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Marantz 8B help needed!

I don't recommend using the amp until you have all of its problems corrected. Why take a chance on causing more problems which could be costly to repair.
 
I don't recommend using the amp until all of its problems have been corrected. Why take a chance on causing more problems that could be costly to repair.
 
Hope you find the issue.

Regarding replacing signal caps- do your homework first. Some caps produced back in the day were mylar-paper and do not have the leakage issues that other caps have (like sprague bumblebees). Usually, the red-print black body spragues are mylar film. As is the Cornel-Dublier avocado green caps and some El Menco's. I can't recall if the good-alls are mylar. Test for leakage. Have an old Radio-Master catalog and check the cap codes. If mylar & good, leave them in place; they will last. Keep it original if possible. A truly legendary amplifier.
 
If you are still having problems, let me know and I will measure B+ etc., it won't be difficult to isolate the problem.

8B's are a legend, sell for a lot, less changes the higher the value. So it can be difficult to decide how much to update. I updated one, left another stock, so I could compare the sound. Coupling caps I mixed PIO's and film in the one I updated. I have used orange drops in lesser value amps, they sound ok. Since they have already been changed to orange drops, I suggest fix your problem first then upgrade them. I have seen original replacements on ebay, that would help the value, but you would need to keep an eye on them.
 
I have nothing to offer on the repairs, but what's the story on a craigslist 8b? I've only seen one on cl, and the ad was QUICKLY edited to say "I had no idea what I was holding, this thing's going on ebay."
 
Marantz 8 after re-cap bottom view rfs.png
Pio1980 said:
Mine is mostly original, except front end caps, elyticaps, bias rectifier, and two screen stoppers.View attachment 1062986
Click to expand...

I see that there are AudioCap Thetas at the "input" (as is mine).

That said, a note to those researching the Marantz 8b set up: connect the amp input RATHER through the "TEST"! Counterintuitive, but true.

There are many authoritative references such as Steve Hoffman who wrote: "By the way, always use the TEST inputs on the back with your interconnects. This insures you get the full bandwidth". The posters go on to say that, the "PREAMP" inputs added low-frequency filtering to the circuit for turntable rumble (not a feature in modern decks), whereas the "TEST" input does not.
 
1N4007 is what I used on my Model 8. For further assistance I suggest you start your own thread as this one is almost six years old.
 
I opened my just arrived Marantz 8B and I wonder if by looking at pictures, should I ask for services even though the unit is working just fine?
Pat
 

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trisho0 said:
I opened my just arrived Marantz 8B and I wonder if by looking at pictures, should I ask for services even though the unit is working just fine?
Pat
Click to expand...
Looks to be, from the pictures posted, completely original. This is both a good and a bad thing. Good in that nothing improper has been done. Bad in that everything needs to be done. Sixty year old electrolytics, "Bumble Bee" capacitors, selenium bias rectifier, etc.
If you plan on doing the refurbishment yourself I suggest you start a new thread and that you search this forum for guidance. If you are going to have a technician do the work look for references. My two cents.
 
The vendor said it was sitting at home without many uses and yes, he recommended me to ask for a service due to the age. But even though the unit was working flawlessly.
I could send the unit for a service, but I can't find a good technician like Terry Dewick (Retired). So, probably I would do the service by myself. I have soldering skills but without knowledge to understand schematics and I only have a Fluke tester to use. I also found now a power fuse is 1 1/2 A instead of 2 1/2 A according to manuals. If the unit is faulty the fuse could be blown but still good.
Pat
 
trisho0 said:
The vendor said it was sitting at home without many uses and yes, he recommended me to ask for a service due to the age. But even though the unit was working flawlessly.
I could send the unit for a service, but I can't find a good technician like Terry Dewick (Retired). So, probably I would do the service by myself. I have soldering skills but without knowledge to understand schematics and I only have a Fluke tester to use. I also found now a power fuse is 1 1/2 A instead of 2 1/2 A according to manuals. If the unit is faulty the fuse could be blown but still good.
Pat
Click to expand...
A question: Where are you located?
Some observations (based on your posts): Basic soldering skills alone are insufficient to refurbish this amplifier. That it functions today does not mean that it meets it's specifications nor does it mean that it will not fail due to aged components. Proper test equipment, the skill to use them and prior knowledge of vacuum tube amplifiers (preferably Marantz 8) is critical to a successful refurbishment.
Again, start a new thread and others on this forum will join in with assistance and encouragement.
 
ramjet said:
A question: Where are you located?
Some observations (based on your posts): Basic soldering skills alone are insufficient to refurbish this amplifier. That it functions today does not mean that it meets it's specifications nor does it mean that it will not fail due to aged components. Proper test equipment, the skill to use them and prior knowledge of vacuum tube amplifiers (preferably Marantz 8) is critical to a successful refurbishment.
Again, start a new thread and others on this forum will join in with assistance and encouragement.
Click to expand...
I am located in Gaithersburg, MD 20886 but willing to fix the unit in a near future. I will prepare posting a new topic thread here. Thanks for your guidance and help.
Pat
 
Don't think the value of the Marantz 8B will decrease after replacing caps just because they are old but still working just fine? I would start replacing caps if they are showing signs of ready to replace if I want to preserve the unit. Any comments are welcome.
Pat
 
If you have the capacity to test them at full operating voltage and find no DC voltage leakage and they match rated capacitance they could be used but then still run the risk of failing in the near future strictly because of their age (speaking specifically of electrolytics and some others like bumblebees) because of electrolyte drying out and physical breakdown.

Yes an all original amp of value may have the highest value, but shouldn't be used. If there is a catastrophic failure due to a failed capacitor and it takes out an output transformer or power transformer, rest assured that will reduce the value more than any parts replacement.

You can always replace parts, saving the originals so that it could be rebuilt to original parts, a common approach.
 
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