C410 mica makes sense as well. I don't trust many cap types from those days, electrolytics often go open and other plastic types can short. Manufacturing wasn't as good as it is today.
Yes, signal strength makes a big difference, and they often kill stereo looking at the AGC voltage on purpose. I route a strong FM signal into my bench in the basement from the second floor (good thing they let me run cable when they were building the house!). The beauty of good generators is that you can dial the signal strength anywhere you want it without worrying about how good the radio signal is that day.
Separation adjustment is done with a stereo FM generator, left only output then right only. You measure in dB. Don't touch that!
Yes, signal strength makes a big difference, and they often kill stereo looking at the AGC voltage on purpose. I route a strong FM signal into my bench in the basement from the second floor (good thing they let me run cable when they were building the house!). The beauty of good generators is that you can dial the signal strength anywhere you want it without worrying about how good the radio signal is that day.
Separation adjustment is done with a stereo FM generator, left only output then right only. You measure in dB. Don't touch that!
I can replace C412 as go thru the caps, the others I will try to test,,, OK,,, thanks for the heads up,,, I wont touch any adjustments til I rule out signal strength,,, I have a Fisher 220T as a shop receiver, I repaired awhile ago,,, it gets good reception down there, but I never tried it on this antenna,,, I'm sure my buddy can help me with alignment,,, its just a matter of when he has time....
Running an antenna wire will be teh easiest part of the job,,, I was an electrician for 50 years!!!
Thanks for the advice and info!!!!
Running an antenna wire will be teh easiest part of the job,,, I was an electrician for 50 years!!!
Thanks for the advice and info!!!!
Hi knockbill,
Early Fisher equipment (tube) was excellent stuff. I have some, sine I was a young boy (and I mean young!).
The difference between aligned equipment and just fixed is like night and day. As far as I'm concerned, equipment is not repaired until it is aligned. It isn't uncommon to exceed new performance because a lot of stuff isn't aligned properly from the factory (it used to be).
I do telecom, and what electricians can do running cable and conduit is amazing. So I contract them for conduit, spec the cable and have them fill it. Runs are straighter I noticed.
Early Fisher equipment (tube) was excellent stuff. I have some, sine I was a young boy (and I mean young!).
The difference between aligned equipment and just fixed is like night and day. As far as I'm concerned, equipment is not repaired until it is aligned. It isn't uncommon to exceed new performance because a lot of stuff isn't aligned properly from the factory (it used to be).
I do telecom, and what electricians can do running cable and conduit is amazing. So I contract them for conduit, spec the cable and have them fill it. Runs are straighter I noticed.
The Fisher is from 1966 IIRC,, pretty early SS hi fi.. I got it for 5bux at a hamfest with one bad channel... I rebuilt the preamp board and the PS and diodes... Its been good for at least ten years... My buddy got some hi end test gear from a tech school that was updating... He's been into antique radios for many years,,, but IDK if he has done much work on MPX FM... He just got a Scott tuner, that he can practice on !! We'll have to see how that goes...
I mostly work on and build tube amps, so SS is a bit of a challenge for me... My eyesight is failing, and the parts are way too small to handle and read!!! But I couldn't pass up this Sui 400 for a buck!!!
I appreciate your help!
I mostly work on and build tube amps, so SS is a bit of a challenge for me... My eyesight is failing, and the parts are way too small to handle and read!!! But I couldn't pass up this Sui 400 for a buck!!!
I appreciate your help!
Hi knockbill,
Your friend is lucky.
Yeah, I used to be able to read surface mount markings. Forget it these days! I learned on tube, trained on SS and IC. I work on both these days.
Your friend is lucky.
Yeah, I used to be able to read surface mount markings. Forget it these days! I learned on tube, trained on SS and IC. I work on both these days.
I'm the lucky one,,,, I'm his friend!!!!!!!
Just finished chores, so going to try my best to check out what you posted... after I get a good antenna set up for this guy!!!!!
Just finished chores, so going to try my best to check out what you posted... after I get a good antenna set up for this guy!!!!!
Well, I'm trying,,, I got my scope calibrated,, TR403 reads C 21V,,, E 21V,, matches the schem,,, there isn't a schem reading for Base...
I put a 19kHz signal on the scope with my signal generator, and tried to match it with tuner playing,,, seems to be the same...
I'll try to do the same with 38kHz... I think there is a bad part or two on the MPX board, TRX-6, I dont think its a transistor as I replaced TR404~407... TR401~403 and are Ge trans and have reasonable Voltages... I read resistors in ckt, none read out of value(within 10%)
I suspect a cap or two is out of value,,, but of the ones you mentioned, I dont have replacements,,,
I put a 19kHz signal on the scope with my signal generator, and tried to match it with tuner playing,,, seems to be the same...
