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Old 29th June 2005, 10:01 PM   #1
kevinkr is offline kevinkr  United States
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Default PS Audio Lambda Drive Disaster

I recently purchased a CDM 9/44 with the plan of transplanting the laser pickup assembly into my ailing Lambda's CDM-9Pro (9/60) I have disassembled the tray mechanism, laser and controller board in the past with no difficulties. I have a wrist strap and static controlled environment.

I disassembled the 9/44 which was in the factory wrapper, and carefully removed the two torx head screws that retained the pickup assembly in the mechanism. I then did the same with the old pickup and installed the new one in its place.

I reassembled everything, and voila... Nothing.. Would not read the disk, would spin for endless ages and once in a while read the TOC. Will not play the disk.

I reinstalled the old pickup which was working prior to disassembly.

Again Nothing!

I have had the whole thing apart repeatedly and have done progressively more damage with each passing attempt. I checked for cold solder joints, I checked supply voltages. I got the data sheet for the TDA8808T which this mechanism uses. I looked at the ac signal at the output of the diode amplifier, looked ok?

Now after another ill-advised attempt it gets to the outer edge of the disk and sometimes doesn't know when to stop, with horrible results. Also the spindle motor stops and then runs backwards when this happens. This behavior is new and probably the result of some of unseen damage done today as I worked on it.

I have 25yrs of engineering experience, some level of patience, fast scope, but no schematics, and they aren't seemingly available.

Anyone have any ideas whatsoever? Schematics, service notes, even for the theta version??

So far it does know there is a disk present, it does correctly detect the disk size, although that funky focusing behavior at the disk edge. (Shouldn't get there should it?) The motor runs ok.

I am actually going to buy something else, as I said in a previous thread I have just about had it with this transport. A shame as it has always been the best sounding one I have owned.

Thanks, Kevin

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Old 30th June 2005, 03:52 AM   #2
kevinkr is offline kevinkr  United States
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Here is a little more information to go on.. I carefully cleaned the board tonight with some alcohol to remove flux residue from the board after resoldering a few connections.

The mechanism is about back to where it was last night. The motor spins up when I insert a disk in the tray, runs for about 10 seconds and returns an error to the display.

I removed the disk and position the pickup so that I can see it, when play is pressed it goes through the normal focusing routine and I can also see the laser output using a white card.

Supply voltages all appear to be correct and the circuitry controlling the spindle motor, focusing coils, tracking coils, and laser all appear to function in what appears to be an expected manner. I was able to observe a nasty looking waveform on the HF output of the diode amplifier which is a TDA8808T, basically a 0.5Vp waveform that appears to be the processed diode output..

I know some of you have encountered problems with the lambda and theta drives of this vintage, and was wondering whether any one has any experience resolving these issues.

The board on the mechanism is not made by Philips and has a moderate component count. More details to follow if warranted.

Kevin
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Old 30th June 2005, 05:06 AM   #3
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sorry bout your troubles. email me at raincheck@covad.net
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Old 30th June 2005, 09:41 AM   #4
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Quote:
Supply voltages all appear to be correct and the circuitry controlling the spindle motor, focusing coils, tracking coils, and laser all appear to function in what appears to be an expected manner. I was able to observe a nasty looking waveform on the HF output of the diode amplifier which is a TDA8808T, basically a 0.5Vp waveform that appears to be the processed diode output..
You are talking 0.5V pp of an aye-pattern signal, aren't you?

This signal (could anyone with a circuit diagram for this model confirm this?) should be around 1.3 - 1.7 V pp. To adjust - turn the little trim-pot located on the laser pick-up PCB clock-wise.

If you can’t obtain the proper info on the proper pp level, try anyway… If it does bananas – set it back to what it was before.

Good luck!
Extreme_Boky
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Old 1st July 2005, 05:07 PM   #5
kevinkr is offline kevinkr  United States
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Hi Boky,
According to the TDA8808T data sheet the HF output should be over 1.0V minimum, and it is definitely much less than that. There are definitely no adjustments on the board, however I have not checked the pickup assembly that closely - however I believe that is also the case. I can take a look at the old pickup to see whether there is a pot.

Schematics are almost impossible to come by for this unit as PS Audio and Theta Digital (Theta made the PSA digital components) were owned by a holding company at the time until around 1999, when it went bankrupt someone destroyed the design information. I have talked to both manufacturers about this.

The board under the mechanism appears to have been made by Daisy Laser based on the markings, but they are not helpful either. The board has got relatively few components - some driver circuitry for the hall effect spindle motor, tracking and focus coils, laser driver and diode amplifier.. Everything else from the radial error correction IC (TDA 8809T) and SAA7310 are on the large board along with the master clock, mpu..etc

Kevin
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Old 1st July 2005, 10:59 PM   #6
tubenut is offline tubenut  South Africa
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Default I have the same problem.....

