Hi Chickenwatt,
Why no 'scope with what you have already? You're overdue.
The FM generator must be extremely accurate and stable. You would love to use something that you could punch in the frequency and it would drop exactly there. There is too much drift with the equipment you have for anything useful in the FM band. That and you would want to modulate the carrier up to 75 KHz.
See if you can borrow a scope over a weekend. Don't adjust anything, just check to see what signals are there. If you have a part failure (probably), alignment may not be needed.
-Chris
Why no 'scope with what you have already? You're overdue.
The FM generator must be extremely accurate and stable. You would love to use something that you could punch in the frequency and it would drop exactly there. There is too much drift with the equipment you have for anything useful in the FM band. That and you would want to modulate the carrier up to 75 KHz.
See if you can borrow a scope over a weekend. Don't adjust anything, just check to see what signals are there. If you have a part failure (probably), alignment may not be needed.
-Chris
I am focusing first in get the white noise, without white noise I feel trouble, I use to have a BK 2025 osciloscope but it got damage the power transformer and as I use it once a year did not try to get another one 🙁
Hi Chickenwatt,
Get the oscilloscope before doing anything else on this receiver.
Consider this. You live in the best country in the world for people in electronics. There are so many good, cheap sources for test equipment that the only reason you don't have a really good 'scope is that you haven't really looked for one. When I buy something off Ebay, the shipping and customs kill me. That and most the stuff I bought doesn't work (even though the ad says it does). The junk gets shipped cross-order because we don't have any effective recourse against a "not as described" return. I have even received damaged face-plates that clearly were damaged before they were shipped. You have access to better equipment, or the same equipment that I have, at a cheaper price (much less expensive!). Then there are the "Hamfests" where you can score extremely good stuff for cheap.
Anyway. You need an Oscilloscope to proceed any further now. You live where test equipment can be had cheaply. I would hope you buy a 200 MHz scope +. If you buy a digital 'scope, you really need 5x the bandwidth of an analog one. I also use a Tektronix 2465B on my bench because there are things a DSO or MSO (Mixed signal Oscilloscope) doesn't do some things well. Good news for you since the analogue 'scopes will be the least expensive. But right now it is critical that you get a 'scope. Minimum 50 MHz, but try for at least a 100 MHz dual trace model. That way you can at least see what's going on in the IF strip (IF section). Then it would support all your other activities. You might find that you use one more if it is a good one.
Tektronix are good, but have fragile knobs (do not buy one with broken knobs!), or the older HP oscilloscopes. They trigger just fine, that rumor is untrue. Hitachi and Kikisui (spelling?) are probably the best commonly available Japanese 'scopes. B&K are made by really cheap contract manufacturers. Leader is made by one of the better OEMs - so a safe choice. I am forgetting another good Japanese brand.
If you buy a Rigol, that's a safe be too. It has a ton of advantages and features the older 'scopes simply don't have. For looking at eye patterns, they may not be the best, but for everything else they seem to be a really nice solution.
Get an oscilloscope before going any further, please. It is that important.
-Chris
Get the oscilloscope before doing anything else on this receiver.
Consider this. You live in the best country in the world for people in electronics. There are so many good, cheap sources for test equipment that the only reason you don't have a really good 'scope is that you haven't really looked for one. When I buy something off Ebay, the shipping and customs kill me. That and most the stuff I bought doesn't work (even though the ad says it does). The junk gets shipped cross-order because we don't have any effective recourse against a "not as described" return. I have even received damaged face-plates that clearly were damaged before they were shipped. You have access to better equipment, or the same equipment that I have, at a cheaper price (much less expensive!). Then there are the "Hamfests" where you can score extremely good stuff for cheap.
Anyway. You need an Oscilloscope to proceed any further now. You live where test equipment can be had cheaply. I would hope you buy a 200 MHz scope +. If you buy a digital 'scope, you really need 5x the bandwidth of an analog one. I also use a Tektronix 2465B on my bench because there are things a DSO or MSO (Mixed signal Oscilloscope) doesn't do some things well. Good news for you since the analogue 'scopes will be the least expensive. But right now it is critical that you get a 'scope. Minimum 50 MHz, but try for at least a 100 MHz dual trace model. That way you can at least see what's going on in the IF strip (IF section). Then it would support all your other activities. You might find that you use one more if it is a good one.
Tektronix are good, but have fragile knobs (do not buy one with broken knobs!), or the older HP oscilloscopes. They trigger just fine, that rumor is untrue. Hitachi and Kikisui (spelling?) are probably the best commonly available Japanese 'scopes. B&K are made by really cheap contract manufacturers. Leader is made by one of the better OEMs - so a safe choice. I am forgetting another good Japanese brand.
If you buy a Rigol, that's a safe be too. It has a ton of advantages and features the older 'scopes simply don't have. For looking at eye patterns, they may not be the best, but for everything else they seem to be a really nice solution.
Get an oscilloscope before going any further, please. It is that important.
-Chris
Hi Chickenwatt. You're just going to get peer pressured until you get a scope. "C'mon. ...c'mon you little weenie. If you're going to hang out with us......" sorry, just a little fun.
