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Marantz PM7200 lack of power?

M

mossieurclo

New Member
Allô everyone, thanks for this forum and your attention.

This Marantz PM7200 cuts out the sound on both channels for a half a second on transients, and recovers. Until the next transient.
It will do it as well on not very dynamic music with volume pushed, at the slightest peak.

It does that on any source. It does it running in class A. It does it with "source direct" selected (no bass/treble controls). With that tone board in function, cutting the bass lessens the problem.

So my first thought was: lack of power reserves, so, bad capacitors?

(Amp draining test tune: Schonherz & Scott "wishing well" on Windham Hill
) (oups, sorry for the splash there)

And it also does it on headphones (Sennheiser HD518, 50ohms), no speakers fed. Which is a big relief as it takes the lovable Elipson 1303 out of the equation.

No hum, no relay clicks when sound cuts, no thumps from speakers, no hiss, no distortion.

As for distortion, i hear a certain "granularity", but i usually evaluate sound quality wearing headphones, and that headphone test was done playing a .mp3 from a Samsung phone...

(((
(i moved the Marantz to the bench to sneak inside. Replaced it (only to hear the Linux Pc used to stream live Radio-Canada 'cause we can't afford the Cable/Satellite Scam) with given to me STK powered Pioneer VSX515. Please everyone use that as last resort. It's awfull...even without headphones)
)))

...so i don't rely on that. Add to that that i don't hear much above 10Khz.

As for relay clicks, i can hear a couple relays clicking on power up sequence, but the speaker relays clicks are very faint. Maybe these click when the sound cut happens and i don't hear them. Anyways the sound always resumes after .5second without cycling Power, until the next transient.

On speaker out (without speakers plugged, no input, Vol at Min) i measured -2mv DC on R, -20mv on L. Same in class A. I did not do the other measurement (quiescent current?) yet, i need probe clips for those hard to reach test points.

On visual inspection (no dismantling, though) i didn't see any burns, bad traces, or bulging or obviously leaking caps. I only saw 2 suspect electrolytic capacitors, with whitish powder nearby on the board or on top. #2203 and #2204 (470mF and 2002mF) on the Tone Board.

And i was surprised to see on the schematic (if i'm reading right) that AC (what voltage??) is fed to that ToneBoard, direct from the main transfo, going through 4 rectifier diodes and to those 2 caps. So i wonder if they can be involved (if bad) and how, as the sound cut happens even with that ToneBoard out of the signal path (source direct).

That fault developped and got worse with time. It was not there when i first used the amp (bought used, 2-3?? years ago). Which makes me hope that some weakness was already present whaen i first played it, for i immediately missed my precedent music companion HarmanKardon PM660. The Marantz lacked the "Ooumph" (what a nicely eloquent audiophile term ;-) ). I was even more sorry when i played a vinyl on it, but i now know i can correct that wrong capacitance on the input, thanx to knowledgable inhabitants of these forums (fora? fori? forae? pardon my poor Latin).

I should also mention that i seldom put the marantz on Standby, it was On 24/7 <slapping own fingers>.

I researched bad capacitors (i now know how to discharge before testing, for one thing) and sound cutting and related stuff for a week. Apart from surface mount, i can manage a soldering iron (i remember replacing diff pairs on the HK, the Marantz will be a joy to work in) and multimeter and basic safety measures (grrr, i need probe clips), so throw it at me ;-)

Sorry for the verbose precision, i think i told you all i observed.

And thank you all for your insights and help.

service manual:
https://www.hifiengine.com/hfe_downloads/index.php?marantz/marantz_pm7200_service.pdf
 
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I haven’t worked on that model but a similar one that came through seemed worthy of a look.

I discovered that they started to use fuse resistors in the Marantzs from that time period.

Fuse resistors are notorious for drifting off value. Terrible things. Search the service manual for them and if found, locate and test them.
 
As stated most of these amps will be riddled with dry/cracked joints by now, start there and see how you get on.
 
blhagstrom said:
Fuse resistors are notorious for drifting off value. Terrible things. Search the service manual for them and if found, locate and test them.
Click to expand...

