FM Stereo Indicator Lights on 1973 Pioneer TX-6200

[stinger123]

Good evening everyone. I am a relatively new vintage audio enthusiast, so apologies for posting what might be a dumb question. Recently, I bought a circa 1973 Pioneer TX-6200 for 5 bucks. Its a very simple tuner. It was 'as-is' and quite beat up, but I took it home and proceeded to clean it up- inside and out. I replaced the side wood panels, repainted the black case and polished up the undamaged faceplate and knobs. It looks fantastic:thmbsp:
I also opened it up and carefully followed Dr*Audio's suggestions for cleaning the insides. After de-oxing the contacts, and spraying the pots and switches, I replaced 3/6 fuse-like bulbs that were burnt out. I finally hooked up the tuner and took it for a spin. It sounds great and looks great. Nice blue face lights with am/fm tuning needle fully operational.

As I was listening to my favorite Jazz fm station and marvelling at how good it was sounding, I noticed that there was really no indicator to show whether the station was coming in stereo or not. The main selector switch has 4 options: "AM", "AUTO", "FM MPX" and "FM MONO". I went into google images and discovered by looking at the photos of other TX-6200s, that there is supposed to be a red beacon that lights up the end of the tuning needle when the tuner locks on to a stereo broadcast (that's my guess), and a separate "STEREO" light on the tuner face that comes on.

I tried to carefully discern whether the tuner was capable of stereo by switching from 'auto' to 'mpx fm' to mono, while listening to the Jazz music but could hardly tell if there was a difference between mono and stereo. I am assuming that the Jazz station (91.1 in the Toronto area) comes in on stereo. If anything, I could only sense a slightly brighter, more 'airy' tone in the music when switched in (supposed) stereo mode.

So here are my questions:
1) do you think a tuner of this grade and age is capable of pulling in and actually delivering a stereo signal to my amp?
2) if this is a job for a qualified technician to fix, and is it a relatively easy thing to fix?
3) are there any simple diagnostic tests that a newbie like me can attempt to clarify the problem? ie how to determine if I can get stereo and/or if the tuner is in need of repair.
4) are relatively pleasant 'mono' broadcasts the only thing that I should expect (and enjoy) from this simple, good looking tuner?:scratch2:

Thanks to Dr*Audio for his great cleaning tips, and to all of you who've written all the good advice and comments that I've learned a lot from in these pages!

Stinger

 

[terra1]

It is not unreasonable to expect a vintage tuner to work in stereo, but it also not unreasonable to expect it may need some work to get it back to working condition.

It may need cleaning, a better antenna, be damaged, need parts or alignment.

You say you notice a brighter airy sound in stereo mode. Mono would sound like everything is generally between the speakers. Switching to stereo you should hear a more expanded, fuller sound than mono with distinct individual instruments from the Left, Center, and Right soundstage. You might hear guitar on the right, sax on the left, etc.

First, do you have an antenna attached?
Does the tuning meter center in FM? Does the needle move as you move the tuning knob to the next station?

If you feel comfortable, you might read the sticky thread on how to clean a tuning capacitor. Some say all they needed was use an air blower to clean dust from the fins.

Cleaning and attaching an antenna is the easiest thing to do.

Beyond that it may need some adjustment, parts, or other work best left to a tech.
One of the first questions I always ask when buying from eBay or craigslist is whether the stereo light comes on.

 

[stinger123]

Thanks ALOT, Terra1; very useful information.
Yes, I think I followed the procedure (put up by Dr*Audio) for cleaning the tuning capacitor. And I had a decent indoor RCA fm antenna hooked up with a balun to make the proper 75-300ohm transition. As I rotated the antenna, the station would tune in and out, while the tuning meter also moved. And yes, the tuning needle would center perfectly and move as I switched between channels while turning the tuning knob.

I am going to follow your suggestion and try to determine whether the sound seems to come from between the speakers or if there is a distinct soundstage and any imaging. If not, then I know now that its a job for a technician.

I am not sure whether a tuner like this is worth paying out a lot of money to fix. (I bought it for 5 bucks) But one thing is for sure- even if the fm signal were to only come in mono, the sound quality is quite impressive. The background noise or hiss just isn't there. And its pleasant to look at.

Thanks again for taking the time to comment. I realize that a newbie question like mine is hardly worth responding to, especially when most audiophiles are probably into much higher grade equipment. This simple tuner I picked up is really just the start of my own learning about tuners, so I really appreciate the help.

 

[Sam Cogley]

It could just be some dead bulbs. Try to find an oldies or classic rock station playing something with the hard-panned "fake stereo" that was fairly common in the early to mid 60s - early Beatles tunes work great for this purpose.

 

[terra1]

I was checking some of the completed listings at eBay and there was one listing that said the stereo light was out and they weren't sure it was a bulb or stereo mode not working. It is unsold, so it's not yours. But I mention it as a possible problem with the tuners. Hopefully as you listen it may just be the bulb.

I notice there are FM/AM levels on the back. You may want to see if the Pioneer database has an owner manual for you tuner and see what that is about.

I assume you are in AUTO mode when you say Stereo mode.

