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Old 16th July 2011, 04:33 PM   #441
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The original stock input caps on this amp are actually 16v 220uF Silmics, although the phono stage output signal goes through 2.2uF first. I want to preserve the essence of the Marantz sound that I enjoy but improve the detail and stereo imaging while delivering a controlled, accurate bass as deep as my speakers want to go. Other than following Brent's suggested changes, I'm mostly just replacing stock parts with better quality or closer matched ones of the same value, but I'm feeling confident that there's some room for me to experiment with the coupling caps. I don't have a scope to prove the response doesn't roll off too soon, but I'll play some test sweeps and listen to my favourite bass lines.
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Old 25th July 2011, 12:43 AM   #442
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I'm back in action, guys. All mods re-done on a fresh board and it's sounding great.

A couple of things I learned this time: If you're planning to put mount large off board PSU caps in this amp then Kimber 4TC seems to be the perfect wire for the job. It's just the right thickness to fit through the holes left by the snap-in Elna caps. Also, if you're putting larger caps in, I found that it's best to start by cutting down all those resistors and mounting them flush on the PCB surface so you can keep the new component leads as short as possible. I also shielded my pre-amp chip before it got too crowded in there.
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Old 3rd August 2011, 02:32 AM   #443
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Click the image to open in full size.

Latest shot of the amp, now with 3.3uF Mundorf Silver Oils inserted between the input selection switch and volume pot. They are a massive improvement over the Black Gate AC, which I have replaced with wire jumpers. After redoing all mods from scratch over two days, I reckon they are one of the three most significant improvements, along with the BG FK smoothers and the extra PSU.

I hesitate to say this but I think I'm close to being done. I'm so happy with the sound right now, I've even put the screws in :-)
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Old 3rd August 2011, 08:57 AM   #444
SimontY is offline SimontY  United Kingdom
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Looking EXCELLENT Ben. Great mods.
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Old 31st August 2011, 04:16 PM   #445
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Hi, Really need some help with my Marantz PM66 KI. The r806 resistor has blown, and I can't see the colours. Can anyone tell me what type of resistor I need to buy in order to replace it? Cheers!
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Old 1st September 2011, 02:12 PM   #446
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Quote:
Originally Posted by freshnessben View Post
Hi, Really need some help with my Marantz PM66 KI. The r806 resistor has blown, and I can't see the colours. Can anyone tell me what type of resistor I need to buy in order to replace it? Cheers!
R806 is a 1k2 1/4 Watt, you might want to check R804 as well 47R 1/4 Watt fusible.
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Old 1st September 2011, 03:54 PM   #447
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Thanks a lot eggontoast. I've ordered some resistors and I'm hoping this will solve the problem (once soldered in). Cheers.
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Old 11th September 2011, 01:00 AM   #448
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Default PM-66 KI blowing fuse

Hi guys.

Can't believe the legs this post has ;-) Impressive work going on here.

My question, at least at this stage, is a little more mundane. A 66 KIS I picked up yesterday blows its 1.6amp internal fuse a lot of the time. I bought it cheapish (25), as it was described as being dead as a doornail.

A couple of questions arise: is the 1.6A fuse slow- or quick-blow? Given the in-rush on a toroid, I imagine it's slow-blow, and the fuses I'm using at the moment might be quick-blow (have to check). Are the 12,000uF blue Elna reservoir caps attached to the PCB with that adhesive that quite a few manufacturers seem to use? Around the base, for about half the circumference of each cap, is some brown stuff. Wanted to check if its adhesive or leakage. Not getting any major offset on either output when the fuse doesn't blow (10-20mV).

How prone are these amps to bias drift over the years? I have another 66 KIS which seems to work fine, but I remember it sounding better (I owned one years ago, when they first came out). It's in that classic system of the KIS amp and CDP with Tannoy Mercury M1s. Got the CDP cheapish too (30), as it squeals when loading or unloading a disc. Any pointers there would be appreciated too ;-)

Once one of my amps is fully sorted, the modding will begin!

Cheers, Jon.
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Old 11th September 2011, 01:49 AM   #449
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Hi Triophile,

I'm not sure about the stock fuse, but I'm using a 1.6A slow blow with two transformers and no issues.

Yes, the brown stuff is just glue. It goes quite manky-looking over time.

Whether the bias naturally drifts or not, the pots are very cheap and easily knocked out of place, so I think the best thing to do is just measure it as per the guide in the service manual. I recommend using crocodile clips to save you having to hold the DMM still for several minutes.

Try taking the lid off the CDP and you might be able to tell better why it's squeaking. It might want a bit of white grease on the gears.

Cheers,

Ben
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Old 11th September 2011, 01:50 PM   #450
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Thanks for the reply, Ben.

Mmmm, the plot thickens. The seller was obviously being a little disingenuous when he claimed this PM-66 KIS simply stopped working one day. I finally flipped it over to find that someone has clearly had a go at it internally.

I'm not sure if someone's tried washing the underside of the main PCB, but it looks a bit dirty:

Click the image to open in full size.

There's also been some reworking, as the solder appears to have been sucked/wicked off one of the pads, and one of the thermal tracking trasistors looks as if its either been reflowed, resoldered, or replaced:

Click the image to open in full size.

There's also scorching near some of the larger, un-heatsinked transistors:

Click the image to open in full size.

I'm wondering if someone's tweaked this amp in the past and maybe cooked it slightly, or if perhaps they've biased it into Class A without putting heatsinks on the relevant transistors.

The upshot is that the amp is still blowing fuses, whether slow- or quick-blow 1.6A types. Thing is, it won't blow the first time it's powered up with a fresh fuse, only the second time. Any other suggestions, Ben or anyone else, before I go ahead and check the bias (which might necessitate the purchase of a new DMM, as I barbequed my decent one building a valve amp a while ago)?

Cheers, Jon.
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