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Marantz 8B Restoration

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Derek Miller

New Member
Hello everyone,

I recently picked up a Marantz 8B. It was sitting in a storage area in a church that had been shut down. The local diocese was trying to sell or get rid of whatever they could that was in the building, so I went to get some office furniture on the cheap. I didn't even know what the amp was, just that it was obviously a Marantz tube power-amp, so I asked if I could have it, and the guy said, "Sure, we're just going to throw it away."

So I want to restore it myself. I've done work on electronics before, and am pretty good with a multimeter and a soldering iron, and nothing in the amp looks overly complex, so I'm confident I can do this.

I have not, however, ever restored a vintage amp before, and so I wanted to come here to ask a few questions to head off any obvious mistakes before they happen.

So I'm looking for general advice on restoring vintage amps, common pitfalls/things to look out for, where to source replacement components, and so on. I just registered on this forum last night, so I'm just beginning to look through relevant threads, so I imagine I'll pick up some answers that way, but I thought it would also be worthwhile to make a post--at least to ask, and introduce myself.

As an aside, I also have a Fisher 80-C preamp, which belonged to my grandfather, which I'm going to restore at some point, so these will probably end up being parallel projects. I already have a restored Fisher 80-AZ power amp to go with the 80-C.

Thank you for your help, and I will post about my progress as I bring the Marantz back to life.

Here are a couple of pictures:

Man, that's beautiful craftsmanship.

IMG_1050.JPG

And I can already see that there are some bad caps. Actually, very bad:

IMG_1051.JPG IMG_1052.JPG
 
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Derek Miller said:
Hello everyone,

I recently picked up a Marantz 8B. It was sitting in a storage area in a church that had been shut down. The local diocese was trying to sell or get rid of whatever they could that was in the building, so I went to get some office furniture on the cheap. I didn't even know what the amp was, just that it was obviously a Marantz tube power-amp, so I asked if I could have it, and the guy said, "Sure, we're just going to throw it away."

So I want to restore it myself. I've done work on electronics before, and am pretty good with a multimeter and a soldering iron, and nothing in the amp looks overly complex, so I'm confident I can do this.

I have not, however, ever restored a vintage amp before, and so I wanted to come here to ask a few questions to head off any obvious mistakes before they happen.

So I'm looking for general advice on restoring vintage amps, common pitfalls/things to look out for, where to source replacement components, and so on. I just registered on this forum last night, so I'm just beginning to look through relevant threads, so I imagine I'll pick up some answers that way, but I thought it would also be worthwhile to make a post--at least to ask, and introduce myself.

As an aside, I also have a Fisher 80-C preamp, which belonged to my grandfather, which I'm going to restore at some point, so these will probably end up being parallel projects. I already have a restored Fisher 80-AZ power amp to go with the 80-C.

Thank you for your help, and I will post about my progress as I bring the Marantz back to life.

Here are a couple of pictures:

Man, that's beautiful craftsmanship.

View attachment 2808038

And I can already see that there are some bad caps. Actually, very bad:

View attachment 2808037 View attachment 2808039
Click to expand...


that is a pretty nice find.

I would suggest doing on the electrolytic cap replacements to get the amp running. Part of the sound is all those early bumble bee caps. so would not replace them unless they are leaky (DC leaky, not goo running out of them).
 
mcgjohn said:
that is a pretty nice find.

I would suggest doing on the electrolytic cap replacements to get the amp running. Part of the sound is all those early bumble bee caps. so would not replace them unless they are leaky (DC leaky, not goo running out of them).
Click to expand...
Thanks, it was a really good find.
And yes, my initial strategy is to replace the obviously bad caps, and then go through and test all of the others with a multimeter to see if they're OK. Any that aren't, get replaced.
I've read quite a bit about the original caps being important for preserving the original sound, and I want to keep this amp as original as possible. Do you have any idea about sourcing replacements? Is NOS an option, or are old caps old caps? If modern caps are the only option, how do I figure out which ones are going to be as close to the originals as possible?

Thanks again!
 
I've mentioned this in the McIntosh forum.
I rather doubt Saul and Sydney sat listening to various parts in the amps to pick a "sound" during the design phase, rather choosing readily available high quality parts for consistency and reliability, as they no doubt would do today.
Illinois or Panasonic metallized polypropylene capacitors are two options that qualify. The grey Sprague Telco grade elyticaps are another thing, many folks open and restuff the original cans to preserve appearance and presentation. Sometimes these are fine and need nothing, but this may be long-term risky for the power transformer if not properly fused.
Rather than obsess over the petty choices, your real choice is to rebuild it as well as possible in the spirit of its creation, or preserve it as a time capsule find to serve as a shelf queen collectable, or pass it on to a collector.
 
What you called "very bad" electrolytic capacitors are actually just the insulators rotting away. Vinyl and plastic from the 60's tends to do that after sixty years or so. Having said that, they could still be bad but not because of the way they look. The clamp mounted cap is one half of the voltage doubler, the other identical cap (except for the insulator) is mounted on top next to the meter. The inside cap body must be insulated from chassis ground.
I suggest you have a moderator move this to the Marantz forum as there a number of Model 8/8b owners there.
 
Derek Miller said:
Hello everyone,

I recently picked up a Marantz 8B. It was sitting in a storage area in a church that had been shut down. The local diocese was trying to sell or get rid of whatever they could that was in the building, so I went to get some office furniture on the cheap. I didn't even know what the amp was, just that it was obviously a Marantz tube power-amp, so I asked if I could have it, and the guy said, "Sure, we're just going to throw it away."

