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Marantz 500 Restoration, Here we go...

Salbreth1 said:
So just got back to this and finished the relay board, mostly. All TO-92s, diodes and capacitors were replaced. The relay contacts are in great shape so I put a mirror back on them and soldered them back in. Somehow I deleted the 8200uf caps from my cart so I'm waiting for them... Amplifiers are next!

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WHAT TO-92s are you using for replacements? What Diodes?
The worst part of working on these is those damn Motorola part numbers that don't cross reference.

Please share your replacement parts list. If they are not standard modern replacement parts, where are you getting them?
 
blhagstrom said:
WHAT TO-92s are you using for replacements? What Diodes?
The worst part of working on these is those damn Motorola part numbers that don't cross reference.

Please share your replacement parts list. If they are not standard modern replacement parts, where are you getting them?
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I'v cross refrerenced every transistor in these units myself using the original data sheet info to find new subs. It takes some time but my subs are pretty close. Most of them are used in the 1200b and 250s and I've rebuilt enough of them to know they work nicely. Ill get a list together.

The heat sinks are looking good. I converted the to-66 to to-220. The leads fit very snug into the original pin holes so no modification needed.

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I don't remember even being able to find the original parts data sheets.

That air tunnel is remarkably clean. Either this amp has low hours or you did an amazing job of scrubbing it up (or it lived in a very clean place).
 
It had the typical 40 Years of dust inside. The first pic I posted was after I blew it out, still pretty dirty. But after I scrubbed it and installed the new outputs, it literally looks new. The fan was caked up too but it also cleaned up well.

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rBuckner said:
If the fan is too noisy there's a very nice ball bearing "ebmpabst" fan with ball bearings that is an improvement.
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Thanks Randy, We will see when I fire it up. I'm going to disassemble and clean it out. There is no lateral movement and it spins smoothly.
 
New 50w resistor is in. I just drilled out the rivets and countersunk it from the back for some #8 flat heads. #6 would have made it easier but I can't justify running to home depot for 2 screws. o_O


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I love watching these rebuilds. Kind of like watching a auto accident in reverse?

Great work and even better research. Best of luck
 
The amplifiers are finished! These came out very nice. 24 pins per side to finesse into place wasn't so bad. Doesn't matter how straight the leads are they still need to be tooled into place. The to-220s have to go in after the board is attached to the heat sink to seat them properly.

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So the fan was pretty clean inside, the shaft and bronze bushing are free of defect so I applied a light oil and re assembled. It definitely spins smoother than before. Now I'm just assembling and cleaning things. The relay board is complete and back in. The driver boards at last.


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New filters are in. FYI: the screw terminals on the original caps stand off 7mm. The new ones are 2.5mm . So depending on the replacement caps, the bus bars will have to be shimmed to prevent them from touching the chassis. longer hardware and two extra lock washers per screw worked for me. I'm pretty sure their 12/24 pan heads.

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Well we got pounded with 20" of snow today! I thought we were done for the season :wtf:

Not all bad though, my son and I built a snow fort. He ate most of it lol. He's 2 and a half. Its all fun and games until he face plants into the snow!

Anyway, I have the A channel driver board in and regulated. Like the amps I replaced all of the lytics and changed out the old films for some new metalized poly films. All TO-92s were upgraded with new Fairchild devices and both boards are hfe matched to each other. New diodes, bourns pots and other goodies. I wanted to keep the TO-39s but one board was apparently blown and has newer RCA devices on it. I don't have a good sub for these yet so I might find some nos. Central Semi has the 2n3440 but their data sheets are funny. That and the IC is 50mA lower than the original devices. I don't think they have the 2n5415 at all. Ill have to do some homework.

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So I ended up buying the 2n3440 and 2n5415 made by Central Semi. Digikey only has the 2n3440 and does not have a typical datasheet attached to it. It says the Ic = 20mA. Mouser sells both but only has the correct datasheet for the 2n5415 stating the Ic =1A. Weird. Microsemi has them available too but for $16 each. :yikes:

Littlediode only has the original Moto 3440s but $6 each on their ebay store.

I'm replacing these because the other driver board has a mix of Motorola and PH transistors. Who ever replaced them didnt use the insulators underneath them.

Other than that, I adjusted the amp even though I will have to do it again when I get the new trans. I was able to get the four test points on the driver boards within about 4mV of each other. I have two remote trimmers in for the bias resistor. The service manual calls for a max of 15 watts rise of power consumption per channel when measured with the resistor out and then in. Before I started channel A was good but channel B had a rise of 21 watts. I adjusted both sides for a rise of 14.5 watts.
 
Hi,

I will have to do the same restoration on my 500 - has been lying around for the last 15 years....
I am really curious how you get on with it. I already have most the components. can you share which xtors you used to replace the original after the pre driver stages and which diodes you used for the temperature tracking (CR301 and CR302).
for the power xtors I bought a ton of MJ15003/4 and need to match them with my Tek 577.
I am very worried about stability on this amp ==> probably need xtors with same speed as they had back in those days.

Thanks
Robin
 
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