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Old 21st September 2011, 09:46 AM   #1
seebert is offline seebert  United States
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Default Meridian 207 Pro CD/Pre plays then ...

OK it's old but so am I Problem: CD plays perfectly for about 10-15 minutes then the sound starts to break up - goes from "fuzzy" to periodic bursts of "crackle-noise" then in another few minutes nothing. Preamp section still perfect and unaffected. Switch unit off and leave for an hour or so, switch back on and plays as new for 10 mins then .. uh huh .. repeat problem. There are zero service shops locally but given that it does play for a short while suggests to me with my very limited technical knowledge that it IS repairable: can anyone point me in the right direction please? I'm handy and will have a go as I cannot even locate any repair shop on the net who will work on it and I do still love this aged unit. Heck I'm old too but I'd like to think I'm not ready for the scrap heap just because I'm not the latest model. Any help from a tech would be greatly appreciated. Thanks.
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Old 21st September 2011, 12:50 PM   #2
josha is offline josha  United Kingdom
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Hi - it sounds like something's overheating. Can you get the lid off and just see if anythings generating excessive heat? Anything with a heatsink attached would be a good candidate, probably a voltage regulator. Don't actually touch anything in there but you should be able to feel with the back of your hand if anythings getting too hot.
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Old 21st September 2011, 07:16 PM   #3
seebert is offline seebert  United States
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Hi josha, thanks for getting back to me. I have had a look (just a look) inside and there's nothing obvious in terms of a burnt out R / C / or other component and I can't feel anything getting "way" too hot although I'm not a good judge of that - I have little feeling in my hands. I was thinking of trying a fine-tipped freezer spray on the more obvious heat generating components but then I saw a post (elsewhere) that said doing that could be harmful although I couldn't see why it should be. What do you think - try that or ???
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Old 21st September 2011, 07:46 PM   #4
josha is offline josha  United Kingdom
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Well, let's see. Assuming that's it's both channels that go and that it won't work if you turn it back on immediately then something overheating is (I think) the most likely explanation. The loss of sound could be down to two things, a component getting so hot it stops working (a voltage regulator most likely) or the heat having a mechanical effect somewhere on a components connection.

I can't put my finger on a service manual, a schematic or any internal photos so it's a really tricky thing to diagnose (unless someone else has had this problem).

Would it be possible to take a photo with the lid off? It may be necessary to check that the components are all still seated properly underneath, a bad solder joint could be the cause but it would likely get worse over time, is the unit lasting the same amount of time between failures?

I don't know anything about freezer spray I'm afraid!

Cheers, Josh
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Old 21st September 2011, 08:32 PM   #5
seebert is offline seebert  United States
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Hi Josh. Good to hear from the land of "The Last Of The Summer Wine" ... great series and set in a beautiful place. I lived in Ripon for two years - but a long time ago. Yorkshire people are great - they tell it like it is and I like that Sorry, I digress but wanted to let you know that I've been there and loved it.
I don't think Meridian ever produced a service manual for this unit, or if they did they certainly didn't tell anyone .. I can't find one anywhere. I'll certainly take a series of close-ups of the internals and post them (I know - pics are worth 1,000's of words usually) and hopefully keener eyes than mine might spot something "not quite right".
I cannot see anything obvious, but to answer a point you made - yes it happens on both channels BUT the left channel goes "out" a little before the right. It's not getting worse over time but maybe I haven't had the problem long enough to be sure of that. It's pretty consistent in having that 10-15 minute working-perfect window before the sound starts to disappear. It doesn't distort in the accepted sense of the word, more a breakup/spatter/burst of a small amount of information getting through to the amp, then the periods between burts gets longer but really all this takes just two to four minutes for the sound to go completely.
I saw a freezer spray being used in a repair shop by a tech to isolate a faulty component (I sure don't have his knowledge and it was a long time ago) but I recall him saying it was his standard procedure for certain audio equipment problems - the "frozen" component came briefly back to operational life and in a moment he'd isolated it. However I think it wise if I stick to posting pics for now - as I've said I'm just not that tech savvy
Thanks again and pics coming up very soon - hopefully later tonight.
My best, Mike.
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Old 22nd September 2011, 12:49 PM   #6
seebert is offline seebert  United States
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Well I haven't solved the problem but ....

