Hi Algar_emi,
In the early - mid 70s, the owner's manual may have included the schematic. Marantz practiced this.
Sounds like you really have to ask these days.
Try searching for the manual on Google. Beyond that, the price for a complete service manual from robjak's link is average on the 'net for a complete manual.
-Chris
If the schematic isn't in the service manual, the service manual is not complete. All service manuals from the distributor do include the schematic.
In the early - mid 70s, the owner's manual may have included the schematic. Marantz practiced this.
Sounds like you really have to ask these days.
Try searching for the manual on Google. Beyond that, the price for a complete service manual from robjak's link is average on the 'net for a complete manual.
-Chris
Procedure in manual
Hi,
I was able to do the step 3 on this procedure. Didn't try the others.
Now 95.1 is at 95.1, but the distortion is not gone.
From the previous messages, the problem is at step 1 and 2.
At step one and two, where should I see the "condition" there is not name on the axis!
Also what is step 4 doing?
Hi,
I was able to do the step 3 on this procedure. Didn't try the others.
An externally hosted image should be here but it was not working when we last tested it.
Now 95.1 is at 95.1, but the distortion is not gone.
From the previous messages, the problem is at step 1 and 2.
At step one and two, where should I see the "condition" there is not name on the axis!
Also what is step 4 doing?
Hi spacemen12,
Steps 1 and 2 are the most critical of all. Everything beyond these depends on this being done properly. While it's good that you were successful in dong the pointer alignment, it may have to be redone once you have the first two procedures completed properly.
-Chris
Yes, and these are the critical first steps you need to work on before anything else.
That is where the bandpass filter action of the FM front end is aligned to track with the pointer. It makes a big difference in sensitivity.
Those are a representation of waveforms you are expected to see on a spectrum analyzer and 'scope, respectively. This is what a good alignment will look like.
Steps 1 and 2 are the most critical of all. Everything beyond these depends on this being done properly. While it's good that you were successful in dong the pointer alignment, it may have to be redone once you have the first two procedures completed properly.
-Chris
Hi,
In fact I don't have access to a genescope, but I have a "all chanel sweep marker/generator" that can give me 10.7MHz. Where should I plug it, and where should I measure?
Thanks
Here is a list of equipment that I have access to:
all chanel sweep marker/generator
50MHz oscilloscope
Harmonic distortion analyzer
FM stero signal generator
1M distortion analyzer
Signal generator
Audio tester
In fact I don't have access to a genescope, but I have a "all chanel sweep marker/generator" that can give me 10.7MHz. Where should I plug it, and where should I measure?
Thanks
Here is a list of equipment that I have access to:
all chanel sweep marker/generator
50MHz oscilloscope
Harmonic distortion analyzer
FM stero signal generator
1M distortion analyzer
Signal generator
Audio tester
Hi spacemen12,
Disconnect the IF output from the RF front end and inject your signal in there(into the IF strip). Monitor the end of the IF strip with your spectrum analyzer and sweep from 10.4 MHz to 11.0 MHz. Note the shape and -3 dB bandwidth, also the -20 dB bandwidth. You can use these numbers to find your tuned center, which should correspond with the center of your spec-an display. If you send a 10.7000 MHz signal into the IF strip, you can adjust the discriminator (or whatever) for 0.00 VDC, as close to 0 mV as you can get. The second slug gets adjusted for minimum THD with a modulated signal, normally 1 KHz at 75 KHz modulation. 400 Hz can be used, but power supply hum may interfere with it.
Keep in mind that your signal out (into the IF strip) will be on the order of 40 ~ 60 dBf. In the mV, just watch your signal strength meter. You want to avoid getting into the limiting action so your adjustments can be seen. Higher amplitude for THD testing, about 1/2 scale on the signal strength meter. You can set lower, but your THD figures will be dominated by noise.
Now you are ready to reconnect your FM front end and set it up.
-Chris
Edit: clarified injection point
Disconnect the IF output from the RF front end and inject your signal in there(into the IF strip). Monitor the end of the IF strip with your spectrum analyzer and sweep from 10.4 MHz to 11.0 MHz. Note the shape and -3 dB bandwidth, also the -20 dB bandwidth. You can use these numbers to find your tuned center, which should correspond with the center of your spec-an display. If you send a 10.7000 MHz signal into the IF strip, you can adjust the discriminator (or whatever) for 0.00 VDC, as close to 0 mV as you can get. The second slug gets adjusted for minimum THD with a modulated signal, normally 1 KHz at 75 KHz modulation. 400 Hz can be used, but power supply hum may interfere with it.
Keep in mind that your signal out (into the IF strip) will be on the order of 40 ~ 60 dBf. In the mV, just watch your signal strength meter. You want to avoid getting into the limiting action so your adjustments can be seen. Higher amplitude for THD testing, about 1/2 scale on the signal strength meter. You can set lower, but your THD figures will be dominated by noise.
