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SX-1980 Quartz Lock Issues

Jondubb35

Jondubb35

New Member
I recently acquired a 1980 that was fully cleaned, power supply rebuilt and the tuner supposedly aligned. The unit works and sounds great, however the quartz lock will not stay locked. Usually, right when I power the unit on, the quartz lock works as it should. After about 30 min to 1 hr give or take, the quartz lock comes unlocked and the fine tune light flickers like crazy. I will then try and zero in on a radio station again but the fine tune keeps flickering and the unit will not lock. Every once in awhile the quartz lock will re-engage, but that’s only maybe about 5% of the time. Once I turn the 1980 off and wait about 5-10 min, I’ll turn it back on and it will lock again. Then the cycle repeats. I’m at a loss at what the problem could be.
 
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It is hard to say if it is a cal/adj or a comp/ckt issue. have to go through the adj procedure and monitor what's going on.
Best to ask the last person who supposedly aligned it.
There are a few threads discussing this APC ckt, check them out.
 
I made some extremely minor adjustments to the slot screw labeled “TC” in section next I to FM, which I believe to be the quartz adjustment. Didn’t really do anything other than move the tuning meter needle a little and make the fine tune less/more sensitive.
 
If you are not familiar with the circuit and how it works, I would suggest going back to the person who did the alignment.
I wouldn't adjust anything as its condition will be different from where the tech left it, you really want it to be where it was left for a full diagnoses.
If you can't take it back to the person who did the work and you have to look at yourself, you are in a very complicated tuner, so will need some guidance.
Let us know how you get on and maybe you can get some help here.
 
Unfortunately, I’m not able to take it to the person who did the original alignment as he’s in NY and I’m CO. I understand that doing a full alignment myself is just not possible, for a multitude of reasons. I was hoping there was something relatively simple I could do with the quartz lock mechanism. There is a tech in CO that I may be able to take it to, although the thought of lugging this beast out of the man cave and around town again is not very appealing. Ahahaha. Of course, if there’s nothing that can be done in this situation then I guess that’s my last resort. Ah... the joys of vintage audio...
 
Jondubb35 said:
Unfortunately, I’m not able to take it to the person who did the original alignment as he’s in NY and I’m CO. I understand that doing a full alignment myself is just not possible, for a multitude of reasons. I was hoping there was something relatively simple I could do with the quartz lock mechanism. There is a tech in CO that I may be able to take it to, although the thought of lugging this beast out of the man cave and around town again is not very appealing. Ahahaha. Of course, if there’s nothing that can be done in this situation then I guess that’s my last resort. Ah... the joys of vintage audio...
Click to expand...
I restored a SX1980 quite recently and it also had some issues with the quartz lock which I repaired, let me have a look through my notes and see what I can find out.
I'd say there's a good chance someone has fiddled about in there...
 
kevzep said:
I restored a SX1980 quite recently and it also had some issues with the quartz lock which I repaired, let me have a look through my notes and see what I can find out.
I'd say there's a good chance someone has fiddled about in there...
Click to expand...
Much appreciated, thank you.
 
Is it possible the problem source could be some corrosion in the tuning condenser? I had similar issues with mine. The fix was to inject Deoxit at each point where the tuning condenser shaft joins the fins using a hypodermic needle to inject the fluid. Then I ran the tuning needle clear across the dial repeatedly. I actually had to do this process twice. The second time I used medical grade qtips on long wood shafts to rub away corrosion along the shaft. I was surprised at how much green junk I picked up. She works fine now—quartz lock is solid.
 
I had a look at my notes, the problem with the one I was working on was the 5V supply to the APC board.
If this was your problem the symptoms would be a bit different.
It could be the tuning capacitor as stated above...I have been finding this to be the cause of many intermittent and erratic problems with tuners of late...
 
Thanks all for your assistance. I will give macyjrm’s suggestion a go.

Please excuse my ignorance, but can you perhaps upload a pic of the tuning condenser and the points on the shaft to apply cleaner?
 
So I took a can of compressed air and blew down into where the FM tuning fins, etc reside, without removing the cover, and every time I did that, when the fine tune was flickering, it almost instantly stopped and quartz locked. After awhile it would unlock and start flickering again and I would repeat the process with the same result every time. Not sure if this is telling sign of what the issue is. Thoughts??
 
The tuner needs a bit of a work-over...cap cleaning, and then an alignment. That's what I would be doing if it was on my bench. Just needs a bit of a tweak...
 
Looks like I’m gonna be lugging this beast about town once again! Hopefully it won’t be too difficult for the tech that’s close to my location to do the necessary FM work. Sounds it may just need some slight adjustments.
 