I'll try to do the same with 38kHz... I think there is a bad part or two on the MPX board, TRX-6, I dont think its a transistor as I replaced TR404~407... TR401~403 and are Ge trans and have reasonable Voltages... I read resistors in ckt, none read out of value(within 10%)
I suspect a cap or two is out of value,,, but of the ones you mentioned, I dont have replacements,,,
Last edited:
You have way more patience than I do when it comes to tuners John.
I'm using a 100wpc SS Fisher receiver in my garage system with a bad tuner. I just use it as an integrated amp and added a tuner to the tape in.
I'm using a 100wpc SS Fisher receiver in my garage system with a bad tuner. I just use it as an integrated amp and added a tuner to the tape in.
Hey Paul,,,
Well I've got no attachment to this guy,,, other than its a very cool, vintage Sansui, about the same age as the shop Fisher,,,
and the note on it when I got said FM/MPX works one channel out,,, which would be hard to believe!!!!!!!
So I got the AM and the phono/AUX stages working good,,,, MPX will be a learning process,,, if I can gather the knowledge and tools...
FM works good enough for mono now, but I'd like to see it right!!!
I connected the scope and can get 19 and 38mHz to display from the sig gen,, but not from the receiver points that are listed in post #99, altho FM plays and the light comes on if the signal is strong enough.... But its not stereo...
I don't normally just shot gun capacitors, but maybe the lytics on the MPX board are worth changing?? Something is wrong there, as the light will stay on for a pretty long time when FM is selected,,, since the new transistor, but slowly fades out after a while...
Well I've got no attachment to this guy,,, other than its a very cool, vintage Sansui, about the same age as the shop Fisher,,,
and the note on it when I got said FM/MPX works one channel out,,, which would be hard to believe!!!!!!!
So I got the AM and the phono/AUX stages working good,,,, MPX will be a learning process,,, if I can gather the knowledge and tools...
FM works good enough for mono now, but I'd like to see it right!!!
I connected the scope and can get 19 and 38mHz to display from the sig gen,, but not from the receiver points that are listed in post #99, altho FM plays and the light comes on if the signal is strong enough.... But its not stereo...
I don't normally just shot gun capacitors, but maybe the lytics on the MPX board are worth changing?? Something is wrong there, as the light will stay on for a pretty long time when FM is selected,,, since the new transistor, but slowly fades out after a while...
Since you started working in this receiver you've pretty much replaced everything on that board except caps, ya? It couldn't hurt to do so I guess. I did have a piece of Marantz gear that gave me fits, only to find a failing low voltage cap.
I'm answering that question right now!!! Seems that TRX-6 board has a lot of different kind of caps on it, and soem of them need exact replacements...
Do ya think replacing the lytics on the boards is worth while?? there are 16 on the amp board,, I think I replaced a couple of those,,, and 14 on the MPX board... I didn't think it was a good idea to just shotgun all lytics on a vintage amp/receiver?
Depends on the receiver, and the vintage. The better quality the piece, the more likely the parts are to be worth a dam to begin with. You see Panasonic or Nichicon it’s a good bet they’re still good if they see moderate DC bias and not a lot of stress. Something you’ve never heard of, well…. anything goes. Old 60’s stuff where they used a lot of axials and FP‘s - you pretty much assume they’re going bad. That far back nobody made 50-year cap unless it was a “computer grade” soup can type.
Stop, don't just replace stuff. What that does is create uncertainty. Just find the fault. Once you have it running, then worry about other stuff. If you break it while replacing other things you stand half a chance of figuring everything out.
Hi knockbill,
Use an FM signal, or an FM MPX generator (stereo generator). Trace a normal signal. At least with a generator you can inject a stereo signal with no modulation. (pilot only). Injecting a 19 KHz signal with a generator can cause it to malfunction in all kinds of ways. The level has to be right, the frequency bang on. If you have an AGC pick-off, that can and will kill the MPX.
Do not assume anything, please. Follow the alignment directions in the manual best you can. Make sure signals are at the expected levels or the circuit will not react properly. I sure wish you were close so we could throw it on the bench.
Above all, do not rush or be impatient. Don't expect a good outcome if you don't approach it the way it should be done.
-Chris
Hi knockbill,
Use an FM signal, or an FM MPX generator (stereo generator). Trace a normal signal. At least with a generator you can inject a stereo signal with no modulation. (pilot only). Injecting a 19 KHz signal with a generator can cause it to malfunction in all kinds of ways. The level has to be right, the frequency bang on. If you have an AGC pick-off, that can and will kill the MPX.
