Marantz PM68 tweak

luke2fr

Member
2013-02-15 8:20 pm
Paris
Hi everyone,

Those last week I've followed Ray's advice and started to read the CD53-57-63-67 to mod my cdp.
I'm putting my CD57 mod on hold for a little time. It sounds great (well a lot better than it used to), and I want to get used to it before modding it more. Got many CDs to listen and discover again. So far, most of the time, I'm quiet amazed.

I've started to read my amp's service manual ( you can get it here Free - Envoyez vos documents ) and I'd like to ask you a few (or many) questions about it.


Input section:
From what I understand, DC blocking caps aren't the best thing.
If DC coming out of my CD57 si low enough (how low is low enough as one would write ? ), would it be a good idea to remove them (CD input is my only concern for the moment) ?
Which one are the DC blocking caps ? On page 10, the schematic show many caps on the input. Are they 2601 and 2602 or 2613+3601 and 2614+3602 or all that ?


Power section :
I was thinking about addind a 250VAC/20mm. varistor (100-4357 @ farnell) directly on mains pins of IEC socket or on mains terminals on the PCB, but since I've read Brent's PM66ki tweek thread, I believe it's not really a good idea. What's you point on that ?

Can I swap the multiple 1N4003G diodes (6210 6211 6212 6213 6214 6215 6216) for schottky ? I've only found those one (1431066) at farnell which seems to have the good caracteristics, but they are 3 pins instead of two. (http://www.onsemi.com/pub_link/Collateral/MBR40250-D.PDF)

Since the amp is 13 year old now, changing all the caps would be a good move (also, in the other section) ? Should I keep the same capacities ? According to the schematics, do you think some should be upgraded ?
So far I've only checked the two biggest ones as it seems most improvement can be achieved with them. Original are 12000uf 63V. They are "for audio elna" ones. I didn't find them on farnell. They are (D x h ) 40mm x 70mm. But a height of 100mm would fit. How about 1166570 or 9348140 or 9347941 ? I also found some Mundorf M-Lytic AG 63V 22000µF and 15000µF on a french website. Which one would be a good choice ? Having read Brent's PM66ki thread, I wonder if 22000µF really is ok, or if I should stick to 15000µF (in rush issues seems to have occured to some). Any advice on this ?
I guess decoupling them would be a good idea too, am i right ? But what should I use for that ? I tried to guess from what has been done on the cdp, but I don't get the rule behind the choices made. Ray advised me "an MKT that's anywhere between 2.2 and 4.7uF"


tone and volume section :
About the opamps used there. Looks like they are not the best ones possible njm2068. May I change them for ad8620 ? Or is that a bad idea if other component around them aren't changed too ? I've also read LM4562 could be a good swap too, any opinion one this ?

Last question
I've read (yes, still the same thread) in Brent's PM66ki thread bypassing the tone and tape thing would help. Kimber 4TC is often mentionned for that : where can I find such cable ? Is there a good known alternative ?


That's all for now
Thanks for reading, and in advance for all you answers.
 

luke2fr

Member
2013-02-15 8:20 pm
Paris
some reading but not as much answers as hoped.

Anyway, I've changed the NJM2114D on the volume board for a LM4562.
I've also ordered the Mundorf M-Lytic AG 63V 22000µF caps.

Today, I've spent some time making this list


------
POWER
------
--------------------
page 13 & 26 in pdf
--------------------

part# | original value | new value | comment
6205 | GBU6D | please advise what ref if schottky can be used here
2205 | 12000µF 63V | 22000µF 63V | + bypass? what to use ? same cap but 4700µF ?
2206 | 12000µF 63V | 22000µF 63V | + bypass? what to use ? same cap but 4700µF ?



-------------------
CONTROL CIRCUIT II
-------------------
--------------------------------------------
Volume circuit board / page 23 & 28 in pdf
--------------------------------------------

