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I have a Sansui 4000 receiver that has a problem with the tuning mechanism. It will not go all the way to the left end of the dial, and it over-shoots on the right-hand side. The tuning dial is also off - a 92MHz station is indicated at around 94MHz on the dial. Does this mean that it is out of alignment, or has the tuning string slipped?
Follow Ups:
I would not un-string unless it is absolutely necessary and I had a service manual that shows the correct re-stringing diagram.By removing the dialcord you will not miss-align the tuner but without the correct re-stringing diagram you may very well miss-align the dialcord even worse than it sounds that it is now.After reading all of the posts can you tune in anything lower than 94mhz regardless what the dialpointer indicates?If not then the dialcord will need to be re-strung. If you can then just the pointer has slipped.
Thanks for all of the help so far.However, the tuner will not move below the 94 MHz marker (which is actually 92 MHz as I noted). Thus, I concluded that this is a more serious problem. Am I wrong in thinking this?
If pointer moves above scale at the other end, then we are right & you are wrong. Remove the outer case & observe if the finned variable capacitor rotates full range from open to closed.
Well, here is the thing - I physically cannot tune the receiver to 88.5 MHz. When I turn the dial to the farthest left position, it is at approximately 92MHz (actual), and the pointer reads 94 MHz. It seems like the pointer has nothing to do with this, as it is merely along for the ride.Also, I have removed the cover and looked at the variable capacitor, but it is kind of hard to determine if they are in fact moving through the entire range (I am not sure what to look for!)
I don't know how to adjust the bandwidth on the Sansui, but on the Dynaco FM 3 there are two small adjustable caps under the front end circuit board. One adjusts the whole bandwidth of the tuner; whether encompassing half the dialwidth's range or one and a half the dialwidth's range. The other small cap will shift the entire range of the bandwidth either up or down. Is this what you are talking about?
No, I have not adjusted anything - what I mean is that it seems that there is a mechanical stop that prevents the pointer from moving all the way to 87 MHz. This occurs at about 92 MHz on my unit, and the dial indicates 94 MHz.So, perhaps someone else has molested this recevier in the past, and mis-adjusted both the pointer and tuner bandwidth capacitors? Sheesh, I sure hope not!
If I mess with these, will this throw the tuner out of alignment?
Let's clear up the language first. Is there some mechanical stop which prohibits the pointer from moving below 92MHZ on the dial? If that is the case, then there is something mechanically wrong with the dial string and pointer. No realignment required. What I was talking about was the situation where the dial would read below 87MHZ and yet be receiving stations in the 92MHZ frequency range. In that case, one of the small variable caps would be adjusted to where the whole bandwidth of the tuner shifted upward until the dialed frequency and the frequency indicated on the dial would coincide. The other situation where an underchassis adjustment might be required would be one where both the dialed frequency and the received frequency would be correct at 87MHZ, but by the middle of the indicator's range, around 95MHZ say, the actual received frequency would be above 106MHZ. Again a different variable cap under the chassis would be adjusted in order to spread out the bandwidth of the tuning range.In your situation, what does the tuner do at the other end of the frequency range? What is the highest frequency that you can dial in accurately? Are the indicator and the actual frequency received the same? Can you turn the dial many more turns above that highest frequency?
I cannot move the dial below the 94 MHz mark, due to a mechanical constraint. I have not tried to force it, fearing that I will break something. My initial (shoot-from-the-hip) diagnosis was that there is something amiss with the tuner string routing.I did not try the upper end of the dial, so I am not sure what the maximum tuning frequency is. The dial moves beyond the 108 MHz marking, as I recall.
I will get another chance to look at it this weekend...
So, I think that it is most likely not a problem with the variable tuning caps, right? Which brings me back to the string routing - If I remove the string, can the tuner be thrown out of alignment?
It sounds to me like there has been some slippage of the string. I wouldn't unstring unless you absolutely have to. I have an old Tandberg receiver that I unstrung about 15 years ago. I still haven't gotten it back together.
refers to clarity of received signal, not the mechanical positioning of the pointer.
...that fixed the problem.
Dave
Later Gator,
Crank up your talking machine, grab a jar of your favorite "kick-back", sit down, relax, and let the good times roll.
The dial pointer has just slipped on the dialcord. Adjust tuner to the know station say 94 mhz carefully slide the dial back into the correct position then put a dab of nail polish on the dial and string to prevent it from slipping again..
Far better is to select two stations, one near each end of dial range, and average the pointer's proximity to these stations. In this way the pointer will indicate as accurately as possible to all stations across the dial.
Even better would be to inject a calibrated modulated carrier signal at two or more various points on the dial.But RF signal generator may not be available and likewise a station at each end of the dial.Adjusting any dial cord is a ballpark indication of station/frequency location.If you want dead-nuts accuracy you will have to move to the digital realm. Nough said.............
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