I stripped the 207 down as far as I could (the transport is a b******) and couldn't find anything obvious - no signs of any overheating or fried components - but - playing CD's with the units out of the (tight box) casing works just fine !! I've had it playing continuously now for about six hours and not a single hiccup. It seems that some component or components plural are sitting "on the edge" of dying from old age and heat exhaustion but are okay if not in the Meridian extruded box-oven, at least for now and who knows for how long.

After listening for those hours I've decided to rebuild the two units and upgrade the internal components - new caps / resistors / zeners / etcetera and build an outboard PSU that has a bit of clout, again using top quality components. Is it worth it ... well to me it is and I'll enjoy the 'adventure' of finding out which components make a definite sonic difference for the better. Actually I'm looking forward to it now and that's without a drop of single malt tonight Looks like I've got my calendar filled now what with completely rebuilding / rehousing the Meridian and building my pair of Focal MTM floorstanding speakers.

Thanks again for your input Josh - it really was greatly appreciated that a fellow audio enthusiast chipped in to help. Oh yes, almost forgot - can you PLEASE send me a decent recipe for Yorkshire pudding !!!! Best regards and happy listening, Mike.
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Old 22nd September 2011, 04:51 PM   #7
josha is offline josha  United Kingdom
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Fantastic - I'm glad it's working! And what an opportunity to do some more DIY! For me it's always worth it and it always sounds better in the end ;o)

The only problem with being a Yorkshireman (apart from the weather) is my total inability to pay someone to do something I think I can do myself!

Keep us posted as the tweaks progress!

Cheers, Josh

PS - I'm told the secret to a good Yorkshire pudding is to always add an extra egg!
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Old 22nd September 2011, 11:08 PM   #8
seebert is offline seebert  United States
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Quote:
The only problem with being a Yorkshireman (apart from the weather) is my total inability to pay someone to do something I think I can do myself!
One of a Yorkshireman's most endearing qualities Josh - and two of the many others are directness and honesty - all to be admired !!

Lots of ideas are flashing in .. and I'll keep you (and DIY members) posted.

Best as always,

Mike.
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Old 23rd September 2011, 08:21 AM   #9
UV101 is offline UV101  England
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Hi, I've got a couple of these players. I got both with faults and fixed them. One of them I replaced the drawer motor and repaired the limit switch and the other had a corrupt eprom. I read the good eprom and used it program a new one.

Anyway, I'm quite familiar with this model now. In one of the players, I made the following mods with excellent results.

Main PSU caps replaced with higher value Panasonic FC on board and the 2 larger value caps swapped to Panasonic TSUP 22,000uF mounted on top of the transformer. The same type 22,000uF can used to replace the main pre reg smoothers on the transport PCB (although you need to drill the board to make them fit).

Given the age of the machine, I went for a complete recap of the elco's in the PSU and transport with the exception of the 33uf (?) on the transport. The type of cap used here is fussy.

Moving into the main control unit. On the bottom PCB again you can prelace the pre reg smoother with a 22,000uF TSUP if you drill the board. You also have the 7210(A chip) and 7220(B chip). Both of these (especially the B chip) will benifit from a very good quality low noise regulator and at least replace the local supply pin decoupling with something like rubycon ZA. Again I replaced all the elco's on this board. I fitted a better clock to the 7220 and also direct clocked the 7210 from the new master clock too (originally, the clock cascaded from thr 7220 to the 7210)

The top PCB contains the DAC (at the front) discrete output stage (next to it) PSU's on the fron left and the rest of the output stage behind it. The main bulk of the rear right, is the pre amp section. As I use the fixed out, i didn't change the pre sectin at all. I did replace all local decoupling on the 3 PSU line to the DAC and replace the supplys for this with low noise regs. I also replaced the DEM cap with a different value (details on the long tda1541 ultimate dac thread).

