Early 1030 Restoration Questions

[Jeff W.]

I realize there is much information available on this little guy, but there are couple questions about this early model for which I have not seen the answer or a definitive one. For those that may be curious, mine is serial number 1399 and has a silver (or natural aluminum) engraved faceplate and has preamp input/output jacks.

My first question concerns the power supply board (P800). Mine looked like all the components were original, but resistor R802 was 1.2k ohms (per color code and approximate measured value upon removal) whereas the service manual I have indicates this resistor should have a value of 8.2K ohms. Would someone please confirm the correct value? The amp has been working for over 40 years with this installed, but I'm still curious to know. I do know Marantz Service Manuals of this era are known for many errors. The manual I have shows the preamp jacks in the photos and on the schematics so it has to be a relatively early version, but I'm also wondering if a change in value (for the better) may have been made after mine was built (refer to my final note about my phono board)

My next question is about replacing the H713 and H714 varistors on the power amplifier board (P700). I saw a thread on AK that recommended using one 1N4148 diode. This is what I have installed. Subsequently I have seen another restorer recommend two of 1N4148 in series and another recommendation to use a (or possibly a series of) 1N4448 diode(s) after measuring the voltage drop of the original part. The last sounds like the intelligent, scientific way to go, but I have already committed my originals to the garbage weeks ago so I can't measure them. I can tell you they were the "gob" type with a red dot on them. The service manual gives the number S3016R. I will look to see if I can find any specs. on this old part in the meantime, but if you may have the definitive answer from experience I'd appreciate knowing your results.

For those of you that may embark on restoring one of these early 1030's please be warned that I found many errors on the PCB's silkscreened labeling concerning capacitor polarity. Many capacitors were installed opposite of what was indicated on the board. Mine had all original caps when I purchased it and the amplifier worked, so I knew the silkscreened information was wrong. Please observe installed polarity before removing components and don't depend on what is printed on the board of these early models. I have seen photographs of these same boards on later 1030's where this information has been corrected.

Another note on this early model: On my phono board (P900) caps C909 and C910 did not have the resistors R936 and R937 installed in series with these caps to ground. This must have been a change that occurred after mine was built. It does show them in the manual I have and I did install them on my phono board suspecting that it was a running change for improvement.

Thanks in advance for any enlightenment.

 

[Richs_Trains]

Well, I can't help on the resistor question, but I have found many things different than the SM and pretty much replace with the same value as installed unless it looks like someone was inside the machine before. It is usually pretty obvious if someone has worked on the PCB's in the past and if they look untouched, I replace value for value. Now, about the varistors, most on AK treat those like gold and much prefer the originals as they very rarely go bad. I had a 4060 that I broke the wire on and was able to substitute 2 1N4148 diodes in series as a replacement. They're biggest failure is breaking the connections when working around them. Unfortunate that they hit the trash, I always keep all the old components until I have completed a project in case I messed up somewhere and need to "go back". PCB markings seem to be fairly unreliable, so I always pull and replace noting the original orientation. Good luck Rich

 

[Jeff W.]

Thanks for responding Rich and thank you for the well wishes. I agree, it's rarely a bad idea to keep old parts for many reasons and I should have held on to mine until the project was over at least. I could have measured mine and known the answer.

I did toss them, but I don't think is the same part that you mention. If you are referring to the (thermistors?) that connect to the back of the board and are held against and cooled by the main heat sink then these were different. H713, 14 are on the front of the board. I think they are typically replaced because of their reputation for being unreliable, much like the similar looking ones with a white indicator dot used in much of Sony's mid seventies equipment. I know the ones to which I think you refer and read some threads warning about these being tough to replace as this type of device is no longer made. I did see that these break easily at the device body and was careful working around them. They're still intact on the back of my board and I hope to keep them that way through the end of the project.

I think I did finally locate some good evidence about these two questions in "tonebells" post here: http://audiokarma.org/forums/index.php?threads/marantz-1030-lives-again.646914/ . He has attached a parts list for the 1030 at the bottom of his first post which I hadn't seen the first time I glanced through his thread. He lists 8.2K ohms for R802 and that he subbed a single 1N4148 for H713 and H714. He confirms the single 1N4148 in another thread where someone asks about a substitution for these. His 1030 is also an early model like mine. Thanks for publishing this information tonebells! If I don't hear any information to the contrary I'll probably forge ahead using this information.

 

[tonebells]

One 1N4148 will do the trick. I don't recall there being anything different about R802.

Tony