2653 | 100pF 50V | PANASONIC - ECHU1H101GX5 - CONDENSATEUR 0805 0.1NF 50V Farnell 9695125
2654 | 100pF 50V | PANASONIC - ECHU1H101GX5 - CONDENSATEUR 0805 0.1NF 50V Farnell 9695125
2657 | 22pf 50V | LCR COMPONENTS - FSC 160V 22PF+/-1PF - CONDENSATEUR 22PF +/-1PF 160V OR MURATA - GRM1555C1H220JA01D - CONDENSATEUR CMS 22PF Farnell 9519971 or 2218849
2658 | 22pf 50V | LCR COMPONENTS - FSC 160V 22PF+/-1PF - CONDENSATEUR 22PF +/-1PF 160V OR MURATA - GRM1555C1H220JA01D - CONDENSATEUR CMS 22PF Farnell 9519971 or 2218849
2659 | 2.2nF Y5R | ?? what does Y5R mean ? Can i use the same as 2669 and 2670 ?
2660 | 2.2nF Y5R | ?? what does Y5R mean ? Can i use the same as 2669 and 2670 ?
2661 | 22µF 25V | RUBYCON - 25ZLG22MEFC5X7 - CONDENSATEUR 25V 22 UF Farnell 1281815
2662 | 22µF 25V | RUBYCON - 25ZLG22MEFC5X7 - CONDENSATEUR 25V 22 UF Farnell 1281815
2663 | 4.7nF 50V |PANASONIC - ECHU1H472GX5 - CONDENSATEUR 1206 4.7NF 50V Farnell 9695320
2664 | 4.7nf 50V | PANASONIC - ECHU1H472GX5 - CONDENSATEUR 1206 4.7NF 50V Farnell 9695320
2669 | 2.2µF 50V | PANASONIC - EEUFC1H2R2 - CAPACITOR, RADIAL, 50V, 2.2UF Farnell 1848456
2670 | 2.2µF 50V | PANASONIC - EEUFC1H2R2 - CAPACITOR, RADIAL, 50V, 2.2UF Farnell 1848456

those 2 are for the AOP reserve
2665 | 220µF 25V | RUBYCON - 25ZLG220MEFC8X11.5 - CONDENSATEUR 25V 220 UF + 100n PPS farnell 1281814 + 185-5059
2666 | 220µF 25V | RUBYCON - 25ZLG220MEFC8X11.5 - CONDENSATEUR 25V 220 UF + 100n pps farnell 1281814 + 185-5059

those 3 for the motor
2667 | 4.7µF 63V | NICHICON - UPW1J4R7MDD1TD - CAPACITOR ALUM ELEC, 4.7UF, 63V, 20%, RADIAL Farnell 1899885
2668 | 4.7µF 63V | NICHICON - UPW1J4R7MDD1TD - CAPACITOR ALUM ELEC, 4.7UF, 63V, 20%, RADIAL Farnell 1899885
2671 | 10nF 50V | MKT ? which ref ? or PANASONIC - ECHU1H103GX5 - CONDENSATEUR 1206 10NF 50V or WIMA - MKS2C021001A00JSSD - CONDENSATEUR 5% 0.01UF 63V farnell 9695362 or 1890129

7654 | NJM2114D | LM4562NA | already changed
7655 | NJM2114D | LM4562NA | already changed

-----------------------------------------
Tone circuit board / page 22 & 28 in pdf
-----------------------------------------

for the regs on tone board
2201 | 10nF 50V | MKT ? which ref ? or PANASONIC - ECHU1H103GX5 - CONDENSATEUR 1206 10NF 50V or WIMA - MKS2C021001A00JSSD - CONDENSATEUR 5% 0.01UF 63V farnell 9695362 or 1890129
2202 | 10nF 50V | MKT ? which ref ? or PANASONIC - ECHU1H103GX5 - CONDENSATEUR 1206 10NF 50V or WIMA - MKS2C021001A00JSSD - CONDENSATEUR 5% 0.01UF 63V farnell 9695362 or 1890129
2203 | 470µF 35V | PANASONIC - EEUFC1V471 - CAPACITOR, RADIAL, 35V, 470UF ( OR RUBYCON - 35ZLH470MEFC10X16 - CONDENSATEUR 470UF 35V ) farnell 1848452 (or 8126755)
2204 | 2200µF 35V | RUBYCON - 35ZLH2200MEFC16X25 - CONDENSATEUR 2200UF 35V OR PANASONIC - EEUFC1V222 - CONDENSATEUR 2200UF 35V farnell 8126704 or 9692347
2205 | 220µF 25V | RUBYCON - 25ZLG220MEFC8X11.5 - CONDENSATEUR 25V 220 UF + 100n PPS Farnell 1281814 + 185-5059
2206 | 220µF 25V | RUBYCON - 25ZLG220MEFC8X11.5 - CONDENSATEUR 25V 220 UF + 100n PPS Farnell 1281814 + 185-5059
2209 | 470µF 35V | PANASONIC - EEUFC1V471 - CAPACITOR, RADIAL, 35V, 470UF ( OR RUBYCON - 35ZLH470MEFC10X16 - CONDENSATEUR 470UF 35V ) farnell 1848452 (or 8126755)

