MHZS - Mystery of the DAC Chip

Hi Friends od Modification,

working on a MHZS CD66 now I find out the mystery of the chip and another really interesting secret about the circuit. I think the CD33 has the same circuit problem.

Please take a look.


It is not a proprietary development, how it is to read in advertisement. It is a BurrBrown PCM 1742KE from Texas Instruments.


After this I studied the signal path in my CD66.

1. Look at: focus.ti.com/lit/ds/symlink/pcm1742.pdf (Page 6).
The analog output is on pin 7 and 8.

2. The signal goes through the cheap and low quality electrolytic Caps on the right side over the DAC. Imprinted is 100uF/16V. In fact, there are two 100uF/25V.

3. The next is the OPA.

4. Following are the two 0.47 uF Multicaps.

5. The 12AX7.

6. Two really cheap electrolytics again.

7. The Relais


Friends, take care by working o the PCBs. The Multicap 1uF has a voltage of 38 V after taking out the PCB (and after more than 3 hours).

The same is on the other PCB. The Voltage at the Pins ( printed is 100V and Ground) is about 52 V after some hours!

So, can somebody tell me why I cannot find the MHZS homepage?

And which tubes are now really good?

Grettings from Germany

Some of you have changes the two multicaps. Think about it that the signal flow is about Caps No 2 and No 6.  Better to change them first.

....... does anybody know whitch value will be correct to change? Caps No 2 are 100uF, caps No 6 are only 10uF and the Multicaps are 0.47 uF. I think they should be all the same value but I'm not really sure.

Well,

I'll start by saying thank you for having the guts to challenge the proprietary DAC chip. I can't figure out what is wrong with my 33E at all. It starts to make static in the left channel. I recently ordered a new KSS-213C which I believe is a drop in replacement for the KSS-213Q to try to fix the issue.

I ordered GE/JAN 5670 tubes and they sound much better than the original tubes. I also ungraded all the Poly caps with Dayton high tolerance caps. Almost all the ecaps to better brand ecaps. Mine sounds great in my opinion, but it has this intermittent static sound in the left channel. I think I'm going to "free" my DAC chip and pull that cover. I live in Texas so I can probably get a new DAC chip if I need one overnight  :wink:

What is wrong with the CD player you are working on?

Blair

One note to those thinking about attempting this. The block of filling that looks like silicone is actually epoxy, and has the poential to remove the DAC chip and resistors completely from the circuit as it did mine when I attempted this. It is okay for me because I think my issue with my player was related to my DAC chip, and I have a new one coming in a few days. I just thought I'd warn you guys before you attempt this. Oh, and the wires there are dead leads to hold the cover in place so you should remove the solder joint before removing the cover if this is desired.

Blair

Hi,

thats correct.

I didn`t know how the cover of MHZS has been fixed. So at first I have desoldered all solder joints under the cover and then pulled up carefully the cover. Use than a hot-air gun, but don`t blow too long on this epoxy, you will damage the parts around the epoxy. So: max. 20 seconds with 450 degree Centigrade and then carry up 2 Milimeters of this white mass.  Thats to repeat several times. You will need with the hot-air gun 2o - 3o minutes until it lookes like at my pix.

And the second: After turning off the machine some caps stay charged and don't discharge itself. I am going to shot some pix and post them in some minutes.

Now some tips for your health!

I measured high ( dangerous high ) voltage on cap No 1-please look at my photo. Also there is a high voltage on the connector No. 2. This connector is connected on the left side to No. 3 in my photo.

I took a resistor ( 150 kOhms and 2 Watts ) parallel to cap No.1 and soldered him under the PCB.

Next I do the same under the pins of No. 3, because its easier as to solder under the connector No.2. So you dont worry about the voltage coming out of connector No. 2.

Problem is that the wiring of the 2 Watt resistors is to think and goes not through the PCB. At No. 3 there have to be some small caps to clean the high frequencies, but MHZS or who else has economized this caps ( and the other 50 haw you see on your own board). You can use that solder joints to bring your resistor there.

The result is good. After turning off my voltage falls down to 1 Volt in some minutes.  

Hi Blair,

you wrote your CDP has this intermittent static sound in the left channel. Not easy to say something about it. Can you change the tubes again and write what has happened?

Sometimes I mod and mod and mod and after starting I must see the machine works not correctly. The best what I can do - if you believe it or not - is to go sleep and don't touch the machine again. ( You must know I mostly mod at late evening and night ).

