Leestereo Marantz 1090 Revisited

hirscwi · Mar 30, 2014

I'm a big fan of Leestereo's thread. They always have a strong dose of technical information (which is good since I'm a recovering EE). But they're always very practical. So I read his 1090 thread with interest. I like the notion of selectively upgrading the caps to take advantage of technology that either wasn't available when the unit was built or were omitted because of cost pressures from the bean counters. So I acquired a 1090 and am diving into a restoration. My approach will be:

1. Brief, unscientific listening test
2. Reproduce Leestereo's restoration/upgrade (with a couple minor twists)
3. Replace part of the power supply with a kit
4. Replace most/all the signal path resistors with metal film

Here we go - wish me luck

Attached is an extract of Leestereo's original thread and some photos unmolested...

hirscwi · Mar 30, 2014

Listening Test

First step was to test using a dim bulb tester since I didn't know the provenance of the unit and didn'tw awant any surprises.

I compared this A-B to a 2225 that has been fully recapped and had the power supply tweaked a bit. Speakers were Tekton Lore-S.

The 1090 wasn't a pleasant to listen to as the 2225. The 2225 is of course an older topology and has been upgraded. As expected, the treble on the 1090 was a bit harsh and some of the midrange was less than clear. The bass was stronger than the 2225. So I'm hoping to gain the same improvements that Leestereo did.

catrafter · Mar 30, 2014

Tom

hirscwi · Mar 30, 2014

PCB 400 - p/s

First I tackled the PCB 400 which holds the phono amp, pre-amp and power supply. I initially thought I could get access to all the components without removing this board. You probably could do it this way but it was difficult to get to the p/s components, and I wanted to change a couple caps on the PV00 Rear Panel Ass'y. So I removed the screws from all the RCA jacks on the rear and the speaker terminals. I also removed the screws holding the rear case from the sides. The case was pulled away from the RCA jack assembly and then I could flip the PCB 400 to gain easy access to both boards. It was simpler than trying to work through the brace on the case bottom.

In addition to the changes made by Leestereo, I replace the 2 DS-133 diodes (TO220 pkg). I could not find a drop-in replacement so I used UF4005 wired in series, head-to-tail, with the joint covered in heat shrink tubing. Pay attention to the diagram on the board to get orientation correct, but otherwise simple.

hirscwi · Mar 30, 2014

Here's a photo of the new diodes in place of the DS-133.

Also a photo of the old diodes.

hirscwi · Mar 30, 2014

I replaced all the other caps in the power supply as per Leestereo's thread, except the main caps. He used 6800 mfd caps, which were the same value. I wanted to up those caps a bit. With Ben's suggestion, I found a Panasonic cap that would fit. It's a TS-UP 10K/50 volt low ESR snap-in cap that is 25mm x 50mm. The lead spacing is 10mm. The old caps are an obsolete 3 lead pattern, with one of the leads being a dummy for positive positioning. The spacing between the "live" leads on the old caps is 15mm but the spacing between each of the live leads and the dummy lead is 10mm. This allowed me to install the new caps without any modification to the board. On one of the new caps, the dummy lead was inserted through the same trace as the live lead so the new cap dropped in with no problems. On the other cap, the dummy lead was not connected to any trace, so a jumper was needed to connect the lead to the tract. I fashioned this jumper from 18ga. wire (and left some insulation intact to identify it). You should be able to see this in the photos. The last photo shows both caps in place from the bottom side of the board - clearly showing the jumpered cap and the non-jumpered one.

hirscwi · Mar 30, 2014

PV00 - Rear Panel

Next I replaced the 3 caps on the Rear Panel Ass'y - PV00. I used the values suggested by Leestereo. They were an easy replacement with the board detached from the rear panel. Be careful not to flex the ribbon cable more than necessary - the casing could be brittle. After these caps were replaced, I re-installed PV00 and PCB400. The remainder of the work to PCB 400 was done with the board installed - with decent access from the bottom - just a few wires to work around without burning the insulation.

Leestereo · Mar 30, 2014

That 1090 looks to be in great cosmetic condition; and with the upgrades it'll be just as nice sonically! Looking forward to your sound impressions!

hirscwi · Mar 30, 2014

Yes, it is in extremely good cosmetic condition on the inside and the outside. Required only very minor cleaning on the faceplate and virtually no dust on the inside. Just a small amount of film on the PCBs and this came off easily with denatured alcohol.

patfont · Mar 30, 2014

be gentle with them ribbon cables.

hirscwi · Mar 30, 2014

Phono Stage

The phono stage restoration was performed after the PCB 400 was reinstalled. I didn't want to take any chances with breaking connectors. I did leave the shaft extension for the Source and Function switches removed during this process, to give easier access to the top of the board. Note that some of the original caps were installed on their side to provide clearance for the shaft extensions. I retained this configuration.

