Hipocrates
Super Member
how is the project going?
Marantz 2285 (non B) Restoration
- Thread starter MBuras
- Start date
MBuras
Restoration is an Addiction
New rectifier installed. No issues with installation but did not solve any issues. Probably just good preventative maintenance with the large increase in filter cap UF and ripple current.
Cleaned up the tone board again, checking for solder issues, parts issues, etc. Nothing found and no fix.
Cleaned all push button switches on the front panel again and even used the sticky to pull out the switch stems and check contacts. I've never seen cleaner contacts on any switches so these are not a likely source of issues.
I'm going to put this aside for another day or so and have a long think on it. It's gotta be something silly and easy. I'm sure of it.
Again, the problem is loud pops through the speakers when manipulating the tone switch only. The noises don't happen randomly. I can make them happen every time. And only that one switch. No push buttons make it happen. Transistors can be a source of noise but all transistors in the entire unit except tuner boards and outputs have been replaced. Lost as to where to look next.
Cleaned up the tone board again, checking for solder issues, parts issues, etc. Nothing found and no fix.
Cleaned all push button switches on the front panel again and even used the sticky to pull out the switch stems and check contacts. I've never seen cleaner contacts on any switches so these are not a likely source of issues.
I'm going to put this aside for another day or so and have a long think on it. It's gotta be something silly and easy. I'm sure of it.
Again, the problem is loud pops through the speakers when manipulating the tone switch only. The noises don't happen randomly. I can make them happen every time. And only that one switch. No push buttons make it happen. Transistors can be a source of noise but all transistors in the entire unit except tuner boards and outputs have been replaced. Lost as to where to look next.
Hipocrates
Super Member
MMMMM tricky one!
Hipocrates
Super Member
I wonder where you can get those? (if that's the case)
Rasputin47
Woad
I've purchased BA312 ICs from LittleDiode in the past, and they currently show as being available.
http://www.littlediode.com/components/BA312.html
Hipocrates
Super Member
Nice tip!
MBuras
Restoration is an Addiction
Ok. So after some awesome help from the master AK troubleshooting team (in a separate thread) we figured out I goofed with CE39 (local DC filter) on the preamp board which caused some noise issues. The original capacitor was mounted up off the board and bent to lay sideways. There isn't much clearance where this board mounts but I thought the modern replacement would clear in a standard upright position. I was wrong and it shorted. I'm ordering a replacement cap of the same value/size as my previous replacement and this time I'll bend it to lay sideways like the original.
We also established that rotation of the tone switch during the first minute or so of operation will cause the pops I was experiencing. Seems as if this is a Marantz design "feature". Ugh! Also still getting a little cut out/noise when wiggling the rotary tone switch so I'll work on cleaning that up.
I'll update with new photos of the modified tone board next week.
We also established that rotation of the tone switch during the first minute or so of operation will cause the pops I was experiencing. Seems as if this is a Marantz design "feature". Ugh! Also still getting a little cut out/noise when wiggling the rotary tone switch so I'll work on cleaning that up.
I'll update with new photos of the modified tone board next week.
Hipocrates
Super Member
Cool! 
MBuras
Restoration is an Addiction
So here's the finished and confirmed working tone board. CE39 (local DC filter) capacitor was replaced and positioned exactly like the original, up off the board and bent sideways to lay down for clearance. I also replaced all the resistors surrounding the BA312's, not because I had to but I felt bad paying shipping for one capacitor.
Despite the most cleaning of any switch I've ever had (clean, sparkling metal on every surface) the tone mode switch does indeed take a minute or 2 to calm down and stop causing a popping noise. Interesting Marantz "feature".
Now I'm on to diagnosing a previously unknown problem with FM stereo. No light despite it working in other modes. And FM Mute completely shuts off sound. I'll be checking the muting board for issues and maybe tearing back into the MPX board for troubleshooting. Grrrr...
