Recapped 2325 - Signal Strength meter not working

[Leokarma]

About 6 months back I decided to recap my 2325 and started the project. The only problem it had then was the signal strength meter wasn't working and I thought maybe after recap it'll work but even after recap it's not working. The meter as such works in Dolby mode but in stereo mode (Dolby OFF) the Signal strength meter does not work (needle doesn't move at all). Can some one advise on how should I troubleshoot this ? I have already lubed all the switches and controls .

 

[catrafter]

Since the meter works in Dolby, that means the meter it's self is probably OK.

If it's dead in both AM and FM, the problem may be a broken wire or bad connection on the dreaded S002 Dolby mode switch.

Tom

 

[Leokarma]

Since the meter works in Dolby, that means the meter it's self is probably OK.

If it's dead in both AM and FM, the problem may be a broken wire or bad connection on the dreaded S002 Dolby mode switch.

Tom

Thanks for your help Tom. Meter works in AM so the problem is only in FM mode.

 

[catrafter]

OK, that makes it a lot easier, give me a bit to de-spaghetti the schematic and figure it out.

Tom

 

[catrafter]

As with most Marantz schematics, the 2325 is a mess. The way I see it, a DC voltage representing the FM (IF) signal strength comes into J315 of the MPX board. It should be around 1VDC (black meter lead to chassis) when a strong station is tuned in. Current amplifier H316 drives the meter through R374 to J316. H316B should have about 1VDC and H316E should have about 0.5VDC on them when a strong station is tuned in.
Let me know what you find.

Tom

 

[Leokarma]

As with most Marantz schematics, the 2325 is a mess. The way I see it, a DC voltage representing the FM (IF) signal strength comes into J315 of the MPX board. It should be around 1VDC (black meter lead to chassis) when a strong station is tuned in. Current amplifier H316 drives the meter through R374 to J316. H316B should have about 1VDC and H316E should have about 0.5VDC on them when a strong station is tuned in.
Let me know what you find.

Tom

When a strong station is tuned with stereo light ON and FM Tuning needle in center, J315 has only 200 mVDC (not 1 VDC). Moving the tuning dial has no affect on this voltage
H316B has 200 mVDC and H316E has 10 mVDC

 

[rBuckner]

I bet Tom's going to want to know the voltage on H316C (collector). I would!

 

[catrafter]

It would be good to know H316's collector voltage, but since J315 is so low, I would trace the wire from J315 back to the IF amp (P200). I think it goes to J209, but you should verify that. The schematic shows it going to another point as well, but I think it might be an error.
If it does, in fact, go to J209, I suspect the wire is shorted by the metal cover over the IF amp, or there is a problem on P200 with the signal strength detection.

Tom

 

[Leokarma]

It would be good to know H316's collector voltage, but since J315 is so low, I would trace the wire from J315 back to the IF amp (P200). I think it goes to J209, but you should verify that. The schematic shows it going to another point as well, but I think it might be an error.
If it does, in fact, go to J209, I suspect the wire is shorted by the metal cover over the IF amp, or there is a problem on P200 with the signal strength detection.

Tom

Yes you were right Tom. J315 goes only to J209 and the schematic is not right. I tested the voltage on J209 and it did show more than J315 so something was not right. I disconnected the wire between J209 - J315 and ran a new wire between then and the signal strength meter is working now. Thanks for the advice. Another feather for your cap buddy......

 

[wurlyman]

Yes you were right Tom. J315 goes only to J209 and the schematic is not right. I tested the voltage on J209 and it did show more than J315 so something was not right. I disconnected the wire between J209 - J315 and ran a new wire between then and the signal strength meter is working now. Thanks for the advice. Another feather for your cap buddy......

My schematic says it goes from J315 to J209 and also goes to JU03 on the switch assembly which is well hidden without removing PE01 and the cover on PU01. I photo documented my restoration with over 400 photos. I just checked my pictures and the same white wire with a green stripe goes to all three junctions. I think the schematic is correct.

 

[Leokarma]

My schematic says it goes from J315 to J209 and also goes to JU03 on the switch assembly which is well hidden without removing PE01 and the cover on PU01. I photo documented my restoration with over 400 photos. I just checked my pictures and the same white wire with a green stripe goes to all three junctions. I think the schematic is correct.

Yes even my schematic shows that it goes to all 3 junctions . It's the white with green strip. Any idea why it goes to switch assembly could be for multipath function ?

 

[wurlyman]

Yes even my schematic shows that it goes to all 3 junctions . It's the white with green strip. Any idea why it goes to switch assembly could be for multipath function ?

It looks like it is the multipath function. The JU03 junction is a double wire junction, the other wire is solid green. Since we know that J315, J209 and JU03 all have white with green stripe wire, that means there is a fourth connection that is missing on the schematic. That would be whatever the solid green wire goes to. We would have to do some serious disassembly to figure that one out.