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help with homebrew receiver!
Hi:
I am having a problem with a "Simple Receiver for Beginners". It is from a design that was featured in an old (1981) ARRL handbook. It is a DC receiver, looks like alot of fun, but it isn't fun now. Here is the problem. 1) No oscillation! I can't find it (the VFO) on my DX-398 receiver at all, or on my Radio Shack freq counter. 2) The power (+ side) electrolytic is supposed to be a 500uF, 16 volt. I am using a 470uF 35 volt. It gets really hot!! Short somewhere?!?!?! The VFO is REALLY simple, it has one transistor and about 7 other parts. I can't seem to see what is wrong, and I have tried. I would sure appreciate some Elmer'ing here! ANY help would be much appreciated. I have the above mentioned tools at my command, a multimeter, and an old Heathkit "scope. (which I really don't know how to use. Any chance? Thanks in advance, Tom KCØGXX |
"TC Dufresne" wrote in
: Hi: I am having a problem with a "Simple Receiver for Beginners". It is from a design that was featured in an old (1981) ARRL handbook. It is a DC receiver, looks like alot of fun, but it isn't fun now. Here is the problem. 1) No oscillation! I can't find it (the VFO) on my DX-398 receiver at all, or on my Radio Shack freq counter. 2) The power (+ side) electrolytic is supposed to be a 500uF, 16 volt. I am using a 470uF 35 volt. It gets really hot!! Short somewhere?!?!?! The VFO is REALLY simple, it has one transistor and about 7 other parts. I can't seem to see what is wrong, and I have tried. I would sure appreciate some Elmer'ing here! ANY help would be much appreciated. I have the above mentioned tools at my command, a multimeter, and an old Heathkit "scope. (which I really don't know how to use. Any chance? Thanks in advance, Tom KCØGXX Gotta be a short somewhere. Filter caps ain't supposed to get hot, and yours is over rated to begin with. |
"TC Dufresne" wrote in
: Hi: I am having a problem with a "Simple Receiver for Beginners". It is from a design that was featured in an old (1981) ARRL handbook. It is a DC receiver, looks like alot of fun, but it isn't fun now. Here is the problem. 1) No oscillation! I can't find it (the VFO) on my DX-398 receiver at all, or on my Radio Shack freq counter. 2) The power (+ side) electrolytic is supposed to be a 500uF, 16 volt. I am using a 470uF 35 volt. It gets really hot!! Short somewhere?!?!?! The VFO is REALLY simple, it has one transistor and about 7 other parts. I can't seem to see what is wrong, and I have tried. I would sure appreciate some Elmer'ing here! ANY help would be much appreciated. I have the above mentioned tools at my command, a multimeter, and an old Heathkit "scope. (which I really don't know how to use. Any chance? Thanks in advance, Tom KCØGXX Gotta be a short somewhere. Filter caps ain't supposed to get hot, and yours is over rated to begin with. |
Tom: The hot cap has two likely possibilities: either the cap is shorted internally (an ohmeter check will show leakage) or you have bad diode(s) so AC is being applied to the cap. An ohmeter will show the diodes as bad. Of course a wiring error could also be involved, but I am assuming you have double checked that. If the cap is running hot you probably don't have the correct voltage for the VFO, and correcting it may solve the other VFO problem. Roger K6XQ |
Tom: The hot cap has two likely possibilities: either the cap is shorted internally (an ohmeter check will show leakage) or you have bad diode(s) so AC is being applied to the cap. An ohmeter will show the diodes as bad. Of course a wiring error could also be involved, but I am assuming you have double checked that. If the cap is running hot you probably don't have the correct voltage for the VFO, and correcting it may solve the other VFO problem. Roger K6XQ |
"TC Dufresne" wrote in message ... Hi: I am having a problem with a "Simple Receiver for Beginners". It is from a design that was featured in an old (1981) ARRL handbook. It is a DC receiver, looks like alot of fun, but it isn't fun now. Here is the problem. 1) No oscillation! I can't find it (the VFO) on my DX-398 receiver at all, or on my Radio Shack freq counter. 2) The power (+ side) electrolytic is supposed to be a 500uF, 16 volt. I am using a 470uF 35 volt. It gets really hot!! Short somewhere?!?!?! The VFO is REALLY simple, it has one transistor and about 7 other parts. I can't seem to see what is wrong, and I have tried. I would sure appreciate some Elmer'ing here! ANY help would be much appreciated. I have the above mentioned tools at my command, a multimeter, and an old Heathkit "scope. (which I really don't know how to use. It's a good idea to build things in stages, testing each stage as you go. Try disconnecting everything from the power supply and sort that out first. The capacitor shouldn't get hot. 73, Leon -- Leon Heller, G1HSM http://www.geocities.com/leon_heller |
"TC Dufresne" wrote in message ... Hi: I am having a problem with a "Simple Receiver for Beginners". It is from a design that was featured in an old (1981) ARRL handbook. It is a DC receiver, looks like alot of fun, but it isn't fun now. Here is the problem. 1) No oscillation! I can't find it (the VFO) on my DX-398 receiver at all, or on my Radio Shack freq counter. 2) The power (+ side) electrolytic is supposed to be a 500uF, 16 volt. I am using a 470uF 35 volt. It gets really hot!! Short somewhere?!?!?! The VFO is REALLY simple, it has one transistor and about 7 other parts. I can't seem to see what is wrong, and I have tried. I would sure appreciate some Elmer'ing here! ANY help would be much appreciated. I have the above mentioned tools at my command, a multimeter, and an old Heathkit "scope. (which I really don't know how to use. It's a good idea to build things in stages, testing each stage as you go. Try disconnecting everything from the power supply and sort that out first. The capacitor shouldn't get hot. 73, Leon -- Leon Heller, G1HSM http://www.geocities.com/leon_heller |
Try contacting ARRL for corrections to the article. I built a DC rcvr from
about that time frame and it did not work. The ARRL sent corrections to the schematic and there were a lot!! |
Try contacting ARRL for corrections to the article. I built a DC rcvr from
about that time frame and it did not work. The ARRL sent corrections to the schematic and there were a lot!! |
"TC Dufresne" wrote in message
... Hi: I am having a problem with a "Simple Receiver for Beginners". It is from a design that was featured in an old (1981) ARRL handbook. It is a DC receiver, looks like alot of fun, but it isn't fun now. Here is the problem. 1) No oscillation! I can't find it (the VFO) on my DX-398 receiver at all, or on my Radio Shack freq counter. 2) The power (+ side) electrolytic is supposed to be a 500uF, 16 volt. I am using a 470uF 35 volt. It gets really hot!! Short somewhere?!?!?! Electrolytic capacitors are polarized. Probably you reversed the cap and smoked it. The VFO is REALLY simple, it has one transistor and about 7 other parts. I can't seem to see what is wrong, and I have tried. I would sure appreciate some Elmer'ing here! ANY help would be much appreciated. I have the above mentioned tools at my command, a multimeter, and an old Heathkit "scope. (which I really don't know how to use. Start by looking at the voltage at the electrolytic cap, and see if you in fact have voltage or not. Any chance? Thanks in advance, Tom KCØGXX |
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