The DAC I/V and output stage is one of the best OEM TDA1541 output stages I have seen. if you follow the circuit from the transistors back, the 1st opamp is acting as a servo to null the DC. The output to the pre section is after final filter section just after the servo. The fixed output passes through another opamp before getting to the fixed output. I replaced the servo opamp with someting more audio friendly (although I doubt it made any difference as its not actually in the signal path so to speak) and I bypassed the final opamp buffer direct to the fixed output.

There is plenty to do in these players if you want. IMHO they are one of the finest sounding TDA1541 players ever produced and with a few tweeks, they start to be something very special.

One thing to note is that they do not contain an S2 chip as some of the lists on the internet suggest. There will be a heatsink glued to the top of the chip except for on the very early ones meaning you cant see the print. I've managed to get the sink off on both of mine and they are not S2. I think the fact that they are so well implimented may have lead to the suggestion that they are S2's???

Anyway enjoy, its a fine player
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Old 23rd September 2011, 09:54 AM   #10
seebert is offline seebert  United States
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UV101 - many thanks for your truly excellent and very useful information; you've given me a great head start with the Meridian project !! Like you I do believe that it is capable of being transformed into something very special.

Not wanting to damage anything and being new at all of this (even though I'm 69!) I'm pretty much having to pussy-foot around at this stage. What exactly is the procedure used to completely disassemble the player box puzzle??? It looks as if Meridian had access to 2" high miniature leprechaun-techs to go inside the extrusion and put it together!!

Quote:
Moving into the main control unit. On the bottom PCB again you can prelace the pre reg smoother with a 22,000uF TSUP if you drill the board. You also have the 7210(A chip) and 7220(B chip). Both of these (especially the B chip) will benifit from a very good quality low noise regulator and at least replace the local supply pin decoupling with something like rubycon ZA. Again I replaced all the elco's on this board. I fitted a better clock to the 7220 and also direct clocked the 7210 from the new master clock too (originally, the clock cascaded from thr 7220 to the 7210)
What did you use for the LN regulator to the 7210 and 7220? I'm still very much the novice here and I'd be grateful if you could give me details of how to fit a better clock to the 7220 and the method (or route) you used to direct clock the 7210 from the new master instead of the cascaded 'system' used originally. I could assume, but you know what they say about assumptions.

Quote:
I did replace all local decoupling on the 3 PSU line to the DAC and replace the supplys for this with low noise regs.
Could you please suggest the best LN reg to use here?

Quote:
One thing to note is that they do not contain an S2 chip as some of the lists on the internet suggest. There will be a heatsink glued to the top of the chip except for on the very early ones meaning you cant see the print. I've managed to get the sink off on both of mine and they are not S2. I think the fact that they are so well implimented may have lead to the suggestion that they are S2's???
Yes , I wondered what was under that glued on heatsink ... thanks for the 'real' info!! The Meridian board isn't too user friendly to an inexperienced 'audio-tech-wannabe' like myself: I start to wonder if they (Meridian) actually wanted to keep their circuitry to themselves

I was thinking of taking a quite radical approach to the rebuild: I'd like to get everything out of the extruded boxes that do look great but aren't (at least to my thinking) very component friendly in (over)heating terms and re-constructing the whole as a spread out unit on a custom made (please don't laugh too hard) compound steel/sorbo/steel sandwich base. My mental picture has each part (boards, player, completely new PSU) as a separate section in a new full size (19 inch x 'any' depth) case following good RF procedures: I have almost zero experience of building good audio gear but have built a lot of amateur radio gear where good shielding and good earthing practices were essential to stable operation. At this point the rebuild configuration is just at the 'mental image' stage and any comments would be very welcome.

Again, many (many) thanks for your invaluable input that is greatly appreciated. Mike.

Last edited by seebert; 23rd September 2011 at 10:22 AM.
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