I am trying to troubleshoot this device and I believe the problem lies with the U502 chip on the main board, or something controlling it.
The CD player does not do anything at all, and no voltage is getting to any of the motors.
The chip that controls it is an LA6541D. I have the schematics for the radio and the datasheet for the chip.
Dropbox - Wave Radio CD schematics.pdf - Simplify your life
Dropbox - LA6541D.pdf - Simplify your life
(When it asks you to login or create an account click "no Thanks, Continue to View" Then Click Download in the upper right corner. )
The chip gets power (7.5vdc) but does not output voltage to the spindles on pins 5 and 6, nor does it output voltage to the sled on pins 10 and 11 when play is pressed.
I am not sure what tells the chip to turn on the motors so either the chip is bad or the signal to control it is not getting there.
Any suggestions?
The CD player does not do anything at all, and no voltage is getting to any of the motors.
The chip that controls it is an LA6541D. I have the schematics for the radio and the datasheet for the chip.
Dropbox - Wave Radio CD schematics.pdf - Simplify your life
Dropbox - LA6541D.pdf - Simplify your life
(When it asks you to login or create an account click "no Thanks, Continue to View" Then Click Download in the upper right corner. )
The chip gets power (7.5vdc) but does not output voltage to the spindles on pins 5 and 6, nor does it output voltage to the sled on pins 10 and 11 when play is pressed.
I am not sure what tells the chip to turn on the motors so either the chip is bad or the signal to control it is not getting there.
Any suggestions?
Check DC level at MUTE pin (2). I think this has to be pulled high for things to operate. (At least I presume that the simple comparator controls the operation of input LTP current source transistors.) That said, as written it would be an active high signal.
Measure DC levels at Vref (pin 23) as well as each amplifier's VG and Vin pins. Things are never going to operate if Vref and VG disagree.
The chip comes with an integrated 5V regulator using an external pass transistor. Not sure what it supplies, but perhaps an external micro, as it has a reset output for that as well (to perform a power-on reset). Heaven knows what'll happen if that whole reset business does not work properly, e.g. if delay cap Cd is defective in some way. If that's the same micro controlling the mute line, things might be stuck in mute indefinitely. Got a DSO? Might come in handy.
Of course it might just be a dead chip, too. It happens, especially with gummed-up sled or spindle motors that can cause it to overheat.
Measure DC levels at Vref (pin 23) as well as each amplifier's VG and Vin pins. Things are never going to operate if Vref and VG disagree.
The chip comes with an integrated 5V regulator using an external pass transistor. Not sure what it supplies, but perhaps an external micro, as it has a reset output for that as well (to perform a power-on reset). Heaven knows what'll happen if that whole reset business does not work properly, e.g. if delay cap Cd is defective in some way. If that's the same micro controlling the mute line, things might be stuck in mute indefinitely. Got a DSO? Might come in handy.
Of course it might just be a dead chip, too. It happens, especially with gummed-up sled or spindle motors that can cause it to overheat.
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Go back to basics.
System control procedure is;
Door closed/CD inserted detector, laser lights, focus is achieved then and only then will the CD turntable and sled motor start up.
If it does nothing at all, check the control lines have the correct voltages on them.
The LA6541 is unlikely to fail unless it has heat marks on it.
LA6541D Datasheet PDF - Datasheet4U.com
System control procedure is;
Door closed/CD inserted detector, laser lights, focus is achieved then and only then will the CD turntable and sled motor start up.
If it does nothing at all, check the control lines have the correct voltages on them.
The LA6541 is unlikely to fail unless it has heat marks on it.
LA6541D Datasheet PDF - Datasheet4U.com
DSO? Pin 2 reads .8v I think I was measuring the voltages for the spindle and sled wrong. The schematic shows the motors across pins 5 and 6 and pins 10 and 11 of the LA6541 measured across those reads 0v from 5, 6, 10, or 11 to ground I get about 3v.
I was going over the aggravating schematic and decided to check for 5v off the regulator U203 (LM78M05) there is no voltage going to it or coming out. I traced that back to Q208 (PNP bipolar A608 transistor) Base measures 11.6v Collector 0v Emitter 15v. My forte is tube stuff. Does this mean Q208 is bad?
I pulled q208 and tested per some instructions on the internet, it appears to be bad. I found another PNP (bd140) of what I think is similar ratings and put that in. The CD started working and the 5v regulator put out 5v, but something started smoking so I pulled the plug. To work on this it has to be all put together and upside down. so I cannot see or access the top of the circuit board without disconnecting half of the connectors on the board.
with the q208 removed from the circuit the voltages on base are 5v collector 0 emitter 15
if I place the bd140 in the circuit the collector outputs 6 volts but then it starts to get very hot.
After reading up on Bipolar transistors I noted that they are used as a switch. So I jumpered the E and C through my milliamp meter and noted that the CD player attempted to work and the meter showed a current draw of about 135ma.
The 2SA608 is an obsolete transistor though they are available on ebay from china or NOS.
I found a (sort of) compatible substitute from Digikey the SS8550-D the maximum voltage is lower, the pins are in a different order but it can handle more power than the A608.
They came in today, and after carefully bending 2 of the legs so they would be in the right order I installed it.
The CD player now TRIES to work, but the laser does not turn on or try to focus. In the process I had mangled the ribbon cable. I substituted another cable but it did not work any better.
I did find a manufacturer name and part number for the mechanism and Laser assembly it is a Sanyo SF-P100 13 pin.
They are available on ebay and other places but are a bit pricey and it is hard to find the complete mechanism instead of just the laser assembly.
The 2SA608 is an obsolete transistor though they are available on ebay from china or NOS.
I found a (sort of) compatible substitute from Digikey the SS8550-D the maximum voltage is lower, the pins are in a different order but it can handle more power than the A608.
They came in today, and after carefully bending 2 of the legs so they would be in the right order I installed it.
The CD player now TRIES to work, but the laser does not turn on or try to focus. In the process I had mangled the ribbon cable. I substituted another cable but it did not work any better.
I did find a manufacturer name and part number for the mechanism and Laser assembly it is a Sanyo SF-P100 13 pin.
They are available on ebay and other places but are a bit pricey and it is hard to find the complete mechanism instead of just the laser assembly.
At the shop, whenever someone brought in one of those Bose radios, I turned it down.
I told the poor sucker to contact Bose directly, and be prepared for some high costs.
Bose depends on that to keep the money flow going.
I have no time for those glorified chinese-made junk.
I told the poor sucker to contact Bose directly, and be prepared for some high costs.
Bose depends on that to keep the money flow going.
I have no time for those glorified chinese-made junk.
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