Next day you think clearer about your work and then pull out the PCB and check all solder joints with a multimeter in all ways. Set up your multimeter on "Ohm", for messuring resistors. Often it has happened this: A line on PCB goes from point A to B to C to D. My soldering joints look very good, but the multimeter says A to B is OK, C to D is OK, too. The solder joints from B and C are only connected to their neighbour A und D, but not together! So a pod or a way on PCB at point B or D is broken. You will see it because the multimeter says Ohms=infinite.

Then I heat the solder again very carefully and meassure again. If the multimeter says again "infinite", you take a small wire and solder this points manually together. That looks not good but it helps.

After many mods in the last years I find out that there is another way to best caps without damaging the PCB. Look at my next pix. Now I am testing much caps and different combinations on the Headphone Amp Xiang Sheng 708b.

I soldered some hard wire without isolation an that pionts where I am not sure which value is the best and let the cabinet open. Then its easy and goes fast to change values and qualities of caps. Every day another value! :wink:

After two weeks I find out what sounds best and pull out the hard wires and everything what I have burned with the soldering iron. Then I calculate my budget and order the really good caps which should stay in.

Thats the way to find out what applies to your music style and your habits. And its economic. I am sure you have enough unused caps there! :wink:

And your result will be very very good, you will see.

Some posts before I wrote about bypassing ecaps by a resistor. Here are some pics for the same solution on the headphone amp. The only difference is that in CDP I soldered both sides together and in the amp not, because this big blue caps are not part of PSU, they are part of coupling between main PCB and headphone jack. So there is to cut one side after soldering.

When I put out the amp and want to work on it I push the contacts of the resistor and the cap together, but only with an isolated screwdriver!!! The discharging takes two minutes, the voltage falls from 80 V to 2 or 3 V. After last mod I will take this resistors out, of course.  

You go the same way in your CDP, I would recommend it.

Hello Kikko,

I am still waiting for a new DAC chip to come in. I should have it by Wednesday or so, but I have replaced almost all the caps with at least a better/lower ESR cap. I replaced all the signal caps with better DAYTON high tolerance caps. I replaced the OPAMP with a better opamp. I also ordered the KSS-213C which is supposed to be a drop in replacement for the KSS-213Q. It is going to be very difficult to resolder that DAC chip, but I'm going to give it my best. Here are a few of my other projects if you are interested.

http://www.villagephotos.com/pubbrowse.asp?folder_id=1535206

Thanks and I'll keep you guys informed if I get this fixed.


Blair

Now to the MHZS Mystery Chip 8)

In the description of the manufacturer TI the BB PCM1742KE needs two supplies: 3.3 V for Digital and 5 V for Analog Part. A possibility is to take the 3.3 V from the main 5 V supply.   I studied the PCB very carefully and find out thats the way MHZS has gone. BUT: TI recommends in his datasheet ( look here: http://focus.ti.com/lit/ds/symlink/pcm1742.pdf ) to give two separate voltages from two different PSUs to the chip. They write that would be very important to get a good sound quality later. I think I will do that and post the results.

On the other side you will see on your PCB that the cheap ecaps ( in post before ) sit between pin 7 and 8 ( analog signal ) and the OPA.

Now............ the missing small blue caps for high frequency eliminating (about 50!), the missing double PSU, the low quality electrolytics ( 4! ) and and and.........there is much air for new ideas

Now its time to look for new PSU caps. Havent forget them, but only the most important first

Hi Blair,

you picture gallery looks very nice!!    I haven`t webspace so I will post some pics here, two of my projects have been really hard but very good. But one thing is not to forget: My experience is that a good clock can make a CDP coming up from a minicar to a rocket!

Changing caps is sure necessary but changing clock is the best I ever have done. On the next pics you will see it on the example TEAC VRDS-20, my last project........4 month work................ :wink:

Hi Blair,

I  hope you have managed to solder the new DAC. How are the results?

If you have trouble with your pickup try it here, they have everything:

http://www.ersatzteil.justone-schnepel.de/index.html


Now to the pics......at first from the CDP which I used as transport.......

the Audiomeca Elixir DAC, a fine thing from Pierre Lurne. Good to see that there are not so much devices on the PCB as somebody would say, and the DAC is a Phillips, the DigFilter is a Crystal and the OP Amp from AnalogDevices. Interesting how few devices but such unbelievebable good sound.

The Denon DVD Player DVD 2800 Mk II

The second pic is the origin condition....you buy here a lot of free space for more than 1600 USD...... please ignore the advertising of silicon image......this pic is the only one I have found on the net.

oh....I am sorry, this is now the second pic from below .... the forum is sorting pics the other way around......


now the rest.........I think the Vincent ( is the German name, in other countries called SHENG YA ) is to colorless inside........here an original pic ( somewhere between the others, with the white beams ).....

