I have a Grundig "Transistor 305" portable radio. It uses germanium
transistors. I've had this thing for over forty years and although I
don't use it often it has been a nice radio. In 1971 I replaced the
transistor in the FM detector circuit and I have had no problems with
it until just recently. Last month I spent three days in the hospital
and I brought the Grundig with me. I noticed that after it was on for
about a half hour it would start to cut out. I turned it off and then
later turned it on again, and after a period of time it happened
again. After several similar episodes I stopped using it. I wondered
about some type of interference from the hospital but that was wishful
thinking. In any case being in no position to test it I decided to
just put it away. Yesterday I put it on the bench and took a look at
it. Sure enough after a brief time it cut out again. I injected a
signal, (my finger on a small screwdriver) onto the wiper of the
volume control and ascertained that there is nothing wrong up to the
speaker. So now I need to get into the IF's and detector. My problem
is my old signal generators are not working and all I can come up with
for 10.7MHZ. is a CW signal out of my MFJ249 SWR meter. The MFJ puts
out a clean signal however it is CW, and it's amplitude is not
adjustable. I don't think that an unmodulated signal would be a
problem in this application but I don't know what the amplitude of the
MFJ is and I would hate to blow up an otherwise good IF amplifier with
an excessive signal. I''m admittedly a bit rusty having not trouble
shot an IF amplifier/detector circuit in many years so does anyone
have a feel for how I might signal trace this radio with what I have
on hand? Thanks very much for any advice. Lenny

"klem kedidelhopper has six toes "

I have a Grundig "Transistor 305" portable radio. It uses germanium
transistors. I've had this thing for over forty years and although I
don't use it often it has been a nice radio. In 1971 I replaced the
transistor in the FM detector circuit and I have had no problems with
it until just recently. Last month I spent three days in the hospital
and I brought the Grundig with me. I noticed that after it was on for
about a half hour it would start to cut out. I turned it off and then
later turned it on again, and after a period of time it happened
again. After several similar episodes I stopped using it. I wondered
about some type of interference from the hospital but that was wishful
thinking. In any case being in no position to test it I decided to
just put it away. Yesterday I put it on the bench and took a look at
it. Sure enough after a brief time it cut out again. I injected a
signal, (my finger on a small screwdriver) onto the wiper of the
volume control and ascertained that there is nothing wrong up to the
speaker. So now I need to get into the IF's and detector. My problem
is my old signal generators are not working and all I can come up with
for 10.7MHZ. is a CW signal out of my MFJ249 SWR meter. The MFJ puts
out a clean signal however it is CW, and it's amplitude is not
adjustable. I don't think that an unmodulated signal would be a
problem in this application but I don't know what the amplitude of the
MFJ is and I would hate to blow up an otherwise good IF amplifier with
an excessive signal. I''m admittedly a bit rusty having not trouble
shot an IF amplifier/detector circuit in many years so does anyone
have a feel for how I might signal trace this radio with what I have
on hand? Thanks very much for any advice. Lenny


** Might be another dodgy chemical fuse - eh ??



..... Phil

On May 20, 3:21*pm, klem kedidelhopper
wrote:
I have a Grundig "Transistor 305" portable radio. It uses germanium
transistors. I've had this thing for over forty years and although I
don't use it often it has been a nice radio. In 1971 I replaced the
transistor in the FM detector circuit and I have had no problems with
it until just recently. *Last month I spent three days in the hospital
and I brought the Grundig with me. I noticed that after it was on for
about a half hour it would start to cut out. I turned it off and then
later turned it on again, and after a period of time it happened
again. After several similar episodes I stopped using it. I wondered
about some type of interference from the hospital but that was wishful
thinking. In any case being in no position to test it I decided to
just put it away. Yesterday I put it on the bench and took a look at
it. Sure enough after a brief time it cut out again. I injected a
signal, (my finger on a small screwdriver) onto the wiper of the
volume control and ascertained that there is nothing wrong up to the
speaker. So now I need to get into the IF's and detector. My problem
is my old signal generators are not working and all I can come up with
for 10.7MHZ. is a CW signal out of my MFJ249 SWR meter. The MFJ puts
out a clean signal however it is CW, and it's amplitude is not
adjustable. I don't think that an unmodulated signal would be a
problem in this application but I don't know what the amplitude of the
MFJ is

Somehow I feel looking at an oscilloscope might help with determining
the amplitude of the signal.

and I would hate to blow up an otherwise good IF amplifier with
an excessive signal.

