hz for 45rpm, at 100V during startup then 70V for operation. Well, the one I have here works fine for 33rpm but stalls the motor when set for 45rpm. When set at 45rpm it starts with feeding 80V and then drops to 50V, at this point motor stops and just buzzes angrily. Output frequencies are spot-on, if I am to believe my cheap digital scope. The last few days of internet search did not return any Lingo schematics or Service manuals, actually it looks like I am the only one who opened Lingo to photograph its innards. Here it is: http://i.imgur.com/Bxto0QD.jpg?1
Web wisdom says that 33 and 45rpm circuits have their own separate amps and that Lingo synthesizes two independent phases instead of using a capacitor to split one phase into two.
Following the signal is a real pain since the board is printed on both sides, the only good news is that I have a solid signal 33rpm as a "control" for this search.
If anyone can give me more educated guess on where/how to look for the missing 20V at 45rpm, please share!
This is my first attempt at fixing something without any evident signs of mechanical or electrical damage. And it is Not going well... There is always an option of a 10-min drive to my Linn dealer but it does not sound like Fun, so here I am...
Lingo regenerates perfect sinewaves to feed the motor: 50Hz for 33rpm and 67Hz for 45rpm, at 100V during startup then 70V for operation. Well, the one I have here works fine for 33rpm but stalls the motor when set for 45rpm. When set at 45rpm it starts with feeding 80V and then drops to 50V, at this point motor stops and just buzzes angrily. Output frequencies are spot-on, if I am to believe my cheap digital scope. The last few days of internet search did not return any Lingo schematics or Service manuals, actually it looks like I am the only one who opened Lingo to photograph its innards. Here it is: http://i.imgur.com/Bxto0QD.jpg?1
Web wisdom says that 33 and 45rpm circuits have their own separate amps and that Lingo synthesizes two independent phases instead of using a capacitor to split one phase into two.
Following the signal is a real pain since the board is printed on both sides, the only good news is that I have a solid signal 33rpm as a "control" for this search.
If anyone can give me more educated guess on where/how to look for the missing 20V at 45rpm, please share!
The sticker betrays that "Ian" tested this board in November 1994.
Presumably, this pcb made its way into the final product in 1995, and that makes it a nice 20 years old.
At this age, electrolytic capacitors might have started to degrade, but this doesn't seem like a product that would generate a lot of heat ('lytic killer). I would start by going over all solder joints minutely, preferably with a magnifying glass or (USB-)microscope. Cracked solder joints might be hard to spot, but can lead to all sorts of strange behaviour. Solder over any joint that looks in the least bit dodgy.
The black wire from the transformer clearly shows that solder hasn't flowed up well into the hole. It may have soldered fine on the bottom, but redo that one anyway.
If that doesn't solve the problem, measure PSU voltages.
I see an LM317 and LM337. These presumably will be set to about the same voltages (but negative for the LM337).
If those seem OK, in the lower right corner are the reference oscillators for 33 and 45 rpm. They seem to be identical for the most part, so you can trace both. You should only see a difference in frequency (presumably, I have no actual experience with these circuits). You can trace the signals downsteam until a significant difference occurs. That will be the spot to investigate further.
Good luck!
Presumably, this pcb made its way into the final product in 1995, and that makes it a nice 20 years old.
At this age, electrolytic capacitors might have started to degrade, but this doesn't seem like a product that would generate a lot of heat ('lytic killer). I would start by going over all solder joints minutely, preferably with a magnifying glass or (USB-)microscope. Cracked solder joints might be hard to spot, but can lead to all sorts of strange behaviour. Solder over any joint that looks in the least bit dodgy.
The black wire from the transformer clearly shows that solder hasn't flowed up well into the hole. It may have soldered fine on the bottom, but redo that one anyway.
If that doesn't solve the problem, measure PSU voltages.
I see an LM317 and LM337. These presumably will be set to about the same voltages (but negative for the LM337).
If those seem OK, in the lower right corner are the reference oscillators for 33 and 45 rpm. They seem to be identical for the most part, so you can trace both. You should only see a difference in frequency (presumably, I have no actual experience with these circuits). You can trace the signals downsteam until a significant difference occurs. That will be the spot to investigate further.
Good luck!
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Thank you! This sounded promising, meaning like something I could do!! The project, however, ended even before it had a chance to start: today Lingo won't play even at 33rpm. Won't start at all... The last time I played with it, I forgot to ground the board and that must have finally killed it. Or maybe it is just my luck. Or maybe it is a sign that I should put my skills toward something more productive, like finally changing a light bulb in the kitchen?
Yes I did... and I did manage to change the lightbulb so now with restored self-esteem I am going back to fix something from of my collection of broken audio toys. With dead Lingo, however, I do not even know where to start. Power light goes On when I press the main switch but to start the motor you press a remote switch (located on the plinth of a turntable), once for 33rpm and press-and-hold for 3sec for 45rpm. The books I've been reading over the last few months (Electronics for Dummies and such) say that power supply problem is the easiest one to diagnose, so I should have said that Lingo is "comatose", not "dead".
As jitter advice you I will start measuring PSU voltages: AC after the transformer (to know if is OK) and DC after the regulators (LM317, 337).
Good luck.
Good luck.
until the moment when 33rpm have died, power supply must have been OK, but I will check again. In its present comatose state, I do not know where to start...
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