Theta Miles gone bad - Page 1
Forum section: electronics / general

author: IvoS
author_rank: Frequent Contributor
timestamp: September 27, 2012, 11:06:50 pm
content: My Theta Miles CD player stopped working. The CDP behaves like there is no disc. The unit powers up, display comes ON, all function buttons on the panel seem working, there is response on the display when I push buttons. After pushing play button, the main drive motor won't spin but I can see the laser diode lit and trying to focus for a while. I checked all voltages, all power supplies are just fine. I measured all voltages directly on PCB on decoder, servo and control chip, all seems OK. There was no voltage coming out of decoder chip from pin # 2 and 3, that controls the spindle drive, so I changed the chip thinking the decoder was KO, but it didn't help. Now, is the servo control chip or the laser pickup with laser amplifier kaput? What else could it be? My problem is that I can not even check the signals with scope because it doesn't output anything since the disc won't turn.What is the sequence for "playing" mode? Is the decoder processor waiting for valid data coming from servo control and then sends the command to motor drive, or should the motor drive start spinning on "play command" and if no data received it will automatically stop.??Theta Miles is based on Pioneer stable platter mechanism with Pioneer control PCB from PD-S505 model. Schematic attached.Any help appreciated.

author: IanB
author_rank: Super Contributor
timestamp: September 27, 2012, 11:21:13 pm
content: Doesn't it sound like the "disk present check" is failing? I'd guess that the player is trying to sense whether a disk is present in the player and presumably all subsequent events are dependent on whether this test gives a positive result. The question would be how does this test work? Is it an optical test based on reflection from the laser shining on the disk?

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 28, 2012, 03:14:09 am
content: Try cleaning the lens and verifying that the motor itself is good.If you can't easily fix it, you'll most likely be better off replacing it. Now that DVDs are on their way out, it's easy to find a DVD player (which can also play CDs) for cheap.

author: poptones
author_rank: Frequent Contributor
timestamp: September 28, 2012, 05:25:16 am
content: Yes, it would be interesting to see how a fifteen year old "high end" CD player compares to a decent modern unit. I think the reason OP is looking to fix this is because it's not a $200 disposable - it's a $2500 cd player... at least, when it was new, 15 years ago.Did you order a new laser head for the unit? That's usually what fails.

author: baljemmett
author_rank: Unknown
timestamp: September 28, 2012, 01:37:12 pm
content: Quote from: IvoS on September 27, 2012, 11:06:50 pmIt does indeed sound like it's failing to find focus -- players often do that first before trying to spin the disc up.The CD Repair FAQhas some potentially-useful details on the startup sequence and the troubleshooting thereof.

author: SeanB
author_rank: Super Contributor
timestamp: September 28, 2012, 07:03:25 pm
content: You will find that you need a new laser assembly, most likely it is a Sony KSS2xx part number, and will require setup after you install it. Definitely a manual needed time, but quite easy to do, if rather fiddly. The items you need are a good premade CD with music, not a recorded one, and some thin tape to apply to the outer part to make a 0.5mm bad stripe to check servo recovery so that it does not skip on playing the track. You will have to do a fair amount of dissembly to get the laser out, and only remove the shorting solder blob on the new one after it is plugged in ( have left it more than once....) then set up the laser power according to the manual ( generally measure the voltage across a sensing resistor while playing) and then setup servos ( on older units, most modern ones only have a offset that you adjust slightly from where it is).As a quick check look on the optical assembly and you will find a small preset pot that adjusts laser power, turn it slightly up and see if it will then play, as the higher power will allow it to read the disk.

author: IvoS
author_rank: Frequent Contributor
timestamp: September 28, 2012, 08:10:46 pm
content: Quote from: SeanB on September 28, 2012, 07:03:25 pmOh my goodness! When I cranked the laser diode output UP, it plays!! Thanks so much SeanB for tips. But I think that laser pickup will sooner or later fail. I had to turn the trim pot a way UP to make it work, so there must be something impaired or maybe a dust?? I am surprised I made it spin, since I was playing with every screw that makes the lens aligned. I will try to get the laser pickup assembly anyway (Pioneer CMK-54XT) for the future repair and hold on to it.

author: poptones
author_rank: Frequent Contributor
timestamp: September 28, 2012, 08:17:11 pm
content: Nope, that's pretty much the way it goes. Sounds like a new laser head is needed.How long have you had your Theta? Did you buy it new?

