Good Evening,
Have a receiver here that I had since new. Lost one channel, obtained schematic, traced to bad solder joints on power transistors. Repaired bad solder joints. Now on AM stations, speakers are clear and even. On FM, nothing but static, can't pick up any stations whatsoever. Any ideas as to where to start checking. Understand lots of electrical, schematics etc, but repairing receivers new to this guy. Thank you in advance for any help.
Have a receiver here that I had since new. Lost one channel, obtained schematic, traced to bad solder joints on power transistors. Repaired bad solder joints. Now on AM stations, speakers are clear and even. On FM, nothing but static, can't pick up any stations whatsoever. Any ideas as to where to start checking. Understand lots of electrical, schematics etc, but repairing receivers new to this guy. Thank you in advance for any help.
there is absolutely nothing wrong with recaping the tuner as i said though do not try to fix the problem by fooling around with trimmers and capacitors of the tuner ..it will result to destruction of the tuning and that will require knowledge and pro equipment to tune back .
Kind regards
sakis
Kind regards
sakis
the specific approach is wrong when you talk about vintage amplifier ...with the experience of repairing an average of 400 per year i can verify that .
trying to locate if any of the caps is leaky will consume time and one way or another the rest of the caps will eventually need to be replaced .
you cannot expect 25-30years old caps to work properly and even if they do there is no guaranty that they will continue to work for many years to come .
So replacing them all with no questions asked is the way to go and this has nothing to do with upgrade since its a standard service procedure .
It may be a 'standard service procedure' for an experienced repairer, but DIY efforts to 'change all the caps' often seem to end with a dead unit because of newly introduced faults. Then remote fault tracing has to begin on the forum, or a more expensive repair paid for, or the unit gets binned.
Remote fault tracing is easier if it is likely that there is only one major fault. We already started this thread with a number of solder joints 'redone', which fixed one fault and introduced another (solder bridge somewhere?). Recapping is likely to make things worse. It seems to be the modern version of 'swap all the valves until it works' which some TV repairmen used to do instead of fault tracing.
Remote fault tracing is easier if it is likely that there is only one major fault. We already started this thread with a number of solder joints 'redone', which fixed one fault and introduced another (solder bridge somewhere?). Recapping is likely to make things worse. It seems to be the modern version of 'swap all the valves until it works' which some TV repairmen used to do instead of fault tracing.
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I'm back. Hope you guys are still around. So this unit has a mind of it's own and it started working again and has worked for a couple of years now. So here is what is going on. I turn this on and all I get is static. I may pull in one channel on a scan. I can't pull in the local FM channel. If I turn the volume up, both speakers increase in volume evenly. Does this sound like an antenna problem? All I have right now is a piece of wire shaped in a circle that came with the unit back in the dark ages. Let's start fresh and see what happens. I have a DVOM, an oscilloscope (PICOSCOPE on laptop) and a desktop unit which is 20 years old. You may need to show me where to put the leads and settings but I can find my way around the schematic fairly well so don't be afraid to teach me new things.
First check is DC conditions.
Second check is to use a second FM receiver to see if the local oscillator (LO) in the first one is working. Tune the second receiver to 10.7MHz above or below (it could be either) what the first receiver is tuned to. You should hear the LO as a silent carrier. If you thump the first receiver you may hear ringing in the second one.
Second check is to use a second FM receiver to see if the local oscillator (LO) in the first one is working. Tune the second receiver to 10.7MHz above or below (it could be either) what the first receiver is tuned to. You should hear the LO as a silent carrier. If you thump the first receiver you may hear ringing in the second one.
The OP has only "a piece of wire shaped in a circle" for an antenna.
Without knowing exactly how large and effective this piece of wire is, there should be either a ribbon lead of 2 balanced wires, or a shielded coax lead (like TV antenna leads) connecting to an indoor or outdoor antenna of some recognized VHF type.
This is to ensure a reliable, clear FM signal, if one is still available at its original strength in your area, that is. Recent changes in analog broadcast policy have cut permitted transmitter powers drastically in this country. I even had to fix my own ageing antenna to restore the reception.
