Marantz Model 7 Rescued - Gut Rebuild of Hacked Unit at the Bench

In this video I tear down a hacked Marantz 7 and rebuild it from the ground up with modern components.
Time Lapse Music: • Reluctor 176 (For 2 Pi...
00:00 Introduction
00:47 Condition On Arrival
04:36 Transformer Check
05:20 Faceplate Removal
10:14 Pulling the PS and Preamp Boards
18:54 eBay Parts Kit Rant
24:42 Gutting the Boards
28:35 Filament Wiring
30:47 HV Wiring & Carbon Comp Resistors
33:54 Preamp Sub-chassis Completed
35:46 Power Supply
38:52 Rear Panel Extraction
41:09 Reworking the Front Panel
46:31 Volume Control Prep
49:03 Rear Panel Swap
53:59 Transformer Check 2
54:05 Volume Control Installation
56:22 Input Selector Installation & Rear Panel Jacks
59:16 Initial Power Supply Test
1:00:18 Preamp Board Installation
1:01:50 Rebuild Completed
1:02:26 Vacuum Tubes
1:03:57 Power Supply Voltage Check
1:05:34 Initial Audio Check
1:06:38 Troubleshooting & Resolution
1:08:33 Final Voltage Verification
1:10:24 Phono Stage Frequency Response
1:14:04 Detailing the Faceplate & Knobs
1:17:09 Lamp Replacement
1:18:04 Line Stage Testing

[@tomasvalentin6896]

Hey Ben, you truly are a master electrician and a repairman. I couldn’t thank you enough for taking on this project. Thank you so much. Appreciate you.

[@keithtrauner1738]

just amazing restoration. just a rank amateur here trying to remember some of what i used to know 40-50 years ago, and this kind of content is really fun to see. i've managed to repair a few solid state pieces (and blew up one stupidly). But enjoying the process. You're helping my confidence in getting ready to completely disassemble and restore an amp. Thanks!

[@thealphageek1975]

Very impressive restoration. I often have to tell my clients that it's going to look worse before it gets better! You took this concept to a whole new level. Really great job. So few of us are left that can save this old equipment. You gave me a new bar to aim for. Cheers!

[@PrimeHiFi]

Ben, I just finished the video. Phenomenal work on this. You completely renewed the life of this poor Marantz. Can’t put into words how impressive your approach, detail, explanation, and final product are. You’re truly a world class tech. Keep up the great work man.

[@NovaluxStereophonic]

Thanks Connor!

[@dougbarclay9185]

Ben Simply WOW! Truly impressive work. You have raised the bar for all the techs out there. As a vintage audio enthusiast, I wish I had someone of your skills close by. Keep up the good work and enjoyable videos.

[@dennisfrancis1126]

Meticulous and thorough - another ‘MasterClass’ restoration Ben! A pure joy to watch you bring this classic back (and beyond) original spec.

[@oakmountainman7872]

Ben, I am very happy I found your channel. This was very impressive work. I hope you took some still pictures of the more complicated sub-assemblies to share with us. I have always wanted one of these units and if I find one; I will revisit this video. Once again, very well done sir! I just subscribed to your channel.

[@dennisdunkel6731]

Excellent quality restoration. You're very patient with these old amps.

[@johnsampson1096]

Great, thorough resto, Ben! I've salivated over owning one of these units for decades............. Ebay prices have gone through the roof. Non related, I'd love to see a Fisher 50c mono preamp cross your bench. I had one in the mid seventies and lost it in a sudden move. It had a tremendous phono section and clean sound. The kicker, I paid $5.00 for it at a yard sale..........

[@cluna5231]

That’s some very clean work you’re doing, was a pleasure to watch.

[@TrevorsBench]

Bravo, fantastic job!

[@johncunningham5435]

A tough challenge, but nicely done.

[@cjay2]

Wow. I'm only 46 seconds in, and I already can see that Ben's going to do good work on this thing. I'm glad I subbed (6 months ago).

[@adge8405]

Very impressive, showing every step on this amazing and thoroughly comprehensive video. However you have made a grave mistake!! Unfortunately for you now I can restore all of my Marantz 7 7cs without the need of your paid services!

[@monkeysoupman]

I was wondering who bought that back panel! Nice video. Thanks for posting! p.s. glad the new back chassis aligned so well with the parts and front half of the chassis.

[@patmeadows4759]

Great work Ben. Presentation 5 star. Up to your usual super high standard. Lucky customers who have you doing their restorations.

[@MattDealy]

It's such a joy to watch you work. It's true artistry.

[@Amplified208]

Well done restoration of a work of art.

[@cruise2023]

Great job by the way, the unit looks 100%.

