Electronics > Repair
Need Clarification on Yamaha R-500 FM Alignment
whirligig:
I'm in the middle of aligning this Yamaha R-500 and the service instructions threw me in a loop. In the attachments is a table outlining the adjustments to be made to the FM tuner and a diagram of the tuning locations. Where I'm confused is the #2 callout just above the adjustment table. It says 2. Perform this adjustment and a lowpass filter must be used. I don't have any detail what this lowpass filter is and where it should be used. Does anyone have a clue what is meant here?
Step 2 in the table under Adjustment method calls out for a Tuning meter. This Tuning meter appears in Step 2 Tracking adjustment 1 and Step 4 Discriminator balance.The only detail is shown in the tuning location diagram where the Tuning meter is attached to R168 and J161. I'm assuming this Tuning meter is a +/-100uA Galvanometer. Would that be correct?
In the diagram with adjustment points, there is an asterisk describing the tuning meter attachment. It says The tuning meter is to be connected to a circuit which include the Ji00088 or equivalent connected in series to a 47kOhm resistor. I can't find anything about the Ji00088. Any clue what that might be?
bob91343:
My take on it is this:
The low pass filter needn't be hadware; just try to ignore the high frequencies on the scope screen.
The ji number may be the part number of the meter itself.
The bottom line here is to ignore the details and work with the adjustments and what they do. Common sense applies; don't get befuddled by the specifics. What you want is best dial calibration, lowest distortion, greatest sensitivity, and best separation. You know where the controls are and what they do, so use your knowledge of how stereo works and go from there.
If your understanding is lacking, read up on it or enlist the help of a friend who can work with you.
CaptDon:
Did someone screw up the alignment??? Do you have reason to believe it can be aligned for better performance than it is already giving? Do you have a very stable signal generator which can provide an accurate signal with pilot injection and so forth?? Chances are you may end up making it far worse with no way to get it right. Can your signal generator give you the choices of L, R, L+R, and L-R with the options of turning the pilot on and off for good mono summing and great stereo separation (which is never better than about 40db anyway). This is certainly not a job for a C.B.'er with a package of diddle sticks.
whirligig:
--- Quote from: bob91343 on November 29, 2021, 05:33:45 am ---My take on it is this:
The low pass filter needn't be hadware; just try to ignore the high frequencies on the scope screen.
The ji number may be the part number of the meter itself.
The bottom line here is to ignore the details and work with the adjustments and what they do. Common sense applies; don't get befuddled by the specifics. What you want is best dial calibration, lowest distortion, greatest sensitivity, and best separation. You know where the controls are and what they do, so use your knowledge of how stereo works and go from there.
If your understanding is lacking, read up on it or enlist the help of a friend who can work with you.
--- End quote ---
I went back and compared the alignment instructions to my Luxman tuner which I did recently. The tuning meter is a galvanometer. I used one from work for the Luxman and it came out well. i think this time I'll just use the bar graph feature on my Fluke. I won't worry about the low pass filter then.
whirligig:
--- Quote from: CaptDon on November 29, 2021, 02:36:09 pm ---Did someone screw up the alignment??? Do you have reason to believe it can be aligned for better performance than it is already giving? Do you have a very stable signal generator which can provide an accurate signal with pilot injection and so forth?? Chances are you may end up making it far worse with no way to get it right. Can your signal generator give you the choices of L, R, L+R, and L-R with the options of turning the pilot on and off for good mono summing and great stereo separation (which is never better than about 40db anyway). This is certainly not a job for a C.B.'er with a package of diddle sticks.
--- End quote ---
I found this Yamaha maybe 15 years ago on the curb with a bunch of other electronics. There were cold solder joints on the amplifier IC from thermal cycling and so it wasn't working until I reflowed the connections. The tuner performance was disappointing and so I shelved it for 15 years. Recently I decided to restore it. I got rid of the corrosive glue, recapped it, removed the amp and driver IC's and resoldered it, checked many of the diodes and transistors, and repaired the 5V regulated power supply which caused several old 6.3V electrolytics to overheat when it failed. The receiver performance improved but the dial is off and the sensitivity and selectivity could be improved. Yes, it needs an alignment. It'll be the second time I'll use my Danish made Radio Technology RE125 Rf generator that I recently purchased. Some of the lingo on this generator is a little different but the major parameters are there e.g. Rf frequency, signal level in several units, toggle and set the pilot, deviation, modulation on the L & R, etc. This baby is more signal generator than the HP or Boonton I use at work. Unfortunately it's just as big but heavier.
So forgive me, this ME is still learning.
73
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