No problem John ...
Okay
Terminal 4D has to have power, I think that's your stereo mode select signal.
TP402 - 19 KHz, tune T401
TP403 - 38 KHz, tune T402
TP401 - I think that is a bias level to kill or pass the switching signal @ 38 KHz
L401 - 67 KHz trap (feed signal into terminal 4A, or TP44, monitor TP401)
L402 - 71 KHz trap (feed signal into terminal 4A, or TP44, monitor TP401)
Make sure C413 is good (10uF, 25 VDC or higher)
There is some more in the alignment instructions. Let's get it running first.
Okay
Terminal 4D has to have power, I think that's your stereo mode select signal.
TP402 - 19 KHz, tune T401
TP403 - 38 KHz, tune T402
TP401 - I think that is a bias level to kill or pass the switching signal @ 38 KHz
L401 - 67 KHz trap (feed signal into terminal 4A, or TP44, monitor TP401)
L402 - 71 KHz trap (feed signal into terminal 4A, or TP44, monitor TP401)
Make sure C413 is good (10uF, 25 VDC or higher)
There is some more in the alignment instructions. Let's get it running first.
Hey Chris,,, Thanks very much for taking the time,,, I am stopping at my buddys today from a minute but wont have time (he's inundated at the moment!!) ,,, so I wont be able to do these tests but will get back ASAP
Thanks again, this guy may run yet!!
Thanks again, this guy may run yet!!
No problem John, have him look when he has time.
I'm also jammed with work, so I know your friend is probably busy as heck.
I'm also jammed with work, so I know your friend is probably busy as heck.
Hey anatech, this is knockbill's buddy. I joined up to hopefully help him get this Sansui sorted out. I've restored vintage tube radio's for years but only AM/SW so I'm not much of a help for him troubleshooting FM, especially stereo FM. Yesterday I brought over my HP8662A sig gen and HP5334B counter. The 8662A is WAY overkill for what I do and it's capabilities wasted on me but it was a deal I couldn't refuse and even came with a non-functioning spare... but I'm slowly getting up to speed on it and it's my main bench sig gen now.
Anyway John wanted to follow the FM alignment procedure in the Sansui manual so if I remember correctly I set it up for the first step to sweep 98.5Mhz +/- 200KHz and set the amp/mod to what the manual called for. John hooked up his scope but we never saw the signal so something we did was probably wrong. We regrouped and decided to just check the 19k/38k that was mentioned in previous posts. I did not run the sig gen for this. John just wanted to see what the stereo was producing for those signals. So we hooked up the 5334B and that's when we saw the 14-18kHz fluctuation he mentioned. He then went and checked that poly cap and transistor while I looked at the lack of AM in his Bogen project and found the open antenna coil.
This is the only setup I have that will produce the FM frequencies need to do a full alignment, though looks like he's not at that point yet. Correct me if I'm wrong but we will need a multiplex gen along with the 8662A to do the full procedure?
I do have a restored Precision E-200-C sig gen and a Fluke 1900A counter that I can lend him that will allow him to inject the 19/38kHz for troubleshooting that section if you think that will hep him. I'll just have to get him up to speed on how to use them.
Anyway John wanted to follow the FM alignment procedure in the Sansui manual so if I remember correctly I set it up for the first step to sweep 98.5Mhz +/- 200KHz and set the amp/mod to what the manual called for. John hooked up his scope but we never saw the signal so something we did was probably wrong. We regrouped and decided to just check the 19k/38k that was mentioned in previous posts. I did not run the sig gen for this. John just wanted to see what the stereo was producing for those signals. So we hooked up the 5334B and that's when we saw the 14-18kHz fluctuation he mentioned. He then went and checked that poly cap and transistor while I looked at the lack of AM in his Bogen project and found the open antenna coil.
This is the only setup I have that will produce the FM frequencies need to do a full alignment, though looks like he's not at that point yet. Correct me if I'm wrong but we will need a multiplex gen along with the 8662A to do the full procedure?
I do have a restored Precision E-200-C sig gen and a Fluke 1900A counter that I can lend him that will allow him to inject the 19/38kHz for troubleshooting that section if you think that will hep him. I'll just have to get him up to speed on how to use them.
Thanks Chris,,, he joined us to keep me straight on the tests!!!
Hi MGY401,
Welcome to DiyAudio! Hopefully you'll find interesting things going on. Lot's of people will help if you have questions. You're always free to PM me once you're sprung.
The old way of aligning coils is the sweep method. I use a spectrum analyzer. If you find an HP 3585A (good to 40 MHz), it would work very well on your AM stuff and for the FM IF. For the front end I use an HP 4195A. These have built in tracking generators so will supply stimulus and display the results. They can be a lifesaver if a unit has been "messed with". Many 3585A or B have very weak displays, but they have rear outputs you can use an X-Y monitor with if you find one really cheap.