The loudspeakers have been a DIY project from the german magazine Stereoplay.  :arrow:  http://www.stereoplay.de/stp/home

The order is again not correct.....Sorry :roll:  

I brought in some Mundorf caps and coils. As wiring I used Linn K20. Its OK for that price, because there are about 20 meters used for the speakers.

If you have questions feel free and ask

WOW,

Everything looks extremely nice =D>

I don;t have the funds to purchase anything that nice yet. Very nice looking speakers!

I did not get my DAC chip in yet yesterday. It should be here today or tomorrow. It is definitely going to be very difficult to solder. Any advice on this application?

Thanks,

Blair

Hi Blair,

thank you very much.  

Now I am looking at the little DAC. A real advice I dont have.  :?  So I take a look on the datasheet. Thats what I have found:

Storage temperature, Tstg –55°C to 150°C
Junction temperature, TJ 150°C
Lead temperature (soldering) 260°C, 5 s
Package temperature (IR reflow, peak) 235°C

So I wish you a quiet hand and luck, dont solder him too hot or too long. And please dont take too much solder, it will be difficult to remove it later if the circuit points glue together.

Later I will handle the lens. The task is to minimize the diffused light of the laser. Its the same procedure as on the TEAC and DENON. You have seen it on the pics? The border of the lens is to colour with black resistant paint. Thats usually the first I do by modding. I will make pics and post them with description. Do you want to do that too? Its independent from your DAC soldering, easy and has a real effect, not vodoo .  

Good luck,

Kiko

Hello Kikko,

You just paint a non reflective paint around the lens protion of the laser head? Looks easy enough. I'm really a bit scared of this DAC chip. It is going to be a pain to solder, but hopefully I can get it. That is a neat mod though. I'll try to take a few snapshots of my player when I get this DAC wired in.

Thanks for all the advice,

Blair

Hi Blair,

yes it is easy but please dont start it, I have some tips for you.

You need cotton swabs or Q-tips ( whats right now :? ) and pure alcohol. And an usually permanent marker.  This work daubts a little bit, so I can show you how it goes easily and fast. :wink:

Blair, dont give up. If you damage the chip, order a new one and go with him to a specialist. Can you tell me how much you payed for this chip? The only problem you can have is that you damage this fine wirings on your PCB. Then nobody could solder in a new chip.

As I have damaged my first PCB ( with the open cover ) a Hongkong dealer told me, both new full assembled PCBs for CD66 and airmail shipping to Europe will be 190 GBP plus customs tax. For your CD33 it would be nearly the same price.

So be carefull will it.  :wink:

Thanks Kiko,

I will definitely try to be careful with it. I paid less than $20 american dollars for two chips, plus I ordered a new laser assembly for 20 more dollars shipped to my door. So far, I only have about $220 USD invested in this so I am not too terribly upset about the project. I can see a Texas Instruments factory from my back yard though   I am really most worried about the alignment of the pads more than the solder part of this project. They did not give you much room for DIY. It is probably pretty intentional. I believe these chips are found in many smaller digital devices as well such as MP3 players and such, but it is supposed to be considered a good DAC chip. If I lift the traces a bit off the board, I have considered dierctly soldering small leads to the chip and casting it in epoxy to make it easier to work with. Sounds like a pain, but that seems to be the logical repair if I lift the traces.

Thanks and I'll keep the progress up to date,

Blair

OOOOOOPS, have forgotten somehing:

you must totally discharge yourself, the board and the soldering iron! This chip has a electrostatic sensivity.

So put in one resistor as I told before, meassure all pionts where are ecaps are, everything must be at 0 V. If you use a soldering iron with a transformer station you must discharge him with touching the top shortly with your shockproof socket ( on earth!!). And.....hmmmm......I discharge myself when I sit there ( after going about a carpet where your body charges everytime ) by touching the earth phase of my shockproof socket . But be carefull you can touch the hot wire. I hope you dont make this mistake! Or buy a bracelet for technicions, that a wire to the shockproof socket and you are so connected on earth the whole time you have it on. :wink:

HI Blair,

can you make a pic of that and post? If there is some epoxy an the leads, can you use a hot air gun and a screwdriver? The epoxy will be squashier then.