One difference that I noted compared to Leestereo was that C423 was a 47/50 electrolytic (not a 10/50 that Ben had). So I replaced it with the same value (47/50) Silmic II.

The C413/C415 and C414/C416 parallel caps in the RIAA circuit were replaced with a single Xicon 12200pf polystyrene cap. A heat sink was used to avoid damaging the cap. Also the cap was held off the board with insulation from a 22 ga. wire (see photo).

hirscwi · Mar 30, 2014

patfont said:
be gentle with them ribbon cables.:d

amen.

hirscwi · Mar 31, 2014

Preamp Stage

I differed from Leestereo's recommendation on CE01 and CE02. I used a .22/250 Panasonic ECW compared to .47/50 ECQ. This changes the 3db frequency for this high pass filter from .34Hz up to .78 Hz which should still be acceptable.

Leestereo · Mar 31, 2014

hirscwi said:
I differed from Leestereo's recommendation on CE01 and CE02. I used a .22/250 Panasonic ECW compared to .47/50 ECQ. This changes the 3db frequency for this high pass filter from .34Hz up to .78 Hz which should still be acceptable.

The 0.22µF ECW is an excellent choice and it fits nicely on this part of the P400 board; as long as the high-pass F3 is <5Hz there is no problem.

hirscwi · Mar 31, 2014

Tone control board

I replaced CF11 and CF 12 - which were common ceramics with C0G/NP0 ceramics - 200pf/100. I was able to make this swap without removing the board (which removal looked tricky). Simply unsoldered and then pulled them forward toward the faceplate. Curved the leads to install the new caps.

Photo shows one new cap and one original.

hirscwi · Mar 31, 2014

More on the Phono section

I forgot to mention that I replaced C409 and C410 with 220/16 bipolar electrolytics. They were originally 100/10 polarized electrolytics. I used Nichicon UVP caps since the Muse series was out of stock when I ordered (might also have been too large in diameter).

Q407 and Q408 were replaced with 1n4148.

Q409 was replaced with 2 1N4148 diodes in series. There was very little space for this installation and I'll post a photo tomorrow.

hotrodms · Apr 1, 2014

Hello everyone I'm new here and have a 1090 amp that powers and no sound ,it was just making stat untill you wiggled the source knob but when my freind moved it to the other side of the room it has no sound.Does anyone know of a repair shop around memphis tn.?

hirscwi · Apr 11, 2014

Final 1090 results

The 1090 is completed and ready for the listening test. I've attached the final cap list.

Listening test:

Using Tekton Lore-S speakers and after about 50 hours of break-in. Most of the test was done using Winton Marsalis; Awadagin Pratt; and Chuck Mangione CDs with which I am quite familiar. I also checked out a couple vinlys. This is now a better sounding unit. The treble is much clearer and easier to listen to. Mid-range has a bit more definition and there is a bit more "tightness" to the bass. None of these difference are dramatic, but they are noticeable. I also believe tha changes madea substantial improvement to the phono section. And the unit is quieter now - thanks to the UF diodes.

I attribute much of the change to the replacement of the old ceramics with the much higher grade C0G/NP0 MLCCs. These removed some distortion in critical parts of the signal path. I suspect that some of the electrolytics helped also. A nice experiement would be to replace the electrolytics and perform a listening test. Then replace the ceramics. It's my unscientific view that the ceramics might have more impact than some high-dollar films

hirscwi · Apr 11, 2014

1090 Next steps

My plan is to replace the signal path resistors to see if this makes a noticeable improvement. I'm attaching a list of the resistors that I plan to replace. This will be very time-consuming but I've heard that it improved at least one man's 1060 so I'll give it a try.

I also plan to replace part of the power supply with a kit available from Jim's Audio. This will double the filtering capacitance (to 20,000 mfd per rail) and replace the bridge rectifier with MUR3020WT diodes. I'll also add a TRIAC soft switch. I'm not expecting much improvement but it will be a test of this power supply - which I plan to install in an 1120 that I'm rebuilding.

The bottom line - I think the 1090 can be a very nice integrated amp and worth the time to restore/upgrade.

patfont · Apr 11, 2014

.......be careful with resistor replacement you can now move to the realm of very clinical but you may like that. I had a 1070 preamp board with all metal films, and found it better to use a nice sweet sounding resistor at the inputs, other more technical people will disagree but have fun. I base all my work on checking the tech side but listening can override them findings, and often does.

I did however use some vishay CMF series in a Sansui 9090DB and it faired well.

Leestereo Marantz 1090 Revisited

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