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Marantz 18 & 19 Receiver Restorations

BlackScholes said:
My tuning needed a bit of a touch up so I sprung for this MEASUREMENTS 210-A FM Signal Generator. A beautiful instrument after thoroughly disassembling and cleaning the faceplates, knobs, dials, and windows.

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Why this model? A technical bulletin for my Scott 830 MPX generator named this 210-A model as one that would work with the 830 without any modifications. Sold. Now to get the MPX adjustments dialed in.

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Like the rest of this journey, nothing comes easy. The Scott Type 830 needed a good amount of work before I could even think about using it. To avoid this originally, I picked up a Sound Technology 1000A that of course did not work either. So I've been going back and forth as I receive parts and working on both. The Scott is the first to have all functions working and it seems like I'm close to having a functional tool here.
 
KentTeffeteller said:
Marantz Model 10, Model 10B, Model 20, Model 20B, Model 18, and Model 19 are not alignable by normal technicians. They are not meant to be aligned by anyone but the factory. Opto-Couplers aka LDR tend to be the main issues with them.
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Marantz suggested redacting this statement that it’s not alignable from the manual in one of the service bulletins. Wonder why that is?
 
I've been slowly getting the 18s and 19s up and running while gaining confidence with testing the receivers up to rated power (and beyond on the 18). On my HP 8903B, the best results I've achieved on one of the 18s is the following:

1 kHz w/ no filtering, Mono (L+R) pushbutton engaged, scope turned on.

SIDE + INPUT (from the 8903B into the the Tape input on the back of receiver)AC LEVEL (output into 8Ω w/ both channels driven)
SINAD​
S/N (signal-to-noise)​
DISTN (THD+N%)​
LEFT - 0.10 VAC19.18 VAC (46.0 watts)
69.4 dB​
73.4 dB​
0.034%​
RIGHT - 0.10 VAC18.93 VAC (44.8 watts)
69.6 dB​
73.7 dB​
0.033%​
 
With the HP 8903Bs 400Hz filter turned on (all else the same as the previous test):

Side + Input voltage (from the 8903B into the the Tape input on the back of receiver)AC LEVEL (output into 8Ω w/ both channels driven)SINADS/N (signal-to-noise)DISTN (THD+N%)
LEFT - 0.10 VAC19.07 VAC75.8 dB89.4 dB0.016%
RIGHT - 0.10 VAC18.93 VAC76.4 dB88.9 dB0.015%
 
Had to swap a transformer from a very rough, very early production Marantz 18 with a working scope to another that was a clean, late serial number unit with a bad HV winding. Not as difficult as I thought it'd be. Very messy though.
 
KentTeffeteller said:
Likely because that was held over from the 10B. Not an easy tuner to align. Do bear in mind, the 18 is not the best at weak signals or rural reception.
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I think it works generally fine after an alignment. I think to the average tech the available equipment to align them then was nowhere near as sensitive as it is now. I was happy with my 20 (non b) after the alignment but before the reception was mediocre.

I cannot comment on the alignment of the 10b since I have no experience with that model.
 
The 18 and 20 get great reception after alignment and if there is noise the 20 has hi blend feature (not quite as good as a kenwood kt917 though for example). They are all just needing aligned by now. 19 isn’t that much better.
 
They are honestly no different from aligning any other discrete tuner. Peak then adjust for distortion. If you can sweep the AF even better.
 
pjrengineer said:
The 18 and 20 get great reception after alignment and if there is noise the 20 has hi blend feature (not quite as good as a kenwood kt917 though for example). They are all just needing aligned by now. 19 isn’t that much better.
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In areas, which are rural, my once Terry DeWick serviced 18 got strong signals well. I wish I'd kept the Model 18 but used a tuner better for my reception needs. I loved it a lot.
 
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