Marantz PM66 KI tweeks

[Thomo]

Wow can i just say a big thanks to this forum. I've had a Marantz PM 66 Ki that hasn't been working for about 4 years. I wanted to get this beast working again so decided to search the web for common problems of this amp and came accross this thread where user "rowemeister" commented



So i hastily had a search inside my amp and low and behold a 47ohm resistor at R802 had blown, quick trip to maplins and 15 minutes soldering later, she's singing again
To say i'm chuffed to bits is an understatement

Just a quick question, i'm quite new to this (only found out yesterday what the different colours on the resistor meant!!) and couldn't match the resistor exactly at maplins.
The one in the amp is Yellow, Purple, Black, Brown and then White (Can't find a reference for a resitor with white at the end ??)
The one i got is Yellow, Purple, Black, Gold and then Brown which = 47ohm +/- 1 % tolerance.
Do you think it will be ok or should i try and hunt down for the exact colour match ?

Don't worry about it. That resistor will work perfectly.

Great news about the amp!

I really should get around to repairing mine

Regards, Lee.

 

[Fidelity Audio]

Hi Arnell

Glad we could help, that resistor is fine btw

Brent

 

[JonHarrison]

The last band is the tolerance, brown = +/-1% and I think the white is actually silver = +/-10%

 

[Ben Hanke]

Hi guys,

I've been reading this thread for a while now and it's inspiring me to think about modding my hi-fi. I've been the proud owner of a Marantz KI system (PM66-KI + CD63 Mk-II KI) for nearly ten years now. I found this thread when my volume control started to crackle in the right channel - it ended up just being a loose connection, but I got hooked on this thread.

Although I've tinkered with a soldering iron over the years, I'm pretty much a novice. The only thing I've done to my hi-fi is replace the transport in my CDP when it packed in a couple of years ago.

I was thinking of starting with some straight component swaps, such as putting in a decent mains socket, replacing the RCA jacks with Cardas GRFA DBL PRT G, maybe swap the volume pot and binding posts, internal wiring, etc. I'd also like to remove the tape loop circuitry and hardwire the source direct.

Brent - your amps are amazing! You said the extra KI transformer was the biggest single improvement you made, and you said you wired it in parallel - I had a look at your centre amp for reference but wanted to check - do you literally just connect the two identical TXs to the same connectors and that's it?

Also, would you mind awfully just clarifying how you bypassed the preamp stage with your internal rewiring? Any help very much appreciated

 

[Fidelity Audio]

Hi Ben

Yep just wiring the tx in parallel works a treat (you can do this if you use another KI tx as they are identical).

I wired from the input selector switch to the vol pot and then down to the main pcb. This bypasses all tape loops, balance and even the source direct button (all those crappy ribbons are also eliminated).

Fitting an IEC socket and good lead makes a big difference to dynamics too.

Brent

 

[Ben Hanke]

Hi Brent,

Thanks for the super fast reply. Hmm, I'm not sure how easy it is to pick up a matching transformer now...

I had a go at doing the bypass this morning but ended up with a very quiet sound. I'm not sure what I did wrong, and couldn't make out exactly what you'd done from your pics.

Am I right in thinking that it's possible to bypass the preamp by simply re-routing the existing ribbon connectors, or do you have to wire directly to the switch?

Any help appreciated,

Ben

 

[Fidelity Audio]

The pre amp chip is not bypassed as its on the main pcb and it also drives the output section.

I wired directly to the common output on the selector switch, wired from there to the vol pot and down to the main pcb connector. I removed the L/R wires from the ribbons at the selector pcb and the main pcb. You need to leave the rest of the ribbons connected so that the muting relays and phone stage can still work.

There is always a PM66KI or PM6010KI available on ebay for sale. Best if you can buy a faulty amp.

Brent

 

[roley123]

pm 66se

hi

i have been wanting to beef up my marantz pm 66 for a while now and after seeing some of these threads i have been inspired to do so....
i want to do something along the lines of chivvyp's mod as i need a lot more power for my cerwin vegas and this seems to be fairly cheap to do as i'm only 15; i know where to get the parts, but i just dont know what to do so any help would be appreciated
i have changed components in my amp before as the right channel went dead, and i have a decent soldering iron and a multimeter but i was wondering if ayone could guide me through it

thanks for any help,
josh

 

[nuryev]

Hi
I have also been watching this thread for a few months now- after completing my CD67ose mods courtesy Ray vd steen ;-).

Now I am keen to mod my PM66 KI - already have the Mundorf Supremes, BGs N and STD as well as the Silver Micas. Wondering if doing the ps mods along with input and output mods will be detrimental without the TX upgrade?

Any ideas?

 

[nuryev]

Started mods

I have removed pcb and the caps listed by Rowemeister.

 

[nuryev]

PM66 KI caps

Work in progress...

 

[ginetto61]

Dear Sirs,
please excuse me but I lost myself through the pages of this extremely interesting 3D
Has anyone tried a stepped attenuator ?
or replaced the final transistors with something like Toshiba and/or Sanken ?
What about the emitter resistors of the output bjts ?
At which page can I find a resume of all the mods ?
Thank you very much and regards,
ginetto

 

[nuryev]

Pm66 ki

Hi

I blew a 2SA1265N transistor during my PM66 mods - not available in Australia - can anyone help?

 

[Luke]

hi Nuryev,

Wecomponents.com have your transistors, se on the catalog page 3.

http://www.wagner.net.au/catalogue/01_Semiconductors.pdf

 

[nuryev]

transistor help

hi luke

thanks for the help. I have place and order.

 

[nuryev]

Help!!!2SA1256n replaced

thanks for the supplier luke, parts arrived - installed Toshiba chip but now Amp is blowing fuses at power up????Anyone had similar experience?

 

[canetoad]

I'm curious about modding one of these amps. Does it have to be a KI or can you start with an SE model? What difference in sound would the KI give?

 

[SimontY]

I'd think a more upfront sound due to the toroid vs frame transformer. An SE will be worth modding too

 

[ginetto61]

I'd think a more upfront sound due to the toroid vs frame transformer. ...

In my humble experience frame trans give a much better isolation for noise from the electrical grid, like noise from lamps and similar.
I understand that for the same VA the weight and dimension can be even double.
But at least in a preamp would be my first choice.
Kind regards,
gino

 

[nuryev]

Components for channel rebuild have arrived. Work to start this weekend. Thanks Luke.