1070 Restoration

[IASTM]

It's been a while since I worked on a Marantz. Just fished this mid-1970s Marantz 1070. I own a 1060 and it's been restored as well. The 1060 is warmer, more tube-like. The 1070 is very clinical, very clear and such a wide dynamic range. The highs are very high and bass very low.

Replaced the main filter caps with Cornell Dubilier Knowles SLPX 15,000uF and all the other electrolytic caps - audio path mainly Nichicon UFG and Panasonic FC/FR for power. A few WIMAs in there (1uF and 3.3uF).

Changed almost all of the transistors with mainly KSC1845 and KSA992. hFe matched where differential pairs of course. There were two instances of using KSC2383 (one in the PS and one on the amp board). Output transistors left as is, just put on fresh thermal paste. I did swap a few higher ohm resistors on the phono and tone boards for metal film to lower the noise floor (one was actually out of spec). Faraday tape over shields for extra RF shielding, lubed, calibrated, DeOx'd.

Tried the new relay c/o the "milky white" SCHRACK from eBay and it did not work. Instead, I used a heavy duty OMRON LY2-0-DC24 secured in the space where the longer main filter caps were with wires running to the amp board. Left the two Sanyo metal can transistors in (H707/708) in place as is (for now). Also left the H721-724 as is. Left all the big brown film caps in. Didn't change any of the diodes, but perhaps I should have?

Left the original trim pots as this unit was in immaculate condition.

Sounds incredible!

 

[preacherJohn]

I'm getting ready to restore my 1070 I picked up several weeks ago within the next month (pretty busy with other receivers now) and I'm just looking at what others have did or changed in this amp. I see on the schematic the main filter caps are 10000uf and you used 15000uf cans. I'm far from being an engineer, just a retired hobbyist that repairs and refurbs vintage receivers and amps for the last 10yrs or so. What benefit is it using 50% more capacitance? Does it increase the bass sound or anything like that. I also have a 1060 I bought 2 weeks ago with 4 other Marantz products as a group deal. That 1060 does play, and to me it sounds clinical compared to my 2270 or even the 2230 I just finished. I was hoping restoring it might change that sound a little.

 

[rBuckner]

I'm getting ready to restore my 1070 I picked up several weeks ago within the next month (pretty busy with other receivers now) and I'm just looking at what others have did or changed in this amp. I see on the schematic the main filter caps are 10000uf and you used 15000uf cans. I'm far from being an engineer, just a retired hobbyist that repairs and refurbs vintage receivers and amps for the last 10yrs or so. What benefit is it using 50% more capacitance? Does it increase the bass sound or anything like that. I also have a 1060 I bought 2 weeks ago with 4 other Marantz products as a group deal. That 1060 does play, and to me it sounds clinical compared to my 2270 or even the 2230 I just finished. I was hoping restoring it might change that sound a little.

If you do bigger filter caps, I'd also up the amperage on the rectifier diodes. Like 2X or more.

 

[preacherJohn]

If you do bigger filter caps, I'd also up the amperage on the rectifier diodes. Like 2X or more.

I can do that; but what is the purpose of going 50% higher in capacitance?

 

[rBuckner]

People think it gives better bass thump. I'm not amongst them. (Where's my Nomex suit again?)

 

[preacherJohn]

People think it gives better bass thump. I'm not amongst them. (Where's my Nomex suit again?)

 Oh, this might be subjective then. OP says that his sounds clinical. Could be with all the different mod changes it is. I have 10 Marantz's and they're anything but clinical or sterile sounding. I believe the engineers got it right from the get go. I pretty much keep the components the same except for obsolete parts. I do increase the temp range on the electrolytics, and maybe use film caps for anything 1uf or under if they fit on the board. I'll be starting on the 1070 in a couple of days. I had foot surgery yesterday and now I'm wearing a boot and its pretty sore this morning. My shop is in the basement and I've been enlarging my bench for the last week. Almost have it finished. I have to sneak around my wife now, she doesn't like me using that flight of stairs to get down there. The rest is pretty much sitting at the bench.​