Kiko

Kiko,

I have not cast the chip yet. That is going to be a last resort. I did however just order one of these just in case I lift the traces.

http://protoboards.theshoppe.com/proto_chip_jr.html

It looks to be very helpful. We'll see soon   I do have a static bracelet also.

Blair

Blair,

looks very good what you have found there! And interesting how persistent you are!  8)

Do how have changed the both tubes before pulling up the dac?

Kiko,

Yes I have two sets of GE NOS 5670s. Both are new other than the production date. Both make the same static sound, and I checked all the solder joints. I like this hobby. It gives me something to do, and after this, I may never mod another player again but I can say I've done it. Trust me, I've changed everything on this unit besides the DAC chip and a few other control chips that are not in the signal path.

Thanks again,

Blair

Blair,

my position is the same, I like that too. But what I dont understand is why you will never mod again. Is it because your CDP makes this problems? After watching your pics I believe you are in your heart a DIYer and when you buy the next one, or an amp or anything else you will do it again.  :wink:

So I hope it is the DAC what makes this malfunction. What will you do if you change this chip and the intermittant static sound comes again? Where do you bought this CDP? Do they sell spareparts?

Kiko

So, now the work on the lens. I recommend to do that on all players, how you have seen above its a good thing for DVD Pl. too.

You need a permanent marker, some Q-tips and little bit of spirit ( ethyl alcohol ) and 10 minutes time.

You can pull up the cover so you can better paint 360 degree. Now hold that slide with 2 fingers. The slide is undetermined. Be careful not to break the slide. The mounting suspension is very softly. Paint the lens 3 or 4 times completely around, not only the border, but also not in the middle.

If you want to be sure that your painting is 360 degree around you dont need a strong illumination. You have a blue LED there. :

Make the Q-tip wet with ethyl alcohol, dry him a little bit and touch the lens from above, fix the Q-tip with two fingers and turn him on the upper side. Very easy......

Now polish the lens with the other side of the Q-tip. Play a CD. Print forward/backward on your player. Look a the rotation of the CD. Is everything OK you can put the cover back. Something not ok? Does the rotation behave strange? Than take a new Q-tip and make the clear flat of the lens a little bigger. The same procedure.

Dont worry if the CDP wants not to play, that is only a sign that the clear-transparent flat is too small. The CDP is not defective! That has happened here today, too. No problem.

So....the cover and the LED are to screw back. Thats all. Costs = 0. The result: More stability and the music is more flowing.

Try it and you will hear the difference  8)

[quote:2953a1cf51="Kiko"]Blair,

my position is the same, I like that too. But what I dont understand is why you will never mod again. Is it because your CDP makes this problems? After watching your pics I believe you are in your heart a DIYer and when you buy the next one, or an amp or anything else you will do it again.  :wink:

So I hope it is the DAC what makes this malfunction. What will you do if you change this chip and the intermittant static sound comes again? Where do you bought this CDP? Do they sell spareparts?

Kiko[/quote]

Nice mods! Very cool 8)

It is not that I will not DIY again, but I think I prefer amps and speakers. I bought this player form an individual for 150 USD shipped to my door so it is not a big expense. There are only 2 places in the US that retail these players and both are online stores. They do sell separates though. I am currently in the process of trying to start a US based DIY shop. Mostly tube amps and speakers though. We already own a domain, but are currently working with vendors and web designers on this. I'll keep you in th eloop as it goes along. Thanks for the great pictures again!

Blair

Hey Blair,

I like your idea. 8)  Very fine!

Sometimes I play with the same mind. Is there a homepage I can visit?

...deleted message

I emailed you. Let me know if you got it.

Thanks,

Blair

Yes I have got it. Thank you.

hey,

does anybody know good values for caupling caps for mhzs players?

thanks, kiko

Hi,

I have heard of marking the edge of a CD to reduce the reflection by the lens. I have marked one of mine many many years ago with a permanent marker as well.

People suggested using Green & Purple; I can't recall what is the reason behind. They said using different colors gives different results.

The Belafonte disc I mark does give a LITTLE difference. I think my set of equipment may be the constraint as this set is just a budget buy.

I have never tried marking the LENS!

Kiko, do you think you can give us a more "close up" look of the lens after marking?

Hi Alfcat,

marking the edge of a CD to reduce the reflection by the lens is correct, but the reflection happens on the edge of the CD and on the edge of the lens. Think about your camera, the objective is nontransparent, only the lens is transparent. I heard the lenses of laser pickups had to be build in the same way but the industry searches the cheapest way. The different colors have a reason. The pickup works with 650 nm laser. This is in infrared area.

