my ctc17 combo lost stereo separation too. I use the tape input for the cable box.

I figured it was a burnt or failed ground somewhere but you bring up a good point.

O, btw... on both my zenith combos with the same tuner, the bass is mono and the high end is stereo.
I never questioned it because thats the way systems with subwoofers are setup. There should be little to no stereo information in the bass and it makes sense to have it monoed out.

its goofy. I put in a signal 400hz into the left channel thru the phono, then I scope the base of the left transistor and compare to the base of the right. WTF the signal is about 1/3 the Left.

there is a network of resistor that connect the two bases togehter on mine its a 56k/22k/56k. I removed the transistors from the sockets and check the resistance, total was about 160k which would make since after accounting for drift there was nothing else in the circuit but for the disc coupling caps.

I dont know why this would be the case, but I can clearly see the 400hz on the base and of course the collector of the right channel.

I wonder if there would have been any reason to tie the two channes together?

I will check the replacement tuner if it does the same thing then between us thats 3 that lack decent separation, and maybe its just the design.

If so I may be inclined to see what I can do to break that connection and see what happens. Worst case is I muck up a few transistors, but since they are in sockets, big deal....

what bugs me is to go thru all the effort in the mpx to separate the channels just to throw them back together in the amp.

What is the separation at 100hz and what is it at say 2.5khz.

You will never notice if everything below 500hz is monoed out, its better that way. The bass will sound much fuller and fatter.

my osc is just a single hrz, I may have anoher will have to check around

BUT

I did disconnect the singe resistor that connect both the transistors bases, other than the bias voltage being a bit further off than before (it tied them together) I could hear no difference AND much better separation.

about 10 to 1 where it was about 3 to 1. clearly that resistor was the signal path between the two channels, whats left is prob un decoupled from the B+.

I am going to listen the to radio all day tomorrow and see how it does.

I may go thru my stash of transistors and see if I can match some (I have a transistor beta checker). Just to see how close I can get the bias.

I took a look and thats exactly what it looks like to me, low frequency coupling. I would leave it and listen to some music programing and see how it sounds.

4 IF stages, Nice! I never really looked at the schematic because both of mine work perfect.

still not satisfied with the lack of separation, this time over the air MPX fm, I got out my little rat shack stereo transmitter, hooked up a dual trace scope thru the tape out and applied a 400hz tone one channel at a time to the transmitter.

ugh, about 2 to 1 amplitude on the L and R.

I tweeked the 38kc coil, got to about 8 to 1 (best I could get) checked the other channel same ratio. Maybe some drift in a resistor, but only turned it less than a 1/4.

I may check all the transistors in the mpx circuit for gain, just for fun but I think is pretty darn good now for separation. for fun I may put the resistor that ties the two bases on the preamp back in just to see how much it effects the separation when using the transmitter.

ah much better. I connected that resistor back in the circuit and the scope showed BETTER separaion. I dont know whats going on, but it sounds MUCH better now with some actual over the air listening. Before you had to really listen to hear the separation, now its fine like you would expect.

There is a bit of a volume difference, this shows up on the scope as one channel being slightl higher amplitude. It can be compesated of course with the balance, but I would rather see if I can find the problem. there are a couple 5% resistors that feed the MPX detector that look like a likely suspect.

I should be interesting to see how the other tuner stacks up against this one.

ok rookie mistake #3 make sure on a dual trace that the voltage adj pot has been set. after setting up the trim pots for an equal vert on the same voltage the curves lined up perfect. this is at the tape out which is after the 1st stage of AF amp but before the volume control. I suspect my volume control is just not tracking. so next step will be to scope after the volume control and see how the curves line up.

argh just too hard to get a clean signal, too much ac hum. heck with it, if it is the loudness there is nothing I can do about it anyway. There are a couple emitter bypass caps 100uf, maybe something there, if one is weak it could cause neg feedback.

opps already did that. ok DONE...

time to get on the TV....

pic of the separation, this is with a tone on one channel of the FM stereo transmitter, scopt to the tape out.

sounds GREAT now!:banana:

come to think of it I have a fisher 400 that I have never been to keen on the separation. the tape output/dual scope/stereo xmitter/tone generator is a pretty good way to set that 38khz coil. When I get some of these TV's out of the way I may have to go back and work on that one.

