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Yamaha CDX-720

G

guest146

New Member
Hello all.

I am a new AudioKarma subscriber and this is my first post.

I live in the Dallas area and am in my early fifites. I really haven't had a working hi-fi setup for about 12 years, although I have some basic equipment tied into my TV and usually only used to improve the TV's two channel sound.

Since doing some household decluttering and furnitue re-arranging I have moved the stereo equipment to a new listening area in my back den. My legacy system consists of a pair of B&W DM-620 speakers and 2 Yamaha stereo receivers (RX-330 & RX-730) all from about 20 years ago. I am presently using the RX-330 but didn't have a dedicated CD player for the system. After researching available Yamaha models (so that I could have the nice amber/red colored lighting of my receivers match my CD player) I recently scored off eBay a "new old stock" Yamaha CDX-720. I got it from Seattle Goodwill and as advertised both the unit and the remote still had the plastic protective film on them. It must have been a gift that never got used and eventually went to Goodwill.

The unit works fine except that the CD drawer sometimes has problems opening and/or closing. I have read that this is because a belt has gotten a little loose and no longer makes contact with the pulleys. I have read that its not that big a deal to replace them but have yet to find any step-by-step instructions on how to do so.


So my first question is:

1) Can somebody point me to a good description, or an online copy of a service manual that shows how to replace this belt?

The CDX-720 does not seem to be listed as a model that Yamaha ever produced. I have compared my unit to other CDX players' manuals. It looks to be absolutely identical to the CDX-520, except that the CDX-720 has both coaxial and optical digital outputs whereas the CDX-520 appears to only have the coaxial digital output. I have actually found a replacement belt on Partstore.com for a CDX-520 so I am assuming this could be used for the 720.


Which leads me to my other question:

2) Does anybody have any additional info on this CDP?



Well that it for now. Having scanned the CDX thread(s) it looks like the ultimate CDX to have is the CDX-1120 or CDX-2020 (in the USA). I will be keeping my eyes peeled at the local Thrift shops and Craigslist for one of these beauties. In the meantme the CDX-720 seems a very nice unit.

Thanks
 
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The CDX-720 was sold in the US from 1989 with an MSRP of $430, not a bad player. I will see if I can dig out a bit more info.

It seems quite hard to find info on the player, try to put it on a scale. If it weighs around 4,6kg it's properly close to the CDX-520, if it's around 6,5kg look at the CDX-820 for more info.

And if possible pop the cover and take a few pics, espacialy of the DAC - it will be 2 big chips that say BurBrown PCM-56P or PCM-58P. Then you know for sure.
 
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Chips in CDX-720

I pulled the top cover off and found the following.


1) 2 16-pin DIPs labeled:

YM4111 2
911171E

These had the word "DAC" underneath them on the circuit board.


2) 1 16-pin DIP labeled:

YM3414
91 08 67 C

This had the lettering "DF" underneath which I assume is "Digital filter".


I know the YM3404 and YM3414 were used as digital FIR filters (I've found datasheets on both and have them downloaded), which I assume are there to try to correct phase error after sampling upstream of the DACs.



So evidently I have two DACs but I don't recognize the chip nomenclature UNLESS this is a Yamaha sourced version of the Burr-Brown PCM-56p or PCM-58p. There are other chips but none say Burr-Brown and they are labled as Rom, Microcontroller, etc.....

I will try to take some pics and put them up here in the next few days.
 
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The YM3414 is the filter allright and the 2 YM4111-2 are the DACs, it looks like Yamaha used there own DACs in the 720. This is a little surprise since the xx20 was the last linup from Yamaha using the Burr-Brown DACs, only after that they started to use there own DACs.

A nice pic of the main board would be nice, the layout would tell if the 720 is from the 520 or 820 fammily. Maybe even a total different player relabeled for the 110V market.

The laser model would also be of interest.

PS. the weight is still interesting.
 
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Well this CDP is sounding more and more mysterious.

I noticed there was a service manual on eBay for the CDX-520 for cheap so I snagged that and should have it this weekend. Remember that I believe the CDX-720 is almost identical to the CDX-520 due to looking at an online users manual for the CDX-520 and noting the front panel and all controls look identical to my CDX-720.

There was no belt listed on the link given above at partstore for the CDX-720. There IS a belt for the CDX-520 listing for about $3. I will wait till I get the service manual for the CDX-520 to verify as much as I can that the drive systems are the same before I order the CDX-520 belt.

And yes it is very odd that this YM4111 2 DAC was used when all the other models were using Burr-Brown. Could the CDX-720 have been a "experimental" model using a Yamaha produced DAC to see how it would fare in the market??

Lastly, since there is a CDX-720 and a CDX-620 according to a previous post in this thread then the lineup for 1989 would have been:


CDX-2020
CDX-2000
CDX-1120
CDX-920
CDX-820
CDX-720
CDX-620
CDX-520
CDX-420

--- for a grand total of NINE CD Players. 1989 must have been the highpoint for most new models introduced.



Will be getting some pics taken of the board and internals and have them up by sometime this weekend.
 
Well there is a CDX-630E witch I belive also was released in 1989, this would make it 10 CDPs in the lineup.

