Marantz 3300 Preamplifier High/Low Gain Troubleshooting

[Pickel Juice]

Hello Fellow Akers,

I have a semi-functioning Marantz 3300 preamp with a High/Low gain issue. I get high gain volume in one channel, but don't get high gain volume in both channels. I do get low gain volume in both channels. I have deoxit the high/low gain switch with D5, but have not seen an improvement in the high gain switch functionality, just one channel functions at high gain. Today, I left the preamp on in the high gain position and both channels were functioning at low gain volume in the speakers until a few minutes later when one channel jumped to high gain volume. So I have an intermittent problem. I have ordered a replacement switch from Digikey and will slave it in to see if the problem is the switch. IF that doesn't solve the problem, I will tackle the 10X board.

Has anyone had a similar issue with a Marantz 3300 preamp or similar? I'd like to hear your story and any suggestions for troubleshooting. Thanks!

 

[Namlook]

Why don't you measure resistance of the switch in the different positions? That will tell you if the switch is bad or not. Additionally, you should be able to disassemble that kind of switch to clean it properly if necessary.

 

[Pickel Juice]

Switch is good, so I will pull the 10X board and start testing components. Trying to be smarter than a 50-year-old piece of electronics is challenging....

 

[Lavane]

All of the electrolytic capacitors should be replaced. I restored a 33 and a 3300 some years back. I found dried out seals and some of the values of those old caps had drifted. The switches pots, and selectors will need a good cleaning.
When the pots and sliders are cleaned with a good quantity contact cleaner, add a couple drops of Fader Lube to the pots and sliders. That will help to keep them noise free longer. I restored a Marantz 1060 integrated amp some 12 or 13 years ago and just recently put it back into my main system using it as a preamp. All the controls are still noise free.
Does the gain problem show itself with all sources? Have you tried all the inputs on the selector switch? These can cause drop outs and low gain problems also due to needing a good cleaning. I found switching the selectors back and forth, or just bumping them back and forth a bit can effect the output when dirty due to carbon build up and corrosion. A dirty balance control can cause weird things to happen also.
Just a few thoughts and things to try if you haven't yet before getting elbows deep into it. Once sorted the 3300 is a nice preamp.

 

[Pickel Juice]

All of the electrolytic capacitors should be replaced. I restored a 33 and a 3300 some years back. I found dried out seals and some of the values of those old caps had drifted. The switches pots, and selectors will need a good cleaning.
When the pots and sliders are cleaned with a good quantity contact cleaner, add a couple drops of Fader Lube to the pots and sliders. That will help to keep them noise free longer. I restored a Marantz 1060 integrated amp some 12 or 13 years ago and just recently put it back into my main system using it as a preamp. All the controls are still noise free.
Does the gain problem show itself with all sources? Have you tried all the inputs on the selector switch? These can cause drop outs and low gain problems also due to needing a good cleaning. I found switching the selectors back and forth, or just bumping them back and forth a bit can effect the output when dirty due to carbon build up and corrosion. A dirty balance control can cause weird things to happen also.
Just a few thoughts and things to try if you haven't yet before getting elbows deep into it. Once sorted the 3300 is a nice preamp.

The gain problem shows itself when I switch from low gain to high gain. Sometimes I get high gain in one channel, usually no high gain in either channel. I cleaned the switch thoroughly and desoldered and DMM tested all contacts which checked out good. I think the switch can safely be eliminated. The two 47uf electrolytic capacitors tested 104uf with a one ohm ESR. I plan to replace all the electrolytic capacitors. Did you have to replace any transistors? Thanks!

 

[Lavane]

The gain problem shows itself when I switch from low gain to high gain. Sometimes I get high gain in one channel, usually no high gain in either channel. I cleaned the switch thoroughly and desoldered and DMM tested all contacts which checked out good. I think the switch can safely be eliminated. The two 47uf electrolytic capacitors tested 104uf with a one ohm ESR. I plan to replace all the electrolytic capacitors. Did you have to replace any transistors? Thanks!

No, I didn't have to replace any transistors in the 3300, they all tested good.
Good luck with the restore. The 3300 is one of the better top of the tine Marantz preamps.

 

[Pickel Juice]

Just to update the repair of the Marantz 3300 Preamp: I managed to get even sound levels in both channels in low gain and high gain, but have not gotten the 20dB high gain boost when the high gain is switched. The balance pot which I had cleaned earlier needed more attention and I got it working properly after a good plastic-safe electrical contact flush, followed by a single shot of D100 and plenty of knob turning. This is an improvement over the previous condition, so I will live with it for now. I get plenty of volume when the 3300 is hooked up to the 250M amp, even at low gain.

I went and recapped the entire 3300 using Ben from Milwaukee's kit off of EBay. Thanks Ben! Some observations from the recap: The P600 power supply board that I had used 470 uf caps instead of 680 uf caps (See photo). When I compared my PS board to others currently on sale on EBay, I discovered that other 3300 preamps used 500 uf or the 680 uf caps on their PS boards. Apparently, there is quite a mix out there! Several of the old caps on multiple PCBs were 100-125% out of spec. Another observation on my P300 tone board, resistor R322 is missing, never installed (See photo). I guess the circuit design I have was an earlier or later version. The Marantz 3300 serial number I have is 9411. Also on the tone board, in the manual, capacitor C317 is mislabeled as R317. There are two components labeled as R317, an obvious error. Finally, working on the 3300 was a real pleasure, with all boards and controls easily accessible.