Marantz 2230 only left channel works on FM stereo

[misterguitar]

Finnaly got the amps and phono amp and power supply correct. Down to figuring out why the FM only works on one channel. I'm thinking it has to be a problem on the P300 board. Because If I hit the mono switch I get sound on both channels. So it sounds like a de-multiplexing problem. (Let me know if this line of reasoning is not sound.) I ruled out the muting board because I would think that would impact both channels. Or anything further upstream. But the stereo light does come on for local stations. So it must be detecting the 19khz pilot right?

 

[catrafter]

Here's a simplified explanation of the MPX operation for the 2230, 2245 and 2270.

There is a good description in the service manuals for the 2245 and 2270, but it's kind of hard to follow.
The 2230 is slightly different.
Wire-anded: the junction of two or more components where either one can pull that point to or near ground potential.

IF signal strength is monitored by H306. If IF signal strength is above muting level, H306 is ON, H307 is OFF.
If there is excessive noise, then H552 is ON which is wire-anded to J305, keeping H306 OFF.
If the discriminator is outputting DC due to the tuning being off station, either H560 or H561 is ON which are wire anded to H307 as well.

If the station is properly tuned, not noisy and the signal strength is high enough,
H306 is ON, SS OK
H307 is OFF, SS OK AND
H552 is OFF, Noise is OK AND
H560 is OFF Tuning centered AND
H561 is OFF Tuning centered
If SS, Noise and center tuning OK then:
H308 is ON allowing audio signal to pass to the center tap of the 38kHz transformer.
H302, 19kHz amplifier is enabled by H303.
If the 19kHz pilot is present from the broadcast station, then it is doubled to 38kHz by H304 and if of sufficient amplitude to decode stereo, H305 turns on causing the stereo lamp to illuminate.
The left and right matrixed audio signals are recovered by H317-H320, de-emphasis is applied, then they are amplified, filtered of high frequency noise and sent along through the selector switch to the preamp.


Tom

 

[misterguitar]

wow! so succinctly explained! this will be incredibly helpful. Now I just have to figure out how to get to the darn board to poke around and check things. They sure didn't make this one easy to get to or troubleshoot on a live chassis that's for sure.
hmm I don't ahve a H317 or H320. Guessing that is how the 2230 is different?

 

[dr*audio]

Do you have an oscilloscope?

 

[misterguitar]

Yes. I have a really nice Tek 2247a. I also have a Sencore SG-165 AM-FM stereo analyzer. But There is some doubt to its accuracy and I have yet to send either out for calibration. Saving my pennies to get that done lol.

 

[dr*audio]

With the scope, and the receiver tuned to a known station, in Stereo mode. probe the base of H309 and H310 on the P300 board. You could try C317 and C318 if they are easier to get at. Make sure you probe both sides of them. If you have signal on both channels, the MPX is ok. Now go to the output of the filter, J312 and J314. If you have no signal on one channel, check at the coupling caps both sides, C333 and C334.

 

[dr*audio]

The most probable culprits in order of likelyhood:
Broken wire
Dirty switch
Bad coupling cap
Bad transistor.

 

[misterguitar]

OK. I plugged up the scope and got the following.
H309 Base Got a signal. And read about 2.5 volts.
H310 Base Got a signal. Read about 2.5 volts.

So everything seems fine up to there.

J312 Nothing
J314, nice steady signal that mirrors what I'm hearing.
I tried both legs of C333 and got nothing
Should I follow through on the right channel by checking for signal at the base of H311? And guessing to check terminals 1 of the low pass filter looking for signal? And 2 at the exit of the lpf? Base of H313?

You guys are really great. Such a smart group of folks! Thanks so much!

 

[misterguitar]

H311! Ding Ding Ding! Wiggled the transistor to get a voltage reading and boom the channel comes to life. Wiggling it makes it go in and out.

Now I need to figure out what a sub for 2SA494 Green or Yellow band is. And the big challenge will be getting o the bottom of that board. Not looking forward to that.

 

[misterguitar]

Thanks again Tom and Dr. Audio!

 

[misterguitar]

I'm fidning some that sugest KSA992. Does that sound reasonable? I have KSA992 FTA's and FBU's

 

[misterguitar]

OK I had to remove the AM board above it. Got that out. manged to get underneath the 300 board. But it looks like now I can get all the rest of the elctrolytics while I'm in here on the muting board and the detector. I'm wondering though. Will replacing these E caps with same values screw around with the alignment? I;d love to get thema ll while I'm in here but until i can afford to send my SG165 in and Oscope in to get calibrated I'm very hesitant to take on having to deal with an alignment since I have never done one.

 

[dr*audio]

Replacing the caps with the same value will not affect the alignment. Are you sure the transistor is bad and not just bad solder joints? Look for a grainy solder joint or a circular crack in the joint. If not, the KSA992 is a good sub.

 

[misterguitar]

Yeah, Reflowed the solder and got the same results. Hitting it with cold spray make sit wig out too. Think I'm going to go ahead and recap in there since I have it all apart. goign to take the opportunity to get the caps and just go ahead and do these same boards on my sweatheart 2245 champagne face as well. weeeeeeeeeeeeeee! lol

 

[dr*audio]

Sometimes the wire bonds in the transistor between the leads and the silicon die break and become intermittent. That's probably why it worked when you touched the transistor.

 

[quaddriver]

a rule of thumb I use for fm tuners, if the cap value is 1uf or more, wont affect alignment. the truly tuned circuits have very small values, often in the pF range to 'wiggle' at the intended frequency. A lot of times the 1uF or larger caps are just DC blocks. in other words, dont change anything that looks like a chicklet without proper equipment at the ready....

and ALSO, I have gotten great mileage on this: any and all Ge diodes, usually listed as the ubiquitous 1N60, test and replace with a passel of 1N90/99 etc (aka equivalent) with the lowest Vf you can find using the didoe setting. most mileage in the ratio detector and gain controls and then if there us a tranny that can be subbed with the KSA992 - do it. I think I currently stock KSA992FBU or FTA or something like - wakes em right up.

 

[misterguitar]

Well I replaced all the caps last night and got those transistors replaced. Now my problem is some of the sticky labels I had used to label which color wires went where came loos and fell off a few of the wires. Lovely! That's interesting quad, I got like 200 of the KSA992. I used some in the tone amplifier of my baby. (Marantz 2245 champagne face) Between that and the recap it was amazing how much mud that cut out of the sound. I tried hunting down a pic of the 2230 FM MPX board in the cahsis hoping I could see which color wires go to what connectors but no dice. wish they had put it on the schematic! Now I have to chase the schematic and wires all over the chasis. lol

 

[Steven Tate]

I have a couple of 2230's in my garage. I work a half day today. If you still need wire color info later today, let me know and I'll snap some pics.
Steve

 

[catrafter]

The last 3 2230's I did were hooked up this way. (I take lots of notes)

J301 (White) center of orange shielded cable
J302 (Black) shield of orange shielded cable
J303 (Orange)

J306 (Brown)
J315 (Red)
J314 (Blue)
J313 (Black)
J312 (Green)

J307 (Gray or Brown) this is near the front panel

These wires come through the hole under the P300 board:
J305 Bottom of board (Green)
JXX or J316 Bottom of board (Violet)

Hope this helps you should probably trace it out to be sure.

Tom

 

[Steven Tate]

I think this is a pic of a 2230 P300 board from my not-very-well-labeled archives. Not completely sure.