If it sounds good, it may be worth having it aligned or at least get an estimate since it only cost you $5 in the first place. I have an Onkyo T-9 that sounded great but it was in Mono. I began to notice it just seemed like I wasn't getting something. It sounded so good I had to go back and forth from another tuner to confirm it was Mono. The adjustment was simple twist of a trimmer and I got Stereo light.

I did notice a "mint" sold for $49.95 on eBay. So weigh that into consideration if an adjustment and alignment may cost more than a replacement or even better tuner.

When buying I always ask if the stereo light comes on. Since you are not familiar with tuner tweaking I would also ask does the tuning meter center, strength meter show strong signal. All indicator lights work. Is tuning accurate like 101.5 is at 101.5 on the dial (this may or may not be a deal breaker since drift is common and you can always get it aligned).

Even better if the seller has 100% feedback and says he's tested it.

I say that because I also noticed one where they say it was untested, as-is.

 

[DaveWM]

I bought a cheap FM stereo transmitter at rat shack. uses a couple AAA batteriies. I also got some adapters that let me convert the input into two RCA type plugs. To check stereo separation you just plug in an an audio signal into on of the RCA jack at a time.

The transmitter transmitt on the extreme ends of the scale. I have found this very useful when setting up MPX matrix L+R balance to L-R (sometime you will find a "sepration" adj trim pot).

 

[stinger123]

Thanks alot Sam Cogley, Terra1 and DaveWM. I spent some time this afternoon hooking up another tuner (Mitsubishi DA-F10 in mint condition) and comparing it side-by-side, on the same FM station (fm 91.1 Jazz in Toronto). For this comparison, I hooked each tuner up to a dipole (you know- the T-shaped kind that usually come with tuners/receivers?).
Results: So even though the Pioneer SX-1200 is lacking a stereo indicator light(s), its definitely pulling in and delivering a stereo signal. To determine this, I used the Mitsubishi first and tuned in to 91.1. On this Mitsu DA-F10, the 'lock' and 'stereo' indicators came on. I put the volume up on the amp and started switching between 'auto stereo' and 'mono'. I could hear the same difference that I had detected in the Pioneer originally. Now, I put the volume up a bit more on the amp and while the Mitsu tuner was in 'auto stereo' mode, I immediate switched to the Pioneer which was also set in the 'auto' mode: they sounded identical! Then I would switch one unit into MONO mode and there would be an audible change. Just as you said, Terra1, the soundstage on the 'auto-stereo' tuned Tuner just opened up and I could hear the piano notes brighter in the right channel, as opposed to equally in both left and right (when in mono). So I am 99% sure that the $5 Pioneer tuner is operating in stereo. Now, how well the separation is , is something beyond my level of expertise but I am glad to know that the tuner is audibly putting out stereo.
The thing that irks me is that the Mitsubishi, which is in mint condition shows that the FM 91.1 signal is locking in at 91.7 on its dial: is that what you are referring to as 'drift' and a need for 'alignment'? The Pioneer tuner is right on the money; 91.1 is indeed 91.1.
DaveNM; I am going to fiddle with an FM transmitter and try what you suggested, to confirm my own test.
Sam, I will also look for an oldies (1960s?) fm station and listen to some faked stereo. Hopefully I can find something that wasn't produced by Phil Spector!

As always, I really appreciate the time and effort you kind people have taken to lend me your ear and advice. Have a good weekend!

 

[DaveWM]

tune in to a classic rock station that plays some led zep and the like, seems early 70's rock bands really like to use the stereo effect (Queens "a night at the opera" is a good example).

Headphones work well to, in mono the source will sound like it is coming from inside your head when balanced, in stereo you can hear it open up.

 

[standay]

I found on mine I had to have a very strong signal or the stereo indicator would not light up. I use a feed from my regular outside TV antenna which provided it a strong enough signal.

 

[siouxafrican]

Good thread for us beginners....lol. My old Fisher tuner does "drift" when locking on strongest signal and i notice my "stereo bulb" does fade in and out so i keep it in mono..... it hasn't been serviced so I'm sure that's the problem. All lights work!

 

[gadget73]

Ancient thread indeed.

Something I can offer about some early Pioneer MPX units is that they don't really ever switch off. Not sure what board is in the OP's tuner, and 9 years later I doubt we'll find out. Anyway, if it happens to be the same MPX board used in the early SX-990 and SX-1500TD, its basically always in MPX mode. I think its supposed to auto-switch but I have never gotten mine to not be in MPX mode. I pulled a board from a parts unit and it performs the same when wired to an assortment of different tuners. These do have an MPX indicator, but depending on particulars it either drives a low current bulb directly, or runs through a transistor buffer circuit to drive a higher wattage lamp. Seems to depend on the specific application. The board in my 1500TD clone drives the buffer, same as it does in the SX-990, but it was also used in the SX-6000 where it runs the lamp directly. It also does depend on the bulb being the correct one for it to have much chance of operating properly.

Maybe it would act different if I aligned it, but performance is fine and I haven't sat down with my FM-1000 long enough to actually feel confident enough to try adjusting anything on this. If I want mono, I simply change the selector switch to mono.