Somehow I feel that an excessive signal could be tamed with a resistor
divider circuit. Knowing what the input impedance of IF circuits is
might help.


I''m admittedly a bit rusty having not trouble
shot an IF amplifier/detector circuit in many years so does anyone
have a feel for how I might signal trace this radio with what I have
on hand? *Thanks very much for any advice. Lenny

One source of IF signal might be another FM radio. Just a wild, crazy
thought.

Further, if this is an AM-FM as the subject header states, you forgot
to mention if the AM worked.

On May 20, 3:21*pm, klem kedidelhopper
wrote:
I have a Grundig "Transistor 305" portable radio. It uses germanium
transistors. I've had this thing for over forty years and although I
don't use it often it has been a nice radio. In 1971 I replaced the
transistor in the FM detector circuit and I have had no problems with
it until just recently. *Last month I spent three days in the hospital
and I brought the Grundig with me. I noticed that after it was on for
about a half hour it would start to cut out. I turned it off and then
later turned it on again, and after a period of time it happened
again. After several similar episodes I stopped using it. I wondered
about some type of interference from the hospital but that was wishful
thinking. In any case being in no position to test it I decided to
just put it away. Yesterday I put it on the bench and took a look at
it. Sure enough after a brief time it cut out again. I injected a
signal, (my finger on a small screwdriver) onto the wiper of the
volume control and ascertained that there is nothing wrong up to the
speaker. So now I need to get into the IF's and detector. My problem
is my old signal generators are not working and all I can come up with
for 10.7MHZ. is a CW signal out of my MFJ249 SWR meter. The MFJ puts
out a clean signal however it is CW, and it's amplitude is not
adjustable. I don't think that an unmodulated signal would be a
problem in this application but I don't know what the amplitude of the
MFJ is and I would hate to blow up an otherwise good IF amplifier with
an excessive signal. I''m admittedly a bit rusty having not trouble
shot an IF amplifier/detector circuit in many years so does anyone
have a feel for how I might signal trace this radio with what I have
on hand? *Thanks very much for any advice. Lenny

I would first look at mechanical failure of the connections. ...PCB/
traces/etc.

Especially around the FM Detector area where you heat shocked the PCB
when changing that transistor.

I know it's hard to believe battery can heat that much but with age on
a PCB, you'd be surprised. Ever try cold spray when radio failed?

klem kedidelhopper wrote in message
...
I have a Grundig "Transistor 305" portable radio. It uses germanium
transistors. I've had this thing for over forty years and although I
don't use it often it has been a nice radio. In 1971 I replaced the
transistor in the FM detector circuit and I have had no problems with
it until just recently. Last month I spent three days in the hospital
and I brought the Grundig with me. I noticed that after it was on for
about a half hour it would start to cut out. I turned it off and then
later turned it on again, and after a period of time it happened
again. After several similar episodes I stopped using it. I wondered
about some type of interference from the hospital but that was wishful
thinking. In any case being in no position to test it I decided to
just put it away. Yesterday I put it on the bench and took a look at
it. Sure enough after a brief time it cut out again. I injected a
signal, (my finger on a small screwdriver) onto the wiper of the
volume control and ascertained that there is nothing wrong up to the
speaker. So now I need to get into the IF's and detector. My problem
is my old signal generators are not working and all I can come up with
for 10.7MHZ. is a CW signal out of my MFJ249 SWR meter. The MFJ puts
out a clean signal however it is CW, and it's amplitude is not
adjustable. I don't think that an unmodulated signal would be a
problem in this application but I don't know what the amplitude of the
MFJ is and I would hate to blow up an otherwise good IF amplifier with
an excessive signal. I''m admittedly a bit rusty having not trouble
shot an IF amplifier/detector circuit in many years so does anyone
have a feel for how I might signal trace this radio with what I have
on hand? Thanks very much for any advice. Lenny


Any 4 pin Ge transistors in there? if there is then the usual simple fudge
is worth a try

On May 21, 10:05*am, "N_Cook" wrote:
klem kedidelhopper wrote in message

...