Now you are ready to reconnect your FM front end and set it up.
-Chris
Edit: clarified injection point
Hi,
Thank you very much for your step by step help.
I am not a technician, so the last post is not absolutely clear to me, sorry, I will try to pin point my questions.
1. How do I disconnect to IF from to the RF? Is it the plug to the F2730 board (also known as the "FM discriminator circuit board")?
2. Where should I plug my 10.7MHz (TP1 F2678 as in step one of the manual, see previous post for detail)
3. I don't have a spectrum meter, can I do the job by looking at the amplitude one the oscilloscope at different frequency?
4. What is a "spec-an display"?
5. Is the second "slug" T02 on F-2730 (see previous post for detail)?
6. Where should I measure the output impedance (not sure what this means)
Thanks
Thank you very much for your step by step help.
I am not a technician, so the last post is not absolutely clear to me, sorry, I will try to pin point my questions.
1. How do I disconnect to IF from to the RF? Is it the plug to the F2730 board (also known as the "FM discriminator circuit board")?
2. Where should I plug my 10.7MHz (TP1 F2678 as in step one of the manual, see previous post for detail)
3. I don't have a spectrum meter, can I do the job by looking at the amplitude one the oscilloscope at different frequency?
4. What is a "spec-an display"?
5. Is the second "slug" T02 on F-2730 (see previous post for detail)?
6. Where should I measure the output impedance (not sure what this means)
Thanks
First off,verify you're really at 10.700Mhz with a frequency counter!This is important so that you stay centered in the IF passband, assuming "good" ceramic filters for now.
Dont need to worry about a RF/IF spectrum analyser at this point,lets try to get the tuner close with what u got now
For all distortion measurements make sure you are not overloading the dist. analyser, set tuner output level to 6. If you get massive distortion check this first
IF your low distortion FM generator can be set to 10.700MHZ THEN
Remove leg of C25 on frontend side and inject unmodulated carrier at 10.7MHZ signal via 220ohm resistor (assumes 300ohm input impedance and 50ohm generator impedance)
Set output signal high enough so that you hear minimal hiss on tuner output.
1. adjust T03 main for lowest voltage across terminals of tune meter, this centers the meter at 10.700MHz
2. adjust T02 det. board for 0vdc at TP01 det board, get within 10mv with a good digital meter use a wooden or plastic tool!Do this with shield box in place
next set generator for 1KHz mono audio at +-75KHz deviation, 10.7MHZ hook up dist. analyser to output
3. adjust T01 det. board for lowest distortion.
4. go back to step 2 and check if voltage is still minimum, repeat steps 2 and 3 for lowest distortion and voltage
5. adjust T02 and VR01 main board for lowest distortion, this is the group delay eq
IF your low distortion FM generator cannot be set to 10.700MHZ THEN
Use the marker generator set and verified at 10.700Mhz no modulation. Inject signal as above
1.same as above
2 same
Remove injection cable and resistor , resolder C25 to frontend
set Fm generator to 98MHZ mono 1mv (60dbmicrovolt at 75ohm or close enough not too critical) 1khz audio at 75khz dev.
Tune to 98Mhz EXACTLY, measure voltage at TP01 det board and try to get as close to 0VDC as possible. Lock tuning knob in position with tape
4. same
5 same
set Fm generator to 98MHZ STEREO (9% pilot, L+R) 1mv (60dbmicrovolt at 75ohm or close enough not too critical) 1khz audio at 75khz dev.
Tune to 98Mhz EXACTLY, measure voltage at TP01 det board and try to get as close to 0VDC as possible. Lock tuning knob in position with tape
6. adjust T01 main board for lowest stereo distortion (best for strong stations)
OR
Set FM generator in mono to 98MHZ mono 1KHz audio at +-75KHz deviation, output level set so that signal meter is at 2 to 3
6.adjust T01 main board for maximum signal reading, measuring voltage at pin 13 IC03 for best accuracy (best for weak stations)
Sometimes these two methods coincide but usually a tradeoff.
Finally
set Fm generator to 98MHZ stereo (9% pilot, L+R) 1mv (60dbmicrovolt at 75ohm or close enough not too critical) 1khz audio at 75khz dev.
Tune to 98Mhz EXACTLY, measure voltage at TP01 det board and try to get as close to 0VDC as possible
7. switch generator to L only, and minimise R output via VR02 preamp board
8. switch generator to R only, and minimise L output via VR02
Note that the minimums do not coincide so you will have to go back a forth to find a compromise setting that maximises separation for both channels
All done!
If you still hear distortion then you got other problems....
Dont need to worry about a RF/IF spectrum analyser at this point,lets try to get the tuner close with what u got now
For all distortion measurements make sure you are not overloading the dist. analyser, set tuner output level to 6. If you get massive distortion check this first
IF your low distortion FM generator can be set to 10.700MHZ THEN
Remove leg of C25 on frontend side and inject unmodulated carrier at 10.7MHZ signal via 220ohm resistor (assumes 300ohm input impedance and 50ohm generator impedance)
Set output signal high enough so that you hear minimal hiss on tuner output.