So I want to restore it myself. I've done work on electronics before, and am pretty good with a multimeter and a soldering iron, and nothing in the amp looks overly complex, so I'm confident I can do this.

I have not, however, ever restored a vintage amp before, and so I wanted to come here to ask a few questions to head off any obvious mistakes before they happen.

So I'm looking for general advice on restoring vintage amps, common pitfalls/things to look out for, where to source replacement components, and so on. I just registered on this forum last night, so I'm just beginning to look through relevant threads, so I imagine I'll pick up some answers that way, but I thought it would also be worthwhile to make a post--at least to ask, and introduce myself.

As an aside, I also have a Fisher 80-C preamp, which belonged to my grandfather, which I'm going to restore at some point, so these will probably end up being parallel projects. I already have a restored Fisher 80-AZ power amp to go with the 80-C.

Thank you for your help, and I will post about my progress as I bring the Marantz back to life.

Here are a couple of pictures:

Man, that's beautiful craftsmanship.

View attachment 2808038

And I can already see that there are some bad caps. Actually, very bad:

View attachment 2808037 View attachment 2808039
Click to expand...

If you haven't done it already, I suggest you do a search of the Audiokarma Tube Audio forum for "Marantz 8B restoration".
I think that you'll find a lot of relevant information which should be helpful to you before you dig into your project.
 
Pio1980 said:
I've mentioned this in the McIntosh forum.
I rather doubt Saul and Sydney sat listening to various parts in the amps to pick a "sound" during the design phase, rather choosing readily available high quality parts for consistency and reliability, as they no doubt would do today.
Illinois or Panasonic metallized polypropylene capacitors are two options that qualify. The grey Sprague Telco grade elyticaps are another thing, many folks open and restuff the original cans to preserve appearance and presentation. Sometimes these are fine and need nothing, but this may be long-term risky for the power transformer if not properly fused.
Rather than obsess over the petty choices, your real choice is to rebuild it as well as possible in the spirit of its creation, or preserve it as a time capsule find to serve as a shelf queen collectable, or pass it on to a collector.
Click to expand...

yes would agree. Select parts for best reliability.

Also back then there were not as many parts vendors as there are today.
 
That is a beautiful score. Lucky guy. BTW, did it include tubes to go with this amp?
 
You could ask about restoring this amplifier in the Marantz forum or a thread directing to this one. I know several threads have been created on them in the Marantz forum along with the matching 7C preamp. I would be looking closer around that church to see if they may have the 7C also. It's one of those amplifiers that should be restored the "right way" to retain its value. There are certain capacitors, etc. that tend to get a nod when when it comes to restoring these. I've had some TOTL earlier SS Marantz preamps and amplifiers and restored them as close to original as possible. Only replacing tantalums with electrolytic or film caps, etc. The rest was done with same type parts.
I think it was an AK'r that went by cactus joe?, that did a really nice restore.
 
Nice find, I'm glad it did not get tossed.

You do need to check the electrolytics- all of them- there are some that claim the telephone grade can electrolytics are "always" good- I have had as many leaky electrically as good in 7c's, 8B's and Model 5's- strangely the one's in my model 2's are good.

I have posted here on re-stuffing or re spraying new types gray if that is necessary. While the comment on the plastic casings going funky on these caps without the innards being affected can be true- that voltage doubler cap in the snap in clamp looks bad to me. Make sure the replacement is insulated from the metal snap in clamp with two layers of heat shrink- it is part of the doubler circuit.

You have to check.

While the bumble bees are highly coveted for originality- they crack and absorb moisture. Get a good light a magnifying glass and dental probe to clearly observe the case ... if they are cracked - toss them. the one type of spragues you have there are almost always good. The selenium for the bias is supposed to add to the unique sound of the amp. Check the output of it. I have never seen a bad one- and I have never seen one go boom in decades of vintage repair. However, if they do loose output- you loose your tubes and and perhaps transformers.. so you need to be aware.

Lastly make sure your sockets are clean and have good tension. Marantz sockets are very good... but I have seen green corrosion on one's that have sat in bad environments and usually no amount of cleaning will help with those... they need replacement.

Have fun.
 
mcgjohn said:
that is a pretty nice find.

I would suggest doing on the electrolytic cap replacements to get the amp running. Part of the sound is all those early bumble bee caps. so would not replace them unless they are leaky (DC leaky, not goo running out of them).
Click to expand...
Bad advice There’s no sound to the bumble caps .. and they ARE leaky for sure The sound is in the circuit and the transformers
 
detroithifi said:
Bad advice There’s no sound to the bumble caps .. and they ARE leaky for sure The sound is in the circuit and the transformers
Click to expand...

Just remember if you ever decide to sell the amp, its worth a lot more with all the bumble bee caps in place. If you install modern film caps, you are going to kill the value of hte amp. There are guys out there who will hunt down NOS bumble caps to install in their Marantz 8s and 9s.
 
mcgjohn said:
Just remember if you ever decide to sell the amp, its worth a lot more with all the bumble bee caps in place. If you install modern film caps, you are going to kill the value of hte amp. There are guys out there who will hunt down NOS bumble caps to install in their Marantz 8s and 9s.
Click to expand...
Besides heft, another reason I decided to put mine up for sale and get a recently made similar topology Mullard amp with modern components.
I have a couple of nice time capsules that please me as-is not in use, nor will be.
 
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