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Marantz MA500 thread

painttoad said:
i stopped using fedex from mouser/digikey.

they've been dragging their feet the last ...oh, probably 6 months or so.
Click to expand...

Well, that brings up an interesting thing that I have noticed. Most people in the States that I talk with tell me that they get good results with UPS and poor (slow) results with FedEx.
My experience over here the last 10 years has been the exact opposite.
UPS delivers invariably to some office well away from me after 4 or 5 days and I have to go and pick it up.
FedEx normally delivers in 2 working days, Texas to Munich. And I have talked with the regular driver on my route enough that we get along and he knows what to do with my package.
This has been one of the few times that my order took more than normal. The record so far is a bit over 42 hours from last Click to parts in my hand.

James
 
Bratwurst7s said:
Well, that brings up an interesting thing that I have noticed. Most people in the States that I talk with tell me that they get good results with UPS and poor (slow) results with FedEx.
My experience over here the last 10 years has been the exact opposite.
UPS delivers invariably to some office well away from me after 4 or 5 days and I have to go and pick it up.
FedEx normally delivers in 2 working days, Texas to Munich. And I have talked with the regular driver on my route enough that we get along and he knows what to do with my package.
This has been one of the few times that my order took more than normal. The record so far is a bit over 42 hours from last Click to parts in my hand.

James
Click to expand...
fed ex used to be faster and cheaper for me. now ups gets the nod. i'm in illinois.

i was using digikey alot but when combined with fedex, they started holding the package an extra 24-36 hours. i switched back to mouser for everything that i can. when i do use digikey, i use ups and they are not holding my package.

it will probably change next month. :dunno:
 
A couple of things that I forgot to mention earlier.

That jumper wire in this photo.
DSC02090.JPG
Be nice to it. That wire is actually the main signal path from the input jack to C701 and then the Q701 pre-driver IC. I briefly considered replacing it with a length of shielded microphone wire but decided to leave it alone.

Also, there is an undocumented ceramic cap directly after the input end of that wire, CS05. You can see it in this photo snug up against the wire block on the lower right.
DSC02079.JPG
Coded 122 = 1200pF, it tested at 1300pF. Replaced with a TDK FA series 1200pF/50v. This cap is in parallel with the input and ground. It is not shown in the schematic or parts list.

In this photo you can also see the blue 0.1µF ceramic cap in the CS01 position in this early amp that in the later amps was replaced with the 4.7µF elco.

Cheers,
James
 
My first crude drawing of the Q701 heat sink.

DSC02116.JPG

Sometime later I'll try to remember to make a better quality drawing but this will do for now.

DSC02117.JPG

The next step is to fabricate a replacement using a strip of 1.5mm copper. A friend was nice enough to cut the raw material for me on the big bench shear at the hospital where I used to work. I should have them in hand early next week.

It seems clear that the 2 cutouts to the left and right of the chip mounting positions are there to allow vertical convection air flow, and there are holes through the circuit board there also. What I do not understand is the asymmetrical size of the cutouts.

Cheers,
James
 
Well, the basic idea seems to be not totally bad.

DSC02123.JPGDSC02124.JPG

I modified the concept a bit. Instead of the cutouts I drilled a pair of 4.5mm holes on each side of the front.

Cheers,
James
 
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I still have to make a pair of support legs for the rear end of the wings. The whole thing will sit with 1mm of clearance between the heat sink and the board, just like the original one.

DSC02125.JPGDSC02126.JPG
I may drill some smaller flanking holes to let more air through but wanted to leave some amount of metal to assist with the transfer of heat to the wings.

I almost bought 2mm copper and now I am glad that I didn't. It was hard enough to get good bends with the 1.5mm material. It is supposed to be 99.9% pure half-hard copper but feels more like full hard.

I ordered some M3 brass screws and washers and stainless steel self locking nuts but they haven't shipped yet.

Cheers,
James
 
Loosely fitted into position. Now I just have to wait for the rest of the fasteners and RCA jacks.

DSC02127.JPGDSC02130.JPGDSC02131.JPG

Cheers,
James
 
Since I am sitting here with nothing better to do while I wait for parts I decided to replace the diodes D802 ~ D809 with something better. These are RL103 1A 200v general purpose diodes.