And that makes it even more odd, since it uses the Phillips TDA1541A DAC. In the beginning I thought the 720 might be the 630E relabled, but it seems not to be so.

A few good pics of the inside would really be nice.
 
Nope. Not Sony optics. We never, ever used Sony optics (at least not when I was there), they were always Mitsubishi sourced. This one very likely uses a DG-1. P/N is VE188400

Loading belt P/N VG945700
Feed belt P/N VE023400

Sorry, but no PRB belt-equivalents. My book is too old.

This also was a Hi-Bit player (18-bit equivalent resolution). When we first did this, there were no 18-bit DACs, so we kludged our own from 16-bit parts. This player has true 18-bit DACs.
 
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PIctures of the CDX-720

Here are the pics of the CDX-720.

Compare the picture of the front of the unit to a CDX-520 from the CDX-520 Users manual. To me they look the same. Also, the remote is the same model number ( YH03010 ).

Got the CDX-520/CD-1050 service manual. The loading belt shows to be VG945700 as "PacificStereo" said in his e-mail in which he is refering to the correct part for the CDX-720 ( I am assuming?). So they are evidently the same. The transport unit is labeled in the service manual as : "Mechanism Parts (DM-720B)". Note from one of the pictures of the back of the unit it was made in April 1989.

The more zoomed-in PCB picture shows the 2 DACS at the lower middle -- notice they are labeled "YM4111-2". The YM-3414 Digital filter chip is directly above the ribbon cable a little to the right of filter center.

The ICs for the DAC are labeled IC-118 and IC-119. The same two ICs in the CDX-520 service manual are also 16 pin DACS but are called out as PCM56Ls.


Still kind of a mystery on the DACs as the CDX-520 and CDX-720 are both 8-Bit Direct Out players but that is achieved with two different DACS. Again it makes me wonder if the YM4111 was a Yamaha copy of the Burr-Brown PCM56L.



Anyway it looks like the belt I need to replace is now identified. Partstore has them listed for about $3. I think I know how to replace it by removing the cam that sits above the belt pulley and opens/retracts the disk tray.



Thanks to all for their input on this matter.

Mark H.
 

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Very nice! I recently purchased a 720 but upon arrival it won't read disks. Pics of the player in action before purchase verify that It did work before shipping. I'll have to figure out why it won't play.

Glad yours will be working fine :thmbsp:
 
Well it do not look like the CDX-630E inside, that is for sure so no fammily there. It looks as if the CDX-720 really was the first Yamaha CDP with there own DAC inside, it was not before the CDX-XX50 series Yamaha had a line up with there own DACs (except the smallest model CDX-450, that was still BurrBrown).

So this might be quite a special player, I also noticed that on the fromt it sayes 18 Bit so now it would be interesting to compair the layout of the PCB on the 520 and 720.
 
Well that's interesting to know -- the 720 does appear to be a unique beast.

I hadn't mentioned this earlier but I had purchased a new Cambridge Audio Azur 650c CD player right before I found the Yamaha CDX-720 on Ebay. I didn't get the 650c hooked up until yesterday and did some A-B testing. The Azur blew it away. A virtual night and day difference in clarity, detail and soundstage. The poor little CDX-720 just sounded flat compared to the Cambridge Audio. Guess I shouldn't be surprised but I understand that DAC's have really come a long way and I guess 20 years is an eternity in DAC years. Will be relegating the CDX-720 to second tier status I guess. But still enjoy having it and plan on getting the belt fixed.

Mark
 
Yes a lot has happend since then, it is not until you get into the big CDPs from "old dayes" that the DAC becomes a smaller factor in the sound quality and they still can keep up with newer players (even not in the same price range as they where).

The Azur 640c had quite a good reputation and the 650c is a tweek of this model, so it is properly be even better and it do look great inside with the ringkernel trafo.

A comparible CDP from Yamaha would be the CDX-993 with a list price just above $700, but now they are 10 years old - so...
 
Also, the CDX-993 was not made for the US market. I'm not even sure a 120v 60Hz version even exists. The Cambridge Audio 650C got a very good rating at the "What HiFi" website which is what led me to buy it.

Mark
 
I also had difficulty finding any info on the 720. My 2000 unit is also rare, and interesting similar in many general front faceplate design points to the 920 and 720 (versus the 1120/2020 is a whole new faceplate design). Anyway, if your belt is similar to my 2000, than it is real easy to replace. I also purchased my 2000 unit new/old like you did, and I too needed a belt very quickly simply due to the age of the belt.

I pulled out my full-line brochure (USA) from around that time, and it shows the following single disk CDP line-up all in the same brochure:

2020
1120
1030
930
920
730
530

So, we can see that Yamaha's numbering system was not always indicative of a model year, sequential line-up, nor a unit's lineage. The only consistency I see is that the xx30 units represented a dramatic change to a more modern faceplate design from all of the xx20 and xx00 units.

Also, regarding Broonbanes issue, my 2000 unit has a shipping switch on the bottom that is similar to a computer's disk parking system, to protect the disk mech while in transit. Does the 720 have this? If yes, then issues might be it was not "parked" when it was shipped (perhaps some damage), or it was and was not noticed upon arrival and needs to be switched back to play a disk.
 
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