Marantz Model 18 restoration

[pjrengineer]

Q702 looks bad per my voltages. Collector emitter short.

 

[pjrengineer]

Noticed that someone replaced the 34-1011 (q703) transistor with a bad sub. This is what I find a few times of people swapping transistors that are not suitable on units I find that are not working. I chose to use ksa992 based on the marantz 19 parts list. Now the phono channel is restored and time to button things up. Curious if anyone has any comments whether it’s the most suitable sub but I’m one step closer to listening.

 

[Lavane]

Resistors and diodes good. The symmetrical layout made checking them in circuit a breeze.

That's one thing I liked about the older SS Marantz gear. The symmetrical layout of the boards made trouble shooting easier.
Did you look up the data sheets for the two transistors to compare them?
At leased you found the problem and are getting sound out of the phono section now.

 

[pjrengineer]

That's one thing I liked about the older SS Marantz gear. The symmetrical layout of the boards made trouble shooting easier.
Did you look up the data sheets for the two transistors to compare them?
At leased you found the problem and are getting sound out of the phono section now.

There is no data available on the Marantz transistor’s since they used their own labeling and numbers but I did look at the ksa992 data and appears good. The Voltages are now back in line as well. I haven’t seen anyone state a suitable sub on ak for this transistor and that maybe why the last tech who worked on it threw in whatever part they had in their stash and it failed and didn’t work.

 

[Lavane]

It's too bad no one chimed in on what is a suitable replacement.
I know I've seen several thread on restoring this model receiver.
It sounds like what you used will work just fine though. Nice work.
At leased now if someone has the same problem there's a thread showing a suitable replacement.

 

[pjrengineer]

Back in the wood case. What a ton of work! Measures about less than 0.3% Thd 20-20k at 50 watts output. My marantz 19 measured a little lower after restoration but I did a lot more parts swapping and it has further adjustments available on the driver boards. I am ready to be done with this project and use my ears to test.

 

[Lavane]

Very nice.

 

[pjrengineer]

Thanks again

Very nice.

 

[onemug]

I am ready to be done with this project and use my ears to test.

Fellow 18 (and 19) owner here... been admiring your work here. Nicely done!

I've had my 'teens' for about 17 yrs, still can't decide if I like one more than the other and I 'do' hear differences. How about you?

 

[pjrengineer]

Fellow 18 (and 19) owner here... been admiring your work here. Nicely done!

I've had my 'teens' for about 17 yrs, still can't decide if I like one more than the other and I 'do' hear differences. How about you?

I appreciate your input. The 18 is smoother while the 19 is more detailed. The 19 is a little punchier. They both have equal tuners but I haven’t cleaned my 19 tuner yet. Maybe that will improve it some over the 18 then. I can’t seem to find anything that sounds better than a marantz 18 or 19 after being through a lot of tube and solid state gear. Unless you need more power I guess.

 

[onemug]

The 18 is smoother while the 19 is more detailed

That's pretty much what I hear also. Enjoy!

 

[pjrengineer]

This is possibly going to displace some tube amps for the long term. It does a lot and the sound draws you into whatever you put on.

 

[onemug]

possibly going to displace some tube amps

I can see (hear ) that. I love/have tube amps... they have a certain quality about them that I really enjoy.

One thing I like to do, if the 18 is going to be on for awhile, is use one of the centering knobs for the scope to completely move it off the screen. It keeps the phosphorus nice and bright when I do want to watch it dance.

This can be done on the 19 with a push button, and many think the scope will last longer... not true. There is still a lot of voltage going to the scope even with the display off but the display should stay 'brighter/longer' and with less burn spots. That said, along with the 18 and 19, I have two 20b tuners and one 20 all with the same 1" scopes and have never had a problem with any of them in 20 yrs and they are still bright and working as should.

 

[Lavane]

Small Marantz didn't want to change over to SS until the transistors became better. He wanted to be able to design his SS equipment to sound as good as tube equipment. I think he succeeded with the 18 along with the 7T preamp and model 15 and 16 mono blocks.

 

[onemug]

I think he succeeded with the 18 along with the 7T

100%... I bought my 7t just for it's looks, especially in it's wood cabinet. It's one of the best early ss preamps I've ever heard. I have one hooked up to a 250m in one room and an 8b in another and really enjoy their sound. Even had the T hooked up to a Pass XA30.5 and Bedini 45/45 over the years, again with pleasing results.

 

[Lavane]

100%... I bought my 7t just for it's looks, especially in it's wood cabinet. It's one of the best early ss preamps I've ever heard. I have one hooked up to a 250m in one room and an 8b in another and really enjoy their sound. Even had the T hooked up to a Pass XA30.5 and Bedini 45/45 over the years, again with pleasing results.

I read a thread in another forum several years ago where a group of people sat and did a blind A/B test between the 7C and 7T. Most of them couldn't tell the difference between the two.

 

[Robert Moser]

I appreciate your input. The 18 is smoother while the 19 is more detailed. The 19 is a little punchier. They both have equal tuners but I haven’t cleaned my 19 tuner yet. Maybe that will improve it some over the 18 then. I can’t seem to find anything that sounds better than a marantz 18 or 19 after being through a lot of tube and solid state gear. Unless you need more power I guess.

Actually, the model 18 has the Marantz model 20 tuner, which has a passive front end, while the model 19 has the Marantz model 20B tuner, which has an sctive front end and pulls in weaker FM signals..