I have a Grundig "Transistor 305" portable radio. It uses germanium
transistors. I've had this thing for over forty years and although I
don't use it often it has been a nice radio. In 1971 I replaced the
transistor in the FM detector circuit and I have had no problems with
it until just recently. *Last month I spent three days in the hospital
and I brought the Grundig with me. I noticed that after it was on for
about a half hour it would start to cut out. I turned it off and then
later turned it on again, and after a period of time it happened
again. After several similar episodes I stopped using it. I wondered
about some type of interference from the hospital but that was wishful
thinking. In any case being in no position to test it I decided to
just put it away. Yesterday I put it on the bench and took a look at
it. Sure enough after a brief time it cut out again. I injected a
signal, (my finger on a small screwdriver) onto the wiper of the
volume control and ascertained that there is nothing wrong up to the
speaker. So now I need to get into the IF's and detector. My problem
is my old signal generators are not working and all I can come up with
for 10.7MHZ. is a CW signal out of my MFJ249 SWR meter. The MFJ puts
out a clean signal however it is CW, and it's amplitude is not
adjustable. I don't think that an unmodulated signal would be a
problem in this application but I don't know what the amplitude of the
MFJ is and I would hate to blow up an otherwise good IF amplifier with
an excessive signal. I''m admittedly a bit rusty having not trouble
shot an IF amplifier/detector circuit in many years so does anyone
have a feel for how I might signal trace this radio with what I have
on hand? *Thanks very much for any advice. Lenny

Any 4 pin Ge transistors in there? if there is then the usual simple fudge
is worth a try

Well the AM is not working either when this set fails. And since the
set uses the same transistors but different coils for each stage that
doesn't really help me to track this down. I could look at the CW
signal from the 249 with my 50MHZ. scope or my spectrum analyzer but I
still don't know what a safe signal amplitude would be. Does anyone
know what the proper typical amplitude of an IF signal would be so
that I would be able to simulate this and inject this signal into the
IF amplifiers and detector stage? BTW except for the outputs, they're
all 4 pin GE transistors. What do you mean by the "simple fudge"?
Thanks, Lenny

One might reasonably assume that the IF signal would not have a peak-to-peak
value larger than the net forward bias on the IF transistors. You can be
reasonably certain a signal of that level will not damage the transistors.

On May 20, 11:40*pm, "Phil Allison" wrote:

** *Might be another dodgy chemical fuse *- *eh ??

.... *Phil



Fuses, chemical or not, don't become intermittent.


Idiot.


John

"klem kedidelhopper" wrote in message
...
On May 21, 10:05 am, "N_Cook" wrote:
klem kedidelhopper wrote in message

...



I have a Grundig "Transistor 305" portable radio. It uses germanium
transistors. I've had this thing for over forty years and although I
don't use it often it has been a nice radio. In 1971 I replaced the
transistor in the FM detector circuit and I have had no problems with
it until just recently. Last month I spent three days in the hospital
and I brought the Grundig with me. I noticed that after it was on for
about a half hour it would start to cut out. I turned it off and then
later turned it on again, and after a period of time it happened
again. After several similar episodes I stopped using it. I wondered
about some type of interference from the hospital but that was wishful
thinking. In any case being in no position to test it I decided to
just put it away. Yesterday I put it on the bench and took a look at
it. Sure enough after a brief time it cut out again. I injected a
signal, (my finger on a small screwdriver) onto the wiper of the
volume control and ascertained that there is nothing wrong up to the
speaker. So now I need to get into the IF's and detector. My problem
is my old signal generators are not working and all I can come up with
for 10.7MHZ. is a CW signal out of my MFJ249 SWR meter. The MFJ puts
out a clean signal however it is CW, and it's amplitude is not
adjustable. I don't think that an unmodulated signal would be a
problem in this application but I don't know what the amplitude of the
MFJ is and I would hate to blow up an otherwise good IF amplifier with
an excessive signal. I''m admittedly a bit rusty having not trouble
shot an IF amplifier/detector circuit in many years so does anyone
have a feel for how I might signal trace this radio with what I have
on hand? Thanks very much for any advice. Lenny

Any 4 pin Ge transistors in there? if there is then the usual simple fudge
is worth a try

Well the AM is not working either when this set fails. And since the
set uses the same transistors but different coils for each stage

Does it have the old TO7 transistors like OC170/171/AF116/117 etc?