1. adjust T03 main for lowest voltage across terminals of tune meter, this centers the meter at 10.700MHz
2. adjust T02 det. board for 0vdc at TP01 det board, get within 10mv with a good digital meter use a wooden or plastic tool!Do this with shield box in place
next set generator for 1KHz mono audio at +-75KHz deviation, 10.7MHZ hook up dist. analyser to output
3. adjust T01 det. board for lowest distortion.
4. go back to step 2 and check if voltage is still minimum, repeat steps 2 and 3 for lowest distortion and voltage
5. adjust T02 and VR01 main board for lowest distortion, this is the group delay eq
IF your low distortion FM generator cannot be set to 10.700MHZ THEN
Use the marker generator set and verified at 10.700Mhz no modulation. Inject signal as above
1.same as above
2 same
Remove injection cable and resistor , resolder C25 to frontend
set Fm generator to 98MHZ mono 1mv (60dbmicrovolt at 75ohm or close enough not too critical) 1khz audio at 75khz dev.
Tune to 98Mhz EXACTLY, measure voltage at TP01 det board and try to get as close to 0VDC as possible. Lock tuning knob in position with tape
4. same
5 same
set Fm generator to 98MHZ STEREO (9% pilot, L+R) 1mv (60dbmicrovolt at 75ohm or close enough not too critical) 1khz audio at 75khz dev.
Tune to 98Mhz EXACTLY, measure voltage at TP01 det board and try to get as close to 0VDC as possible. Lock tuning knob in position with tape
6. adjust T01 main board for lowest stereo distortion (best for strong stations)
OR
Set FM generator in mono to 98MHZ mono 1KHz audio at +-75KHz deviation, output level set so that signal meter is at 2 to 3
6.adjust T01 main board for maximum signal reading, measuring voltage at pin 13 IC03 for best accuracy (best for weak stations)
Sometimes these two methods coincide but usually a tradeoff.
Finally
set Fm generator to 98MHZ stereo (9% pilot, L+R) 1mv (60dbmicrovolt at 75ohm or close enough not too critical) 1khz audio at 75khz dev.
Tune to 98Mhz EXACTLY, measure voltage at TP01 det board and try to get as close to 0VDC as possible
7. switch generator to L only, and minimise R output via VR02 preamp board
8. switch generator to R only, and minimise L output via VR02
Note that the minimums do not coincide so you will have to go back a forth to find a compromise setting that maximises separation for both channels
All done!
If you still hear distortion then you got other problems....
C25 is on output of T01 main board, column C, row 1 of schematic.
You need a digital frequency counter unless you O-scope has an accurate (5 decimal places) period measurement function.
75Khz dev. is the standard maximun amount of FM modulation (ie 100%) of the carrier.
http://en.wikipedia.org/wiki/Frequency_deviation
Basically its the total amplitude of audio required to make the carrier move or "deviate" in frequency 75Khz above and below the stations center frequency.
This makes the station look 150 KHz wide on the dial, which is why FM stations are allocated in "channels"
http://www.fcc.gov/mb/audio/bickel/oddno.html
.2MHz apart in most countries to keep interference low as stations usually add extra signals in on top of the audio
http://www.compolinc.com/sca_technology.htm
Don't even get me started on "HD" Radio crap
This non-audio junk above +- 75KHz is filtered out by A.C.F01 on det. board
But even then problems with IF filters selectivity and center frequncy matching may keep you from recieving stations .2MHz apart, these are called adjacent channels, and need good matched filters to get clean audio.
This why the governing bodies don't allow high power "local" stations to be on adjacent channels.
So you typically see only "alternate" channels every .4 MHz
You need a digital frequency counter unless you O-scope has an accurate (5 decimal places) period measurement function.
75Khz dev. is the standard maximun amount of FM modulation (ie 100%) of the carrier.
http://en.wikipedia.org/wiki/Frequency_deviation
Basically its the total amplitude of audio required to make the carrier move or "deviate" in frequency 75Khz above and below the stations center frequency.
This makes the station look 150 KHz wide on the dial, which is why FM stations are allocated in "channels"
http://www.fcc.gov/mb/audio/bickel/oddno.html
.2MHz apart in most countries to keep interference low as stations usually add extra signals in on top of the audio
http://www.compolinc.com/sca_technology.htm
Don't even get me started on "HD" Radio crap
This non-audio junk above +- 75KHz is filtered out by A.C.F01 on det. board
But even then problems with IF filters selectivity and center frequncy matching may keep you from recieving stations .2MHz apart, these are called adjacent channels, and need good matched filters to get clean audio.
This why the governing bodies don't allow high power "local" stations to be on adjacent channels.
So you typically see only "alternate" channels every .4 MHz
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