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Marantz 10b

J

JohnChi

New Member
Just picked up a Marantz 10b. It has been sitting in the owner’s attic since he was in college in 1978. That was the last time he used it and he said it worked well. It’s never been serviced which I assume is good because nobody has screwed it up. It’s dusty/dirty as you would expect but cosmetically looks pretty decent. I’m tempted to fire it up (I have a variac) but don’t have a tube tester. Should I bother? Or should I just bring it in to a tech? If I do power it up any suggestions for best procedure? I’ve used variac on old Scott amps but this is my first Marantz Tube. Thanks in advance!
 
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You might want to PM Punker X. He repairs and restores tuners. That 10B is worth some $$$ as is unmolested. It will need some work and a few updates I'm sure. But Punker would be a good place to start.
 
Here are some 10b pics in all its dirty dusty glory. Been in hibernation for 42 years so, it’s about time for it to wake up and make some music again. If any of you see anything out of the ordinary or worth mentioning please let’er rip. Thanks as always for the help!

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That's quite a find there indeed! Given its value, you'd be wise to seek out a qualified technician to bring it back to spec.
 
If you are going to fire it up, bring it up slowly with a variac. Also check the underside of the chassis for insect nests, egg sacks, etc. before bringing it up. I've never seen the lettering on a Marantz faceplate get all droopy and look like it's sliding off the glass before. Moisture in the winter causing it maybe? Also, that scope uses some high voltage along with some big electrolytic caps. You do not want to blow that scope tube!! They are getting very rare. There is another you can use, but it means some modifying to get it to work.
 
The lettering is a common issue on this model. If you attempt to clean clean the back side of glass, use extreme caution as the lettering will fly off from breathing on it.

Good news is that reproduction glass is available and decent quality. If you ever need a scope tube I have about a dozen NOS.
 
Lavane said:
If you are going to fire it up, bring it up slowly with a variac...
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I'm adventerous so I'm with Lavane on this one. BUT, before you even begin firing it up, I'd clean the socket and tube pins at the very least so that you can be confident the tubes will conduct. Inserting a DBT in the chain wouldn't hurt either. Also, I'd set it up for sound, i.e. connected to a pre/amp set up. Any inkling of sound you're well over the hump in terms of a knockout find!
 
Definately good advice about about cleaning. Get all the dust off, give it a good cleaning. I would also pop the bottom panel off and give a good inspection for any leaking electrolytics (thankfully not many in there), burned resistors, broken parts, etc.

It also couldn't hurt to post up in another forum (bartertown is best) looking for a fellow AK member that may be nearby with a tube tester to assist. A word of advice, if you plan on keeping this thing and using it regularly, you'll want to have it checked out and stock up on good 6jk6 tubes. They havent been made for a very long time. They're not easy to come by at decent prices.

Does your variac have an ammeter? When ramping up voltage on an unknown it's best to be able to see what kind of current its drawing and could be a good immediate indicator if things are starting to go wrong. Dim bulb tester can do this also visually and actually limit the current somewhat which buys you time to shut down. Tube amps can be somewhat forgiven in this regard but I'm not sure if tube tuner can be also but I'm no expert by any means.

You've got a great unit there. Its reportedly one of the best tuners made if operating properly.
 
bryans12v said:
Definately good advice about about cleaning. Get all the dust off, give it a good cleaning. I would also pop the bottom panel off and give a good inspection for any leaking electrolytics (thankfully not many in there), burned resistors, broken parts, etc.

It also couldn't hurt to post up in another forum (bartertown is best) looking for a fellow AK member that may be nearby with a tube tester to assist. A word of advice, if you plan on keeping this thing and using it regularly, you'll want to have it checked out and stock up on good 6jk6 tubes. They havent been made for a very long time. They're not easy to come by at decent prices.

Does your variac have an ammeter? When ramping up voltage on an unknown it's best to be able to see what kind of current its drawing and could be a good immediate indicator if things are starting to go wrong. Dim bulb tester can do this also visually and actually limit the current somewhat which buys you time to shut down. Tube amps can be somewhat forgiven in this regard but I'm not sure if tube tuner can be also but I'm no expert by any means.

You've got a great unit there. Its reportedly one of the best tuners made if operating properly.
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The development of the 10, 10B, 20 and 20B damn near bankrupted Marantz. Superscope bought them soon after. I would love to have a 10B or 20B. Even if everything checks out and it works I wouldn't use it very much before getting it restored. It would be a shame to have one of those old cap cans fail and POOF!
 
I would rather have purchased a unit that had been used daily and treated with care. You are in for a big can of worms. I had to have My MR 80 and MR 78 gone thru about 10 years ago and they are doing great today. But they were clean and looked like new when they needed repairs. Fortunately I live in a very dry climate and that helps.
 
Great feedback. Thanks for all the advice. I think I’ll start with a slow thorough cleaning this weekend. I’ll open that bottom panel and see how healthy it looks. I’ll take some pics of the underbelly and check back in. You guys are the best!
 
It’s cleaning up nice.

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Still some pitting on the nameplate. Any good remedies for this?

Here’s a pic of the guts. Looks OK to me but if anyone sees anything that jumps out at them I’m all ears.

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So. I cleaned tube pins, switches, etc. I’m thinking about bringing it up with the variac and DBT. Any last thoughts (warnings) before I cross the Rubicon? Thanks as always.
 
One volt at a time, watch the current, wait 5 minutes, next volt. Have had two for decades, they are not real troublesome in my experience.
 
Ok, so I fired it up yesterday. Did a soft start with a metered variac and DBT just to be sure. Brought it up slowly over the course of several hours. Somewhere around 70-80 volts I started to get some lights and a little bit of noise. Everything thing looked good on the meter (no crazy amp draw). Got up to 120 volts and the meter read .80 amps at 100 watts. At that point there was some buzzing in one of the optocouplers so I shut it down. I wasn’t able to get a radio signal just static. Had a dipole antenna hooked up. All of the tubes lit up (I don’t have a tube tester). Scope seemed to work (I was able to move the vert/hrzt adjustment). The scope showed a short horizontal line (bit blurry). The stereo light came on at about 80 volts and went out as the voltage went up, not exactly sure at what voltage. Anyway that’s where I’m at. Looks like it’s headed for the shop. As an aside I’m in Massachusetts and would love a recommendation of a good tech if anyone has one. Not really looking to ship it. Thanks again for any help, guys.
 
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