Is it possible to bypass or turn quartz lock off? It’s not essential to the FM being able to work properly, correct?
 
Not very elegantly!!
I wanted to disable the Quartz when I was working on the one I had here to help me find out what was going on.
The tuning knob, when you touch it, disables the quartz lock, so what you can do, is connect a long piece of wire to it, and it will have the same effect as touching the knob all the time.
Try that and see how you get on.
From your description of what is happening, it sounds like the tuner is basically a bit deaf because of the tuning capacitor having a bad connection, plus your RF and IF alignment might be a bit off....who knows, someone may have fiddled about in there, so its worth checking.
 
The reason it comes on and then off when you fire compressed air at the tuning gang is that it is highly sensitive to temperature. You cool it down, it locks, it warms back up, the tuning drifts and the quartz lock flickers because it is dancing between being close enough to lock and far enough away to loose the lock.

Since the tuning gang is housed in a metal enclosure it does not get dirty, maybe corroded, but if you are getting good signal on stations, its unlikely that it is dirty on the fins causing the problem.

What is more likely is that the tech did do an alignment but maybe did not account for the temperature change as it warms up which is important when re-aligning. Also, the Quartz lock circuit would also need re-alignment and it seems not many are familiar or able to do this.

What I would suggest, is to look at other posts here about Quartz lock not working. There is a small adjustment on the APC board next to the tuner which controls the quartz lock and with the TINIEST adjustment, you will likely be able to get quartz lock to stop flitting in and out and properly engage and disengage. However, you must exercise caution as adjusting it too far will stop the quartz lock disengaging at all. I hope the helps!
 
Jondubb35 said:
So I took a can of compressed air and blew down into where the FM tuning fins, etc reside, without removing the cover, and every time I did that, when the fine tune was flickering, it almost instantly stopped and quartz locked. After awhile it would unlock and start flickering again and I would repeat the process with the same result every time. Not sure if this is telling sign of what the issue is. Thoughts??
Click to expand...

Are you SURE it's compressed AIR? 80% nitrogen, 19% oxygen . Canned "air" isn't usually "air", but some other substance that is liquid in the can and gas when released - with some cooling effect BEYOND the usual expected cooling under the gas laws of physics..

You are changing the dielectric constant of the space between the fins and altering the capacitance.
 
QSilver said:
The reason it comes on and then off when you fire compressed air at the tuning gang is that it is highly sensitive to temperature. You cool it down, it locks, it warms back up, the tuning drifts and the quartz lock flickers because it is dancing between being close enough to lock and far enough away to loose the lock.

Since the tuning gang is housed in a metal enclosure it does not get dirty, maybe corroded, but if you are getting good signal on stations, its unlikely that it is dirty on the fins causing the problem.

What is more likely is that the tech did do an alignment but maybe did not account for the temperature change as it warms up which is important when re-aligning. Also, the Quartz lock circuit would also need re-alignment and it seems not many are familiar or able to do this.

What I would suggest, is to look at other posts here about Quartz lock not working. There is a small adjustment on the APC board next to the tuner which controls the quartz lock and with the TINIEST adjustment, you will likely be able to get quartz lock to stop flitting in and out and properly engage and disengage. However, you must exercise caution as adjusting it too far will stop the quartz lock disengaging at all. I hope the helps!
Click to expand...
Thanks for info. I found the adjustment and made a few small turns both counter and clockwise I ended up getting it to lock and stay on for a awhile but maybe after about 1 or 2 hours it started to drift again and I couldn’t get it to lock. When I shut it off and wait 15-20 mins, it locks as normal and then the cycle repeats. Sounds like my problem may be dirty fins. I’m hesitant to remove the cover from this section for fear of making a small problem much bigger. What I’m doing now is once the lock disengages, I turn dial slightly left or right within the tuning range and disregard the quartz lock all together. At this point, I’m not sure what else I can do short of taking to a local repair shop. Not sure I want to do that again.
 
markthefixer said:
Are you SURE it's compressed AIR? 80% nitrogen, 19% oxygen . Canned "air" isn't usually "air", but some other substance that is liquid in the can and gas when released - with some cooling effect BEYOND the usual expected cooling under the gas laws of physics..

You are changing the dielectric constant of the space between the fins and altering the capacitance.
Click to expand...
You are correct, the “compressed air” is one of those electronics dusters I get at Costco in a six pack. Gets extremely after using for so minutes. So it sounds like when I briefly change the temperature by spraying down in this section, which is why it locks and then unlocks once it heats back up?
 
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