Marantz PM 94 Help

[brams]

Hi there

I have two Marantz PM-94-BL Digitals one of them is a slightly different to the other CD direct vs CD/Phono direct making them Mk1 & Mk2 respectivly I guess.

I've had both amps from new in 1990 and I love them dearly, I do not anticipate selling either of them now or ever. In order that I may enjoy these monsters for years to come I have a couple of questions that I hope somebody can answer.

They run extremely hot and as a result of themal cycling, certain solder joints fracture with age, I've read on Audio Asylum that Marantz released a service bulletin way back to address this issue and apparently they adjusted the bias to reduce the heat, reading between the lines I think this is why the PM-95 had reduced power output at 120 watt RMS vs 140 watt RMS (8 Ohm).

Can somebody tell me where to get this bulletin?, is it included in the Marantz PM-94 service manual?, if so can somebody recommend a source of manual?

At 16 years of age which they are, most of the capacititors will be dried out by now, what are the best caps to use on these beasts?. What else could be done to prolong the life of them and also make them sweeter in the process, I have no complaints about the sound but if they need service now then I might as well put better quality components in.

I am no electronics wizz, I can solder well and can follow circuit diagrams and have a fundemantal knolwedge of what does what. If recapping and adjusting the bias is beyond my scope, is there anybody in the UK, Greater Manchester area who can deal with these amps?, I'd prefer a recommendation if possible or a Marantz specialist.

Many thanks
Regards
Mick Bramley

[derguteton]

Hi,

I uploaded it at eservice:

http://fileshare.eshop.bg

good luck

[anatech]

Hi derguteton,
Did a browse and couldn't find the manual.

Mick,
Raising or lowering the bias current will not affect the output power. This will affect the average temperature in the chassis and heatsink assy. I do not have the service information, but you can replace the electrolytic caps with 105° types instead of the 85° ones in there if you want. Don't replace the supply capacitors unless they are bad, they would be expensive.

-Chris

[brams]

Hi derguteton

Thanks for diagrams, there seem too be two of them posted by you on there?, downloaded both and they look the same, will look more closely today.


Chris

Diagrams are on the site, just search for PM 94 and they come up, if you have trouble I'll email them to you. Altering the bias current, what other effects other then making them cooler will it have?, I'd like to do it as it should help them survive a lot of years to come as they are built like Tanks.

When you say change the caps, you mean all the electrolytics in the pre-power stage except for the 4 bigs ones next the the toroiodal PSU?

Cheers
Mick Bramley

[anatech]

Hi Mick
I did a browse for all Marantz. I'll try looking for the model - thanks.

A debatable topic. The best advice I can give would be to replace the small electrolytic caps used throughout. Be thankful we aren't point to point anymore. Try replacing any 1uF values with film types if you can. This has worked well for me in the past.

Leave the big filter caps unless they are bad.

-Chris

Edit: Bingo, found it by model.

[bigpanda]

Hi brams,

If you are still looking for the schematics for PM94, give me your email, I can send it to you.

[sajti]

Originally posted by bigpanda
Hi brams,

If you are still looking for the schematics for PM94, give me your email, I can send it to you.

Would You please send to me as well? If it large (>1MB), please send to asajtosATpantelDOThu.

many thanks: sajti