if you isolate R10 ( lift one lead ) you measure how many ohms?
Like I said the coil windings usually show low ohms. Usually IF transformers show open if they fail.
I thought that we want to check out the LO operation, if the LO shows dead, you can isolate the LO from the mixer by pulling C20, then if that does not work you have to focus on the oscillator comps. You can swap parts around if need be or replace with new.
I think we have figure out enough to wire it up for test?
Like I said the coil windings usually show low ohms. Usually IF transformers show open if they fail.
I thought that we want to check out the LO operation, if the LO shows dead, you can isolate the LO from the mixer by pulling C20, then if that does not work you have to focus on the oscillator comps. You can swap parts around if need be or replace with new.
I think we have figure out enough to wire it up for test?
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Rick, I thought that the remaining unidentified pin must be IF Out but now I don't think so. That pin does not seem to be connected to anything on the board- nor earth. It is also a long way from the IF transformer. So, I am thinking that there is something wrong with the IF transformer and one of the leads that is showing earth connection is actually connected to IF out pin which is now shorted to earth. Glenn
The IF o/p, secondary consists of a few turns, it is supposed to show a DC short, it is not a short at 10.7MHz however.
I have had enough and it still morning , good night, dream about RF design.
Hi Glenn,
Simplify.
Make observations, not conclusions (that is how you get stuck)
Resistors tend to fail open, not short. Capacitors tend to fail open or short depending on what happened. With age as a factor here, the cheap ceramic caps I can see shorting.
Have you replaced those two capacitors for the AMosc and FMosc yet? Once you do that, install the tuner pack again without shields and try it. Then list a new set of observations. You may find that the AM or FM now works.
You guys are all over the place.
-Chris
Simplify.
Make observations, not conclusions (that is how you get stuck)
Resistors tend to fail open, not short. Capacitors tend to fail open or short depending on what happened. With age as a factor here, the cheap ceramic caps I can see shorting.
Have you replaced those two capacitors for the AMosc and FMosc yet? Once you do that, install the tuner pack again without shields and try it. Then list a new set of observations. You may find that the AM or FM now works.
You guys are all over the place.
-Chris
Chris, my thinking is the fm pack is out, so test it on the bench, taking it in and out imo will just do more damage and not resolve the issue any further.
If it was a big deal to do on the bench then putting it back is the only option, but it is a very simple assembly to test on the bench, if you know what you are doing which is why the hand holding. The simple idea of a RF short vs a DC short is a concept that has to be explained if asked. I have done this lots, I even have a test jig for Pioneer tuners. It can be a royal PITA to have trouble shoot RF with little idea of how it works. My first job out of college was tuning hand held 2way radio production at Motorola, RF is black magic and this is what we are seeing from a layman's perspective.
It is your call follow your directions or mine or the poor man will be even more confused.
As it is today is a another hot chain saw day for me, not RF.
Rick
If it was a big deal to do on the bench then putting it back is the only option, but it is a very simple assembly to test on the bench, if you know what you are doing which is why the hand holding. The simple idea of a RF short vs a DC short is a concept that has to be explained if asked. I have done this lots, I even have a test jig for Pioneer tuners. It can be a royal PITA to have trouble shoot RF with little idea of how it works. My first job out of college was tuning hand held 2way radio production at Motorola, RF is black magic and this is what we are seeing from a layman's perspective.
It is your call follow your directions or mine or the poor man will be even more confused.
As it is today is a another hot chain saw day for me, not RF.
Rick
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Hi Rick,
At this point I really don't care. Replacing the capacitors was the path a while ago,
and as there was confusion over where the problems were (AM-FM), it made sense to clear up a known fault before moving ahead. That way the condition of the tuner pack would be known before diving into it again. You joined in after that and as far as I know, this test has not been done and the known bad parts are still in circuit.
You will notice that I said to install the tuner pack without the shields, which would avoid the extra damage you're talking about. You're 100% correct about confusing Glenn. He hasn't had a chance to complete the logical path he was on before.
Mooly was the first in and I was trying to support him. The question about replacing those coupling caps directly answered Mooly's question.
-Chris
At this point I really don't care. Replacing the capacitors was the path a while ago,
and as there was confusion over where the problems were (AM-FM), it made sense to clear up a known fault before moving ahead. That way the condition of the tuner pack would be known before diving into it again. You joined in after that and as far as I know, this test has not been done and the known bad parts are still in circuit.
You will notice that I said to install the tuner pack without the shields, which would avoid the extra damage you're talking about. You're 100% correct about confusing Glenn. He hasn't had a chance to complete the logical path he was on before.
Mooly was the first in and I was trying to support him. The question about replacing those coupling caps directly answered Mooly's question.
-Chris
I would agree and would add to make the observations as non invasively as possible.
I'm still reading all the posts but feel this has gone a bit to far down the rabbit hole
to bring back in one piece. My doubts are whether the tuner can itself could be resurrected now... once print starts looking the worse for wear the possibility of issues occurring increases dramatically.We suggest things, they are not followed, forgotten, no response, people have their own ideas, it can get confusing for sure. Know one is keeping track of suggests & results.
Welcome to DIY tuner troubleshooting.
I do not think the tuner is damaged but finding the fault can be beyond the capabilities of the owner and many tech's I'll add.
Welcome to DIY tuner troubleshooting.
I do not think the tuner is damaged but finding the fault can be beyond the capabilities of the owner and many tech's I'll add.
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I think it should be put back on track. We know the caps are bad (At least one), so replace them and see how things work once that is done. Only then can meaningful observations be made. This will tell us where the fault is and probably get the AM working again.
Rushing through will not help anyone and Mooly had a very valid question. Now, soldering the tuner pack in again without the heavy metal shielding will probably not cause any damage. Same for removing it again. If it appears to work now, the shields can be installed and the tuner pack returned to the PCB. If not, it is easy enough to test the tuner pack out of the chassis. But, we aren't there yet. One thing at a time.
Glenn, if you have to buy the capacitors, that's fine. Also buy a large sized solder sucker. The good ones run between $20 and $35 in Canada. The $5 and $10 one are junk and will break maybe even the first time you use them. Some solder wick would also be a wise investment. The wide or semi-wide braid is you best bet. The skinny stuff is useless for normal repair work. This stuff is a basic need for the service bench, it isn't just for this tuner. They will make your life so much easier and greatly reduce solder pad damage.
-Chris
Rushing through will not help anyone and Mooly had a very valid question. Now, soldering the tuner pack in again without the heavy metal shielding will probably not cause any damage. Same for removing it again. If it appears to work now, the shields can be installed and the tuner pack returned to the PCB. If not, it is easy enough to test the tuner pack out of the chassis. But, we aren't there yet. One thing at a time.
Glenn, if you have to buy the capacitors, that's fine. Also buy a large sized solder sucker. The good ones run between $20 and $35 in Canada. The $5 and $10 one are junk and will break maybe even the first time you use them. Some solder wick would also be a wise investment. The wide or semi-wide braid is you best bet. The skinny stuff is useless for normal repair work. This stuff is a basic need for the service bench, it isn't just for this tuner. They will make your life so much easier and greatly reduce solder pad damage.
-Chris
Hi all, I see you have had some interesting deliberations. I jumped the gun on R10 in the pack. It is only a 10 ohm resistor so should be OK. Chris, will replace those suspect caps on the board today and try to put the pack back in without shield. I have plenty of solder wick and a cheap solder sucker. I find the sucker difficult to use so normally use the wick. Glenn
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