Hi!
Got a more or less working CDB650 for a very good price.
PS caps a bit bulging so replaced. Replaced OP amp supply caps and output caps. Outputs were 100uf 25v polarized, replaced with 330uf 25v NP Muse. All bypassed with .01uf 100v Wimas or other film caps.
Replaced ne5532s with OPA2604s.
Problem.
CD will play for 5-15 minutes, then both channels will mute for 3 seconds. No pattern discernable. No components getting hot.
During that time the counter advances normally, and, after the 3 second period, resumes playing at the indicated time point.
Sound is great before and after the muting. It's as though the output cables were pulled for those few seconds, then reconnected.
Have a DVM, schematic/circuit diagram reading and soldering skills, but no 'scope.
Could replacing the polarized outputs with NP have been the cause? (doubt it, but you never know). I even installed them with the longer lead to what was the + pad.
Have done similar Mods on more than a dozen Magnavox/Philips players successfully, but never ran across this before.
Any ideas as to where to start?
Can supply schematics/diagrams/photos on request.
Thanks!
Dan
Got a more or less working CDB650 for a very good price.
PS caps a bit bulging so replaced. Replaced OP amp supply caps and output caps. Outputs were 100uf 25v polarized, replaced with 330uf 25v NP Muse. All bypassed with .01uf 100v Wimas or other film caps.
Replaced ne5532s with OPA2604s.
Problem.
CD will play for 5-15 minutes, then both channels will mute for 3 seconds. No pattern discernable. No components getting hot.
During that time the counter advances normally, and, after the 3 second period, resumes playing at the indicated time point.
Sound is great before and after the muting. It's as though the output cables were pulled for those few seconds, then reconnected.
Have a DVM, schematic/circuit diagram reading and soldering skills, but no 'scope.
Could replacing the polarized outputs with NP have been the cause? (doubt it, but you never know). I even installed them with the longer lead to what was the + pad.
Have done similar Mods on more than a dozen Magnavox/Philips players successfully, but never ran across this before.
Any ideas as to where to start?
Can supply schematics/diagrams/photos on request.
Thanks!
Dan
The output caps absolutely can't be the cause.
The first thing to do with any old Mag/Philips cd is to replace ALL electrolytic caps that are not already Nichicons, especially any Matsushita/Panasonic and any European caps(Siemens, Philips, etc.). Until you do that, you can't count on ANY weird behaviour to not be cap-caused.
The first thing to do with any old Mag/Philips cd is to replace ALL electrolytic caps that are not already Nichicons, especially any Matsushita/Panasonic and any European caps(Siemens, Philips, etc.). Until you do that, you can't count on ANY weird behaviour to not be cap-caused.
Thanks, Stephen...
There are only a few left untouched ATP. Around the SAA7220, IIRC.
I did think of that, Kevin, but wouldn't that pass switching noises between tracks?
Thanks!
Solved, or, so it seems.
The NP caps were the cause.
Replaced with 470uf 35V Silmic IIs and played a full CD without issue.
The NP caps were the cause.
Replaced with 470uf 35V Silmic IIs and played a full CD without issue.
Danveee; I had one of those back some years ago. I also have a Arcam 5. I removed the muting transistors as suggested above without adverse switching noises on either unit, YMMV. This mod also improved the sound and I think it is a worth while mod. To try it just pull the collector of each muting transistor, if you don't like what it does, put it back.
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Thanks, but they're surface mount. Have to pull the whole tiny device (both of them).
The issue was cured by replacing the NP output caps with polarized.
The issue was cured by replacing the NP output caps with polarized.
I have to say that I think there is something weird still amiss in your player, as the NP caps should NOT have influenced the fault in any way without either leaky(dc-wise) muting transistors or some other secondary issue causing maybe an output-side dc charge buildup that would leak backward through the polarised caps, rather than charge up a voltage on the np cap. It really bears additional investigation.
Already replaced all electrolytics with upgraded 105°C versions.
Where would I start looking?
I would start by putting the same NP caps back in place, then play a disc while looking with a dmm for dc voltage change on the output side of the caps. There should be a steady 0VDC, if all is normal, with some slight meter movement just from the low freq content of the music signal.
In that case, the muting transistors would be the first things to suspect, so you would lift the terminal of each transistor that is attached to the signal output line. If the dc then goes away, you have a defective mute transistor, which you can either replace or simply leave out. If voltage does not go away, then I'd need to go dig up a schematic on the model to assist further.
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