I have the same problem with a Lambda I have been trying to sort out. I also have a DATA. If I swap the loader assembly including PCB between these two machines (the Theta is fine) the problem stays with the lambda. I therefore do not think the fault is on the small pcb but the theta designed larger pcb with the dig outputs and SAA7310GP. I have replaced all the regs and lytics on this board without joy. I have also swapped the 7310 and 8809 but it came from a non working player so I do not know if they were good chips. I have swapped the 3702 and 5664 chips as well.
I have given up for now.....

I really do not know what to say except I hope you find the fault and tell me what it is....

Guillaume
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Old 2nd July 2005, 01:08 PM   #7
kevinkr is offline kevinkr  United States
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Hi Tubenut,
I hope eventually to get some schematics for this thing. I suspect the problem in mine is also perhaps in the main board. I have found sources for most of the ic's in the machine, all of course are obsolete..
The drive is redundant now as I recently purchased a low hour theta data basic. (I hate Philips, but I can't afford something a whole lot newer so my hands are tied. LOL)

Kevin
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Old 2nd July 2005, 10:52 PM   #8
kevinkr is offline kevinkr  United States
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Well I got some bad news today, looks like the theta data I was getting has the dreaded drawer gear disease and I had to cancel the deal so I am back to square one. I thought that the mechanism and loader would be useful to trouble shoot the lambda as well as giving me a decent source to use in the interim..

I am going to look for other options after the holiday and see what I can come up with. In the meantime I am not experimenting too much with the drive as I don't want to make it any worse than it is already.

I have heard quite a lot on a board located in Singapore about having to fiddle with the HF filter response when replacing the pickup assembly with the 9/44. It may be that the pickup for the 9/65 was not exactly the same afterall. The comments seem to apply to both the theta and the psa drives.

Unlike earlier drives there are absolutely no adjustments anywhere on the pickup assembly or any of the boards.

My suspicion is that a lot of passive components have "aged" over the 12 yrs or so since the boards were manufactured. The drives were manufactured over a range of years, but the few I have seen have many components that date to as early as 1992. Mine was made in 1995 according to the guy I bought it from 8yrs ago, and the newest component date codes as well as the board date code bear that out.

The IC's are all discontinued but most are available from several sources in the UK - I have not had much luck finding them in single lot quantities elsewhere.

The Lambda design leaves EVERYTHING powered except the laser itself even when the unit is turned off, and unfortunately if you know anything about component life that means that EVERY component in the thing is now well beyond end of design life.
Mine has been continuously powered for most of the last 8yrs and probably for most of the 2yrs before that - that equates to 88,000hours! Way beyond the design life of every resistor, capacitor and semiconductor/IC in the unit. IC's and semiconductors have an MTBF, although I do not know it for any of the devices in this unit for consumer grade stuff it probably is much less 100K hours.

It was an unfortunate design choice, but PSA claimed that the Lambda took 72 hrs to reach sonic perfection after power was applied and that may have been the motivation for powering everything on a continuous basis. (I think they could have accomplished much the same thing by just powering the master clock continuously.)

The Sony SACD player, Sony DVD player and Panasonic LD Player I own all kill the power at the primary of the power transformer. None of them sound anywhere as good as the PSA Lambda Drive/Ultralink II combo however!

The first owner of a theta/PSA digital product of course would not care because in the USA at least no one keeps them for long because only the toy boys have that kind of money to invest - it's us second tier semi-impoverished owners who bear the brunt of the problems with these products. Some of us are likely to be able to fix them in at least some cases as well.

Well I guess I am just ranting now.

I am going to fix this thing eventually, it is too good and I am too cheap not to, however it may take a while..

Kevin
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Old 3rd July 2005, 07:18 AM   #9
tubenut is offline tubenut  South Africa
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Default Kevin, send me a PM

I may be able to help with the disease.....
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Old 3rd July 2005, 07:24 AM   #10
tubenut is offline tubenut  South Africa
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Kevin. I have done a few laser swaps on Theta Data units with no problems. The Lambda is the first that did not like it.... The problems I had after the swap were the same as your Lambda...
I must llok at the 2 boards again next to each other and see if I spot any differences anywhere... Except for the fitted AT&T
I can not get the Data loader to work in the Lamda but I can get the Lamda loader to work in my Data...

I think you may be on to something with the HF story but I have replaced all electrolytic caps on the Lambda as well as regs so I am not so sure about component ageing.

PM me!!! The Data you turned down may be rescueable!!!
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