motor
2207 | 470µF 35V | PANASONIC - EEUFC1V471 - CAPACITOR, RADIAL, 35V, 470UF ( OR RUBYCON - 35ZLH470MEFC10X16 - CONDENSATEUR 470UF 35V ) farnell 1848452 (or 8126755)
2210 | 470µF 35V | PANASONIC - EEUFC1V471 - CAPACITOR, RADIAL, 35V, 470UF ( OR RUBYCON - 35ZLH470MEFC10X16 - CONDENSATEUR 470UF 35V ) farnell 1848452 (or 8126755)
2208 | 220µF 63V | RUBYCON - 63ZL220MEFC10X23 - CONDENSATEUR 63V 220 UF Farnell 1281839

6201 | 1N4003G | VISHAY FORMERLY I.R. - VS-11DQ10 - DIODE SCHOTTKY 1.1A 100V Farnell 364472
6202 | 1N4003G | VISHAY FORMERLY I.R. - VS-11DQ10 - DIODE SCHOTTKY 1.1A 100V Farnell 364472
6203 | 1N4003G | VISHAY FORMERLY I.R. - VS-11DQ10 - DIODE SCHOTTKY 1.1A 100V Farnell 364472
6204 | 1N4003G | VISHAY FORMERLY I.R. - VS-11DQ10 - DIODE SCHOTTKY 1.1A 100V Farnell 364472

7201 | L7915CV | Raygulators ?
7202 | MCT7815CT | Raygulators ?



To deactivate treble & bass & balance control
EITHER THAT (easy option)
1)
signal input
2501 | 22u 50V | REMOVE
2502 | 22u 50V | REMOVE
signal output
3526 | 220R | REMOVE
3525 | 220R | REMOVE
2520 | 4.7n | REMOVE
2519 | 4.7n | REMOVE

OR THAT (best option)
2)
add 4 coax (what ref ?) from volume board near 1652 get RG R L LG and go to RG R L LG near 1251 on main board. Then remove 1506 which is now useless.


AND in both cases but ONLY IF one of the above as been done
3)
to isolate +/-15V from treble & bass control aop
3514 | 47R | REMOVE
3513 | 47R | REMOVE
to isolate +/-15V from balance control aop
3524 | 47R | REMOVE
3523 | 47R | REMOVE
 
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Can't read such long list of numbers. No need to replace everything.

I've modded several PM68's with good result.
Don't use schottky to replace GBU6D. Use 6-8A ultrafast diodes, soft recovery type recommended. No need of any heatsink, unless your amp is PM78.
If you use good ultrafast soft recoverys it's impact on sound will be very significant (more dynamic, more speed on bass).

[IMGDEAD]https://www.audiostereo.pl/index.php?app=core&module=attach&section=attach&attach_rel_module=post&attach_id=45178[/IMGDEAD]
Most of effort needs a "volume" board. An opamp needs to be replaced, it's wise to solder a socket and try several different ones (LM6172 is fine, but sometimes it oscillates, safe choice will be OP275 or OPA2132, 2134). 2,2uF lytic Elna Cerafine replace by same value finest quality foil cap, Mundorf EVO alu oil will be excellent. 22uF Elna Cerafine replace by same value finest guality foil capacitor, and again Mundorf Evo aluminium oil will be excellent.

There is a pair of 47uF lytics in signal path on input at the power amp board, it is essential to replace them by good quality foil capacitors. And again Mundorf Evo alu oil is my recommendation.
One can replace also a bunch of capacitors and diodes in diverse places, but IMHO it's impact on sound is marginal and no use to doing it.
 

luke2fr

Member
2013-02-15 8:20 pm
Paris
Thanks for you answer !

Can't read such long list of numbers. No need to replace everything.
I thought, as the amp is old, most lytics would need to be change. Well, those in the signal path or in the power section.

I've modded several PM68's with good result.
Don't use schottky to replace GBU6D. Use 6-8A ultrafast diodes, soft recovery type recommended. No need of any heatsink, unless your amp is PM78.
If you use good ultrafast soft recoverys it's impact on sound will be very significant (more dynamic, more speed on bass).
I have a stock PM68.
I'm a newbie here, could you please give me a ref (at farnell at best, or anywhere else) for those diodes ?