You can also use an RF generator that has a ramp output and a normal oscilloscope. Yours is an excellent generator, I don't know if it will sweep or not without looking, it will serve you very well. It's just heavy as sin! lol! Your 5334B is an excellent counter, close to my 5335A. Much better than most service shops have in fact.
Don't worry about aligning the IF yet, or RF. As long as it hasn't been adjusted, it will not have drifted too far from where it should be. Just send a signal modulated with 400 Hz or 1 KHz (whatever) and see if you get output. Modulation is 75 KHz (100%). If you can get that signal through, ignore RF and IF alignment for now. We can do some things easier these days than the manual procedure anyway.
You will need a separate audio generator to modulate the carrier in your HP 8662A. It doesn't have to be fantastic, I use a Chinese DDS based generator when I need a quick, non-critical signal. If you got your hands on an MPX generator they make those stand alone), you can modulate your generator with that and have stereo. If you ever see a Radio Copenhagen SMG1 or similar you can use that. FM stereo RF generators seem to be expensive. You need this only for separation adjustments to be honest. You also should have a meter calibrated in dB, could be an analogue type. Newer DVM's tend to have restricted high frequency range - so watch for that. Mine is good to 300 KHz, my handheld to 100 KHz, many struggle to reach past 400 Hz. They used to use a VTVM, that works fine.
The Precision E-200-C may work on band "H", but I would worry about frequency stability and dial accuracy. He could find the signal, but it may drift. Worth a try, the counter may help him find the frequency it is really sending. He will need an oscilloscope, that is key along with a decent voltmeter.
You're teaching him valuable skills. Right on!
-Chris
Welcome to DiyAudio! Hopefully you'll find interesting things going on. Lot's of people will help if you have questions. You're always free to PM me once you're sprung.
The old way of aligning coils is the sweep method. I use a spectrum analyzer. If you find an HP 3585A (good to 40 MHz), it would work very well on your AM stuff and for the FM IF. For the front end I use an HP 4195A. These have built in tracking generators so will supply stimulus and display the results. They can be a lifesaver if a unit has been "messed with". Many 3585A or B have very weak displays, but they have rear outputs you can use an X-Y monitor with if you find one really cheap.
You can also use an RF generator that has a ramp output and a normal oscilloscope. Yours is an excellent generator, I don't know if it will sweep or not without looking, it will serve you very well. It's just heavy as sin! lol! Your 5334B is an excellent counter, close to my 5335A. Much better than most service shops have in fact.
Don't worry about aligning the IF yet, or RF. As long as it hasn't been adjusted, it will not have drifted too far from where it should be. Just send a signal modulated with 400 Hz or 1 KHz (whatever) and see if you get output. Modulation is 75 KHz (100%). If you can get that signal through, ignore RF and IF alignment for now. We can do some things easier these days than the manual procedure anyway.
You will need a separate audio generator to modulate the carrier in your HP 8662A. It doesn't have to be fantastic, I use a Chinese DDS based generator when I need a quick, non-critical signal. If you got your hands on an MPX generator they make those stand alone), you can modulate your generator with that and have stereo. If you ever see a Radio Copenhagen SMG1 or similar you can use that. FM stereo RF generators seem to be expensive. You need this only for separation adjustments to be honest. You also should have a meter calibrated in dB, could be an analogue type. Newer DVM's tend to have restricted high frequency range - so watch for that. Mine is good to 300 KHz, my handheld to 100 KHz, many struggle to reach past 400 Hz. They used to use a VTVM, that works fine.
The Precision E-200-C may work on band "H", but I would worry about frequency stability and dial accuracy. He could find the signal, but it may drift. Worth a try, the counter may help him find the frequency it is really sending. He will need an oscilloscope, that is key along with a decent voltmeter.
You're teaching him valuable skills. Right on!
-Chris
Hi Chris,,,
Just rechecked C413 and its one of the caps I replaced while checking them (used a 10u/50v),,, FWIW every cap I checked/replaced in this set so far was between 4 and 10x out of value,,, and each replaced transistor or diode was either bad or had its leads corroded,, some leads were snapped off... Since the amp board is working well, and holds bias, I am replacing the lytics and coupling caps in it,,, Still working on the MPX and FM boards when Mike and his test gear have time!!!
Thanks again for your help,,, I'll be back!!!
