EQUIPMENT HISTORY:
Everything I am describing below is IMPORTANT, read it please!
This amplifier is part of my "collection" of all things audio, both professional and consumer gear. Marantz gear is often considered "not too bad" build and sound quality but this particular unit was a "to be looked at" as was NOT WORKING CORRECTLY when I last looked at it about 7 years ago! - see the FULL details below.
I have over the years collected together a LOT of quality audio equipment due to my business activities in pro audio post production and general electronics but the day of reckoning has finally arrived!
Well, my wife says "for goodness sake, get rid of that mountain of gear" so them's my orders ... out they all go.
Because this equipment does have issues, and it is extremely important that the complete description is read in full.
THE CONDITION OF THIS EQUIPMENT IS CLEARLY STATED BELOW, BOTH COSMETICALLY AND ELECTRICALLY
There is no warranty, there are no returns - but I am very thorough and do not "gloss over" any issues I might discover in my evaluation!
Always keep in mind, even if the new owner doesn't feel up to servicing, or restoring this equipment, it's is still a great source of some very hard to find parts - what I call a "component farm".
MARANTZ Stereo Amplifier
Model: PM-500 DC Series Console
Designed in USA
Built in Japan
Multi-voltage version - currently set to Australia 240V AC input
NOTE: Marantz used an annoying input socket, rectangular 2 flat pins!
Market release around 1980
Weight: 13Kg unpacked, 15Kg packed
Dimensions: 416mm x 146mm x 330mm
BASIC TECHNICAL SPECIFICATIONS:
50W per channel RMS into 8 Ohms
80W per channel RMS into 4 Ohms
Frequency response (+/- 0.25dB points!) 10Hz to 60Khz - the frequency response is extremely flat
Total Harmonic Distortion (THD) 0.03% at full rated output into 8 Ohms with this rising to 0.06% when driving a 4 Ohm load at full output
Damping 110
Input sensitivity - Phono (1.8mV) Line (21mV)
Signal/Noise ratio - 93dB (Line) 88dB (Phono)
5 band Equaliser built in, centre frequencies 50Hz, 200Hz, 800Hz, 3.2Khz, 12.8Khz
EQ Defeat front panel switch
Low Frequency Filter ON-OFF (to cut Lo-end noise such as from a poorly performing turntable)
Loudness ON-OFF (Lo-end boost)
Mono ON-OFF
Headphones output
Built in red LED two channel horizontal bargraph Power Amplifier output display, showing Watts RMS into either 8 Ohm or 4 Ohm loudspeaker loads
REAR PANEL CONNECTIONS:
Phono - 2x inputs (MM only)
You can run two turntables through this amp
Aux or Tape
Tape connections are available using either standard RCA or DIN 5 pin
Tuner input - line level
This power amplifier was built with tape machines in mind, two outputs (switchable) for tape machines (reel to reel or cassette) on either RCA sockets or DIN standard 5 pin at the rear
Dual speaker output connections (called SYSTEM 1 & SYSTEM 2)
COSMETIC CONDITION:
Wow factor is 7/10
Thick sheet aluminium front panel with heavy screen printed labelling. Case is folded steel with the top U section easily removeable and the underneath plate also easily removeable.
For servicing, great layout with easy to access and understand layout.
The case is straight and true, no dropping has occurred (although it is quite heavy, carry with care!)
NO significant scratching to the sides, front or rear panels.
Front panel controls are complete, no knobs or switches are missing. These are solid aluminium knobs with a plastic insert to grip the fluted shafts.
The push buttons though are that dreadful metalised plastic, these always show some corrosion (greenish colour) after many years and even though I tried to clean them up, you can see the blemishes still.
All EQ knobs are present and the power output display area is clean and easily readable
Rear panel connections are ALL clean and shiny although the top most 2 rows of RCA connectors (all to do with tape connections) show some underlying corrosion.
The lower "main" connections are much cleaner and provide very good electrical connection.
Speaker connectors are spring loaded type, large diameter for fat speaker cables.
TESTING (This is what it is really all about ....)
First up, the visual inspection...
I did notice when looking inside and taking a few measurements that there are signs of OLD water penetration near the rear panel or the amplifier has been in an environment with high humidity. I am talking about the rear of the unit, particularly the top removal cover and a little on one side. This is not serious but does indicate that something happened back in the past some time ago.
In summary regarding this rust issue, the PM-500 looks very nice and it is only with closer inspection that you can see some surface rust showing its ugly head near the rear panel (top) and that is about it. The rust does not rear it's ugly head externally, the black coating of the top section does not show the rust.
Please see the photograph of the inside top cover so you can see what I am talking about.
A close inspection of the PCB's (upper and lower) show NO damage to any component or the tracks/laquer coating. It was a bit dusty so I have extensively (but not completely) cleaned the boards so I can check properly for any signs of trouble.