They're prone to internal whiskering, most commonly the can/screen to one of
the 3 electrodes, lifting the screen lead might get it going, some people
zap the whiskers with 47uF charged to 50V (twist C,B & E together first).

If the whiskers have reached 2 or more electrodes you're pretty much
stuffed, some people use BF450/451 as replacements but you usually have to
tweak the base bias resistors to suit silicon 0.7V and you might have to
align out the different collector capacitance (do one stage at a time).

If you have extreme manual dexterity and bloody good eyesight you can melt
the solder seal between can & header and put the TO92 inside the TO7 can to
preserve the appearance of originality.

"John-Del"
"Phil Allison"

** Might be another dodgy chemical fuse - eh ??


Fuses, chemical or not, don't become intermittent.


** Then you have not seen everything.

Imbecile.


.... Phil

klem kedidelhopper wrote:

On May 21, 10:05 am, "N_Cook" wrote:
klem kedidelhopper wrote in message

...



I have a Grundig "Transistor 305" portable radio. It uses germanium
transistors. I've had this thing for over forty years and although I
don't use it often it has been a nice radio. In 1971 I replaced the
transistor in the FM detector circuit and I have had no problems with
it until just recently. Last month I spent three days in the hospital
and I brought the Grundig with me. I noticed that after it was on for
about a half hour it would start to cut out. I turned it off and then
later turned it on again, and after a period of time it happened
again. After several similar episodes I stopped using it. I wondered
about some type of interference from the hospital but that was wishful
thinking. In any case being in no position to test it I decided to
just put it away. Yesterday I put it on the bench and took a look at
it. Sure enough after a brief time it cut out again. I injected a
signal, (my finger on a small screwdriver) onto the wiper of the
volume control and ascertained that there is nothing wrong up to the
speaker. So now I need to get into the IF's and detector. My problem
is my old signal generators are not working and all I can come up with
for 10.7MHZ. is a CW signal out of my MFJ249 SWR meter. The MFJ puts
out a clean signal however it is CW, and it's amplitude is not
adjustable. I don't think that an unmodulated signal would be a
problem in this application but I don't know what the amplitude of the
MFJ is and I would hate to blow up an otherwise good IF amplifier with
an excessive signal. I''m admittedly a bit rusty having not trouble
shot an IF amplifier/detector circuit in many years so does anyone
have a feel for how I might signal trace this radio with what I have
on hand? Thanks very much for any advice. Lenny

Any 4 pin Ge transistors in there? if there is then the usual simple fudge
is worth a try

Well the AM is not working either when this set fails. And since the
set uses the same transistors but different coils for each stage that
doesn't really help me to track this down. I could look at the CW
signal from the 249 with my 50MHZ. scope or my spectrum analyzer but I
still don't know what a safe signal amplitude would be. Does anyone
know what the proper typical amplitude of an IF signal would be so
that I would be able to simulate this and inject this signal into the
IF amplifiers and detector stage? BTW except for the outputs, they're
all 4 pin GE transistors. What do you mean by the "simple fudge"?
Thanks, Lenny


Check the collector voltages on the IF and mixer stage. Use at least
a 1 meg resistor between the probe and the transistor to keep from
disturbing the circuit. I saw a lot of this in old germanium transistor
car radios. Noise induced into the circuit would momentarily restore
the transistor enough to work for a while, but of there was zero
collector voltage, one of the IF transformers was open. If it was high,
the transistor was bad. I troubleshot those radios and repaired most of
them in under five minutes with that simple method.


--
It's easy to think outside the box, when you have a cutting torch.

On May 21, 8:58*pm, "Michael A. Terrell"
wrote:
klem kedidelhopper wrote:

On May 21, 10:05 am, "N_Cook" wrote:
klem kedidelhopper wrote in message

....