Ah, another possibility...never thought of that...

How do i spot those fusible? Are they those resistors marked with the (!) safety symbol? Some resistors also have 1 or two lines drawn along their sides in the schematic, are they "special" too?

And what are those F, N, U annotations? different countries?

thanx
 
Thank you all for your suggestions (i'm open to more!).

As mentioned, i will get back to investigating once i fixed the plumbing here. 2x 25 feet lines in the basement's ceiling ii have to replace. And the cracked toilet bowl and leaking jet pump fittings decided to join the party 8-(((((
 
mossieurclo said:
Ah, another possibility...never thought of that...

How do i spot those fusible? Are they those resistors marked with the (!) safety symbol? Some resistors also have 1 or two lines drawn along their sides in the schematic, are they "special" too?

And what are those F, N, U annotations? different countries?

thanx
Click to expand...

They may have the safety symbol on the schematic but other critical fuses may have that symbol. If there is a parts list in the service manual, they may say FR type.

Worst case is to hunt down the things marked with the safety symbol and test them.

I can usually spot them once I know they are in there. The ones in the Marantz I fixed were slightly larger and a chalky grey color. One side was out and the fusistors were the problem.
 
I did some measurements, on the speaker protect board in place, exploring RS232 's (over on diyAudio, he had the same trouble) suggestion.

On the relay output of that speaker protect board, i read about 1V when there is sound. I was expecting 0V?, but 1V is below "must release" (1.3) of the MR62-24SR relay it drives.

When sound cuts i read about 4.5V on that line, with a digital multimeter that i guess is not fast enough to display the real value. The "analog" bar graph does go higher, to the 30 mark (30 V??).

And i now hear those relays click when sound cuts. Only that small red one (MR62-24SR) with earphones fed (or not) and speakers off, and those big VB24MBU as well when speaker selectors switches are on.

I read -10mv on the DC input line with no input, that value varies when music is playing (to the 5 mark on the bargraph).

So i'll be taking that board out and testing components later today.

It would be nice if someone could point me to the suspect, as i'm not good enough at reading schematics to see the guilty party. BTW, are those grey 1W resistors (3364, 3358) fusible?

Bic410 on HiFiEngine suggests cap 2278, i'll start there.

Please anyone enlighten me as to how it (cap 2278, bridging DC input to ground) could be the culprit: in my limited understanding of electronics, if that cap is short it will send everything to ground (and that poor 7289 transistor would be overworked?). Nothing would get to the dc sensing input of the chip, so no relay output. Right?

If it's open, DC and AC will get to that input. Is there AC on that DC line? If yes (i think so, as i see nothing blocking AC to those 2 transistors downstream of the oouput stage), would that AC "cheat" up the value of the DC sensed, so tripping the relay ?

It might be not the proper place here to educate me on basic electronics, so i won't mind if i stay intrigued ;-) and everyone's time will be better used to help others.

Thank you everyone for reading (and helping!).
 
Ok, the speaker protect board is fixed. No more sound cutting. Thank you Bic410 on HiFiEngine and RS232 on diyAudio

But there were 2 surprises:

Component 2285 is not on the schematic, but it's there on that board. Right next to and in line with cap 2278 (on PCB assembly drawing (p.20 of the PDF), it would be just above the "tz" of the word "Marantz"). Connecting DC input line (pin 2) of the chip, and ground.

That would put it in parallel with cap 2278, correct?

AND dear cap 2278 was misplaced 1 hole to left, both legs on ground. I was quite amazed. It makes me wonder where is part 2284 (2283 is on main board), and what other "customisation" there is in my amp ;-)

My digital multimeter could not measure (out of circuit) capacitance of cap 2278: the display was overrange, alternating between nano and microFarad. Strangely (to me in my inadequate experience), the DC voltage test gave a few mv, a lower value after shorting the cap, and the ohm test was normal (growing).