NO mods have been made however it is clear that sometime in the relatively distance past, both sets of output transistors (2SC2681/2SA1141 NEC) have been replaced. If ever these required further servicing/replacement in the future, they are currently readily available onine for around A$15/pair. The service work has been done to a high standard, it looks good and the only clue really was the "fresher" looking white silicon grease and resoldered pads on the board. I have had this amplifier since the early 2000's and this work was definitely undertaken prior to my purchase of it.
I can see no signs of any other soldering work inside this amplifier.
All capacitors, particularly the large electrolytics in the main supply filtering have no bulging or leakage apparent.
All electrolytics are ELNA
TIME TO POWER UP ... (using a custom cable I had to make for the power input - this lead will NOT be supplied but I have on order correct leads, due in around 7 days)
I WILL SUPPLY A CORRECT AC POWER LEAD (Marantz 2 pin rectangular connector one end and Australian 2 pin plug the other) with this equipment but ONLY when I receive the leads I have ordered!
Power ON red LED indicates (above the power switch)
Power output meters "flick" across to the right then back to zero, waiting for signal
Protection relay operates as normal after 1 ~ 2 seconds.
Prior to connecting my precious Vifa loudspeakers, I checked both outputs for the dreaded DC voltage being present, none at all thank goodness! Never ever should you see DC voltages at your amplifier speaker outputs because if you connect your prized speakers to such an amplifier, your speaker voice coils suddenly turn into little heaters and then go POOF! This is something you must prevent at all costs - ALWAYS check an unknown amplifier for DC at the speaker outputs before connecting your speakers.
No issues at all on either channel (no AC or DC of any significance), I connected my 8 Ohm test loudspeaker system.
I then wound up the volume to "8" the maximum level with NO audio inputs, listening very closely for background hum. Nothing of any significance heard so this indicates that at least the main filter caps/power supply is doing its job filtering the DC main rail.
I then wound back the volume (important!), switched to AUX, TUNER and TAPE inputs successively and was greeted with wonderful "Marantz sound" remember their marketing slogan was "We Sound Better" - so nice and clean, NO distortion and plenty of grunt! I wound up the system level and no signs of any problems at all.
While playing the source music, I checked the operation of the various conrols such as Balance, Volume, Loudness and of course the central EQ system (which can be easily disabled) etc
The power output meters work a treat, pretty cool in fact!
ISSUE 1: If I had any comment at all it is that the Balance control has some very low level noise as it is rotated. It is tucked away behind the front panel and not easy to access without taking the amplifier apart so i have left it alone but a good "squirt" of aerosol pot/switch cleaner will most likely solve this - from what I can see, the pot is NOT a sealed type.
I have had the amplifier running for the last 12 hours or so at various levels and there IS another issue!
ISSUE 2: A good burn in does wonders! Yes, there is a more sinister issue at play here.
After running for a while, the protection relay drops out. Then after a very short time, it activates once again and this cycle repeats although somewhat randomly. It makes no difference if only the left or right channel is being driven or even with no speakers connected at all!
This power amplifer needs the bias settings and/or DC offset voltages checked and most likely adjusted. Now this could be as simple as a dirty trimpot track (wouldn't be surprised at this one), dry joint or more something more involved and this is when you will need to call in your technical skills. This type of fault is not for the inexperienced! Don't take technical advice from most online "audio forums" many are "numb-nuts" - I have seen utterly stupid comments on some forums that with issues like this, the relay is faulty! That is EXTREMELY unlikely, the relay has turned off to protect the loudspeakers and it does not do that "just for fun" i.e the relay turns off because the protection circuit "sees" a problem around the output.
I do have two versions of the PM-500 Service Manual and one does have very good instructions for both measuring and adjusting the bias/DC offset on each channel. I will be supplying both copies (pdf format) if you should need them.
As outlined above, my wife says "no messing around" get rid of that equipment so I will not spend any more time on this equipment, it is now up to a new owner to take on the task of getting the power amplifier running properly.
Oh by the way, I couldn't help myself so while checking out this protection relay issue, I did measure both main supply rails (measuring 45V + & -) so all is sweet here!
SUMMARY:
This grand old Marantz is looking pretty fine and dandy, EXCEPT for the protection relay issue which of course means the audio keeps stopping and starting!
A nice amplifier if you have the skills to tackle the issues or have a friend who can help you out! I noticed the asking price for these PM-500 amplifiers is currently anywhere between A$500 and over A$1100!!! so it would be a worthwhile project even if just from a financial point of view
Keep in mind that I am using a custom AC power lead for my testing which will not be supplied but I will supply a "proper" Australian power lead once my order for these has arrived. Of course if you already have one of these power leads to suit this Marantz (lucky you!) then I will supply the amplifier immediately - it is up to the buyer to decide about this.
I do offer FREE shipping around Australia for this Marantz PM-500 or if you wish to pickup, a lower asking price will apply (saves me safely packing and of course shipping)