I have a Grundig "Transistor 305" portable radio. It uses germanium
transistors. I've had this thing for over forty years and although I
don't use it often it has been a nice radio. In 1971 I replaced the
transistor in the FM detector circuit and I have had no problems with
it until just recently. *Last month I spent three days in the hospital
and I brought the Grundig with me. I noticed that after it was on for
about a half hour it would start to cut out. I turned it off and then
later turned it on again, and after a period of time it happened
again. After several similar episodes I stopped using it. I wondered
about some type of interference from the hospital but that was wishful
thinking. In any case being in no position to test it I decided to
just put it away. Yesterday I put it on the bench and took a look at
it. Sure enough after a brief time it cut out again. I injected a
signal, (my finger on a small screwdriver) onto the wiper of the
volume control and ascertained that there is nothing wrong up to the
speaker. So now I need to get into the IF's and detector. My problem
is my old signal generators are not working and all I can come up with
for 10.7MHZ. is a CW signal out of my MFJ249 SWR meter. The MFJ puts
out a clean signal however it is CW, and it's amplitude is not
adjustable. I don't think that an unmodulated signal would be a
problem in this application but I don't know what the amplitude of the
MFJ is and I would hate to blow up an otherwise good IF amplifier with
an excessive signal. I''m admittedly a bit rusty having not trouble
shot an IF amplifier/detector circuit in many years so does anyone
have a feel for how I might signal trace this radio with what I have
on hand? *Thanks very much for any advice. Lenny

Any 4 pin Ge transistors in there? if there is then the usual simple fudge
is worth a try

Well the AM is not working either when this set fails. And since the
set uses the same transistors but different coils for each stage that
doesn't really help me to track this down. I could look at the CW
signal from the 249 with my 50MHZ. scope or my spectrum analyzer but I
still don't know what a safe signal amplitude would be. Does anyone
know what the proper typical amplitude of an IF signal would be so
that I would be able to simulate this and inject this signal into the
IF amplifiers and detector stage? BTW except for the outputs, they're
all 4 pin GE transistors. What do you mean by the "simple fudge"?
Thanks, Lenny

* Check the collector voltages on the IF and mixer stage. *Use at least
a 1 meg resistor between the probe and the transistor to keep from
disturbing the circuit. *I saw a lot of this in old germanium transistor
car radios. *Noise induced into the circuit would momentarily restore
the transistor enough to work for a while, but of there was zero
collector voltage, one of the IF transformers was open. *If it was high,
the transistor was bad. *I troubleshot those radios and repaired most of
them in under five minutes with that simple method.

--
It's easy to think outside the box, when you have a cutting torch.

The IF's are AF124,and 126. And to answer a previous question I did
use cold spray on everything but the detector, which is inside a can.
It didn't seem to have any effect. I plan to open the can and hit the
detector too. The "whiskering" as well as the method to remove it are
both kind of interesting, sort of like what happens to nicads it
seems. Well the transistors seem to have lasted forty some odd years
so I can't complain much. The NTE 160 is a germanium and it seems to
replace all of these however it does not have a fourth can lead. I
don't know if that could make much of a difference.To check one of
these for whiskering, would you simply look for leakage between any
junction and the can? I never thought of this. On another note,
considering the bias issues, I really would not want to use a silicon
transistor if I don't have to. Lenny

klem kedidelhopper wrote:

On May 21, 8:58 pm, "Michael A. Terrell"
wrote:
klem kedidelhopper wrote:

On May 21, 10:05 am, "N_Cook" wrote:
klem kedidelhopper wrote in message

...

I have a Grundig "Transistor 305" portable radio. It uses germanium
transistors. I've had this thing for over forty years and although I
don't use it often it has been a nice radio. In 1971 I replaced the
transistor in the FM detector circuit and I have had no problems with
it until just recently. Last month I spent three days in the hospital
and I brought the Grundig with me. I noticed that after it was on for
about a half hour it would start to cut out. I turned it off and then
later turned it on again, and after a period of time it happened
again. After several similar episodes I stopped using it. I wondered
about some type of interference from the hospital but that was wishful
thinking. In any case being in no position to test it I decided to
just put it away. Yesterday I put it on the bench and took a look at
it. Sure enough after a brief time it cut out again. I injected a
signal, (my finger on a small screwdriver) onto the wiper of the
volume control and ascertained that there is nothing wrong up to the
speaker. So now I need to get into the IF's and detector. My problem
is my old signal generators are not working and all I can come up with
for 10.7MHZ. is a CW signal out of my MFJ249 SWR meter. The MFJ puts
out a clean signal however it is CW, and it's amplitude is not
adjustable. I don't think that an unmodulated signal would be a
problem in this application but I don't know what the amplitude of the
MFJ is and I would hate to blow up an otherwise good IF amplifier with
an excessive signal. I''m admittedly a bit rusty having not trouble
shot an IF amplifier/detector circuit in many years so does anyone
have a feel for how I might signal trace this radio with what I have
on hand? Thanks very much for any advice. Lenny

