Marantz Model 1250 Full service/upgrade...please advise

After flipping through a couple of restore/recap projects in AK I'm starting a new thread for a service & upgrade project of my recently acquired Marantz 1250.
Hope I can get much help and advice from the fellow members who have done it already.

I'm from Singapore & the amp has been bought and shipped from Australia a couple of weeks ago. I've been looking for one for some time and finally pulled the trigger on this clean looking unit. My brother helped me with the deal & shippment to Singapore. I'm very happy to have it as it's (vintage amps, especially Marantz) a very rare commodity here.

Initial findings:

The unit is pretty clean inside and out.
As I opened up the covers one by one, a few things caught my attention though!

1) The original big dual core filter cap has been replaced with two Nippon chemicon 12000uf 71v filter caps tightly squeezed in the original metal clamp.
2) It seems the 680uf 80v & 220uf 63v caps (light blue) on either side of heatsink on the power supply board has started showing signs of leakage.(as far as I can see no other caps has been replaced in this unit except the filter cap)
3) There's some signs of soldering works at the wire connecting pins on pcbs.
4) But when I removed the bottom cover actually surprised to see some totally careless repairing works done. I've a few melted wires (those soldered to the main filter caps) at the bottom.

5) As the unit is already in working condition, I've powered up the unit and started listening to it for first time.

A couple of things which I've noticed while playing music is only the left channel is working fine and the right channel is muffled. If I increase the volume the right will have something but still too low. After playing like this for more than 30-45 mins the right channel slowly comes alive. But the following day when i powered up the unit and started playing music happened to press tone deactivate button and the right channel suddenly came alive and played in stereo. So I tried pressing the button again and there goes the right channel again dead!
Now, I can listen to it in stereo with tone deactivated!

6) While switch off the power button, there's a nasty popping sound from the speakers.

Apart from all these troubles, the kind of sound it make is super addictive.
It's really mellow and has a very defined soundstage ( the instruments are not mixed up).

I've also hook it up to the TT via phono inputs and the sound it makes is not as enjoyable as the other sources.
My PM6004 sounds better in this department and I enjoy listening vinyl too.
But in comparison, 1250 sounds very thin and bass shy playing vinyl.

I hope a proper service and restoration, probably I call it an upgrade ( as I can't find the original components anymore) will make it a fantastic piece of equipment which I can keep for very long time.

I seek all the help I can get from the AK members who have done the restoration previously.
My intention is to prepare a parts list n place the order before going to the work station and strip it down.
I'll include some pictures in the following posts...

Dear frnds, What do you say?

I'll be also upgrading the standard power cable to an IEC type UK plug.
The existing cable is a very short & thin one and it's an Aussie plug which I think changed by previous owner.
I already have an Isotek Evo03 premier power cable and Furutech 3 prong IEC inlet lying around and can make good use of it.
I've plans for upgrading the speaker terminals to binding posts which can accommodate banana plugs. Currently the cables that I've are 12awg and above and it's a pain connecting this to the existing spring loaded speaker terminals.
Anyone has replaced these before and if so how did you do it?

I currently have a 1250 in the shop and can help you with pics if you'd like.

Bob

Oh! Great.
Please put up pictures of your 1250.
So what have you done so far on your 1250?
Please share so that it will be helpful for me as well.
Thanks

The 1250 is in for a restore and missing pushbutton/shaft.
I have 2 Pioneer SX1250's, a 2330B, a 140 amp and a Citation XX in ahead of it but I'll try and squeeze it in.
In the meantime though I can help you with internal pics.

Bob

Thanks Bob, eager to see those pics.
So what's your plan for 1250 restoration...you've a standard parts list or what?
My main intention is to remain close to the vintage original sound as much as possible at the same time get rid of all those faulty or out of spec components.

Got your PM...will answer here:

1) The right channel makes no sound( can hear a little bit if increase the volume beyond 12) in normal condition on all the inputs.
If I press the tone defeat button both channels function as normal & sound is even.

2) There's a loud poping sound from both the speakers when I switch off the power button (even though the volume is min)

3) Just a couple of days ago I've opened up the amp and did a deoxit cleaning all over the PCBs and the rear panel. Afterwards, I've noticed while playing via Aux input and if I select tuner input on the front panel, I can also hear the same source connected to the Aux input but at low volume. Actually, tuner input has nothing connected to it physically. I've only connected aux & phono. Why am I hearing other source inputs via Tuner input!!!

Click to expand...

1. Sounds like a problem on that board, or a problem with the switch. Also, any of the tone pots can block the signal. The schematic for this one is a typical Marantz mess, so I feel for ya on this count. It does look like there are four transistors that get bypassed with the tone defeat on...HE11, HE12, HE14, and HE16 (if I've chosen the proper channel). Might be as simple as one of these transistors.

2. That's the protection relay letting go. One of two things is happening.
a. If the relay is disengaging immediately on power-down, then DC offset is not good. Check it.
b. If the relay is NOT opening immediately on power-down, then you're getting transients from DC voltage decay of the circuitry. The decay is normal...but the relay is supposed to already have disconnected the speakers so you shouldn't hear it. If you rebuilt the PN00 relay board with oversize caps, that would do it. Most mfgrs build a 'loss of AC detect' circuit to open the relay on power down. Marantz does not on this one. It relies on the discharging of the caps on this board to open the relay. If you oversized the caps on this board, you need to go back to stock values. If not, might have to consider a smaller cap for CN03.

3. Common issue. Bleedthrough. Most vintage amps will do this. If you connected a tuner, this would short out the bleed and quiet things down.