Yamaha PC5002M extremely rare

[brutal]

Awesome info Mark!

 

[Vint Age]

Thanks Vint Age. My M-2 uses slightly different transisters from ...

Thanks Mark. :thmbsp:

You asked the question and I received the answer; sorry for the misinformation.

I wonder if those devices aren't just larger versions of the ones described in the M-4 tech report? :scratch2:

 

[Mark B]

Thanks Mark. :thmbsp:

You asked the question and I received the answer; sorry for the misinformation.

I wonder if those devices aren't just larger versions of the ones described in the M-4 tech report? :scratch2:

You're correct, the transisters in the M-2 are a slightly higher power version of the high-ft transisters used in the M-4. The M-4 uses 2 pair of 12A 120 watt transisters per channel. That's pretty beefy for a 120wpc amp. That's probably why the M-4 is more capable of driving low ohm loads than the M-2.

 

[PowerMOS]

Interestingly, im not sure if its widely known but the Yamaha PC5002M is a rail switching amp. Id assumed it was AB.

 

[SoCal Sam]

Interestingly, im not sure if its widely known but the Yamaha PC5002M is a rail switching amp. Id assumed it was AB.

That would mean the PS caps should have two different voltage ratings. Mark B, can you confirm?

 

[Mark B]

That would mean the PS caps should have two different voltage ratings. Mark B, can you confirm?

I'm not very knowledgeable about the technical side of audio gear. Looking at the circuit diagrams for the PC5002M I can see that there is a 70V power supply and a 120V power supply. Each channel has 2 63V 39000µf PS caps, and 4 100V 18000µf PS caps.

 

[SoCal Sam]

I'm not very knowledgeable about the technical side of audion gear. Looking at the circuit diagrams for the PC5002M I can see that there is a 70V power supply and a 120V power supply. There are 63V PS caps, and 100V PS caps.

Yup, dual voltage rail. Similar to the R-2000 and other Eighties metal. There is a chip that switches rails above a certain power output. I'm not certain on the Class operation but I sure would like to know.

 

[theophile]

Yup, dual voltage rail. Similar to the R-2000 and other Eighties metal. There is a chip that switches rails above a certain power output. I'm not certain on the Class operation but I sure would like to know.

Is that also what the Kenwood Basic M2 and M2A do with their 'DLD'(Dynamic Linear Drive)?

 

[cdfac]

[EDIT] the switching rail will make it fall into "class G" regardless of how the transistors operate in the two different regions.

 

[bikehorn]

That is a massive block of iron. I can only imagine what it would sound like powering a pair of El Pipe-O subs :drool:

 

[cdfac]

below is a basic schematic of one channel, i'll see if i can make it easier to read. they call it "single-ended push-pull" in the literature:

 

[avionic]

OMG!

The find of the century - a pair of them. You dog...

:ntwrthy:

Not anymore...I'll let cdfac explain.:scratch2:

 

[cdfac]

Not anymore...I'll let cdfac explain.:scratch2:

yeah...i, uh, COUGH, sort of picked up a third one from the same seller it does have a bad channel though :thumbsdn:

 

[SoCal Sam]

Your scans of the PC5002M test results belong here.

http://www.audiokarma.org/forums/showpost.php?p=2707255&postcount=13

Congrats on your THIRD PC5002M!

 

[ke4mcl]

my experience in working with this vintage yamaha pro gear at the planetarium...

they used an adhesive to hold large caps in place while on the assembly line awaiting soldering. the adhesive becomes conductive with age. check the inside of the amp for a brown goop slopped around large capacitor bases. if the goop got slathered into transistors or other components you may want to take the time to clean it off. by now its quite brittle and can be picked and scraped off with an awl.

i had three rack mount yammies here that would all got into protect at random. turned out the adhesive was slathered into some transistors and causing them to act up. cleaned the crap off and they were now happy. amps have been in use 8hrs a day for almost two years now with not a bit of trouble.

 

[cdfac]

that's a good point. it does look like they might've used some of that stuff underneath the red ELNAs here:

 

[cdfac]

ok, here are the most interesting pages from the owner's manual:

 

[sunboy]

Hi all,

Anyone have the full manual for PC5002M / 101M ??

THX

 

[sunboy]

Seem there is a little bit different between PC5002M & 101M.....

 

[SoCal Sam]

Check out the square waves. Vertical attack and decay with flat tops means accuracy that you can hear.