Any 4 pin Ge transistors in there? if there is then the usual simple fudge
is worth a try

Well the AM is not working either when this set fails. And since the
set uses the same transistors but different coils for each stage that
doesn't really help me to track this down. I could look at the CW
signal from the 249 with my 50MHZ. scope or my spectrum analyzer but I
still don't know what a safe signal amplitude would be. Does anyone
know what the proper typical amplitude of an IF signal would be so
that I would be able to simulate this and inject this signal into the
IF amplifiers and detector stage? BTW except for the outputs, they're
all 4 pin GE transistors. What do you mean by the "simple fudge"?
Thanks, Lenny

Check the collector voltages on the IF and mixer stage. Use at least
a 1 meg resistor between the probe and the transistor to keep from
disturbing the circuit. I saw a lot of this in old germanium transistor
car radios. Noise induced into the circuit would momentarily restore
the transistor enough to work for a while, but of there was zero
collector voltage, one of the IF transformers was open. If it was high,
the transistor was bad. I troubleshot those radios and repaired most of
them in under five minutes with that simple method.

The IF's are AF124,and 126. And to answer a previous question I did
use cold spray on everything but the detector, which is inside a can.


I may still have a couple new ECG160 in stock. I'll try to get into
the old shop and check, if I can climb through some of the junk that's
piled up to be hauled off.


http://www.nteinc.com/specs/100to199/pdf/nte160.pdf is the datasheet
for the NTE version.


I only used freeze mist as a last resort. On early transistor
equipment it seemed to cause more failures. Thermal expansion & cooling
inside the transistor case caused metal fatigue.


It didn't seem to have any effect. I plan to open the can and hit the
detector too.


AM or FM? A bad diode shouldn't affect both bands.


The "whiskering" as well as the method to remove it are
both kind of interesting, sort of like what happens to nicads it
seems. Well the transistors seem to have lasted forty some odd years
so I can't complain much. The NTE 160 is a germanium and it seems to
replace all of these however it does not have a fourth can lead.

A short between the shel & the collector was a common failure.

I don't know if that could make much of a difference. To check one of
these for whiskering, would you simply look for leakage between any
junction and the can? I never thought of this.

Using an analog meter would caue open juctions to start working
again, for a short time. All this did was make you waste time, since
they invariably quit again. You probably have a crack weld inside the
can, or a fractured bonding wire. That is why I monitored the collector
voltages, with added isolation and used a VTVM, and later, a FETVM.

On another note, considering the bias issues, I really would not want
to use a silicon transistor if I don't have to.


It's not that difficult to change. If it uses the typical two
resisotor bias, you need to raise the E_B voltage to get .6 volts
instead of .1 volts. Since the silicon parts have less leakage
currents, raise the value of the bottom resistor in the string. Tack a
trimpot or use a resistors sub box to find the new value, and solder it
in.


--
It's easy to think outside the box, when you have a cutting torch.

On May 22, 12:38*am, "Michael A. Terrell"
wrote:
klem kedidelhopper wrote:

On May 21, 8:58 pm, "Michael A. Terrell"
wrote:
klem kedidelhopper wrote:

On May 21, 10:05 am, "N_Cook" wrote:
klem kedidelhopper wrote in message

...