Thanks for posting the pics. Yes, no varactor tuned front-end here. That's good. No prescaler and other things like that. After looking at the schematic and understanding the problem as, "AM okay, no FM" maybe you can get lucky here? Switch to FM mode and measure the DC voltage on Q3's Collector, the Local oscillator Xsistor. The schematic say's it should be around, "9.4V". See if it's around there. If it's low, check C18, a 3.3uF filter cap. If it's leaky, or shorted, your LO doesn't come on. Also another thing to check. With the Receiver still in "FM" mode, check to see if the Center tune meter stays (pretty much) in the center. If not, it points (har, har) to an IF problem. If it stays in the center, it does,'t eliminate an IF problem, it just means not an obvious IF problem.
Thanks for posting the pics. Yes, no varactor tuned front-end here. That's good. No prescaler and other things like that. After looking at the schematic and understanding the problem as, "AM okay, no FM" maybe you can get lucky here? Switch to FM mode and measure the DC voltage on Q3's Collector, the Local oscillator Xsistor. The schematic say's it should be around, "9.4V". See if it's around there. If it's low, check C18, a 3.3uF filter cap. If it's leaky, or shorted, your LO doesn't come on. Also another thing to check. With the Receiver still in "FM" mode, check to see if the Center tune meter stays (pretty much) in the center. If not, it points (har, har) to an IF problem. If it stays in the center, it does,'t eliminate an IF problem, it just means not an obvious IF problem.
Thanks Chris for your advice on the osciloscope I now know how important they are to fix tuners
Mrshow4u thanks for your help, Q1, Q2 and Q3 voltages are very near from the specified in the squematic, C18 is good, the center tune meter in FM mode does not move anything, but in AM it does
Hi Chickenwatt,
Well, I'm not only hoping for your success with this tuner, but also in all future endeavors. The two most basic tools on any bench are a good digital voltmeter, and a good oscilloscope. My current thinking is that you might be best served with a new Rigol oscilloscope. As good a model as you can afford.
The one thing new oscilloscopes don't do well in is over-voltage at the inputs. The older 'scopes could deal with 500 VDC on the input while in AC coupled mode. The absolute maximum allowed on most USB and digital 'scopes is 5 VDC. That means above that and you cause damage. This also means that with a 10:1 probe, you can poke around with up to 50 VDC on the input in x10 mode. I strongly urge everyone reading this to use epoxy and glue the switch (x1 to x10 modes) in the x10 position. I also saw on Ebay somewhere that there are x100 probes available! About time! That then extends your range with the newer products to the limit the probe has - or 500 VDC peak, whichever is the lower limit. If you ever get a chance to examine really good 'scope probes, they are not switchable. They are typically x10 fixed. Same for the x100 probes. No switches.
The problem is more of a big deal with the older folks, like me. I learned bad habits using 'scopes that could stand off high voltages without too much worry. I can't tell you how often the switch was knocked into the x1 position as I moved the probe. That could cost you an oscilloscope. It's also good practice, given that most RF equipment is 5 VDC peak maximum as well. Oops will cost a huge amount with these pieces of test equipment. Play it safe and glue those switches before it takes out something you hold dear!
Oscilloscopes and meters will generally last a great long time. Typically over 20 years, and they go by quickly. So it makes sense to buy good equipment. You'll use it for a long, long time.
Then there are guys like me who like to restore equipment. There is now an HP 1722A dual trace 'scope I use occasionally. It was built before 1974 and is rated at 275 MHz (!). There is nothing like a restored piece of equipment that you can actually use. Also in the works is an old RCA 151 oscilloscope (1" diameter screen). It's ... older. But it will be restored and working some day soon. Just goes to show you how long test equipment can hang around if looked after. Get a good 'scope and look after it.
Best, Chris
Well, I'm not only hoping for your success with this tuner, but also in all future endeavors. The two most basic tools on any bench are a good digital voltmeter, and a good oscilloscope. My current thinking is that you might be best served with a new Rigol oscilloscope. As good a model as you can afford.
The one thing new oscilloscopes don't do well in is over-voltage at the inputs. The older 'scopes could deal with 500 VDC on the input while in AC coupled mode. The absolute maximum allowed on most USB and digital 'scopes is 5 VDC. That means above that and you cause damage. This also means that with a 10:1 probe, you can poke around with up to 50 VDC on the input in x10 mode. I strongly urge everyone reading this to use epoxy and glue the switch (x1 to x10 modes) in the x10 position. I also saw on Ebay somewhere that there are x100 probes available! About time! That then extends your range with the newer products to the limit the probe has - or 500 VDC peak, whichever is the lower limit. If you ever get a chance to examine really good 'scope probes, they are not switchable. They are typically x10 fixed. Same for the x100 probes. No switches.
The problem is more of a big deal with the older folks, like me. I learned bad habits using 'scopes that could stand off high voltages without too much worry. I can't tell you how often the switch was knocked into the x1 position as I moved the probe. That could cost you an oscilloscope. It's also good practice, given that most RF equipment is 5 VDC peak maximum as well. Oops will cost a huge amount with these pieces of test equipment. Play it safe and glue those switches before it takes out something you hold dear!
Oscilloscopes and meters will generally last a great long time. Typically over 20 years, and they go by quickly. So it makes sense to buy good equipment. You'll use it for a long, long time.
Then there are guys like me who like to restore equipment. There is now an HP 1722A dual trace 'scope I use occasionally. It was built before 1974 and is rated at 275 MHz (!). There is nothing like a restored piece of equipment that you can actually use. Also in the works is an old RCA 151 oscilloscope (1" diameter screen). It's ... older. But it will be restored and working some day soon. Just goes to show you how long test equipment can hang around if looked after. Get a good 'scope and look after it.
Best, Chris
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