Marantz 2245/2270 P750 Amp Board Replica

[ton4eff]

3 years ago I did a Marantz 1060 P700 amp board replica, it came out pretty well, trying to preserve the original look/layout of the PCB. You can take a look at this old thread.

I had a few requests to do the same thing with P750 amp board for 2270/45 models. Since I don't have this board yet to use as an example for measuring the exact physical dimensions (I'm using pdf files from SM for now), I'll have a few questions about it. I'm also accepting suggestions for minor modifications, if needed for easier fitting modern parts, maybe changing some hole/slot sizes, distances etc... So thanks in advance for everybody participating in this thread!

First thing I noticed - they used too completely different layout versions of this board:

The early one:

And revised:


Hmm, so I have to make 2 boards instead of only one...

 

[Steven Tate]

Making both would be great. But, if the revised version started at 3901 (not sure if that can be determined or not), then there would be much more demand for that one. I'm not sure the low demand would warrant the work on the original one.

 

[ton4eff]

I'm doing this mostly for fun as a hobby. Preventing some units from parting out because of the scorched/burnt amp board is a good thing too I think. Demand is not a priority for me. And the two boards will use the same parts library in PCB editor... We'll see. I need the exact physical dimensions of this board while I'm waiting one to arrive, so if someone have one to measure hight/width would be a great help for a start.

 

[ton4eff]

OK, figured out the board size - took the standard TO-66 socket (H758 and H759) distance between the holes - 24.4mm, interpolated the board in AI and resized the PDF to fully match with this transistors holes distance - the result is 150x110mm. Now it's time to vectorize some holes and slots...

 

[Mike Sweeney]

15cm x 11cm new design

ref 1 center mount hole for L751 left to right 2cm x 5.5cm
ref 2 H759 top mount 5.5cm 3.56cm bottom 5.5cm x 1cm
ref 3 C751 14cm x 5.2cm 14cm x 1.2cm

 

[Mike Sweeney]

I've got scans of top and bottom too..

 

[ton4eff]

Thanks for the measurements Mike, as expected, there are some discrepancies, they will be corrected if you send me that real board for reference.

 

[Mike Sweeney]

Thanks for the measurements Mike, as expected, there are some discrepancies, they will be corrected if you send me that real board for reference.

Discrepancies? no, tell me it's not so Not to worry, the board will go out into mail on Monday.

 

[quadtech]

I've got scans of top and bottom too..

Hi Mike, could you post the scans here for future reference?

 

[ton4eff]

Just finished "drilling" the pad holes and slots above the PDF files. They are only 430 if wondering... You can count them if you don't believe me.

 

[Mike Sweeney]

 

[Mike Sweeney]

 

[Mike Sweeney]

OEM Parts load out.

 

[ton4eff]

Oh, this is an earlier P750 version, that's why the huge discrepancies with your references, Mike. I checked against newer revised version. Now, comparing against the older version PDF, it looks much better.

 

[Mike Sweeney]

For replacing C751.. here are some sizing differences. The smaller is a Nichicon and the bigger is a Panasonic. The Panasonic is a near perfect match for the wide holes.

 

[ton4eff]

I'll make the pad hole diameter for this one 1.2mm just in case. Most of the smaller caps and resistors I left with 1mm. Making the distance between the pads shorter is possible, but I'll live it as it is. Somebody may wish to put 630V cap instead 250V. The chances to fit one will be greater.

 

[tranguru]

Nice work!

what would happen if you made it double sided, where the other side would only be the ground (in addition to the ground circuits in the regular side ? )
This a low frequency circuit so maybe it will no effect at all.

 

[ton4eff]

The best effect could be a ground loop problem.

 

[Mike Sweeney]

I was thinking you could extend the trace for this cap with double holes. Since it's on the edge and nothing traverse the cap ------O----O O---O------

 

[ton4eff]

I'll think about this cap when I get there... The holes are already in the PCB editor and a little progress with the silkscreen layer today: