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Marantz 2240B crackling/popping

N

nhecht

New Member
Hi All,

First time posting here, but I've definitely perused the forums for awhile -- you guys are very legit!

I have a Marantz 2240B receiver that I've had repaired a few times over the years and decided that when the two most recent problems came up I'd try my hand at repairing it myself. This is my first attempt at soldering/DIY electronics repair.

The first issue was a long delay for the speaker relay to kick in. I recapped the power supply board and replaced the relay. 1st issue solved.

The second issue, and the one I'm looking for some help with, is a persistent crackling and popping sound, only in the left channel. I hear it on the various settings -- phono, fm/am, aux. I read on this thread that someone was able to solve a similar issue on a 2245 receiver by replacing transistors on the tone board. I went ahead and tried the temperature test on the left channel amp board with an upside-down duster can/hair dryer that someone suggested on the above thread, to see if a transistor was failing because of temperature related issues. Results were inconclusive, though mostly because I was unable to get the board off of the chassis to pinpoint which transistor might be acting up (one of the screws holding it in place is stripped, so I need to look into that).

Beyond the above test, I'm not totally sure how to go about troubleshooting this as I'm pretty green with all of this. which is why I'm turning to you all! Any ideas? Thanks so much!
 
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Connect an iPhone or iPad to main in via RCA cable. Before switching on the unit reduce the volume of your iPhone or iPad to minimum. You will control the volume from your phone or iPad. If both channels run fine then your problem is in the tone board and if crackling still remains in the said channel then the problem is in the main amp.
 
Thanks Sanjib. Both channels of audio come in clear and even, but with loud crackling and popping in the left channel only.
 
I plugged my iphone into the aux input first, and then i tried the phono stage as well, with headphones plugged into the phones jack.
 
Would you recommend recapping and replacing the transistors in the left main amp, or is there a way to chase down the problem more specifically?
 
So obviously the problem is in the left main amp. Do you have any other receiver so that you can connect pre-out of this one to the main-in to other one?
 
2SC458 and 2SC1344 are well known problem-prone transistors that have to be replaced. Let me know the result of your test with pre-out and another receiver.
 
Thanks for the tips re:transistors. Ok, this is the chain of audio, am I doing this correctly?

iphone > marantz via main in > other receiver via marantz pre-out > headphones. Is that right?
 
No, iPhone in aux of marantz, then connect the main in of your other receiver to the preout of marantz at rear pannel via RCA cable
 
I am wrong about the transistors in your main amps. Those transistors are not in this unit's main amp.
 
noted, re: transistors. Ok I set up the test correctly and there is no crackling. Is this bypassing the main amp somehow?
 
Yes, so the problem is in main amp board. I would suggest to do a full recap and change the differential transistor pair.
 
Thanks so much for walking me through this! Now, what's a differential transistor pair and how do I identify it?
 
Those are H702 and H703 you will find these markings on the board they are placed close to each other. Replace them with two gain matched KSA992FBU
 
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