• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Marantz 2225 Noise Issue

Ray66

Ray66

AK Subscriber
Subscriber
I have a 2225 that the owner reported a loud intermittent noise issue through his speakers. The unit appeared to be all original inside. It took a few hours for the noise to start. It was independent of volume setting and limited just to the RCH. I replaced all electrolytics on P700 MAIN AMP. BOARD. The differential pairs on P700, H701/703 and H702/704, were 2SA722. The SM I have listed them as being 2SA763. While neither of those are known to be problematic I went ahead and replaced them with matched pairs of KSA992. While I was at it I also recapped PE01 PRE TONE AMP. BOARD, cleaned all the controls, set the bias and offset. All seemed good...until it wasn't. After several hours the static noise came back, and this time much louder than what I had initially experienced and more like what the owner had described. Again, only in the right channel. I swapped P700 signal input pins J701 and J702 and the noise was now in the LCH. So this suggests to me that the issue is upstream from the power amp. The transistors listed in the SM for then PE01 preamp PCB are 2SC1328 and 2SA763, neither of which I believe are problematic. I haven't confirmed what's actually on that PCB yet. Thoughts anyone? There is a board marked PH01 that seems to be in the signal path between the pre and power amp. No active devices on it, but there are a couple of tantalum capacitors. I've pulled enough bad tantalums in the past that I generally replace them, however in this case there would be a bit of work involved to get access to that board.

1776262553082.png
 
Register to hide this ad
Have you cleaned all of the switch contacts? What about cleaning the Volume and Balance controls with Deoxit? It could be an oxidized contact.
 
Thanks for the suggestion. Yes, all controls had been cleaned.

Rather than tracing the signal path and probing voltages on PE01 PRE TONE AMP. BOARD I just went ahead and replaced the 8 transistors on this board; 2SC1328 with KSC1845, and 2SA722 (again, not 2SA763 as listed in the SM) with KSA992. That appears to have taken care of the issue. I'll give it a day or two of listening before I'm convinced the problem is gone. As mentioned I've not read anywhere that these original transistors are known to be problematic, but these particular ones appear to be. The transistors I pulled all returned reasonable results on the Peak DCA55.
 
I have come across a few 2SC1328s that were also problematic. They were in a receiver's preamp stage and would sporadically trigger the protection relay.
 
ring said:
An old Marantz just yielded a very noisy 2SC1328, first I can recall seeing.

Input pair of one channel were discharging too - 2SA722. I think I found warnings in this thread about this part, but it's the first I've seen go noisy.
Click to expand...
I didn't realize at the time these could be a problem, however I see now that both 2SC1328 and 2SA722 are flagged in the Top Ten Worst Transistors post.
 
You must log in or register to reply here.
Back
Top Bottom