I would get the biggest VHF antenna I could lay my hands if I had the slightest wish for clear reception away from the transmitter's immediate coverage area. Of course, if another tuner or FM wireless has adequate signal to hold the FM stereo indicator on steadily at the same spot, that may not be necessary.
Without knowing exactly how large and effective this piece of wire is, there should be either a ribbon lead of 2 balanced wires, or a shielded coax lead (like TV antenna leads) connecting to an indoor or outdoor antenna of some recognized VHF type.
This is to ensure a reliable, clear FM signal, if one is still available at its original strength in your area, that is. Recent changes in analog broadcast policy have cut permitted transmitter powers drastically in this country. I even had to fix my own ageing antenna to restore the reception.
I would get the biggest VHF antenna I could lay my hands if I had the slightest wish for clear reception away from the transmitter's immediate coverage area. Of course, if another tuner or FM wireless has adequate signal to hold the FM stereo indicator on steadily at the same spot, that may not be necessary.
I imagine so but last time this receiver's tuner was proclaimed deceased after performing a repair to the amplifier, it had much the same low-signal fault:
The tuner board dominates the receiver inside and is apparently an early (1981) fully synthesized type with battery memory backup.
That seems like lousy signal strength to me but the easiest way to check without instruments is by boosting it, peering at the signal strength display and even moving an antenna lead direct to the tuner's input connection. Pioneer SX-5 Manual - Computer Controlled Stereo Receiver - HiFi Engine
The tuner board dominates the receiver inside and is apparently an early (1981) fully synthesized type with battery memory backup.
Good Evening Gents,
I am going to try the antenna route first as it is easiest and makes the most sense to me. This receiver still pulls in stations when it wants to. Perhaps I do have more bad solder joints so I will start easy and work my way into the hard things. From what I understand,we do not have analog signals in the area any more although they were supposed to be phased out last year and yet I still had reception last week so I doubt that is my issue. I sit between two radio towers so I should be able to pull something in and my little antenna is a stiff circular wire, roughly 16 gauge and connected to the antenna connection on the rear of the receiver.
I am going to try the antenna route first as it is easiest and makes the most sense to me. This receiver still pulls in stations when it wants to. Perhaps I do have more bad solder joints so I will start easy and work my way into the hard things. From what I understand,we do not have analog signals in the area any more although they were supposed to be phased out last year and yet I still had reception last week so I doubt that is my issue. I sit between two radio towers so I should be able to pull something in and my little antenna is a stiff circular wire, roughly 16 gauge and connected to the antenna connection on the rear of the receiver.
There are radio towers on either side of me a couple of miles away. There are several FM stations within 30-40 miles from here. All I get is static. So I'm a newb that can identify parts, signals etc and have the tools (DVOM, oscilloscope etc). Where do I start. Can I check the incoming signal and compare it to the output signal? I know, newb questions but I want to learn how to diagnose this thing. Any help is good.
First, have you checked actual reception with another FM receiver of some description yet?
If you do presently have acceptable signal right where your receiver is located, you can then start looking for where the signal chain might be breaking down. Here is a link to FX5 manuals so that we have a block diagram and schematic to follow for the tuner at least. Now you can start identifying the 2 FM tuner ICs, PA3001, HA1156 and so plot the general run of the signal path through to its output at the source selector switching chip.
FM is not a simple deal to test unless you use what amounts to another receiver as a reference. DF96 raised this point when he suggested you get another receiver to check operation with a simple test process. Believe me, you don't want to try the hard way, disturbing the receiver's alignment by prodding components or altering capacitor and coil adjusters - that will mark the point of no return for most mortals.
If you do presently have acceptable signal right where your receiver is located, you can then start looking for where the signal chain might be breaking down. Here is a link to FX5 manuals so that we have a block diagram and schematic to follow for the tuner at least. Now you can start identifying the 2 FM tuner ICs, PA3001, HA1156 and so plot the general run of the signal path through to its output at the source selector switching chip.
FM is not a simple deal to test unless you use what amounts to another receiver as a reference. DF96 raised this point when he suggested you get another receiver to check operation with a simple test process. Believe me, you don't want to try the hard way, disturbing the receiver's alignment by prodding components or altering capacitor and coil adjusters - that will mark the point of no return for most mortals.
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