"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?!?!?!

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

"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

Everyone:
Thank you all for some great ideas! I will have more time tomorrow and see
if I can make 'er go.
This thing looks sooo easy, maybe that is why I am so frustrated with it!!
I DO have schematics at my work, if anyone wants I could post tomorrow
night......if it would help.
best wishes
Tom

Everyone:
Thank you all for some great ideas! I will have more time tomorrow and see
if I can make 'er go.
This thing looks sooo easy, maybe that is why I am so frustrated with it!!
I DO have schematics at my work, if anyone wants I could post tomorrow
night......if it would help.
best wishes
Tom

TC Dufresne wrote:

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.

If you happened to insert the diodes in the fullwave rectifier reversed, you
will have negative voltage at the input of your filter instead of positive
voltage, and the input filter cap will conduct, and get hot (in a fullwave
rectifier supply). If that happens you hope the filter cap DID short the supply
to ground instead of passing the reverse polarized voltage on to other solid
state devices! In time this will be rough on your transformer, too.

You might want to recheck all the polarities of the diodes.

Dick

TC Dufresne wrote:

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.

If you happened to insert the diodes in the fullwave rectifier reversed, you
will have negative voltage at the input of your filter instead of positive
voltage, and the input filter cap will conduct, and get hot (in a fullwave
rectifier supply). If that happens you hope the filter cap DID short the supply
to ground instead of passing the reverse polarized voltage on to other solid
state devices! In time this will be rough on your transformer, too.

You might want to recheck all the polarities of the diodes.

Dick

Everyone. I fixed the VFO. Its a good news/bad news thing.

Apparently my MPF102, the heart of the VFO, was either shorted out or not
working. I removed it and replaced it with another.

Good news..Cool! Now I have a good VFO in my receiver, I can hear it in my
trusty DX-398. I adjust the RF coil so its low end (with maximum capacitance
on my Hammerland 1-10pF variable capacitor-fully meshed) is around 7.00mHz.
When I go to minimum capacitance (no meshed), I hear it only around
7.060mHz. According to specs, I should get a range from 7.00 to 7.2mHz.

Why do I not get more range? As far as I know, all caps are up to spec as
called for.
Do I need to add/subtract capacitance somewhere?
Thanks again,
Tom

"TC Dufresne" wrote in message
...
Everyone. I fixed the VFO. Its a good news/bad news thing.

Apparently my MPF102, the heart of the VFO, was either shorted out or not
working. I removed it and replaced it with another.

Good news..Cool! Now I have a good VFO in my receiver, I can hear it in my
trusty DX-398. I adjust the RF coil so its low end (with maximum
capacitance
on my Hammerland 1-10pF variable capacitor-fully meshed) is around
7.00mHz.
When I go to minimum capacitance (no meshed), I hear it only around
7.060mHz. According to specs, I should get a range from 7.00 to 7.2mHz.

Why do I not get more range? As far as I know, all caps are up to spec as
called for.
Do I need to add/subtract capacitance somewhere?

Tolerances.

Try removing a turn from the coil (if it is one you wound) and/or adding
some capacitance.

Leon
--
Leon Heller, G1HSM

http://www.geocities.com/leon_heller

"TC Dufresne" wrote in message
...
Everyone. I fixed the VFO. Its a good news/bad news thing.

Apparently my MPF102, the heart of the VFO, was either shorted out or not
working. I removed it and replaced it with another.

Good news..Cool! Now I have a good VFO in my receiver, I can hear it in my
trusty DX-398. I adjust the RF coil so its low end (with maximum
capacitance
on my Hammerland 1-10pF variable capacitor-fully meshed) is around
7.00mHz.
When I go to minimum capacitance (no meshed), I hear it only around
7.060mHz. According to specs, I should get a range from 7.00 to 7.2mHz.

Why do I not get more range? As far as I know, all caps are up to spec as
called for.
Do I need to add/subtract capacitance somewhere?

How much did you allow for stray circuit capacitance?