Marantz 1070 Preamp issue - Left channel low

Hey guys, just wondering if there is anything obvious I can check for to see if a cap or transistor is gone in the preamp section my 1070. It has been cleaned and deoxited properly and the Idle/DC offset and Power supply adjustment is now correctly set.

The problem occurs with both headphones and speakers and goes to other side when I use a jumper on the pre out/main in with 1 side swapped left to right. The bass pot was my first suspect as it seemed to cause a popping sound through the bad channel but it came good with a clean so I'm thinking it has to be HE01/03/05/07 or CE09/11/03/05 on the preamp board (in the middle near front of amp) if not a resistor somewhere around them? Is there anything I can check with a multimeter to narrow it down?? Also, what is the best way to remove the board...it has those spring type connections at 12 points on the board...are they just supposed to slide off or is there a trick?

Thanks guys!

Just finished a 1070 for a customer. 1 channel was 20 db low. Replace all of the electrolytic capacitors in the tone amp and the driver (output) amps. be aware that some of the caps in the tone amp are non-polarized. As for the connectors, those are wire-wrap connections. If you must remove them, just cut the wire, and solder it back to the post when done.

Sometimes it's easy enough to just unsolder the post, leaving the wire wrap connection intact. Then just resolder the post when ready. I go both ways

I've been thinking about snagging one of these. Does anyone know if the preamp section is similar or the same as the 3200 preamp? If so I'll pass. But the 1070 looks to have a decent phono stage after a proper recap.

Thanks guys

previd01 said:

Just finished a 1070 for a customer. 1 channel was 20 db low. Replace all of the electrolytic capacitors in the tone amp and the driver (output) amps. be aware that some of the caps in the tone amp are non-polarized. As for the connectors, those are wire-wrap connections. If you must remove them, just cut the wire, and solder it back to the post when done.

Click to expand...

The output section seems fine...do you think if I were to replace all the preamp caps it would come good? Any suggestions as far as type/brand?

rBuckner said:

Sometimes it's easy enough to just unsolder the post, leaving the wire wrap connection intact. Then just resolder the post when ready. I go both ways

Click to expand...

Oh so I can unsolder the posts? I'd prefer to do that so it looks as the factory intended...just couldn't see underneath to see what was going on. Might be a bit fiddly I suppose haha

*edit* never mind...I just realised the only thing holding it down was an earth. Once that is undone, you can position the board so the suspect caps can be unsoldered from the bottom

If we have read this right, You have low output. Is this distorted or just low?
You ruled out the mains like you figured.
What Randy meant is that the wire should stay wrapped around the post and the post heated from the bottom and carefully wiggled out of the board.
It is real important that you make a drawing of all the wires before removing them. Heating the post to get it out is easy enough, but Resoldering it back in requires you to be able to look at your work.
My personal preference is to keep it stock looking, but that is not always possible. They make a tool for wrapping them, but i haven't been able to get over to Randys shop to steal his yet, so i stick to removing the post
Look for bad solder joints while your rebuilding the board.
As far as capacitor preference, A lot of guys like the Elna silmic2 and Nichicon Muse, but there are many more. The preferred route is to replace all electrolytic and tantalum capacitors. Use film(wima/panasonic/kemit) capacitors in place of any electrolytic caps, 4.7uf - 1.uf .

Make darn sure you right down the cap direction before removing it, and as said before, there are a few non polar caps to look out for.

Beware of anything that was done to it before you start working on it. Someone before you could have a wire misplaced or a cap in ass backwards. Do not trust your memory or the board markings, right it down on paper and do your work alone. Distractions can have undesired results.

Most importantly., Google "dim bulb tester" and make a quick one out of a lamp. Use a 60w bulb, unless somebody reading this suggests otherwise. It may save your amp from smoking. Ask me why i know this. Being positively sure you did the job right, and bypassing the DBM, could end in disaster.
BKMarantz pounded this into my head and i pass it on to you. :thmbsp:

KutzlerTrans said:

If we have read this right, You have low output. Is this distorted or just low?

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A bit of both i think...mainly low though

KutzlerTrans said:

As far as capacitor preference, A lot of guys like the Elna silmic2 and Nichicon Muse, but there are many more. The preferred route is to replace all electrolytic and tantalum capacitors. Use film(wima/panasonic/kemit) capacitors in place of any electrolytic caps, 4.7uf - 1.uf .