Despite the most cleaning of any switch I've ever had (clean, sparkling metal on every surface) the tone mode switch does indeed take a minute or 2 to calm down and stop causing a popping noise. Interesting Marantz "feature".
Now I'm on to diagnosing a previously unknown problem with FM stereo. No light despite it working in other modes. And FM Mute completely shuts off sound. I'll be checking the muting board for issues and maybe tearing back into the MPX board for troubleshooting. Grrrr...
catrafter
Marantz Specialist
It takes a few minutes for the charge on some of the capacitors in the tone circuit to stabilize at power up. If you cycle the switch before then you will hear a 'pop'.
The antenna muting board only contains the control. The rest of the circuit is on the P200 IF and P300 MPX boards.
This might help, it is for the 2275, etc., some of the reference designators may be different in the 2285.
The antenna muting board only contains the control. The rest of the circuit is on the P200 IF and P300 MPX boards.
This might help, it is for the 2275, etc., some of the reference designators may be different in the 2285.
MBuras
Restoration is an Addiction
Many thanks to @catrafter for providing knowledge on the MPX board. Finally got the stereo light working.
Now I just need to do some final cleaning on the faceplate, knobs and backplate, make sure the voltage settings are all still where they should be and then measure final output. I'll post some picks later.
Now I just need to do some final cleaning on the faceplate, knobs and backplate, make sure the voltage settings are all still where they should be and then measure final output. I'll post some picks later.
Steven Tate
CEO Flat Forehead Soc.
Just curious. What turned out to be the problem with the Stereo light?
Steven Tate
CEO Flat Forehead Soc.
Interesting. I'm going to write that one down for future reference. 
MBuras
Restoration is an Addiction
This receiver has been the ultimate test of my skills to date and continues to cause me headaches. Good news is I think it'll be worth it in the end.
Was buttoning everything up and prepped for final output testing to measure wpc before clipping using my standard 8-ohm loads. Right channel has a crisp clean line on the scope and clips at 30.0vac which equates to 112.5 watts. Wow!! For an 85 per channel receiver that's pretty impressive even for Marantz who we know liked to overbuild their equipment. Left side is a different story. Only gives me a fuzzy line and can't reach clipping. I can get it to around 20vac [50w] but run out of volume. I'm pretty sure one or more of the outputs on that side are bad. Back to pulling the outputs and measuring for open/short. Should have done that when I had them out [smacks own head]. Doh!
Was buttoning everything up and prepped for final output testing to measure wpc before clipping using my standard 8-ohm loads. Right channel has a crisp clean line on the scope and clips at 30.0vac which equates to 112.5 watts. Wow!! For an 85 per channel receiver that's pretty impressive even for Marantz who we know liked to overbuild their equipment. Left side is a different story. Only gives me a fuzzy line and can't reach clipping. I can get it to around 20vac [50w] but run out of volume. I'm pretty sure one or more of the outputs on that side are bad. Back to pulling the outputs and measuring for open/short. Should have done that when I had them out [smacks own head]. Doh!
Steven Tate
CEO Flat Forehead Soc.
There is an old joke in dentistry. "Why do dentists have flat foreheads?"..... From slapping themselves in the head and saying "what was I thinking when I did that?" Sounds like it might apply to electronics techs too.
There is an old joke in dentistry. "Why do dentists have flat foreheads?"..... From slapping themselves in the head and saying "what was I thinking when I did that?" Sounds like it might apply to electronics techs too.
Yes it does! (I'll be checking my dentist's forehead next time I see him
)
catrafter
Marantz Specialist
IIRC, the 2285 utilizes plug in power amps. As a sanity check, it might be worthwhile to swap the left and right amp modules to be absolutely sure that the problem lies in the power amp and not in the wiring or test set-up.
If I had a nickel for every time an issue turned out to be self induced I would be rich. My first thought when troubleshooting something is 'what have I screwed up?'.
Tom
If I had a nickel for every time an issue turned out to be self induced I would be rich. My first thought when troubleshooting something is 'what have I screwed up?'.
Tom
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