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Checking MDAC caps

Thank you all so much - especially flatpopely for your kind offer. Turns out I'm very close to toprepairman from these shores, so will contact him first.

What a great place pfm is!
 
misterdog said:
The Caps on the main board look fine though, they are the PITA.

If you want a good increase in SQ. do away with the power board and feed the mainboard with 5 rails of clean DC.
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I agree, that they look ok, the problem with MDAC capacitors was the smaller electrolytics not the big ones. I had to replace mine, it was so bad the sound was distorting, but it's a horrible job and I had access to a metcal desoldering station and I wouldn't recommend you do it unless you have to.
 
hc25036 said:
In the Audio room I've been told that AIG will service for £48 plus parts,

Rick
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Be interesting to know how many of the mainboard capacitors they would change for that price !

I contacted them via email about something and am still waiting for a reply 2 years later.
 
misterdog said:
The Caps on the main board look fine though, they are the PITA.

If you want a good increase in SQ. do away with the power board and feed the mainboard with 5 rails of clean DC.
Click to expand...

On my M-DAC:
Tweak of the internal stabilizers digital DC, with a conventional power supply, much more increases the SQ than 5 rails clean DC.

Replacement of all Lelon OCRZ series capacitors in digital DC is not effective.
 
Robert said:
Wow, pretty bad that something this old needs recapping so soon.

Shoddy TBH.
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Should have been built with proper components and sold for £ 3/4 K.

9949490.jpeg
 
misterdog said:
Could you give us some more details please. ?
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My M-DAC:

The oscilloscope showed the instability of the digital DC (U5 /1V2DC, 3V3D) ESS9018, which depended on the presence of the input signal and the selected input. Replacement of all Lelon OCRZ series capacitors in digital DC is not effective.

IMXO, for perfectionist reasons, you can replace the capacitors of the OCRZ series. In addition to digital, they shunt the audio part of the ESS9018
Capacitors of this type are very effective on the HF range, but are much less effective on the LF (sound) range.

Datasheet. Ripple current (RC)
Lelon OCRZ series - RC(120Hz) = 0.05 RC (100kHz). And RC(20Hz) = 0.0?? RC(100kHz).
FPCAP Nichicon capacitors are 2 times more efficient in this parameter. RC (120Hz) = 0.1 RC (100kHz).
For example: Panasonic FC series, RC (60Hz) = 0,55-0,8 RC (100 kHz).

Tweak's internal DC digital stabilizers solved this problem.

This is just my experience. It is not a recommendation for repetition. Not responsible for any consequences.

All signs from the M-DAC service manual.
- Replaced the U5 NE5532D with AD8066, the most suitable one that was at hand.
- Changed the output voltage monitoring points.
- Radically reduced the values of resistors R319, R321 (the values may depend on the selected chip). Oscilloscope stability chip control is mandatory.
- I installed additional shunt capacitors directly on the chips of the stabilizers.

External power 5 rails clean DC can not solve this problem.

Best Regards
 
Quick update - IAG replied to my email with an offer to replace 'leaking' caps foc save for carriage. I've asked for clarification about 'bulging' caps and will update as we go.

Otherwise, servicing is £48 per hour plus parts....
 
Many thanks for the updates, please us posted Re - the IAG situation, many here are having trouble.

I think maybe your upgrades are a little advanced for my level but good to know anyway.

Have you been able to a direct comparison of your upgraded dac with a stock version ?
 
Now SQ upgraded M-DAC is confidently better than a stock version.

Several big PSU, Audio and a lot of small tweaks were made. This is a very laborious work.

Therefore, I understand the reasons and stages of the evolution of the JohnW Project.

It is easier and more correct to make a new one than to improve the old one.

Best Regards
 
After this, one of the first stages of tweaks, the DAC became noticeably better than stock:

- Replacement of all RXY Lelon cap's;

In Audio replacement of :

- 24 cap's 4700uF 16V with Panasonic FK;
- all MELF with Dale resistors. (Here's the next stage) Top wiev.
https://www.dropbox.com/s/260lhgg6n44vg45/Dale_Mica top MB audio.JPG?dl=0
- some more changes, which were subsequently modified;

In PSU Board, a little bit more:
External power 5 rails clean DC is a very good and correct engineering solution.
But, after tweaks, because of the lack of advantage in SQ (IMHO), and for other reasons, I use a regular PSU.

- replacement 5 Lelon capacitors on the Panasonic FC (my preferences and on the totality of the characteristics) such as http://uk.farnell.com/panasonic-ele...c1e472/cap-alu-elec-4700uf-25v-rad/dp/9692231 ? MER = sy-me-pd-mi-alte.

- replaced all rectifying diodes S2J on diode Schottky. Digital PSU diodes are located between C4 and C5.

IMHO. A noticeable increase in SQ is due to Schottky diodes.

Due to the increased rectified voltage, the heating of the radiators U58, U59, U61, U62 and especially U60 (Digital PSU stabilizer) will slightly increase. Therefore, it is better not to put on the M-DAC other devices that make ventilation difficult
 
Quick update - IAG asked for photos which I provided but I've had no reply (my caps are bulging rather than leaking).

I've snagged a Beresford Caiman as a temporary replacement from legolas in the classifieds so will send the MDAC off to IAG to see what they will do. Next update probably in a month or so!
 
i just bought a 2nd MDAC from a friend who has had it for several years. Opened it up and not a single bulging or leaking cap to be seen so it's not every unit which has a problem.
 
hc25036 said:
Quick update - IAG asked for photos which I provided but I've had no reply (my caps are bulging rather than leaking).

I've snagged a Beresford Caiman as a temporary replacement from legolas in the classifieds so will send the MDAC off to IAG to see what they will do. Next update probably in a month or so!
Click to expand...

I replaced all the 'faulty' ones in mine 6 months ago but since then a few more have become swollen.

If IAG only replace the ones that are currently showing signs of fatigue then the rest may follow suit later.

Are IAG only allowing one free of charge repair per unit ?

Mine was one of the 1st production batches, a friend has a pre production unit which has no signs of failure.
 
Another quick update as requested - MDAC was delivered to IAG 2 weeks ago and there's been no confirmation of receipt, estimate or comment regarding the repair.

I've also had no reply to my email regarding whether 'bulging' caps came under their free replacement policy.

Luckily, patience is my middle name...
 
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