Thanks for the warm welcome and equipment advice Chris! I'll look into the 3585 and might have to put one on my wish list. I've been slowly upgrading my bench as I get better at this stuff. My 8662A will sweep and has 5 markers if needed. It's just heavy as hell so I don't want to drag it over John's without a good plan in place! I figured I needed a separate generator for the stereo so I'll see if a reasonable option pops up to use with my 8662A.
I'll try a test with the Precision E-200-C with my Fluke 1900A counter and see how stable it is on the H band. If it passes that test it might be a good enough setup for now so John can run some signals through and get a few answers. It's also a fairly simple setup I can get him up to speed with quickly.
I've been telling John I really don't think it's an alignment issue. Like you said unless someone got in there who didn't know better they rarely are out more than a tweaking. That step is just the final tune-up. The markings he saw on the coil cans look like factory notes to me.
I guess John has given me an excuse to finally learn some of this "new" FM tech LOL!
Mike
I'll try a test with the Precision E-200-C with my Fluke 1900A counter and see how stable it is on the H band. If it passes that test it might be a good enough setup for now so John can run some signals through and get a few answers. It's also a fairly simple setup I can get him up to speed with quickly.
I've been telling John I really don't think it's an alignment issue. Like you said unless someone got in there who didn't know better they rarely are out more than a tweaking. That step is just the final tune-up. The markings he saw on the coil cans look like factory notes to me.
I guess John has given me an excuse to finally learn some of this "new" FM tech LOL!
Mike
Hi Mike,
Yes, you have a wonderful generator! With an oscilloscope and using the ramp output, you should be able to sweep the response of tuner circuits. A spectrum analyzer normally has a log response on the vertical which is often more convenient. It also has movable markers and can do peak searches. Very handy. Don't worry about the stereo modulation aspect just yet.
I agree with you. There is more likely a circuit failure with John's receiver. Tracing audio signals should be enough for now. He will require an FM signal modulated with 19 KHz to test that, but a normal FM broadcast that is strong should work. Above all, he needs a decent analogue oscilloscope. Alignment of any 19 KHz and 38 KHz components requires a very accurate 19 KHz signal source. So a normal FM broadcast is far better than an audio generator adjusted to be close. You need crystal accuracy for this alignment. My earlier FM stereo generators used a 19 KHz crystal. Today a DDS generator should be accurate enough as long as other frequencies are accurate, their referenec is a crystal or similar oscillator, not L-C or R-C types.
Yes, you have a wonderful generator! With an oscilloscope and using the ramp output, you should be able to sweep the response of tuner circuits. A spectrum analyzer normally has a log response on the vertical which is often more convenient. It also has movable markers and can do peak searches. Very handy. Don't worry about the stereo modulation aspect just yet.
I agree with you. There is more likely a circuit failure with John's receiver. Tracing audio signals should be enough for now. He will require an FM signal modulated with 19 KHz to test that, but a normal FM broadcast that is strong should work. Above all, he needs a decent analogue oscilloscope. Alignment of any 19 KHz and 38 KHz components requires a very accurate 19 KHz signal source. So a normal FM broadcast is far better than an audio generator adjusted to be close. You need crystal accuracy for this alignment. My earlier FM stereo generators used a 19 KHz crystal. Today a DDS generator should be accurate enough as long as other frequencies are accurate, their referenec is a crystal or similar oscillator, not L-C or R-C types.
I got the Digi order and the caps I forgot at Mikes over the weekend, and finished the amp board,,, really sounds good, with AUX/CDP ,, I'll test it on the scope next time Mike is free.... Since not one cap I tested on this guy measured good out of the ckt,,, I pulled some caps out of the MPX board,,,, I found C412(.47) installed backwards, and replaced it with a new one in the proper polarity,,, Test showed the indicator light stayed on a bit longer, and responded to the trim pots,, but no stereo separation... Continued pulling/checking caps and found C408 (.47) in backwards also,,, These two caps were not Elnas like all the other small caps in this set, so possibly were replaced at some point,,,, There are Green/Red marks on the top of all teh small caps that Mike thought were from the factory, I don't think so now,,, The FM locks in better with less distortion now, but still no stereo separation,,,, There are 4 more caps left on this board that I need to pull to measure,,, I hope I'm getting close enough that an alignment or tweak will make the difference!!!
Sounds like progress John.
Get the stuff you know is a problem fixed first. I think you need the scope to go further to see what is working and what is not.
Get the stuff you know is a problem fixed first. I think you need the scope to go further to see what is working and what is not.
Yep,, it is progress,, I finished the caps on that board,, didn't find anymore wrong polarity,,,, but the rest were way outta value,,, Seems all the work i did on the stereo indicator board was worth while, as the lamp tracks stereo stations even if there's no separation, trim pots will allow good adjustment also..