I really think removing that resistor is a mistake. I checked both my combos again last night and they have great stereo separation with both channels going. With only one, yes there is some bleed over but it seems to go competently away with both signals.

The fm multiplex we use is the Zenith system and invented by Zenith. They knew how to do Stereo and I really doubt they would intentionally cripple their unit with a single resistor.

forgot to mention, I did put it back, and it did IMPROVE the stereo separation with the MPX. Not sure what the deal was but yes you are correct, leave it as designed. that last scope pic was with the resistor back in.

It appears they have some fancy phasing going on there where it blends the channels if one is missing and increases separation if both are there. I will study the circuit when I get time.

Stereo is one of those arts that has faded and been killed in modern music and programming. They got a 60/40% maximum separation rule they go by now. We wouldnt want all those home wired car stereo installs where all the speakers are out of phase and hooked up to the left channel to miss part of the crappy song.

I would like to implement something like this resistor deal at the dance club I am the sound tech for. That way when the djs crappy equipment drops a channel it blends and doesn't kill the party yet its still stereo when the information is there. I have gone to lengths to keep that place stereo, you really cant find a canned music venue anywhere that's true stereo. In fact most of the new equipment out of the box is default mono.

prob why the best separtion can be found on old early 70's rock. I listen to the classic rock station and get a good dose of separation (think whole lotta love by led zep).

Beetles and Doors weren't too shabby. Phil Spector cuts things up real nice too.

ok next up the phono, went to power it up on the variac, instant 3 amps at 10v, opps thats not good. pull the phono out and the motor coil is all toasted melted etc. guess that is what blew the fuse. the motor armature was seized up. pulled the motor and tried the turntable by hand, spent a couple hours finding out the issue there (it would not cycle properly) one tine little arm was out of place and the spring goofed up. after lubing and check reinstalling the spring is cycled correctly. Good thing too, there was a zenith TT on ebay with a starting bid of 1.99, the shipping was high but what the heck, well next thing you know the dumb thing is over 40$ bid and one day left. Needless to say there is no way I will pop for 70$ plus (inc shipping) for a cheezy zenith TT. So now I have to get this one fixed. I am pretty sure I can get a replacement motor (one of those induction motors with the stepped shaft that drives and idler pulley) from my local vintage guy (Dennis at radio relics) or Sky junk suplus. the issue maybe how to get that stepped driver off the shaft. It looks to be pressed on, too bad it did not use a set screw.

anyhoo I know the cart works (spun a record by hand) so I will deal with the motor next week.

I prob should have started with the TV at this rate it seems like it has to be easier that this TT (all automatic TT's were designed by the devil himself IMHO).

I would like to have know the failure sequence when this thing went bad. As badly as the motor is toasted I am suprized the fuse would not have cut it off before it melted down (it still had the orig fuse in, blown but in).

Try www.thevoiceofmusic.com. Most Zenith turntables from this era were built by VM and Gary can likely fix you up with a motor for a reasonable price. If not, any motor from a similar vintage VM record changer should work. And, I don't blame you for not plunking down $70 on a basic record changer. VM built changers were very common back then; and, you will find one much cheaper if you look.

I just looked at the pictures again and that is a VM built changer. Try that site I mentioned above and I'll be on the lookout for you a motor, as well.

well I was able to get the bearing unstuck, the plan now is to use the old front bearing with the wedding cake drive and just use the a new C frame if I can find one. I may have one in the shop.

this is really not something I want to spend a dime on since its unlikely I will be spinning any records on this thing. I think I only paid 15 or 25 cant remember for the whole console so this turnable is not going to blow the budget :)

Aint that a hoot about the TT on ebay. Some other guy over at ARC has an issue with his zenith as well. My guess is two guys have a need, and bingo, bet you will neve see a zenith TT go like that again. I do like magnavax micromatic imperials the older ones with the gold trim. they are solid and I dig the way the tone arm taps the record to size it. Plus they use two idlers, one for the platter and one for the tone arm drive. Now those are worth a few bucks, but man this zenith thing is CHEAP!!! I am tempted to get a later model magnavox micromatic (the early astrosonics came with a nice one, just a bit more modern looking than the imperials) and put it in there, but I wont since I am not into frankensteing vintage gear.

I plan to put the orig tuner back since I have it working so well. the replacement is identical but for some very minor differnence in the dial face.