author: IvoS
author_rank: Frequent Contributor
timestamp: September 28, 2012, 08:28:16 pm
content: Quote from: poptones on September 28, 2012, 05:25:16 amAbsolutely right! This is not an "el-cheapo" unit that deserves to trow it to dumpster. Theta is famous for their own DAC, especially their digital filters they developed themselves instead of using commercially based chips. The DAC is famous of being able to extract "every single" bit from the disc. I would put to against any contemporary CD player.

author: poptones
author_rank: Frequent Contributor
timestamp: September 28, 2012, 08:31:33 pm
content: What's the blue board? It looks like an afterthought.

author: IvoS
author_rank: Frequent Contributor
timestamp: September 28, 2012, 08:34:14 pm
content: Yes, I bought it new from the dealer online I don't remember where exactly. The dealer had it on sale. I think I purchased it in 2004-5 when it was already considered obsolete. It was sitting in my other home overseas for 3 years unplugged. I think that transportation back to US have something to do with the laser pickup. It was mishandled on the airport my guess.

author: IvoS
author_rank: Frequent Contributor
timestamp: September 28, 2012, 08:36:14 pm
content: Quote from: IvoS on September 28, 2012, 08:34:14 pmThat is the S/PDIF output.

author: SeanB
author_rank: Super Contributor
timestamp: September 28, 2012, 08:40:41 pm
content: There is a commercial board under providing the transport, control and digital data out, with the DAC and microcontroller being supplied by the added on boards. Cranking the power up says the laser is dying ( common) so order yourself a new laser assembly, and if they are cheap order 3 or 4, to use next time. You will need a manual to install it, google the SRBP board part numbers to get the original unit that was torn apart to make this from, and get the manual for that to install the laser if the manufacturer does not have it.

author: IvoS
author_rank: Frequent Contributor
timestamp: September 28, 2012, 09:18:23 pm
content: Thanks SeanB. I think all signal outputs are in the service manual PDF file I posted in the first post. So, I should be able to adjust it accordingly using my scope. Will see. The god damn laser pickup is not easy to get, I have to keep looking. There are 2-3 websites I found but they sell it over 100 Euro a piece.

author: SeanB
author_rank: Super Contributor
timestamp: September 29, 2012, 06:25:12 am
content: Have a look and see if you can pick up the complete sled mechanism, could be cheaper. Or look for the complete Pioneer player on Ebay and strip it.

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 29, 2012, 01:22:08 pm
content: What signal does the DAC accept? Maybe you can connect it to the S/PDIF output of a cheap (but good) DVD player.

author: IvoS
author_rank: Frequent Contributor
timestamp: September 29, 2012, 01:33:40 pm
content: I am not sure. I would have to do some wire tracking. Standard I2S maybe?

author: SeanB
author_rank: Super Contributor
timestamp: September 29, 2012, 01:50:19 pm
content: From the datasheer a standard data, bitclock and LR switch signal. Not SPDIF but a 3 wire bus common to most audio DACS.

author: IvoS
author_rank: Frequent Contributor
timestamp: September 29, 2012, 03:03:40 pm
content: If you are looking at the PDF file, perhaps. But original Pioneer board has DAC chip unsoldered and bunch of wires run to Theta own DAC board.

author: grenert
author_rank: Frequent Contributor
timestamp: September 29, 2012, 03:45:32 pm
content: For what it's worth, when I recently replaced the Sony laser in my Arcam player, I simply swapped out the old laser and put in the new one. Worked without any adjustments.This web page will show you all of the CD players that use the same mechanism. Perhaps you can find the parts cheaper when they are listed for a different player.http://www.dutchaudioclassics.nl/?strPage=Daclist&strBrand=Various

author: poptones
author_rank: Frequent Contributor
timestamp: September 29, 2012, 07:39:38 pm
content: I would be very tempted at this point to construct an SPDIF interface for it so I could drive it from my PC. I realize you may have a lot of CDs, but wouldn't it be nice to have that DAC available for the main channels of movies, and FLAC files from the intarweb?

author: dangthanhlinh
author_rank: Newbie
timestamp: July 13, 2016, 05:08:20 am
content: Hi everybody,I am using Theta Miles CD, now it run normal but don't have sound go out from analog gates.There is sound go out from digital gate.Could you advise for me to resolve this problem?Thanks very much.