Can I assume that testing the chip as if it were discrete components is valid?
If TR4 and TR8 are bad, the chip is bad...
If TR4 and TR8 are bad, the chip is bad...
An externally hosted image should be here but it was not working when we last tested it.
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I think so in the case of the TCA240. It is a transistor array and AFAIK there are no other on chip components.
If tr4 and tr8 are unused and not connected, they must be collateral damage from some other on-chip disaster. Assuming they were good at time of manufacture.
However, if the chip isn't working, then how come the machine plays CDRs? That could only happen if four of the active transistors are good, and the gain-controlling transistors are open-circuit, so you would have fixed gain.
How did you measure? None of the transistors have all three electrodes available on pins.
What is your lowest red arrow pointing to? I don't know what those rectangular symbols mean
Whilst measuring my working CD104, I found 3V offset on my HF 🙁
Anyone seen a circuit for the thick-film HF amp? It's not in my CDM1 manual...just a block diagram with hieroglyphics.
However, if the chip isn't working, then how come the machine plays CDRs? That could only happen if four of the active transistors are good, and the gain-controlling transistors are open-circuit, so you would have fixed gain.
How did you measure? None of the transistors have all three electrodes available on pins.
What is your lowest red arrow pointing to? I don't know what those rectangular symbols mean
Whilst measuring my working CD104, I found 3V offset on my HF 🙁
Anyone seen a circuit for the thick-film HF amp? It's not in my CDM1 manual...just a block diagram with hieroglyphics.
It has stopped playing CDRs now!
In service loop A when I move the RAFOC manually to the outer edge of a CD, the speed slows down accordingly. That's something I guess.
The rectangles are ground connections.
How it ever managed to play CDRs?
I haven't got a clue.
In service loop A when I move the RAFOC manually to the outer edge of a CD, the speed slows down accordingly. That's something I guess.
The rectangles are ground connections.
How it ever managed to play CDRs?
I haven't got a clue.
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A TCA240 replacement has restored the ability to play anything.
That's already something, the TOC being displayed and the CDs and CDRs playing.
Only, the RAFOC vibrates badly, and I can see that the discs spin with some excentricity.
So after near the end of the CD (the last tracks) it will stop doing anything.
That's already something, the TOC being displayed and the CDs and CDRs playing.
Only, the RAFOC vibrates badly, and I can see that the discs spin with some excentricity.
So after near the end of the CD (the last tracks) it will stop doing anything.
Edit: some CDs pose no problem and I can read them completely.
The new one is the Philips!
An externally hosted image should be here but it was not working when we last tested it.
The new one is the Philips!
An externally hosted image should be here but it was not working when we last tested it.
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That's brilliant. Well done 🙂
Is the eccentricity problem when viewed from above (which would be strange) or when the disc is viewed edge on ? If edge on then its usually some small foreign matter on the platter lifting the disc.
Some discs do give the appearance of being eccentric when spinning. The real test is whether the radial arm is moving rapidly as it follows the disc.
Is the eccentricity problem when viewed from above (which would be strange) or when the disc is viewed edge on ? If edge on then its usually some small foreign matter on the platter lifting the disc.
Some discs do give the appearance of being eccentric when spinning. The real test is whether the radial arm is moving rapidly as it follows the disc.
I take that to mean the disc spins as if the hole in the centre were misaligned.
Any "edge on" eccentricity problem is "magnified" greatly as you get toward the edge of the disc, and that would certainly cause problems with "last tracks", but I'm just trying to think of the misaligned hole theory 🙂 That would have the same amount of error at any point, the only difference being the mechanical aspect as the radial arm would move slower at the disc edge due to the disc slowing down. That could I suppose cause the servo to react differently as the whole mechanical/electronic servo is taken as a whole. We talk of Nyquist stability in amplifiers but the same applies to the mechanical/electronic interaction of a servo. Any visible eccentricity needs looking at. A good (full price reputable label) CD should have no detectable eccentricity.
Any "edge on" eccentricity problem is "magnified" greatly as you get toward the edge of the disc, and that would certainly cause problems with "last tracks", but I'm just trying to think of the misaligned hole theory 🙂 That would have the same amount of error at any point, the only difference being the mechanical aspect as the radial arm would move slower at the disc edge due to the disc slowing down. That could I suppose cause the servo to react differently as the whole mechanical/electronic servo is taken as a whole. We talk of Nyquist stability in amplifiers but the same applies to the mechanical/electronic interaction of a servo. Any visible eccentricity needs looking at. A good (full price reputable label) CD should have no detectable eccentricity.