[@craigbrown7929]

Just did a restoration on one. The power supply had been worked over but unit was in good condition overall. I did notice two things and the owner noticed them too. One, the volume seems a bit low and the balance control affects the overall volume. I believe all the voltages were within spec and I did not have to do anything with the front panel wiring (input selector, tone switches). Other than needing to have the volume setting up high everything appears to work just fine.

[@NovaluxStereophonic]

The balance circuit in the 7 actually boosts audio when put far left and far right unlike many other designs. You can use the output controls on the back of the unit to fine tune the output level if volume control is not responding well.

[@ReyciclismoMTB]

What a hack, oh my god. Great job.

[@richardadelberg8961]

You are becoming a genus !

[@danhorton6182]

I appreciate your work and nice job on this unit. I do this full time as well and I too will not use third party parts, nor do I use rebuild kits of any kind. That being said I disagree with you on a few points. I think you can give a client a better end result by letting them choose on individual electrolytics vs buy multi section cans. Multi cans are always going to be more expensive than buying individual caps from someone like Nichicon. Generally the individual caps from Nichicon, Panasonic, Rubycon, etc are going to be better overall than what you get in the multicap cans (ripple current, leakage, hour rating). If a section of one of those cans goes open then you need to replace the entire can if you want to keep that stock look, where as if something happens to an individual cap then you can address it. Now with Hayseed, I used to use them pretty frequently, but three times it has happened where about 6 months or so after installation one of the sections goes bad. Trust me, I’m not the only one this has happened to. There are videos on KZbin of techs having problems with new Hayseed cans and documentation online of it as well. So I stopped using them completely. If a client wants to pay me the extra amount I am happy to stuff the original cans. Otherwise if it’s on the bottom of a chassis and they don’t care, I’ll place them on the bottom in a neat and orderly way. I mean you’re putting new polypropylenes and whatever else in there, so it isn’t going to look factory anyways. For my personal units though, I re stuff the cans. I do really like the cans you make, maybe you could make a video on the process of making some? I’d love to see that.

[@NovaluxStereophonic]

I appreciate the comments. If I mention making custom cans it simply refers to placing a custom order to hayseed with my specifications. On units without exposed caps I sometimes use adapt-a-cap or rebuild the can under the chassis on terminal strips (This is the best if it can be made yo fit as if one fails in the future it’s super easy to replace) I have an example of this in my Marantz 9 video. I restuff cans for some personal projects but it’s actually cheaper for the customer in most cases to pay for the hayseed cap rather than my time to restuff. I have not seen any failures yet from Hayseed after 50+ caps ordered. I have though seen CE multi-sections fail multiple times.

[@LewpyDrewpy714]

This is the best rotisserie restore that I've seen in awhile. Keeping all the good parts. Replacement parts are to speck. Mostly. First fire up. The 7 was missing a little. Little fine tuning with better parts. Purrs like a kitten now. Fuel economy isn't that bad either. GGs.. Your testing bench is a Tech drool fest. What was the neutral load going back to your AC power supply? Just curious.

[@fagundesmartins7061]

perito no serviço.

[@jeremiahchamberlin4499]

Great job! I’m curious about the history of this unit in the Marantz line, and in the HiFi world generally. You may have assumed common knowledge, but I’m ignorant. Just curious.

[@stevenjackson8226]

Excellent. Loved watching this. Can you explain a little more about "marking the outside foil to minimize the noise floor" on the film caps? How do you do identify the foil side and does affect how the capacitor is installed?

[@NovaluxStereophonic]

If you do a search for “Mr. Carlson’s Lab outside foil” that should get you pointed in the right direction. He does a very good job of explaining it. The process involves testing and marking each cap and then installing them in the proper orientation to effectively make the outside foil of the cap act as a shield. It’s not 100% necessary but on tube gear I try to go the extra mile to keep noise / hum as low as possible.

[@stevenjackson8226]

@@NovaluxStereophonic Thanks for the reply. I've seen that video. Mr. Carlson's Lab is very informative and thorough. Sounds (kind of a pun) like a good idea. Can this be done accurately/reliably without an oscilloscope?

[@NovaluxStereophonic]

@@stevenjackson8226If you are interested in his circuits consider subscribing to his patreon page. For the circuit he shows on KZbin and oscilloscope is needed.

[@JimOltman]

I've got a Marantz 3300 with a bent corner due to shipping as well. How did you straighten that corner without damaging it? Great job on the restoration! Thanks!

[@NovaluxStereophonic]

It’s never going to be perfect but a bench vise with a couple pieces of leather can go a long way to straighten things out. Better to grip and bend rather than cranking on the vise as that will compress the aluminum. Take it slow and use your best judgment. Good luck!

[@cruise2023]

Wow! what a mess, surely the cost of re building this pre-amp would out way the actual worth of the unit, unless it was a gift.

[@mdav1632]

I was thinking the same thing but of course, this video is a masterclass in itself!

[@70smarantz61]

Congratulations on this nice restoration. @marantzhistory