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I'm in the process of repairing a 18, downloaded all of the service information, and it seems that a large number of the semiconductors have factory numbers.
Anyone know of a cross reference?
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Are you talking about Marantz's own numbers?
They did that and it is going to be hard to find out the actual replacements?
I'll see if I have any info being I did have that receiver.
Thank you.
I am starting to lean towards "whatever works", or more accurately whatever I can find. The only ones I would like to keep stock is the output transistors. I replaced the right side transistors over ten years ago with NTE replacements. The original left side are still original.
Proudly serving content-free posts since 1984.
If the transistors are working you should just leave them alone.
Replace the electrolytic capacitors. They need to go
I still have the 18 I bought with an entire month of stipend in1967 when I was a post-doc at Stanford. As far as I know, it's functional, but I occasionally think to take it to someone for servicing. I used it drive AR3a speakers and an AR turntable as source, and I still have those. I imagine someday firing up the combination, but this thread suggests getting the 18 serviced may not be trivial.
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Servicing it could be trivial, from your description, it sounds like there may be little, if anything wrong with it.The typical problems are the 500vdc secondary on the power transformer opening, (used to help power the scope), and the usual bad caps, most often the electrolytics, they dry up with time.) The good thing about the electrolytics in the older equipment is they were very good quality, and often are still good. Also very common on the older Marantz's is the lettering on the dial glass falling off, that has happened to both my 18 and previously my 10b.
I checked last night, my scope is dead, but after measuring it, the 500vdc is still alive. I will have to find out what is wrong.
If you ever think about selling, let me know.
Proudly serving content-free posts since 1984.
Edits: 08/15/15
Tried Googling the Marantz part number? Be careful where you buy the bi-polar transistors for the amp heat sinks. Lots of fraud transistors out there. Stick with Digi-Key and Mouser as your suppliers to ensure original On-Semi replacements.
Just because you didn't know about it, doesn't mean it's a secret.
Acually, I don't need the bipolar outputs, (I used NTE's) but I would like to replace the NTE's with the original p/n. I know that many will say the originals are not as good as the replacements, but I'd like to keep it as stock as possible. My other option is to replace all 4 with the same replacement.
Proudly serving content-free posts since 1984.
I've done a few projects that needed transistors replaced, and if you go with new, finding the exact replacement can be tricky, but you may wind up with superior parts. I've done the "find the original parts" thing and it gets expensive, and that's *when* you finally find them.
The problem I'm having now is that while working on a Philips 5781 (BIG power amp), the slew rate of the current equivalents I've found so far is below what they used originally. Smaller transistors have been pretty easy, if not very straightforward - Philips frequently used internal part numbers and private labeled the actual parts with those numbers, but they often can be tracked thru ECG numbers, then NTE, and then to other manufacturers' equivalents.
Finally, it's common to hear that if you replace old with new, you really should consider replacing them all with the same part, then do the rebias, etc, according to the manual. The Philips I mentioned above has *16*, hence my leisurely pace.
Then you need a parts list and be prepared to scour the vintage forums and ebay to find original parts. I'd guess that's going to be pretty tedious and difficult. I can appreciate your desire to keep the receiver as original as possible, but in this case I'd go with new, exact, quality replacement parts. Good luck whichever way you go.
Just because you didn't know about it, doesn't mean it's a secret.
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