Most of effort needs a "volume" board. An opamp needs to be replaced, it's wise to solder a socket and try several different ones (LM6172 is fine, but sometimes it oscillates, safe choice will be OP275 or OPA2132, 2134). 2,2uF lytic Elna Cerafine replace by same value finest quality foil cap, Mundorf EVO alu oil will be excellent. 22uF Elna Cerafine replace by same value finest guality foil capacitor, and again Mundorf Evo aluminium oil will be excellent.
I already put a socket on my volume board, and fitted a LM4562 as TI gladly sent me some free samples :)

Are the Mundorf Evo alu oil those ones Mundorf Mcap Evo Oil - Audiophonics - Câbles, Amplificateurs et Accessoires DIY ? If so, is there a version < 450V : they are quite big !

are the 2.2µF 2669 & 2670 ?
are the 22µF 2661 & 2662 ?

There is a pair of 47uF lytics in signal path on input at the power amp board, it is essential to replace them by good quality foil capacitors. And again Mundorf Evo alu oil is my recommendation.
One can replace also a bunch of capacitors and diodes in diverse places, but IMHO it's impact on sound is marginal and no use to doing it.
Are those 2251 and 2252 on the main circuit (page 19 of the pdf or 23 in the real manual) ?

PS: there's a link to the pdf in my first post.
 
Thanks.
Unfortunately, RS seems to be the only one to sell them in europe, and they don't sell to particular, only professional :/ Got to find a way to place an order with them, they have some toroidal tx too i'd like to get from them. Or if anyone as some for sale or can help me order there as a middle man, contact me please !
 
Shame on me : I noticed a bit later after my last post here, that RS has both a professional and a home user website. And I also made a request sample to Vishay for those Hexfred diodes.
Pics and anyother ref are still welcome McGyver.
I also had a look at your website. I was happy to find your section about the pm68, but none of the pics shows up, and google translation is not very good :p
 
I've changed the main power caps, and bypassed them. Well, at first, I thought that. Powered it up, and saw sparks on the regs' legs (no smoke or bad smell). Both on the tone board, and the main board.
I did try a few times. Then I had a thought what could be wrong. Suddendly I remembered what I ve done. The bypass caps were not in parallel but in serie with the main caps :/
I've changed that, powered it up again. Everything seems fine, but I got no sound at all :/
May have I fried the various Regs on the board ?

Looks like it's time to start modding the spare amp I had in case such thing happens.
 
pb fixed.
I swapped the main pcb (too lazy too check if the 4 regs are the only broken part), and swapped the two regs on the tone board.

But I have another issue now. The main power switch, don't want to stay on the "ON" position. It always comes back to "OFF". Had to put some tape so it stays "ON".
Anyone experienced this ? The switch seems to be similar to the one in some other marantz gear.
 
Really ? Because both stopped working today. I didn't wrote it earlier, but as the switch stopped working after I changed the big caps on power pcb, I thought I should use the power pcb from my spare amp. So I changed the big caps on the power pcb of 2nd amp (correctly this time :p ) and when everything was assembled, I noticed the switch having the same bad behaviour. I'm now wondering if it could be something else that make it stay on position once every two push on it.

Both switch were working fine before the cap upgrade.

Also, I've found the part number for this switch, 482227612924 made by philips, but I can't find it online. Any advise to get one ?
 
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Hi Curiosogti,

Well, that's a new idea.
But I guess the opamp on the volume board is here for a reason, and would be happy to know which one(s). Would the signal be in the correct voltage range if sent directly after the volume pot to the power amp ?


Back to my WIP :
I've changed the two 47µF lytics (2251 &2252) on my power amp 5-6 month ago.
I've also ordered the two other set of lytics McGyver suggested, 2.2µF (2669 & 2670) and 22µF (2661 & 2662) a few days ago.
All of those being Mundorf Evo/oil.
I hope I'll be able to spot a (positive) difference, as the first mod were not that obvious. On the other hand, I have better speakers now, so it may be easier to notice anything that could be.
 
the 2.2µF (2669 & 2670) are now in place. They are bigger than the replaced ones, but it was easy to fit them.

The 22µF (2661 & 2662) are still out of the amp. I'm struggling to find how to make them fit inside, as they are big, and there's not much room, unless I put them far away from their mounting holes.

Would I lose the benefit of using them if I have to add 5cm on each wire to be able to mount them ?

Otherwise, I think I'll remove everything I dont use on the balance board to free some space, since I've already forced the use of direct source.

McGyver, if you read that, I'll be very happy to see some pics of your previous mod.