Troubleshooting a random crackle in a Marantz 2270

[dankik]

@ivandezande, the OP has said a couple of times he does not have the equipment or knowledge to do any circuit troubleshooting or repairs. So I was trying to help suggest ways to isolate and eliminate all other potential problem sources that may not require component replacement. Thanks.

Unfortunately I don't have any other equipment available to use for testing.

I know less than nothing about repairing and/or soldering electronics, so any replacing of transistors will likely mean hiring someone to take a look at it. (I literally don't know the difference between a transistor and capacitor).

 

[ivandezande]

@ivandezande, the OP has said a couple of times he does not have the equipment or knowledge to do any circuit troubleshooting or repairs. So I was trying to help suggest ways to isolate and eliminate all other potential problem sources that may not require component replacement. Thanks.

Totally understand, but it’s clear that the issue is beyond the OP and it needs to go to a tech.

 

[dragnalus]

Good so far, but the purpose of this test was to try to determine the circuit location of the crackle, but you did not report on the details of which speaker the crackle was heard.

• The test was to press ONLY the L Mono button, then listen. Is the crackle still there? Does it come out of both speakers?
• Then, un-press the L Mono button, then press the R Mono button and listen for the crackle. Is it still there? Does it come out of both speakers?
• If pressing these buttons one-at-a-time does not affect the sound of crackle in only the L speaker, then it is being generated after the switches. The way the Mono switches work is to take either the L OR R channel audio and "connect" it to both the L and R channels for amplification. This test was designed to try to locate the part of the Preamp that was causing the crackle.
• If pressing the buttons, does affect the crackle sound then it is being produced before the Mono switches, if it doesn't then it is being produced after the switches.

I wouldn't spend time cleaning anything until we finish conducting these tests to isolate the part of the circuit that is causing the crackle.

Thanks for reiterating everything. I had noticed that the crackle was still happening regardless of whether the L Mono or R Mono buttons are activated, however I didn't confirm which speakers it was coming from. I've just done this testing again to double check, and I can confirm that the crackle still happens only on the right side channel regardless of whether the L Mono or R Mono button is activated. So it seems to be happening after the mono switches...

 

[tarior]

Thanks for reiterating everything. I had noticed that the crackle was still happening regardless of whether the L Mono or R Mono buttons are activated, however I didn't confirm which speakers it was coming from. I've just done this testing again to double check, and I can confirm that the crackle still happens only on the right side channel regardless of whether the L Mono or R Mono button is activated. So it seems to be happening after the mono switches...

You have a bad transistor or two on the preamp board, on the bottom of the unit, in the front. No amount of cleaning will change this fact.


The board in question looks like this:

Those white capacitors (at the very least) should be replaced as well.

 

[dankik]

While I agree that it's probably a bad transistor, @dragnalus doesn't know how to repair electronics and no tools. So, if we can narrow down the causes, it may help with shop repairs.
Please check the wire to board solder connections for the Jxxx numbers highlighted in green. This is for the Preamp (P400) and tone control board (P450) (circled in red). Make sure there are no loose wires or bad looking solder connections.

 

[dragnalus]

This will be interesting to do, however I'm travelling this week but will report back once I'm home and have a chance to open it up.