No sound on AM Marantz 2252

[goldswimmerb]

Hey guys, so this 2252 is just a bundle of surprises. After putting it back together, the AM section seems to have gone silent on me no static, get the occasional pop if I poke the AM antenna connector at the back. Any ideas where to look? It's not a huge deal since where I am located pretty much no one uses AM anymore, it's just going to bother me if I can't figure it out. The AM was working before my recap and reassembly. The FM works fantastic.

 

[goldswimmerb]

Update, so I checked the IC HA1197 and the voltages on pins 1-8 seem normal, I'm assuming 9-16 are something for FM? It didn't seem to want to measure in AM on that side of the chip. But was measuring fine when I switched to AM. I also checked the built in antenna for continuity and had no issues there. Anyone have any ideas?

 

[goldswimmerb]

Pin 9 10 and 11 on the IC checked out normal, anyone have any ideas where to look?

 

[catrafter]

Q151(HA1197) is the AM tuner IC. Here is the datasheet, If it was operating before you worked on it and doesn't now, perhaps it's something you did.

Tom

 

[goldswimmerb]

Q151(HA1197) is the AM tuner IC. Here is the datasheet, If it was operating before you worked on it and doesn't now, perhaps it's something you did.

Tom

Thanks for that, looks like someone was in here replacing capacitors with resistors, look at the brightly colored ones on my board

 

[catrafter]

C203,C204 and a couple of others may be resistors or small value axial capacitors. I would lift one end and test them to see.
Tom

 

[goldswimmerb]

C203,C204 and a couple of others may be resistors or small value axial capacitors. I would lift one end and test them to see.
Tom

They seem to all be axial caps.

Why would my voltages be checking out but I get no sound, except for when I poke at the ground for the AM I get a pop

 

[catrafter]

Did it ever work?
How well versed are you on single conversion superheterodyne AM receiver theory?
The AM 'Loopstick" antenna can test fine with continuity tests and still be defective, substitution may be the only way to be sure.
Do you have an oscilloscope with a 10:1 probe?
Is the local oscillator running? Scoping HA1197 pin 6 may tell you that.
Another way to tell is to tune this receiver to the low end of the dial (say 540kHz) and then listen with another AM receiver at 540kHz+455kHz or 995kHz for a squeal. A portable handheld battery set would be ideal for this, you could hold it close to the Marantz AM tuner section.

There should be AM modulated 455kHz ( local oscillator frequency minus station frequency) at pin 8.
Pin 12 should be AM audio to Q152, an audio amplifier.
I hope this is of some help.
Tom

 

[goldswimmerb]

Did it ever work?
How well versed are you on single conversion superheterodyne AM receiver theory?
The AM 'Loopstick" antenna can test fine with continuity tests and still be defective, substitution may be the only way to be sure.
Do you have an oscilloscope with a 10:1 probe?
Is the local oscillator running? Scoping HA1197 pin 6 may tell you that.
Another way to tell is to tune this receiver to the low end of the dial (say 540kHz) and then listen with another AM receiver at 540kHz+455kHz or 995kHz for a squeal. A portable handheld battery set would be ideal for this, you could hold it close to the Marantz AM tuner section.

There should be AM modulated 455kHz ( local oscillator frequency minus station frequency) at pin 8.
Pin 12 should be AM audio to Q152, an audio amplifier.
I hope this is of some help.
Tom

That should be some help, unfortunately I failed out of EE (was a wireless engineering major) at my University.

I actually have another receiver sitting right next to this one on my test setup so I may try your suggestion of at least listening for a squeal.

Thanks for the advice with the IC, I don't currently have a scope (broke college student), but when I get one I will certainly attempt.