The surprise 2285, i thought it was a resistor (did not notice its number and symbol on the PCB, dummy me). It measured like an open resistor. And resistance was not going up as on a capacitor (film) that it is.

So i replaced both capacitors, putting the 2278 cap in its proper place. I used 20 years old NOS, 2278 capacitor not reformed but it did not heat up or explode ;-)

I had trouble deciphering the color bands taking up all the space on the ever so tiny film cap. I read: Red Black Orange Black Brown, so opted for 22nano because of the barely perceptible (almost imagined) gap between Black Brown. Does that make sense in that context? Or would the reverse reading 10nano be better?

And i wonder why would that film cap would be put in parallel to the 47microF 2278? The only thing i learned, google overdosing, would be to divert more high frequency "noise"??

Anyway, it works. Sound is steady, no cutouts. It worked with the the new 2278 and 200ohms resistor i put in before realising 2285 is a cap, it worked without the resistor and only the replaced 2278 cap, and it works with the replaced 2278 + the 47nano i put in for 2285. Which is the closest I had in my NOS stash (Mouser is far away), a Philips orange Chiclets thing (mica??), 10% 100V. Am I in trouble??

Thank you all for your suggestions, they all make sense and i took note of all of them.


(and for those googling "sound cuts out" or "speaker protection" or "bottoms out" or "transients" or..., the chip used here for speaker/overcurrent protection is TA7317p (but was not involved))
 
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(Disclaimer: I am BRANDNEW to the forum and not super versed when it comes to electronics ...I own a soldering iron and a level of common sense, but no experience with or knowledge of testing equipment multimeters etc...) THANK YOU for pointing me in a direction!!

HERE'S MY QUESTION/PROBLEM: I recently bought a '05 Marantz PM 7200 Integrated Amplifier that looks like new and had come from a very well maintained environment (hardly ever played, no excess etc). Setup: Connected to '02 KEF Coda 70 speakers and '77 Onkyo CP-700M turntable with Ortofon 2M Blue MM cartridge (which until now have all performed beautifully with my '02 NAD 322BEE integrated amplifier), I hear a clicking sound on and off (the sound goes in and out) and only the connection via earphones works without problem... For the very first half hour of listening to music the amplifier, sound etc worked without ANY issue, and only on the second day the clicking (like a relay clicking in and out) appeared.

Any pointers where to loo, how to approach and how to fix? Is this a potential issue with capacitors, or the relay or a fuse or something else?

Any older forum threads that I could go to for pointers? All help will be greatly appreciated, thanks a bunch!!
 
"I hear a clicking sound on and off (the sound goes in and out) and only the connection via earphones works without problem... For the very first half hour of listening to music the amplifier, sound etc worked without ANY issue, and only on the second day the clicking (like a relay clicking in and out) appeared."
Click to expand...

Your problem looks like what i went through: speaker protection board. Except that it should affect earphones as well.

First test: listen to music on earphones, but with speakers OFF, see if it still happens.

And check if you don't have a stray bit of wire between black and red speaker posts, at the amp AND at the speakers.

I'll send links to pertinent posts tomorrow (that you could find yourself ;-) )

And i will update this thread to where i'm now in my repairs....
 
rollandd:
I got great help there:
https://www.hifiengine.com/forum/marantz-pm7200-lack-of-power.shtml

and there, which is the sequel adventures:
https://www.hifiengine.com/forum/ma...dle-current-and-dc-offset.shtml#comment-25396

here, ambrosia heart makes a thorough analysis of the protection board, but has difficult to read english:
https://www.eevblog.com/forum/repair/marantz-pm7200-cant-adjust-bias-or-dc-offset/

And if you search for the exact title of my posts you'll find a couple other boards with pertinent ideas. You'll have to bear with my verbosity, but maybe many hints through all that.

And maybe you could reask your question on a new thread, this one here might be too old to attract readers (and answers ;-/).

Did you do the checks mentioned on my 1st reply to you? And of interest might be is the trouble happening on all sources? In ClassA? With source direct in function?
 
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