Marantz 2330 - slight pop when turning on and off

[Redkarter]

I purchased this 2330 in non working condition from an electronics recycler some time ago and tried my best at cleaning it up. Everything went rather well, it does look and sound great with lots of power to spare.

Unfortunately there is a slight pop on turnoff. Also a very quiet, possibly 60hz buzz that does not increase with volume. The pop does exist when changing the speaker selectors after the unit is on.

The bias, offset and ps voltages have been set. I have recapped the amp boards, power supply, tone, dolby, phono board and replaced the main filter caps as well. Mostly with the same value caps and only the electrolytics. I have checked over all of the grounding wires and their connections, cleaned and bypassed the powerswitch. I have also cleaned the amp connectors. Some things I have not done: changed the relay in the power supply. I have not put bypass caps at the filter caps or a new snubber cap for the power switch, although the old one is in there.

I have been enjoying this beast otherwise and its currently hooked up to a pair of heresey and pioneer cs63dx and powers all 4 to unbearable volumes.

 

[sanjib]

I will suggest replacing the relay and check all the new solder joints.

 

[Redkarter]

I will suggest replacing the relay and check all the new solder joints.

I'll give that a go first. I have a new replacement relay that will work for this.

 

[catrafter]

I wonder if the power amp's (one or both) DC offset is creeping up as it gets warm.
Tom

 

[rBuckner]

^^^ If not, I bet it's the BA312 ICs in the tone amp. I tracked this down in a 2275 once. Some make the popping noise and some don't for some reason. Also have had a unit with the very nice Sparkos Labs upgrades and it did it too, right at the module output. Maybe it's how the power supply comes up and down? Gotta play with this someday!

 

[Redkarter]

Just wanted to give an update as my memory is letting me down. The pop is evident when turning ON and OFF.

I will be replacing the relay and also replacing the cap that controls the relay timing to hopefully slow it down a bit. Currently I get the relay click/pop after about 1 second, then .5 second after the relay closes the sound comes in.

It really doesn't have an exact pattern unfortunately. Sometimes turning off after playing for awhile it won't pop at all, but turning on then off in quick succession it will pop slightly on turn on and a bit louder turning off.

 

[AE Bob]

"Unfortunately there is a slight pop on turnoff. Also a very quiet, possibly 60hz buzz that does not increase with volume. The pop does exist when changing the speaker selectors after the unit is on."

You say the pop exists when changing the speaker selectors after it is on. This would indicate that you have a DC offset. I would check the DC offset again. The speaker switches cannot make much of a pop in the speaker when turned on or off, unless there is a DC offset of well over 10 or 20 mV (likely over 50 mV if it is truly annoying) that is being switched on and off to the speaker.

 

[Redkarter]

"Unfortunately there is a slight pop on turnoff. Also a very quiet, possibly 60hz buzz that does not increase with volume. The pop does exist when changing the speaker selectors after the unit is on."

You say the pop exists when changing the speaker selectors after it is on. This would indicate that you have a DC offset. I would check the DC offset again. The speaker switches cannot make much of a pop in the speaker when turned on or off, unless there is a DC offset of well over 10 or 20 mV (likely over 50 mV if it is truly annoying) that is being switched on and off to the speaker.

That makes sense. I just popped my meter in the terminals to take some measurements.

Turning on: R and L channel produce ~2v spike that settles completely after 3-4 seconds. (Saw as high as 4.3v spike once)
Changing speaker selectors: ~ 1mv spike very subtle pop.
Turning off: Unable to reproduce pop for some reason, no noticeable spike on meter.

Offset is less than 5mv on both channels after 3-4 seconds, settling to ~1-2mv after 10 or so seconds.

 

[AE Bob]

Is your protect relay closing too soon? It should stay open at least 4 or 5 seconds after turn on.

 

[Redkarter]

Is your protect relay closing too soon? It should stay open at least 4 or 5 seconds after turn on.

I think that's one of the issues. If I could get 4-5 seconds in protection I think a lot of this will be alleviated.

I believe caps c811, c812 and c813 control the protection circuit but I'm not sure which specifically controls timing. Possibly c811?

 

[mbz]

I believe caps c811, c812 and c813 control the protection circuit but I'm not sure which specifically controls timing. Possibly c811?

I'd lean towards C813. C811 is more for smoothing

 

[AE Bob]

C 813 is the timing capacitor. It gets charged through R816, and turns on H806 and H807 which turns the relay on (through the two temperature sensors on the heatsinks). If C813 has lost value or is open, it will shorten or eliminate the turn on delay. No turn on delay could also be caused by leaky or shorted H806 or H807.

 

[Redkarter]

Finally got around to swapping C813 for a 25v 470uf cap and it seems to have slowed down the relay. It is still faster than all of my other Marantz units, but I will accept good enough for now as I have more pressing projects.

Sorry for the bump but wanted to say thanks and let folks know it did help.

 

[Redkarter]

Update here!

Following the advice from the below thread I repaired a Model a 2240 with this exact symptom. Exhibiting a harsh turn off snap. On the 2240 C807 was changed to a 4.7 uf and it resolved the issue. I remembered I had my 2330 with a similar issue, changing C811 on the 2330 seems to have majorly resolved the issue. The schematic shows it as 10uf and there was a 22uf in place likely making the issue worse off.

https://audiokarma.org/forums/index.php?threads/2275-stumper.102160/