If you can see visible eccentricity and the radial arm is visible moving and following that eccentricity then you have to look at the platter. The discs won't be the problem... I just put that as an example to make it easier to visualise. If the disc isn't running true then there is a problem with the platter. Compare with your other players.
Run out errors (disc up/down wobble when viewed edge on) should be minimal. A good player should have zero detectable run out although many cheap (not the radial types) laser mechs have terrible platters with big run out problems.
If you decide that the mechanical issues are acceptable then that comes back to a servo/pickup issue issue again. Is it possible (and I'm just trying to cover all bases and possibilities here) that the TCA has just "changed" the fault but not corrected it... different characteristics and so on, and the player is still "living on the edge" when it come to playability.
Success!
I noticed that the upper lens coil was slightly rubbing inside its magnet as I was cleaning it, a bit like a speaker with a defective outer foam suspension.
So you were right, well partly!
A bit of adjustment later (nay, a lot) and the player now works perfectly!
A return to the old TCA confirms it was dead anyway. Perhaps I still have to do a bit of adjustment, I'll see.
Now why did CDRs ever play, that is a mystery to me.
I noticed that the upper lens coil was slightly rubbing inside its magnet as I was cleaning it, a bit like a speaker with a defective outer foam suspension.
So you were right, well partly!
A bit of adjustment later (nay, a lot) and the player now works perfectly!
A return to the old TCA confirms it was dead anyway. Perhaps I still have to do a bit of adjustment, I'll see.
Now why did CDRs ever play, that is a mystery to me.
Once again... great you have it working.
There seems to be an awful lot going on with this player 😀 Why did it play CDR's. I don't know. How could it play CDR's with a dead TCA... well it can't. I wouldn't put money on that TCA being faulty (as in faulty faulty) just yet 😛
There seems to be an awful lot going on with this player 😀 Why did it play CDR's. I don't know. How could it play CDR's with a dead TCA... well it can't. I wouldn't put money on that TCA being faulty (as in faulty faulty) just yet 😛
My theory was that one half of the TCA worked, but this can't be checked of course!
And by the way, that -4V at pin 1 of the LM324? Now correct!
Lid back on then.
And by the way, that -4V at pin 1 of the LM324? Now correct!
Lid back on then.
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The TCA failed slowly from overheating whilst trying to cope with the lens problem. Before the TCA failed completely, CDRs played because the track is effectively wider. Seems a plausible hypothesis. Failure towards end of disc may be because of the angle of the pickup to the tangent.
Lucky you discovered the lens problem before the new TCA burned out.
Good to see a happy ending laugh in the face of skepticism.
Meanwhile, I found my other CDM1 machine, a Japanese-made Marantz in a CD104 case, also shows about 3Vdc on the eye pattern. The manual implies 0.5V in the diagram but it doesn't actally say so. What's yours?
Lucky you discovered the lens problem before the new TCA burned out.
Good to see a happy ending laugh in the face of skepticism.
Meanwhile, I found my other CDM1 machine, a Japanese-made Marantz in a CD104 case, also shows about 3Vdc on the eye pattern. The manual implies 0.5V in the diagram but it doesn't actally say so. What's yours?
I'm off to work, but I'll check on that in the afternoon.
Today I'll let the CD1104 play continuously for 12 hours to see whether it is definitely fixed.
I say whether but I'm sure it is fixed!
Today I'll let the CD1104 play continuously for 12 hours to see whether it is definitely fixed.
I say whether but I'm sure it is fixed!
Perhaps some misunderstanding. If you have 1Vpp then there must be at least 0.5V offset or the signal would be partly negative, which isn't possible AFAIK.
Manuals I've seen all show a diagram with the eye pattern touching a horizontal axis, but the axis isn't labelled and the only information is 1Vpp.
Since both my players work and show more or less the same eye pattern, and apparently have the same thick-film HF amp, I'm not very worried. I still haven't found a circuit diagram for the HF amp. I assume the DC on the output arises from the photodiodes' bias. I should find out more about photodiodes.
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