So the modders try to find a way to absorb the light on the edge and because we cannot see infrared light everybody searches his own way of the best absorption. So some modders believe in purple, some in green. The modding scene has true differences here in Germany.

I have often heard of green as the right colour. You have seen I used black. Thats why I believe that black absorbs best. But if its true I cannot say. I tried that different time and had with black color the best performance. Of course if you believe something else would be better, try it.

Will you please post what you are doing? Will be interesting!

I will post the pics, hope they are better as the last one. They are the best my camera is able. On the last pic the lens seems to be complete black. It is of course not, it is a mistake of my cam!!

Greetings!

Hi KiKo,

I haven't got the chance to mark the lens yet. Instead, I discoverd that there are "BLACK" CDs here in Hong Kong. Never heard or seen one before. I think they incorporate the logic you mentioned.

A photo is attached below. The set of CD comes with two discs. The Black (They call it the Purple Crystal) CD and the normally Silvery CD. The contents are the same but the sound quality is indeed different. The Black one is far superior to the silver one.

Will try to blacken the lens later.

Cheers!

Alfcat,

WHERE DID YOUR GET THAT

Do they sell them in the US?

Thanks.

Blair

Blair,

I don't think these CDs are sold in the US nor Europe. Even my Hi Fi friends are NOT aware of their existence. I discovered them just by chance and so far, there are only TWO I know in existence. One is a female vocalist (shown here yesterday) and the other is a Chinese Orchestra (Drum + other Chinese musical instruments).

Follow this link:
http://modernaudio.hkcdnet.com/main/index.php?main_page=index&cPath=2&zenid=bd7a8f2fc56551100dc08eace4416c7b

The THIRD with the lady and purple background is the first one I mentioned above.

And this link:
http://modernaudio.hkcdnet.com/main/index.php?main_page=product_music_info&cPath=8&products_id=2&zenid=bd7a8f2fc56551100dc08eace4416c7b

Gives you the Chinese Orchestrial one.

You should note that they are NOT expensive at all. Just HK$ 60 & $ 90. Total equivalent to US$ 20 or so. Very worthy of buying.

I listened to both of them. The purple one is far superior to the silver one. My set of equipment is no good for complex performance like an orchestra but still I can more or less locate where the instruments are in the setting.

Unfortunately, I can't find the English Version of the website. The reason, I guess, is because most of the discs are in Chinese. It will be really hard for them to translate the titles and the information into English.

I am not sure whether the company will mail to US or Europe. You may try to drop them an email.

CAT

Hi Alfcat,

I know the black CDs. But I know them only for Playstation Games. The PS 2 uses them. Audio CDs in this form have never been sold here in EU.

Cheers!

Hi KiKo,

I don't think they are "Black". Perhaps I used the wrong term in my previous post. They are "URPLE". If you look at the reflection of the photo I posted last time you can see purple light bouncing back from the surface of the CD.

I lent them to a friend of mine for a close listening as his equipment are much better than mine. He also agreed that the purple one sounds much better, tho' he doesn't really like the lady singer way of singing, ha..ha..

It is said the purple CD has error level < 1/1000 mm and the way it is produced has great significance in reducing signal loss due to high spinning speed of the CD. The Purple CD is capable of "neutralizing" the defect of the red laser ... blah blah blah.

Anyway, it is a new toy for us ...  :

hi, Vash,

I also have CD-33.
please let me know the sony 213C is suitable for 213Q leaser head??

many thanks.

Hello,

I am not at a point where I need to replace my laser yet. I thought it may need replacing, but it was the DAC chip instead. I do have a spare 213c here, but will only install it if necessary. I'll let you know if I try it. The part was cheap enough $12.5 USD.

Blair

Dear KiKo,

In your first post in this thread I can see that you have TWO CD66 PCB sitting next to each other

Where did you get the extra PCB? I have ruined my CD 33 PCB (post in CD33 wrecked thread) and I need to consider getting a replacement PCB.

Can you provide me some information please.

CAT

Dear Cat,

I must say that has been a great problem. After I have broken the first CDP I buyed a second one. Now I pulled up everything on the PCB to see more and get more information.  

I asked different Ebay Dealers if I could bid on the same CDP and if I will be the winner they should put out the PCBs and the rest in the trash, because of saving the expensive shipping. They agreed all.

For the first CDP I payed 132 GBP shipping and import tax, for the replacement PCB about 15 or 18 GBP and no tax, because the PCBs have been marked as repair material.

Sorry that you have ruined your CD 33.

KiKo