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Help with Marantz 2220B AM circuit

glend123

glend123

Active Member
Hey guys, I'm looking for some help troubleshooting the AM of my 2220b Marantz receiver. Unfortunately before I started my recap I did not make a note if the AM worked or not. The FM worked before my recap and works great now. Problem is the AM is completely silent, no hum, no buzz, no meter movement whatsoever. Absolutely nothing. I checked a bunch of voltages and although they seem overall slightly low they're pretty close. Except for the HA1151 IC chip, there's a couple voltages that are very low. The voltages at the transistors look ok also. All the switches have been cleaned and I checked all the continuity of the wires from the tuner board to wherever they go. I tried an external loop antenna and still nothing. I tried poking and prodding looking for loose connections and nothing.....I do have another 2220b receiver that works fine that I could use to troubleshoot. Let me know if anybody has some ideas to help me solve this issue. The receiver is completely restored except for this AM problem.

2220b am schematic and voltages.jpg
 
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I might if I could read the voltages. Try zooming in and have enough light for a readable pic.
 
@rBuckner
thanks, if you can help.
pin 1=1
2=11
3=11
4=11
5=3.5
6=1.25
7=2
8=6
9=0
10=11
11=? must have missed this one
12=2.1
13=1.8 MV
14=0
J113 should be 14v. actual 12.6
 

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  • 2220B am schematic zoom.jpg
    2220B am schematic zoom.jpg
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First observation is about the low supply voltage. The schematic has it coming into the board at 14.0V and 13.1V at the IC, so down 0.9V. By that, you should have 11.3V. Not real far off though.

Pin 12 being high is a bit odd as it doesn't have a dc path on the board unless there's a short somewhere. Hmmm.

Pin 13 being near zero is the biggest issue I can see. Maybe cap C136 has a short between the pins or is in backwards. The only other part on it is the 10K R119. See if there's any voltage on the other side. If not, measure the resistance to ground and if shorted see if there's a short across C135. If there is voltage I'd guess it's about 0.75Vdc with 1.5V being on the other side of R118 (10K) going to pin 11 which has 1.5v on it.
 
rBuckner said:
Fixed it?
Click to expand...
@rBuckner No, not yet, Been busy with other stuff, trying to enjoy the decent weather while it lasts here in Wisconsin. Going to get back at it Wed. morning.
I'm going to follow up with your suggestions and report back. Oddly enough the other 2220b I have has a malfunctioning AM circuit also. It's not dead like this one but I was hoping to use it as a troubleshooting tool.
 
I could not find anything unusual going on with this and I'm stumped. I have to shelve it for now. Everything works great except AM, so not a big deal for now.
thanks for the help.
 
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