I replaced them with Vishay Dale SBYV27-200 2A 200v ultra-fast-soft-recovery parts.

DSC02133.JPG

Cheers,
James
 
So how bored am I while waiting for parts?

The original heat sink for Q701 was 24mm by (about) 150mm. That is 3600mm² in surface area.
The 2 cutouts in the front total approximately 265mm².
3600 - 265 = the original heat sink had about 3335mm² in surface area.

The new heat sink is 25 x 160mm = 4000mm².
A 4.5mm hole is about 15.8mm², x4 = 63.6mm².
A 2.5mm hole is about 4.9mm², x4 = 19.6mm².
4000mm² - 83.2mm² = the new heat sink has about 3917mm² in surface area.

Roughly 17% more surface area than the original.

I was that bored.
Now it is time for some beer and Blues.
James

edit, that is surface area for one side of the form. Total surface area would be doubled plus a bit. I am not so bored that I want to calculate the surface area of the 1.5mm edge circumference.
 
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Here is a rough sketch of the new copper heat sink, flat. It doesn't conform to the drafting rules that I learned oh so long ago in middle school but is will do I suppose.

DSC02134.JPG

Cheers,
James
 
I worked hard at getting the face of the heat sink as flat as possible but it is not perfect. So I decided to cut some silpads instead of using thermal paste.
This is some of ShinEtsu's highest performing 0.2mm material, carefully saved from back when I used to work in that line.

A good silpad works as a better gap filler than paste.

DSC02135.JPG

Cheers,
James
 
What the heck, might as well use brass screws and washers to maximize heat transfer. But the nuts are self locking stainless steel.

You have to be careful to not over tighten, or more correctly not over compress silpads. A maximum of 20% of their thickness is the most that they should be compressed. After that they will be damaged and not work as well as they should.

DSC02138.JPGDSC02139.JPGDSC02141.JPGDSC02142.JPG

Cheers,
James
 
As of last night I have first hand experience that the overcurrent protection functions.

I was listening to some John Mellencamp, first Scarecrow and then The Lonesome Jubilee. But I forgot to turn down the volume between disks and TLJ has a lot more gain than Scarecrow.

After the first half second of very loud the amps went straight into protection. A jog down on volume and they came right back on.

So I know now that works, and I also know that as much as I like these amps they are not a long term solution for me with my 4 ohm speakers. As soon as I finish with the work on them I need to get busy getting the Denon POA 6600 amps working.

Cheers,
James
 
Not my most beautiful work but the new RCA jacks are now installed. The thought of using the shielded microphone wire was not well thought through, there is simply no room for that. As it was it was a job just getting some 0.5mm flexible wire through the holes in the board.

DSC02146.JPG

And then the speaker binding posts.

DSC02147.JPG

So as of now there is no hard, non-flexible direct connection between the board and the back panel. No more potential damage to the board from abuse.

Cheers,
James
 
And then the main filter caps.

DSC02148.JPG

And a couple of 0.01µF ECW film caps in parallel. Should have done that from the start.

DSC02149.JPG

That's it for tonight. Assembly tomorrow.

Cheers,
James
 
Today I got the amp all put back together and for the first startup put it on the dim bulb tester. Turned it on and nothing happened. o_O

We all know "That Feeling". That rising blood pressure "What did I do wrong This Time!?" feeling. Turned the power button and dim bulb tester switch back off and calmed down for a minute.

Then I reached over and plugged the dim bulb tester into the power strip and proceeded to test the amp. :biggrin:

Setting the idle current with the 25-turn trimpot is so much easier. Btw, the service manual states that it takes 10 minutes to warm up enough to get a stable idle current. My experience with all 5 amps that a minimum of 15 minutes is more realistic.

Here is how the rear panel looks now with the replacement RCA jacks.

DSC02152a.jpg

The plastic washers were a bit too large and I had to trim them. The astute reader will notice that I had a tough time keeping them from turning when I tightened the jam nuts.

Now I will take a nice Old Guy nap and afterwards there will be a sound check.

Cheers,
James
 
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