• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Sansui 5000X really odd tuner problem.

wlgrant6

wlgrant6

AK Subscriber
Subscriber
My 5000X will only tune up to 107. Stations clear across the dial are coming in at the correct dial indication. 97.5 comes in half way between 97 and 98 on the dial. 103.5 likewise, comes in half way between 103 and 104. The highest station that I can tune in is at 106.9, dial reads 107. At this point, the dial can be turned no further. Both the AM and FM tuning capacitors are maxed out at their stops. The logarithmic scale runs from 0 to 100. Tuned as low as it goes, the pointer is sitting on 0, max on top end is about 88. Anyone ever seen this before? Bill
 
Register to hide this ad
wlgrant6 said:
...dial reads 107. At this point, the dial can be turned no further. Both the AM and FM tuning capacitors are maxed out at their stops...
Click to expand...

I think the most likely way this situation could occur is if someone has already been messing with tracking adjustments, perhaps in an attempt to compensate for the real problem, which might be something like a bad trimmer or other capacitor in the FM local oscillator.

How's the AM band correspondence between reception and dial pointer?

Oh, wait a sec - the FM front end is enclosed, so it might be difficult to be certain that the FM tuning capacitor is really at its end stop. Could it be that it's really only the AM tuning capacitor that's at its end? In that case perhaps it's just (or at least, mostly) a matter of syncing up how the FM and AM pulleys are staked to their shafts.

Cheers,

chazix
 
Last edited:
I think you are on the right track, CHAZIX. I just got thru checking AM (I never listen to AM) and I found that the pointer is apx 5/8" off. If the pointer were readjusted to agree with AM, then the pointer would then move all the way to the end of the dial on the right side. But, of course, would no longer be correct for FM. It does appear that someone has either maladjusted something in the FM tuner, or there was a problem of some sort, and they maladjusted the dial pointer to compensate for it. I am a fair amp tech, but, unfortunately, I have neither the equipment nor the knowledge to do any serious tuner work. Does anyone have any pointers as to which trimmer cap would be capable of shifting the entire fm signal?
 
Before tryng any electrical adjustment, I think it would be a good precaution to check the synchronization of how the AM anf FM tuning pulleys are staked to their shafts.
 
I had already checked that, and both tuning capacitors are reaching the end of their
turning radius at the same time. When the FM tuning capacitor is all the way at the end of it's travel, then I am tuning in 106.9.
 
There is an adjustment on the FM tuning cap to adjust or line up the frequency with the pointer, not sure if this would fix what you are seeing. I suspect it would, then you'd have to adjust the pointer to get the AM and FM in sync. Not real sure which screw it is, or if it would do the trick, food for thought though.
 
It's the oscillator that would need to be tweaked. If the needle won't go to the end it's been either restrung wrong or the needle has been moved. Once the needle goes to the end of the dial , the upper and lower oscillator need to be adjusted to line the needle up properly.


Sent from my iPhone using Tapatalk
 
Usually (I haven't checked the 5000 manual) the tuning caps should be fully closed (low frequency end) with the pointer aligning with zero on the linear scale, or some other reference point. It should tune freely to the other end of the dial, but the low end is always the mechanical reference. Only when that condition is satisfied can you do the electrical alignment. The oscillator is simple (in theory) because you only have to work with two adjustments to get the end points correct. It's easiest with a sig gen because you always know what frequency it's set to, but local stations will work too, especially if you use another radio to be sure of what station you're tuning to. The adjustments will be sensitive, so it's easy to get confused about which station you're picking up. If you satisfy the mechanical conditions, but can't get the oscillator to hit the correct frequencies, there's something wrong. Might be dirty cap plates, contaminated PCB or a defective oscillator component. The high end is always fussier than the low end because it takes a smaller problem to mis-tune the higher frequency.
 
Last edited:
Sounds like it is time to round up a Signal Generator, and dig into the service manual. Any recommendations for a moderately priced "occasional use" generator?
 
I would summarize thus:

There is a mechanical problem that must be fixed first if the patient is to get better. If the two tuning pulleys are staked with proper synchronization, I think the only other possibility is that the tuning needle has been shifted, such that it is now acting as the lower end stop. The needle should be positioned on the tuning string so that it points to 0 and 100 on the log scale when the tuning pulleys are at their end stops.

Next, the FM local oscillator needs adjustment, or maybe repair. I'll be optimisitc and assume the former. The adjustments are L104 and TC104, the coil and trimmer capacitor (respectively) that are the farthest from the perimeter of the chassis. To get to both, you need access to the underside of the FM tuner assembly. For more help locating them, you can find the service manual at elektrotanya.com and probably other places, possibly including AK's data base (haven't checked).

L104 should be adjusted for low-frequency tracking. You need a non-metallic hex tool of the right diameter to adjust it. TC104 should be adjusted for high-frequency. You'll need to alternate between the two adjustments repeatedly until tracking is satisfactory across the dial.

If there's any chance of getting the patient to an experienced alignment tech, I think that would really be best.

Good luck,

chazix
 
Signal generator options are pretty widely discussed on AK. Search for "SG165" and you'll probably find most of the hot spots.

My two cents:

If you only plan to touch up the FM front end, you could either use off-air signals, or any RF generator that will go up to 108MHz. For front end adjustments, you don't even really need the generator to be capable of FM modulation.

For general service-grade alignments of FM stereo tuner sections, you could get by with a Sencore SG165. Its performance is not really adequate for tuners that are more modern than your Sansui's, but it has all the functionality you need, and it has a pretty good manual.

For more serious work, a Sound Technology ST1000A, or something modern, but now we're not talking moderately proced any longer.

Cheers,

chazix
 
Sounds like maybe the best option might be to try it by ear first, and if no success there, then start looking for a sig gen. But I would like to learn at least the basics of tuner alignment, so I may start looking for an affordable sig gen. I already have an hp scope and a fluke DVM, so with a gen I should be ready to tackle some basic alignments.
Thanks to everyone for their input. Bill
 
Hey Folks! Jumping on here as it appears I've got the same issue as @wlgrant6

I'm working with a 5000a here. FM tunes perfectly, but the pointer won't move below about 89.5. Stations agree with the pointer from this point all the way to the high end of the dial. AM reception is spotty at best; I'm hoping replacing black-leg transistors on the 1038 board will help.

My hope is that I can reposition the AM tuning capacitor so that its rotation agrees with the functional FM one, but one issue is that I can't actually see the FM tuner, as it's shielded by an enclosure. So my question is this:

This photo shows the AM tuner as it appears with the pointer at one end of the dial. Can anyone verify that this is the actual limit of rotation? (Seems unlikely but I can't find a verified reference online.) If this is NOT the limit of rotation, it supports my hunch that the FM tuner is dead-on, and that the AM tuner being misaligned is that cause of the pointer not being able to be tuned below 89.

I'd really love to be able to get this sorted by low-tech means. I have some experience revamping stereos (this unit had a blown driver board) but aligning a tuner is probably beyond my pay grade (and definitely beyond my possession of necessary test gear)!

Sansui5000Tuning.jpg
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom