EQUIPMENT HISTORY:
This MARANTZ PM 630 Preamplifier - Power Amplifier has issues as it has been sitting in the spare room with a label reading "sorta nice, but needs a look at"
While my wife has an eye for "the arts" in all it's forms, she is not so keen on all the electronic gear that I used to acquire for later investigation ... my wife now says (after it having been in the spare room for 15 odd years) "for goodness sake, get rid of that mountain of gear" so them's my orders ... out goes all the equipment, some working fine and others are sick or dead!
I will give a pretty comprehensive description of this PM630 but I can tell you straight up, she is a "dead one"
If you are looking for a nice Marantz you can plug in and play your music through, move right along as this amp will not satisfy you.
If however you are the type of person who likes to restore gear or even use non-working equipment as a "component farm" to restore other gear, this Marantz could be right up your alley.
Personally, I don't like this amp much at all - it is of the "new generation" from Marantz, all digital operation and lots of push buttons. I much prefer the "old school" amps with glowing bottles, big round volume knobs and lever switches with a great backlighted analog power output display!
MARANTZ - Monitor Amplifier
Model: PM630
Circa 1980's
Designed & manufactured in Japan
First thing you notice, no knobs! Marantz went the "digital way" with this one as almost all controls use soft touch buttons, even the Volume control is a pivoted button arrangement.
This is from the Champagne Gold series.
International AC voltage switching (110-120-220-240V) currently set to 240V
Input socket is a standard "figure 8" non-earthed type. I will not supply this AC lead unless requested as most people undertaking servicing will have plenty of those leads already. But ask if you wish to get one!
If going to a lower AC voltage input (USA etc) you will need to upgrade the primary fuse to 3.15A.
Pretty stock standard inputs: Tuner, CD, Tape 1, Tape 2 & Phono (MM cartridge)
This equipment has the preamplifier and power amplifier available separately, so you can use the preamp only section and send the audio to another power amp or the reverse, forget the preamp and just use the power amp section. If you want both working together, just bridge the preamp and power amp at the rear panel.
Intended for speaker impedance range of 4 ~ 16 Ohm
Power output with 8 Ohm impedance loudspeakers will be around 55W per channel, higher power for lower impedance values.
Strange little push button on the rear panel to RESET the volume control system, if ever the need arose - perhaps this was a design bug as I wouldn't expect a good amp to need the volume control systems to be reset ... anyway, it's there.
The front panel is laid out "Super Hi-Tech" (for the 1980's), all flat with soft touch buttons and indicator LED's. There is no audio power output display though.
For more technical detail about this PM630, just have a search around online as there is plenty of generic information about these.
OBSERVATIONS:
Nice compact, reasonably well balanced amplifier (when held in your arms it doesn't droop too much to one side although not as good as the ROTEL amps) but she is a heavy one at just over 7Kg!
Removed the top U shaped Champagne Gold case and the bottom plate to take a good look around inside. The Champagne Gold look is actually just a coating over a formed metal sheet - this means that if it gets marked or scratched, repair of the damage would be very difficult to achieve. Loads of ventilation in the top of the case, that's good.
The amplifier frame is ALL steel, tough as nails but this is what makes it so heavy to handle.
Nice well constructed AC transformer (TS19620030 3X4ZD) with Copper flux band, perfect for audio use. Interesting that the secondary outputs all go to a PLUG IN fuse board, nice touch for testing!
Well laid out boards (no rats nest), of which there are a few. This could also be a pain as to work on some areas of the amplifier, you need to "peel away" other boards first. These boards are all single sided and use a combination of wire-wrap (for the higher currents) and plug/clip lok connectors, which are at least easy to work with.
The semiconductors used are a combination of integrated circuits (both analog and digital), discrete transistors (particularly the power output stages) and one SANKEN STK3062II (voltage amplifier block)
The large electrolytics which are under the most stress (power supply filtering) are all Nippon's and the through-hole resistors a mixture of metal film and carbon (for less critical areas)
The heatsink (raw Aluminium) extends almost the entire width of the chassis.