Do not assume anything, please. Follow the alignment directions in the manual best you can. Make sure signals are at the expected levels or the circuit will not react properly. I sure wish you were close so we could throw it on the bench.
Above all, do not rush or be impatient. Don't expect a good outcome if you don't approach it the way it should be done.
-Chris
Thanks,,, I never was a shot gun tech!!! I always want to know why,, that's the education!!! Even if I replaced an electrical part on a job I always took the bad part with me and opened it up to find out why it failed!!!
I didnt connect my sig gen to the receiver, just to the scope, to make sure I could see 19/38mxHz waves...
I can keep poking around with the list you gave me,,, but I cant seem to read any frequency off the 19 and 38 TPs you posted,,, however, I did read 19kHz before, but never saw 38kHz on the scope,,, so this is operator error...
I have to back track and see what I'm doing wrong!!!
I dont think there is enough amplification of the signal in the MPX board to keep the signal constant (which is why the light flickers or goes out after a while),,, and/or there are bad caps/resistors that overheat or otherwise change value...
This is by far the most complicated audio piece I ever worked on, and my 1st stereo tuner... So unless I find a definite problem, I won't mess with any caps or coils til I can get it on my buddy's test gear,,, tho I am tempted to replace lytics on the MPX board!!!!
I thought I found the problem yesterday as I was moving the thick braided copper wire that is the main ground from the tuning condenser to the chassis and the light was blinking,,, turns out it was only attached by a strand or two,,, That's secure now, and cleared up some noise...
I am not going to waste all the time you and Netlist spent trying to help me by changing parts that work and/or test good!!!!
I still haven't changed the 458 transistors in the Sansui 800,, just the PS caps/diodes, about ten years ago, when they got noisy,,,
The 800 amp is still in rotation dead quiet!!!!
Thanks again for the continued help!!!!
Regards,
John
I didnt connect my sig gen to the receiver, just to the scope, to make sure I could see 19/38mxHz waves...
I can keep poking around with the list you gave me,,, but I cant seem to read any frequency off the 19 and 38 TPs you posted,,, however, I did read 19kHz before, but never saw 38kHz on the scope,,, so this is operator error...
I have to back track and see what I'm doing wrong!!!
I dont think there is enough amplification of the signal in the MPX board to keep the signal constant (which is why the light flickers or goes out after a while),,, and/or there are bad caps/resistors that overheat or otherwise change value...
This is by far the most complicated audio piece I ever worked on, and my 1st stereo tuner... So unless I find a definite problem, I won't mess with any caps or coils til I can get it on my buddy's test gear,,, tho I am tempted to replace lytics on the MPX board!!!!
I thought I found the problem yesterday as I was moving the thick braided copper wire that is the main ground from the tuning condenser to the chassis and the light was blinking,,, turns out it was only attached by a strand or two,,, That's secure now, and cleared up some noise...
I am not going to waste all the time you and Netlist spent trying to help me by changing parts that work and/or test good!!!!
I still haven't changed the 458 transistors in the Sansui 800,, just the PS caps/diodes, about ten years ago, when they got noisy,,,
The 800 amp is still in rotation dead quiet!!!!
Thanks again for the continued help!!!!
Regards,
John
Hi John,
Yes, finding out and understanding why something didn't work teaches you a lot and makes future experiences much easier. I get a lot of "unrepairable" units from people who just start changing parts - and they always cause additional problems. It makes the fix more expensive. My least favorite comment is "I already spent $xxx on this and don't want to spend much more". Okay, so it's my problem you did silly things, or took it to someone unqualified? I don't think so! That and I really hate cleaning up after someone else!
Early circuitry can be ... creative let's just say. Early MPX circuits also included features to kill the stereo mode if the signal would cause it to go in and out of stereo mode. These included signal strength, and in the case of Marantz, high frequency noise or off centre tuning. So you can have faults in any of these circuits that will kill the pilot signal (19 KHz or 38 KHz). That includes any faults in the actual tuned circuits and amplifiers.
The basic old style MPX works by using a tuned filter to pull out the 19 KHz pilot signal in the broadcast signal. That 19 KHz pilot tone is 9% modulation out of a total of 100% (75 KHz deviation). In FM modulation, the loudness of a signal is the amount of deviation from the main RF carrier, unlike AM modulation. So the expected level is controlled within a small range and some circuits will not operate properly outside of these bounds. I can feed an MPX signal (audio) into these circuits using an FM stereo generator designed for the purpose. Feeding an oscillator in may or may not work - depending on many things. That 19 KHz signal must be close to exact by the way. It is crystal controlled at the station modulator.
