What ps to dac you mean - Vcc or Vdd? And how come there can be any AC voltage? And if there is any , how to fix that?
Help help :CD CDP MHZS CD33E
Help help :CD CDP MHZS CD33E
I have a CD CDP MHZS CD33E with problem out analogic out signal.
The player work very well, but now only digit out is function.
Please have you che electric schema of the scheda with the dac o is sufficient the electric connection of the PCM 1742, that I control voltage and signal with oscilloscope.
Thank very much.
Giampietro
Treviso-Italy
Help help :CD CDP MHZS CD33E
I have a CD CDP MHZS CD33E with problem out analogic out signal.
The player work very well, but now only digit out is function.
Please have you che electric schema of the scheda with the dac o is sufficient the electric connection of the PCM 1742, that I control voltage and signal with oscilloscope.
Thank very much.
Giampietro
Treviso-Italy
Hello Giampietro,
i do not have found any schematic for the MHZS players. But i have modified and repaired a lot for the last years.
Most common options for failure,
- HV, Heater or opamp supply defect.
- Output mute relais defect.
- DAC defect.
What can you measure yourself?
In can help you to point out some measurepoints on photo's
Ronny
i do not have found any schematic for the MHZS players. But i have modified and repaired a lot for the last years.
Most common options for failure,
- HV, Heater or opamp supply defect.
- Output mute relais defect.
- DAC defect.
What can you measure yourself?
In can help you to point out some measurepoints on photo's
Ronny
possible repost MHZS mod?
Hi Koifarm, i am very new to the site and was wondering if you are able to repost this original mods post as the images no longer exist in the post. and are there any other essential mods you would recommend since posting the original thread? thanks
We buy the MHZS players on Ebay for € 200,- ( MHZS 33 ) til € 350,- ( MHZS 88) Incl.shipping and tax.
MHZS33
MHZS66
MHZS88
It is very popular in the Netherlands, Germany and China.
Below I will try to tell how we do the mod’s at a total cost of € 20,-.
We do the following mods:
1 – Remove the opamp and filter( it calls the passive mod)
2 – Bridge and replace capacitors in the audio path.
3 – Higher the anode voltage from 80 to 100V and replace the buffercapacitors.
It all takes a hour of work, and give you much more detail, bigger staging and it is like the curtain is falling down.
1- passive mod.
C11 and C12 must be bypassed on the other side of the board and a few other points must be short. See below.
Connect the yellow points with solder tin.
Then remove the 3k9 resistors and the opamp. See below.
These are the light blue parts. And ready is the the passive mod.
It is possible that the output signal is lower then before to correct that you have to replace two resistors a channel see below.
Replace the green 33K for 22k/1/4 Watt and replace the 68K for 82K/1 watt and the output signal is higher.
2- Brigde and replace the capacitors in the audio path
Replace C7 and C8( see first picture ) for PIO Capacitors of 0,27 uF or 0,33 uF. Good and cheap brands are Sprague Vitamine or Russian pio k40-2. Replace C13 and C14 ( output capacitors ) for PIO Russian 2 uF (2 x parallel 1 uF) or Neutral MKP between 2,2 uF and 10 uF like Clarity Caps APW. See below.
C11 and C12 we already bypassed in the passive mod. So we have just two capacitors a channel.
3 – Higher the anode voltage from 80 to 100V and replace the buffer capacitors.
Replace zenerdiode D1 for a 100V/min. 2 Watt type, Replace C1,C2, C3 for 220uF/160V ( Panasonic or so ). We also replace D2,D3,D4,D5 for scottky diode’s like BYW100/200.
On the other board you have to replace C4 for 220uF/160V.
This mod is only for the MHZS 33 and 66, the MHZS88 already has a higher anode voltage.
I hope this description is useful for you.
Ronny
Hi Koifarm, i am very new to the site and was wondering if you are able to repost this original mods post as the images no longer exist in the post. and are there any other essential mods you would recommend since posting the original thread? thanks
Hello everyone,
I bought a MHZS CD88H on eBay a few months ago at a nice price. However it since developed a No Disc error which does not allow it to play. My local audioshop is asking for schematics but neither the eBay vendor nor China HiFi does respond. Any chance of where can I get these, or better jet how to fix it? perhaps is a common defect of these units someone can help me with. Thanks.
I bought a MHZS CD88H on eBay a few months ago at a nice price. However it since developed a No Disc error which does not allow it to play. My local audioshop is asking for schematics but neither the eBay vendor nor China HiFi does respond. Any chance of where can I get these, or better jet how to fix it? perhaps is a common defect of these units someone can help me with. Thanks.
MHZS cd 88 E Modding with 12au7 tube
Hello everyone, to my immense amazement, i discovered that on board my 88E cd player there are two 12au7 instead of 12ax7 and strangely it sounds good the same. At this point I wondered if I could adapt the polarization resistors for the 12au7 and I think I should do the one in the attached photo.
Could some tube expert confirm that I am on the right track?
Thanks!
Hello everyone, to my immense amazement, i discovered that on board my 88E cd player there are two 12au7 instead of 12ax7 and strangely it sounds good the same. At this point I wondered if I could adapt the polarization resistors for the 12au7 and I think I should do the one in the attached photo.
Could some tube expert confirm that I am on the right track?
Thanks!
Attachments
Leave 470k as it is. The one to be adjusted is 1k.
Measure the voltage at upper end of 11k resistor and post it here. We could calculate the value of this resistor for you.
It is very low supply voltage for 12AU7/ECC82. You should consider to redesign the power supply to obtain higher supply voltage. It can be done easy. You should rebuild anode PSU following a picture below:
The gretz bridge is to be connected to the extreme leads of the transformer. Leave the middle lead not connected to anything (break its connection to the ground of the system).
R2 and R3 can be 1k/2W.
You should obtain about 220V supply voltage that way.
And you may use 47k/2W anode resistor and 560 ohm cathode resistor for 12AU7.
The gretz bridge is to be connected to the extreme leads of the transformer. Leave the middle lead not connected to anything (break its connection to the ground of the system).
R2 and R3 can be 1k/2W.
You should obtain about 220V supply voltage that way.
And you may use 47k/2W anode resistor and 560 ohm cathode resistor for 12AU7.
Attachments
These are my current ground test points with the 12au7.
Honestly converting the PSU is something I would rather not do as I love the tube PSU.
I would therefore be happy to change the polarization resistors by optimizing them for the 12au7.
Is there any expert who can help me?
Honestly converting the PSU is something I would rather not do as I love the tube PSU.
I would therefore be happy to change the polarization resistors by optimizing them for the 12au7.
Is there any expert who can help me?
Attachments
I am of the opposite opinion. I get great results with semiconductor power supplies for tube circuits, far better than with tube based power supplies.
In the case of MHZS, the key problem is the dramatically low supply voltage which practically makes impossible for 12AU7 tube to operate correct.
Insisting on the tube power supply at the expense of such a low supply voltage is a rotten compromise.
The most reasonable compromise for the MHZS is to achieve a much higher supply voltage at the expense of giving up the tube power supply. Such a compromise can provide much better sound quality than a desperate rescue of a tube power supply at the expense of an absurdly low supply voltage.
It makes no any sense if you insist on such low supply voltage for 12AU7 tube.