COSMETIC CONDITION
The main chassis is straight and undamaged, the same goes for the front and rear panels
NO labelling has rubbed off or worn - all is easy to read
The front metallised plastic buttons do seem just a little "grubby", I am not sure if these will clean up ok or not. The rear phono sockets are reasonably clean and shiny.
The top section of the case has not fared so well though, there is a decent "scuff" mark on the top left side around the centre area but other than this, the top and bottom sections of the case are in pretty good condition and not bent!
ULTRA QUICK TESTING ... remember my wife says "get rid of this stuff" so I have alloted myself just 30 minutes to take a quick look around to get an idea of what is up with this amplifier.
Schematics and board layouts are readily available online and I will reference sometimes to the Service Manual
THE FAULT: Dead As mate ...
Now this can be a good thing, certainly much better than an intermittent fault to track down.
First I checked the obvious - the fuses - ALL of them (and there are a few: F001 main fuse, F851,F852,F853 & F854) and the 3 devices described as "2.7A protectors" F801,F802 & F803 - these look to be surge protectors and do measure very low resistance as I believe they should.
NO fuses are open circuit or show any signs of having been stressed.
Powered up (240V AC) - no smoke, no smells, no LED's light up on the front panel at all and no audio output.
Measured the AC transformer secondary outputs are all perfectly "spot on" at the fuse board output pins.
Orange - Grey (centre tap) - Orange (20.75V - 0V - 20.75V)
Red - Red (68V)
Yellow - Blue - Black - Yellow is a single multi-tap winding
Yellow - Blue (11.6v)
Yellow - Black (19.9V)
Yellow - Yellow (39.9V) across the whole winding.
Next I measured across the filter capacitors (C807,C808,C809,C810) and I have good DC voltages here ... -32V at C808/810 & +32V at C807/809
I then took a quick look at the voltages on the various power semi's mentioned below (easy to access = no time removing other boards), in particular QU09 & QU10
Here is a diagram cut from the schematic relating to these devices, which some manufacturers voltage measurements.
My readings were a little higher than expected, particularly at the emitters, some further investigation will be required here. I have designated my test measurement points as T1,T2,T3 & T4
T1 44.8V
T2 43.9V
T3 44.8V
T4 43.9V
Here I stopped ... time was running out and my 30 minutes was up. So all I have established is that the AC transformer is fine, the fuse board and the bridge rectifiers/electro's for the main PA DC supply - I have not continued with the other lower voltage supplies for the low level signals and digital circuits as it looked as though I would need to start lifting up boards to access test points and time was beginning to run away from me.
I suspect the lower voltage supply rails and regulation could be the issue here ... without them, just about everything stops dead.
While these voltage measurements were being made, there were NO smells or other signs of component stress. In fact I have carefully looked over the boards I can see (mainly the Main board) and nothing looks amiss at all.
However, I suspect at some stage someone has serviced the power output transistors ... I am not 100% about this though. Mounted on, but electrically isolated from the heatsink channel are these power semi devices ...
Q755 2SC2580 .
Q756 2SC2580 .
Q757 2SA1105 .
Q758 2SA1105 .
QU09 2SD1065 .
QU10 2SB829 .
All device types are exactly as the schematics indicate they should be (no substitutes) but I get the impression that at some stage the transistor legs have seen non-factory soldering. If indeed it had been serviced in the past, it has been undertaken professionally - the soldering is very clean and undertaken by someone who knew what they were doing.
I have looked over the rest of the main board and can see absolutely no indications that work has been done in any other area on the board, particularly around the large Nippon caps which is one component that is more likely to fail over time than most others.
For me, this description is rather brief but I hope it gives someone at least a vague idea of what time may be required to get this girl up and running again, or just remove some of those hard-to-find parts such as the AC transformer for other Marantz equipment.
This integrated amplifier has now been safely stored away awaiting a new workbench to visit.
Keep in mind that due to the shipping cost discounting I undertake, ANYWHERE in Australia will cost a flat $9 for shipping - this will automatically show in the Check Out area of my website