I have a Tek 2225 scope,,, dont have a FM signal generator tho,,,
I have a Tek 2225 scope,,, dont have a FM signal generator tho,,,
Okay, look for the 19 KHz signal and 38 KHz signals as I mentioned before. Use a strong, normal FM station (even if you don't like the music). Make sure it is in stereo mode and look for those signals.
Since I'm on hold with the FM/MPX problem for now,,, I started to chase the Phono/Tape head board's noisy, unequal output,,,
replacing TR601/603(2SC548) with 2SC1845s,,, along with the 6 lytics on that board... Now the Phono stage is dead quiet, but still has uneven output,,, I got Voltage readings from the new 2SC1845s and the old 2SC281s, which are on the chart.,.
I haven't pulled the 2SC281(TR602/604) to test, as I dont have closer replacements than 2SC1815s, which will need pinout modifications,,, However, they are the only major parts I haven't tested yet...
I can balance the L-R channels with the balance control at least 90% to R,,, and can raise the volume to reasonable level, without noise/distortion,, but as long as the readings are so far off, I want to find the problem... Seems the untested TRs are the next step?
replacing TR601/603(2SC548) with 2SC1845s,,, along with the 6 lytics on that board... Now the Phono stage is dead quiet, but still has uneven output,,, I got Voltage readings from the new 2SC1845s and the old 2SC281s, which are on the chart.,.
I haven't pulled the 2SC281(TR602/604) to test, as I dont have closer replacements than 2SC1815s, which will need pinout modifications,,, However, they are the only major parts I haven't tested yet...
I can balance the L-R channels with the balance control at least 90% to R,,, and can raise the volume to reasonable level, without noise/distortion,, but as long as the readings are so far off, I want to find the problem... Seems the untested TRs are the next step?
Hi John,
Gain will be set by the feedback loop. The capacitors are smaller film types and should be fine, but I have seen polystyrene types open and short. Resistors going out of tolerance is another solid bet.
Failing that, if the EQ is switchable (like early tape head - phono types), contacts or broken wires can do this. Sometimes they use the phono amp for a mic by changing the EQ.
Gain will be set by the feedback loop. The capacitors are smaller film types and should be fine, but I have seen polystyrene types open and short. Resistors going out of tolerance is another solid bet.
Failing that, if the EQ is switchable (like early tape head - phono types), contacts or broken wires can do this. Sometimes they use the phono amp for a mic by changing the EQ.
OK,, Thanks for the input,,, I can use the Parts list to ID polystyrene caps,,, and check them for opens and shorts,,, Resistors on this board seem to be sealed and not the common carbon type,,, all I tested so far read almost dead on value,,,
I see you didn't mention last two transistors, which are powered thru the mentioned resistors,,, Those old 2SC281s, were next on my remove to test list,, but I'm not sure the pins on them will survive removal,,, I guess I could try to pull them and if they break I'll need to use the 1815s in their place... I will try to eliminate the other parts before I mess with the TRs...
There is a separate Phono and Tape head switch, as Phono has the RIAA network included,,, but the output is unequal using either mode...
Thanks again!
I see you didn't mention last two transistors, which are powered thru the mentioned resistors,,, Those old 2SC281s, were next on my remove to test list,, but I'm not sure the pins on them will survive removal,,, I guess I could try to pull them and if they break I'll need to use the 1815s in their place... I will try to eliminate the other parts before I mess with the TRs...
There is a separate Phono and Tape head switch, as Phono has the RIAA network included,,, but the output is unequal using either mode...
Thanks again!
Well, compare the specs for the two transistors and just replace them. Anything is possible with early transistors with decades under their belt. Normal failure modes are noisy junctions, leakage and intermittent connections. I guess beta could drop into the basement, and that is what it would take to reduce gain that much. The newer devices would be less noisy, but that is important for the transistors at the input.
Okay, you cleared the EQ switching network - unless it was disconnected for both.
I would have to examine the schematic to give you better information.
Okay, you cleared the EQ switching network - unless it was disconnected for both.
I would have to examine the schematic to give you better information.
Thanks again Chris,,,
The closest I can find to Polystyrene caps on the Parts list is Mylar,, there are 6 Mylar caps on the board,,,
I researched the TR subs at length, and the most highly rated sub is 2SC1815, which I have,, pins B and C need to be exchanged but its the only common sub I can find,,,
Thanks again for the info!!!
The closest I can find to Polystyrene caps on the Parts list is Mylar,, there are 6 Mylar caps on the board,,,
I researched the TR subs at length, and the most highly rated sub is 2SC1815, which I have,, pins B and C need to be exchanged but its the only common sub I can find,,,
Thanks again for the info!!!