I am once again having problems with a 7 & 8SE. My question is; To convert a 7 to a 8se is it simply taking out the link board and fitting the dac board, or are there other links or bits to add/subtract. Any help would be gratefully welcome. I am going mad as the 8SE board is faulty but I have a good 7 board I can use. Barry
The problem with the 8SE board is both resistive fuses (R44 and R45) have blown, for no apparant reason. Both regulators read OK. I don't want to replace them without knowing the fault as I would have to use the ones on the 7 board. I have tried the DAC in the 7 board and although it works for a while I get distortion and skipping after a few minutes which leads me to think I have a dodgy component on the DAC penninsula or there is some other mods to perform before the board can be used.
Barry, R44/R45 are on the main board ? If the +/-18V just feeds the DAC board do the MFR25 resistors blow when the DAC board isn't connected ? If they do then check the components around Z204/Z205. Otherwise I guess you'll just need to work your way through the DAC pcb starting at the +/-15V regulators Z16 and Z17. Checking the voltages/ripple on the main board power connector would probably be a good place to start.
Barry, so to confirm you have two problems :-
1. The two resistors on the 7 mainboard (R44/R45) blow when you plug the 8SE DAC into it.
2. When it 7 mainboard is running on its own (no 8SE DAC board fitted) the player starts to skip after a few minutes.
Distortion and skipping - have you looked at the supply rails on the mainboard with a scope and checked the clock on the mainboard, perhaps the supplies are collapsing and/or the clock is becoming unstable.
Power supply overload - have you checked continuity of the ground between the mainboard and the DAC board through the SK204 ribbon and have you tested all of the electrolytics on the DAC board ?
1. The two resistors on the 7 mainboard (R44/R45) blow when you plug the 8SE DAC into it.
2. When it 7 mainboard is running on its own (no 8SE DAC board fitted) the player starts to skip after a few minutes.
Distortion and skipping - have you looked at the supply rails on the mainboard with a scope and checked the clock on the mainboard, perhaps the supplies are collapsing and/or the clock is becoming unstable.
Power supply overload - have you checked continuity of the ground between the mainboard and the DAC board through the SK204 ribbon and have you tested all of the electrolytics on the DAC board ?
Hi Jon, No. The 7 mainboard is OK. The fuses do not blow. This happened with the 8SE mainboard. I have now disregarded that one for the time being. I have now fitted the 7 mainboard and all is well with it. When I fit the 8SE DAC board it does not work, although it did for a time. I did get distortion and skipping, and then it started working when hooked up without fitting permanently. but now I get nothing.
Sorry I misunderstood, I thought you had a 7 mainboard and a 8SE DAC board. So you have a 7 mainboard (with DAC components fitted) and an 8SE mainboard (without DAC components fitted) and 8SE DAC board ? I have a couple of mainboards without the DAC components fitted + 9 DAC boards and (I think) a mainboard with the DAC components fitted which must have come from a 7.
The jumper board routes the DAC signals and clock either through the mainboard or from the DAC board to the mainboard. When a DAC board is fitted I assume you remove the jumper board. If you get nothing with the 8SE DAC fitted have you checked the clock signal coming from the DAC board ?
Going back to the fusible resistors did they blow on the 8SE mainboard with the 8SE DAC fitted or just with the 8SE mainboard powered on its own ?
The jumper board routes the DAC signals and clock either through the mainboard or from the DAC board to the mainboard. When a DAC board is fitted I assume you remove the jumper board. If you get nothing with the 8SE DAC fitted have you checked the clock signal coming from the DAC board ?
Going back to the fusible resistors did they blow on the 8SE mainboard with the 8SE DAC fitted or just with the 8SE mainboard powered on its own ?
I spoke too soon. It played 3 tracks and then the distortion started. Sounds like an accumalation of faults. Now something is breaking down after it gets hot. I'm thinking a transistor near the crystal or an electrolytic. Have not got time to look at the moment, but I will get back next week. Barry
Hi Barry,
Firstly I'd play a test CD on repeat (say a sinewave of a few hundred Hz) so that the mechanism is tracking in more or less the same place, the CD is spinning at a more or less constant speed and you have a constant output signal. Check the pcb for dry joints and resolder anything that looks marginal, replace any electrolytics which have bulged,vented or show signs of leaking and if you think it's temperature related use a can of freezer spray to see if you can narrow the fault down to a chip or a passive component.
The regulators on the DAC board may struggle with the volt drop across a 4R4. If that's all you've got you could always parallel two up though. I don't think there is a lot of headroom with the input, output and regulator drop-out voltages for you to drop much across those resistors.
Cheers,
Jon
Firstly I'd play a test CD on repeat (say a sinewave of a few hundred Hz) so that the mechanism is tracking in more or less the same place, the CD is spinning at a more or less constant speed and you have a constant output signal. Check the pcb for dry joints and resolder anything that looks marginal, replace any electrolytics which have bulged,vented or show signs of leaking and if you think it's temperature related use a can of freezer spray to see if you can narrow the fault down to a chip or a passive component.
The regulators on the DAC board may struggle with the volt drop across a 4R4. If that's all you've got you could always parallel two up though. I don't think there is a lot of headroom with the input, output and regulator drop-out voltages for you to drop much across those resistors.
Cheers,
Jon
CD8SE
Hi, I have been trying to figure out a similar problem with my 8SE cd. Its fine from a cold start, but gets lots of noise/distortio on the channels after about an hour of play.
I've got the service manual and have probed around the DAC board with a scope and multimeter. I replaced the electrolytics caps on the dac as these seemed to be a known problem- but no change.
I have noticed today that the transisitor q6 on the daq voltage control gets very hot very quickly (to hot to touch) - any ideas before I try repalcing it.
Thanks.
Hi, I have been trying to figure out a similar problem with my 8SE cd. Its fine from a cold start, but gets lots of noise/distortio on the channels after about an hour of play.
I've got the service manual and have probed around the DAC board with a scope and multimeter. I replaced the electrolytics caps on the dac as these seemed to be a known problem- but no change.
I have noticed today that the transisitor q6 on the daq voltage control gets very hot very quickly (to hot to touch) - any ideas before I try repalcing it.
Thanks.
Hi, I have been trying to figure out a similar problem with my 8SE cd. Its fine from a cold start, but gets lots of noise/distortio on the channels after about an hour of play.
I've got the service manual and have probed around the DAC board with a scope and multimeter. I replaced the electrolytics caps on the dac as these seemed to be a known problem- but no change.
I have noticed today that the transisitor q6 on the daq voltage control gets very hot very quickly (to hot to touch) - any ideas before I try repalcing it.
Thanks.
I've got the service manual and have probed around the DAC board with a scope and multimeter. I replaced the electrolytics caps on the dac as these seemed to be a known problem- but no change.
I have noticed today that the transisitor q6 on the daq voltage control gets very hot very quickly (to hot to touch) - any ideas before I try repalcing it.
Thanks.
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