Click to expand...

Any particular reason to use film caps instead...Sound/reliability? I noticed there are 1 per side that are the big funny shaped orange ones and 1 per side that are a rectangular square shape. What's that all about? Do they need to be the same? They are all listed as electrolytic in the service manual

KutzlerTrans said:

Most importantly., Google "dim bulb tester" and make a quick one out of a lamp. Use a 60w bulb, unless somebody reading this suggests otherwise. It may save your amp from smoking. Ask me why i know this. Being positively sure you did the job right, and bypassing the DBM, could end in disaster.
BKMarantz pounded this into my head and i pass it on to you. :thmbsp:

Click to expand...

Sounds serious...I'm confused but will google


Thanks!

Reliability first. They should outlive us. I have no experience with swapping out capacitors for sound differences, but the film is known to let the signal through without altering it in any way.
The waxy looking brown capacitors never fail and should be left in. As far as the funny looking orange ones, I'm not sure what you mean.

If this was my problem, i would swap sides on the input pins of the pre amp to confirm it is actually in the preamp or switches.

By the looks of the shrinkwrap on the caps of the preamp, they are due for changing, that's for sure,

KutzlerTrans said:

Reliability first. They should outlive us. I have no experience with swapping out capacitors for sound differences, but the film is known to let the signal through without altering it in any way.
The waxy looking brown capacitors never fail and should be left in. As far as the funny looking orange ones, I'm not sure what you mean.

If this was my problem, i would swap sides on the input pins of the pre amp to confirm it is actually in the preamp or switches.

By the looks of the shrinkwrap on the caps of the preamp, they are due for changing, that's for sure,

Click to expand...

That's probably a good reason for me to stay with electrolytics really...I don't want to mess with the sound AT ALL. If the original electrolytics have lasted 40 years, I'm sure a fresh set will last a few years!

What do you mean when you say input pins? I'm curious to try...although I'm probably just going to replace all the caps in the preamp anyway.

Oh, and it was the funny looking brown ones I was referring to...not orange


p.s. That pic above is not mine, just for illustraltion purposes

Went with a hunch and replaced a couple of caps and the second one nailed it...turned out to be CE05. Pretty stoked it was an easy one.

Did they look as bad as the ones in your "example" picture? They looked pretty used up.

As far as the "changing capacitors ruins the sound" theory, that IMO is simply not true.
The Marantz sound comes from its design. You just learned first hand what old capacitors are capable of doing when they fail.
That deceitful theory is to hide the fact that replacing them cost money and takes a lot of work and time.
You will not find a single experienced technician that would agree with that "masters of deceit" theory.

I may be stepping out on a limb here and can only tell you what i have read and found out firsthand. A capacitor can change the sound. it can ruin it.
When a Band goes into a studio to record, they expect the recording to be an accurate rendition of the song. It must be clear and void of noise. Capacitors play many roles in a receiver. some to pass and filter frequencies, others to filter voltage and smooth it. Smooth DC Is the goal. As a capacitor is no longer able to store voltage, your power supply voltage sags.

Nowhere, have i read, that Sagging Unpure dc is required to get the "Marantz Sound" Marantz used good quality capacitors and they were new. That is why, 35 years later, these units are still sounding good. Restoring them, makes them sound great. When you can hear the band talking in the recording, you will understand what i mean.
Mr Buckner has been a mentor to me and has beaten two words into my head about capacitors. Clarity and Accuracy.
The trick is in finding the right capacitor for the job that they are to serve for the next forty years.
This is a subject for the experts. I am just a novice that hangs out and causes havoc and spreads bad information. When that happens, these guys correct me and push me back into the hole i crawled out of.:yes:
So, back to the subject at hand,
The Power Supply capacitors must be running on empty also. Replacing them would be a wise move, and may just wake that thing up. I wouldn't be surprised if you noticed a big improvement in sound quality.
Keep up the good work!:thmbsp:

Nah they looked ok! Sorry to sound like a noob, but by power supply caps, you're referring to which ones? Not the massive ones obviously?

If your interested,

Put a voltmeter on your rail voltage , Load the amp down and turn it up. Check and see if it drops.
Put another voltmeter on the power supply and check for AC on your dc. (Checks your diodes)

If all is well, then your good to go. If not, you know what to do.

I added info on the last post about changing the sound through a recap. Its worth reading.