Got me a rusty old Marantz model 8 to restore

[cptnCanada]

And also, the majority of Model 8's I've seen have unpotted power transformers with end bells. That's the way they came from the factory. The later 8B, of course, had all potted transformers.

That is what I found while researching this thing before purchase. It was advertised as having one non original transformer, but the numbers on them definitely are matching. I should probably test them before I get too deep. My simple multimeter resistance tests before I removed them seemed to indicate that they had life.

 

[Pio1980]

The amp's interest and value is mainly the OPTs. If they are good, you have a Marantz 8 as genuine as anyone elses, including mine.

 

[cptnCanada]

THAT sir, is a very nice 8!

 

[Brice]

Great project. Looking forward the completion and how you like the sound.

 

[Bert 1100]

 

[Pio1980]

THAT sir, is a very nice 8!

Fellow AKer in barter town within driving distance, a bucket list aquisition pending since Jr high school and Kennedy's candidacy.

 

[kcin]

Nice project. You should be able to make up a transformer shroud if you are so inclined. As to the caps you can keep the bumble bee's in as noted and use the direct inputs.

I'd test the couplers, I have had experience with leakage on some of the goodalls under test. I like the idea of re-stuffing the cans to preserve the look and shooting them with grey paint. The value in the amp is the transformers and of course the jewel like assembly techniques of the time.

With my 8b I experimented with caps from VAC that did the re-issues... I actually liked them better than the goodalls... I left it that way - however may change it back sometime just for fun.. Good luck with it !

 

[Pio1980]

Nice project. You should be able to make up a transformer shroud if you are so inclined. As to the caps you can keep the bumble bee's in as noted and use the direct inputs.

I'd test the couplers, I have had experience with leakage on some of the goodalls under test. I like the idea of re-stuffing the cans to preserve the look and shooting them with grey paint. The value in the amp is the transformers and of course the jewel like assembly techniques of the time.

With my 8b I experimented with caps from VAC that did the re-issues... I actually liked them better than the goodalls... I left it that way - however may change it back sometime just for fun.. Good luck with it !View attachment 794119 View attachment 794120 View attachment 794120 View attachment 794123

Just a thought.
Do you know why the model 5 was introduced if the model 2 was in the line?

 

[kcin]

Cost.... from what I have discerned . The 2 was parallel 6au4 damper diodes, triode switchable and switchable speaker damping options. Maybe trying to put more room between the 2 and the model 9 as well from a marketing perspective. I do think bean counting is the reason.

The 5 is much simpler less costly..

IMO the 2 beats hands down any of the Marantz amps in tone and body and resolution. Thanks

 

[Pio1980]

Hmmmm. Should guessed as that would meet the goal of offering the best, regardless of cost, to meet or exceed any commercial, professional, or broadcast standards of construction and performance. Have to wonder about the OPT OEM.
Never seen a model 2 anywhere, us mere mortals will have to take our model 8 as a consolation prize. Marantz appears to have sold a grunch of the 8B, assume they along with the 7C were the cash cows until r&d on the new products broke the company bank.

 

[crooner]

The Model 5 was indeed a lower cost version of the Model 2, but it also happened to come at the right time when stereo was starting to take off. Being more compact it was easier and less expensive to setup a stereo system based on two Model 5's. The Model 2 was still offered until at least 1960 as some of the brochures show...

I am surprised the Model 2 offers so much resolution. The output transformer lacks the single tertiary winding that first appeared on the Model 5. It also has that byzantine variable damping arrangement, I guess to offer something similar to the competing Fisher "Z Matic"....

 

[cptnCanada]

Is there any info on the production runs of each Marantz model?

It seems to me the serial number on the 8 continues on to the 8b. What is the highest number anyone has ever seen on an 8b?

 

[cptnCanada]

That's a nice looking 8b kcin. Glad to see all you model 8 experts here as I will definitely be seeking your expertise. One thing I have noticed with the transformers removed is that there is some chaffing of the wires coming from the transformer where it runs the housing. Not through the rubber insulator but on its way. I think I may install a small piece of heat shrink on the transformer wires where it enters the chassis to prevent any further chaffing.

Anyone run a three pronged plug with a ground? Would it be as simple as grounding the ground to the chassis?

 

[crooner]

Model 8 started at 1000 to around 4000 (3000 made).
Model 8B ended at around 11000 (approx. 7000 made). Highest serial number I have in my database is 10936. Kcin's example is very early at 4009.

 

[kcin]

Model 8 started at 1000 to around 4000 (3000 made).
Model 8B ended at around 11000 (approx. 7000 made). Highest serial number I have in my database is 10936. Kcin's example is very early at 4009.

Yes, I originally thought my amp was an '8' when I saw just pictures of it because it had the shadow residue of the Marantz logo on the transformer shroud . I thought only 8's had the logo on the shroud with '8B's' locating the logo on the front apron. I was mistaken.. Crooner is correct mine is a very early 8B. I think they moved the logo to the front apron somewhere midway in the production of the 8b. Mine is clearly an 8B as identified on the rear silkscreen and has the tertiary windings on the OPT.

I run a 3 prong cord + ground to the back apron through an existing screw- can't remember which one -for safety - no hum , no stray voltage on chassis.. you can try it.

 

[Auto Analog]

And also, the majority of Model 8's I've seen have unpotted power transformers with end bells. That's the way they came from the factory. The later 8B, of course, had all potted transformers.

The PTs in my Model 5s are unpotted, but the OPTs are potted. A 5 equals half of an 8...

 

[cptnCanada]

So had a chance to test all the carbon comp resistors and only found two that have drifted significantly. R20B and R21B are supposed to be 100 Ohms and are reading 128 and 156. After checking out the cost of the Arizona Cactus caps I think I'm going to go with the Russian PIO caps due to the cost. If I don't like them I can always upgrade down the road. Those little Sprague 15uf 6V (C3A, C3B) electrolytic caps that look PIO, do those need replacing as well, what is their purpose ?

Also, I am going to need schooling on what to do with the selenium rectifiers. I have never dealt with ss rectifiers and am clueless what diodes to use and if I need to modify the circuits or just drop in and replace. Any thoughts there?

Here is a pic of the simple green/water after soaking the chassis for around 1 hr. Amazing amount of crud that solution dislodges!

 

[kcin]

The 15uf electrolytic is a cathode bypass for the input it maintains gain at audio frequencies due to degenerative feedback- you can look it up....but yes change them

Change all the diodes I use GI856 I believe but 1n4007 will work you may not have to add any dropping resistance for the bias check your voltages after install

 

[cptnCanada]

Had a go at straightening out the chassis today an I am quite happy with the results. I used a ball peen hammer and a level to get it to what looks nice and square, only took about an hr of gentle manipulation.

 

[crooner]

Looking good!