Whatever you do, please don't stick one of those plastic '70's BSR's in there! I have a '58 Magnavox console hi-fi that someone did that to. I'd like to find an original Magnavox turntable to go in it; but, I'm running into the same situation as you did. I only gave $15 for the console and, by the time I factor in shipping cost, I'd have $50+ in a turntable, which is a bit much for a $15 semi-beat up console.

Those VM built Zenith branded changers were decent for what they were; but, certainly nothing special. The main thing they have going for them is the "micro touch 2G" cartridge. These are among some of the better ceramic cartridges that won't ruin your records as fast as many of the more conventional cartridges.

Zenith also used a belt drive changer in their highest end models. I've never actually seen the insides of one of these turntables; but, I did see a couple consoles that had them. One was an early solid state model in a nice cabinet with a dead right channel and a malfunctioning turntable. The seller wanted $75 and got PO'ed when I tried to get him down. The other was a tube type model in a beat to heck cabinet that didn't half work. This one was at the SA, priced at $75, and they also got PO'ed when I pointed out it's flaws and tried to get it cheaper.

Is it the motor with the single coil on one side? if its just the coil, you should be able to rewind that motor fairly easily. Its not even critical how many turns. Use the same size wire and get about the same amount on the bobbin and it will work fine.

No BSr for me :)

yes its just the single coil, if I can't find a replacement frame ai will consider rewinding it, yes it looks like it would be easy.

found an c frame doner in a fan. removed the bearings mounts and the rotor, reused the old rotor and bearings. It was a bit more involved since I had to grind out a rivut that was in the hole where the mount needed to go, press out the old rivut. then I had to sleave up the main bearing mound hole on the new c frame with some nested alum tubing. got it all together. Running slow, since I reused the old rotor it should be turning the correct RPM, so its prob a just a bad idler.

I may have goofed up the new motor, dumb me forgot to check the voltage, I was running in on the variac and it was cranked to 140v. the motor was getting hot, I figured it was just being overloaded some how by the TT, now I realize it was overvoltage. duh...

I am going to see if I can fabricate a new idler, I know I can buy one, but again it goes against my princples on this one. I tried turning down some of the old rubber, but its hard though and though. I also tried my old standby of a large rubber band, it worked fine but ran slow. I replaced the grommets so that is not the problem. what a pita

new ider done, oversized square edge rubber ring was glued to the cut down idler with super glue. Freeze it to harden up, turned a bevel on the new rubber edge to match the correct thickness. Looks good, will try tonight.

what a mega PITA this carp tt is.

got the new idler, got another phono motor, had to turn down the idler a bit, lube the replacement motor bearings all good. Then the cheap a$$ plastic switch messed up. Geez I mean cheap.

Anyway I had to perform surgery to take out the switch, monkey with it for a while (the detent overcenter spring was not seated correctly) get it all back together. It works (cycles thru and will turn it self off) about 75% of the time. the other 25% the switch will not go all the way to off and the end of the cycle, leaving the ilder engaged.

I am going to play with it some more and make sure its got good lube were ever I can find a rubbing point to max the force applied to that stupid switch.

argh.....

I so want to stuff a magnavox imicro matic in there.......

I just hope the TV goes smoothly.

lots of careful clean/degreasing/regreasing... seem to work ok now, no more miss fires. listening to it now so the cart is good as well.

just have to wire up the motor back to the plastic plug then figure a way to attach the orig plug back in place. I may just cut the orig power plug and make it a more perm attachement since I dont think I can work the zip tie and the orig plug all in one. hard to explain, but at least it seems to be working ok now.

yea, got it back in the cabinet, works fine now, but for a noisy idler (guess thats it, I am picking up some rumble sounding noise when the needle engages the record groove, but at least the speed is good and it cycles completly.

Next week I finally will get to the TV. will start with the HOT/VOT pulled and do a current metered variac slow start, checking for currrent and temps on the caps. will check for all filaments lighting up. If that goes well I will progress to a power up with tubes in and the HOT current metered and see how that goes.

I prefer to do this prior to pulling the chasis even for a general cleanup as a base line, so if it works I know that much before a general cleanup. I look at clean up as a good thing to do just because I dont like the idea of bringing into the house something that is real nasty (garage now). I will also have to start looking around for a replacement needle, I have no idea of the current condtion of the existing one, but I like to replace with a new one anyway.

has good vitals....