If you feed in a normal signal with good strength, you should see the filtered 19 KHz pilot at TP402. It is full wave rectified to create your 38 KHz signal, the transformer filters out the fundamental so you have a sine wave. The 19 KHz signal is also fed to the lamp circuit (TR501), TR502 switches that on and off from a signal; on terminal 50, wherever that goes. Might be the stereo switch (function). If TR501 is active (TR502 is on), TR503 amplifies it and drives TR504 and therefore TR505 to turn on the lamp. Looks like it also goes to the mode FM Auto switch if I had to guess.
So, first make sure all the transistors are biased on in an active mode and not cut-off or saturated. Then just chase the signal with your 'scope. If there is a mute, make certain it is off as the kills all the audio including your pilot tone. Let us know how you make out.
Remember, as always, beer after you're done! lol!
-Chris
Yes, finding out and understanding why something didn't work teaches you a lot and makes future experiences much easier. I get a lot of "unrepairable" units from people who just start changing parts - and they always cause additional problems. It makes the fix more expensive. My least favorite comment is "I already spent $xxx on this and don't want to spend much more". Okay, so it's my problem you did silly things, or took it to someone unqualified? I don't think so! That and I really hate cleaning up after someone else!
Early circuitry can be ... creative let's just say. Early MPX circuits also included features to kill the stereo mode if the signal would cause it to go in and out of stereo mode. These included signal strength, and in the case of Marantz, high frequency noise or off centre tuning. So you can have faults in any of these circuits that will kill the pilot signal (19 KHz or 38 KHz). That includes any faults in the actual tuned circuits and amplifiers.
The basic old style MPX works by using a tuned filter to pull out the 19 KHz pilot signal in the broadcast signal. That 19 KHz pilot tone is 9% modulation out of a total of 100% (75 KHz deviation). In FM modulation, the loudness of a signal is the amount of deviation from the main RF carrier, unlike AM modulation. So the expected level is controlled within a small range and some circuits will not operate properly outside of these bounds. I can feed an MPX signal (audio) into these circuits using an FM stereo generator designed for the purpose. Feeding an oscillator in may or may not work - depending on many things. That 19 KHz signal must be close to exact by the way. It is crystal controlled at the station modulator.
If you feed in a normal signal with good strength, you should see the filtered 19 KHz pilot at TP402. It is full wave rectified to create your 38 KHz signal, the transformer filters out the fundamental so you have a sine wave. The 19 KHz signal is also fed to the lamp circuit (TR501), TR502 switches that on and off from a signal; on terminal 50, wherever that goes. Might be the stereo switch (function). If TR501 is active (TR502 is on), TR503 amplifies it and drives TR504 and therefore TR505 to turn on the lamp. Looks like it also goes to the mode FM Auto switch if I had to guess.
So, first make sure all the transistors are biased on in an active mode and not cut-off or saturated. Then just chase the signal with your 'scope. If there is a mute, make certain it is off as the kills all the audio including your pilot tone. Let us know how you make out.
Remember, as always, beer after you're done! lol!
-Chris
Thanks again for your help!!!! Dont be concerned about me skipping steps or rushing this project!!!! First, my buddy told me he has the test gear to do this,,, whether I/he get to it anytime soon isn't even in the cards!!
I live by wants and needs, my next breath is a need,,,, everything else a want!
So,,, just to keep you posted as ya asked,,, I backed up a day or two and remembered an abandoned CATV cable run from the basement to attic and dropped into the office room... (your mention of the cable you ran in your new house sparked it) ,,, So I found the ends,, rang it out and am in the process of building a new FM antenna to put in the attic, fed to the basement shop,,,
As you said,, I need the tools to do the job,,, Since the FM signal the receiver puts out is my test signal, as I dont have any other FM stereo tools here,,, the strong antenna is necessary!!!!
I will read and try to absorb the steps you are posting, but proper antenna first!!!
Thanks again!
I live by wants and needs, my next breath is a need,,,, everything else a want!
So,,, just to keep you posted as ya asked,,, I backed up a day or two and remembered an abandoned CATV cable run from the basement to attic and dropped into the office room... (your mention of the cable you ran in your new house sparked it) ,,, So I found the ends,, rang it out and am in the process of building a new FM antenna to put in the attic, fed to the basement shop,,,
As you said,, I need the tools to do the job,,, Since the FM signal the receiver puts out is my test signal, as I dont have any other FM stereo tools here,,, the strong antenna is necessary!!!!
I will read and try to absorb the steps you are posting, but proper antenna first!!!
Thanks again!