I replaced all the HV/sweep tubes (they all looked very very well done). Getting 25kv at about 220ma so that all looks good. got a raster but did not look full (but hard to tell since I had the CRT to the wall). Waiting for the HOT to cool down and then I will pull the tube bias adapter and re seat the HOT. after that I can pull it out and get a better look at the crt.

I did not have a video source hooked up, so that will be done also.

there was no sound at all, but this set uses the cabinet speakers, and not sure if they are hook up, I willl have to trace around and see what is going on there.

I can see its going to need a lot of tube socket cleanign etc. so the video test will be short, now that I have the HV and sweep baselined as working (mostly).

I will need to check the B+ of course to see if that is being pulled down. I did the slow power up on the caps (about 10 min total) and checked again after the raster test, not warm at all.

I finally got up the nerve to tug on the HV cage hard enough to pull it back so I could get to the reg tube. That one looked REAL bad.

anyway off to a good start :D

I also see there is a jumper that allows for horz adj if needed, not sure how it was set.

What is it about BSR record changers that's so terrible? :scratch2: I had a Zenith 4-mode integrated stereo system in the early '80s (was probably manufactured in the late '70s) that had a BSR changer. I did not have one bit of trouble with it, and I used it a lot in the 17 years I owned the system.

When I graduated from Claricon to Dynaco in 1970, I found out. Rumble.

They were good for what they were; and, that is their use in cheap "all in one" systems of the '70's and early '80's and they usually did their job until whatever sort of grease that they used turned to cement. Since these are so cheaply made, one has to be very careful when freeing one of these up as the parts bend very easily. BSR did make some changers that used a metal platter, a four pole motor, and a magnetic cartridge; but, the mechanism was basically the same as what was used in the lower end plastic platter models. When I was about 14, I bought a used Electrophonic 8-track/radio/BSR 3 speed record changer combo along with it's matching speakers for $2 at a church rummage sale because they thought something was wrong with it. It turned out that what was wrong with it was that they were plugging the speakers into the AUX input jack. That stereo was quite a step up from the late '60's el cheapo Westinghouse portable with seperate L and R volume controls that I'd been using; but, it didn't take long for me to find a '70's era component stereo system and once that happened, the Electrophonic with it's BSR changer found a new home. And, I have a '58 Magnavox console that someone pulled the original micromatic changer from and replaced it with a cheap BSR (which is frozen solid by now). One day, I plan to correct that. I don't mind sticking a BSR in a cheap '70's "all in one"; but, I tend to frown on doing it to an older instrument.

made some progress

hooked up a signal, Lots of snow but it would sync lock and audio was fine.

I sub in new IF tubes, no change, subbed in tuner tubes, no change.

B&k analyst, IF and its fine, (well lin/vert all off but that was with the snow as well).

This was the 1st time I used the B&k as an IF source, so I dont know if I still have an IF problem (and the B&K was just putting out enough signal to blast thru) so I will leave the settings and try on another zenith.

Maybe just a real real real dirty tuner.

another problem, the CRT was blooming so I checked the HV, with brighness turned all the way down its about 24kv, but with brightness up enough to get a decent pic its only about 14kv.

I checked the CRT and it was fine back when I 1st got the set.

I replaced the regulator tube. I have not checked the B+ to see how its holding up. I replaced the HV rectifier (3A3).

I will prob start by checking around there.

not so fast big boy...

I was over my metered variac, so I got my big boy variac out, adj line voltage to 117 and HV returned to normal, well regulated etc...

even got good color bars from the B&K and I did confirm the output settings by checking against a good set.

So... it seems like its just the tuner. I will sub tubes on last time from a known working tuner, my tube testers can't check them (HK 533 and Bk600) so I cant be 100% sure I have good tubes in there. My guess is the osc must be ok since it was working, but I will sub them both anyway.

I have heard of lightning strikes messing up tuners, not sure what gets fried but I will check. I am hoping its just dirty contacts.

I must admit I am tempted to just run a composite signal to the test point just after the video detector.

think I will check the tuner AGC voltage before I go too far

tried a new 6BA11 (agc keying/syc sep/noise cancel), no joy, need to find the tuner AFC source lug and see what its reading. Or just try adj the agc pot. Getting late tomorrow morn looks good to continue.