I have a Grundig "Transistor 305" portable radio. It uses germanium
transistors. I've had this thing for over forty years and although I
don't use it often it has been a nice radio. In 1971 I replaced the
transistor in the FM detector circuit and I have had no problems with
it until just recently. *Last month I spent three days in the hospital
and I brought the Grundig with me. I noticed that after it was on for
about a half hour it would start to cut out. I turned it off and then
later turned it on again, and after a period of time it happened
again. After several similar episodes I stopped using it. I wondered
about some type of interference from the hospital but that was wishful
thinking. In any case being in no position to test it I decided to
just put it away. Yesterday I put it on the bench and took a look at
it. Sure enough after a brief time it cut out again. I injected a
signal, (my finger on a small screwdriver) onto the wiper of the
volume control and ascertained that there is nothing wrong up to the
speaker. So now I need to get into the IF's and detector. My problem
is my old signal generators are not working and all I can come up with
for 10.7MHZ. is a CW signal out of my MFJ249 SWR meter. The MFJ puts
out a clean signal however it is CW, and it's amplitude is not
adjustable. I don't think that an unmodulated signal would be a
problem in this application but I don't know what the amplitude of the
MFJ is and I would hate to blow up an otherwise good IF amplifier with
an excessive signal. I''m admittedly a bit rusty having not trouble
shot an IF amplifier/detector circuit in many years so does anyone
have a feel for how I might signal trace this radio with what I have
on hand? *Thanks very much for any advice. Lenny

Any 4 pin Ge transistors in there? if there is then the usual simple fudge
is worth a try

Well the AM is not working either when this set fails. And since the
set uses the same transistors but different coils for each stage that
doesn't really help me to track this down. I could look at the CW
signal from the 249 with my 50MHZ. scope or my spectrum analyzer but I
still don't know what a safe signal amplitude would be. Does anyone
know what the proper typical amplitude of an IF signal would be so
that I would be able to simulate this and inject this signal into the
IF amplifiers and detector stage? BTW except for the outputs, they're
all 4 pin GE transistors. What do you mean by the "simple fudge"?
Thanks, Lenny

* Check the collector voltages on the IF and mixer stage. *Use at least
a 1 meg resistor between the probe and the transistor to keep from
disturbing the circuit. *I saw a lot of this in old germanium transistor
car radios. *Noise induced into the circuit would momentarily restore
the transistor enough to work for a while, but of there was zero
collector voltage, one of the IF transformers was open. *If it was high,
the transistor was bad. *I troubleshot those radios and repaired most of
them in under five minutes with that simple method.

The IF's are AF124,and 126. And to answer a previous question I did
use cold spray on everything but the detector, which is inside a can.

* *I may still have a couple new ECG160 in stock. *I'll try to get into
the old shop and check, if I can climb through some of the junk that's
piled up to be hauled off.

* *http://www.nteinc.com/specs/100to199/pdf/nte160.pdfis the datasheet
for the NTE version.

* *I only used freeze mist as a last resort. *On early transistor
equipment it seemed to cause more failures. *Thermal expansion & cooling
inside the transistor case caused metal fatigue.

It didn't seem to have any effect. I plan to open the can and hit the
detector too.

* *AM or FM? *A bad diode shouldn't affect both bands.

The "whiskering" as well as the method to remove it are
both kind of interesting, sort of like what happens to nicads it
seems. Well the transistors seem to have lasted forty some odd years
so I can't complain much. The NTE 160 is a germanium and it seems to
replace all of these however it does not have a fourth can lead.

* *A short between the shel & the collector was a common failure.

I don't know if that could make much of a difference. To check one of
these for whiskering, would you simply look for leakage between any
junction and the can? I never thought of this.

* *Using an analog meter would caue open juctions to start working
again, for a short time. *All this did was make you waste time, since
they invariably quit again. *You probably have a crack weld inside the
can, or a fractured bonding wire. *That is why I monitored the collector
voltages, with added isolation and used a VTVM, and later, a FETVM.

On another note, considering the bias issues, I really would not want
to use a silicon transistor if I don't have to.

* *It's not that difficult to change. *If it uses the typical two
resisotor bias, you need to raise the E_B voltage to get .6 volts
instead of .1 volts. *Since the silicon parts have less leakage
currents, raise the value of the bottom resistor in the string. *Tack a
trimpot or use a resistors sub box to find the new value, and solder it
in.

--
It's easy to think outside the box, when you have a cutting torch.

Good idea about the VTVM. I don't get to use my RCA Senior Voltohmyst
much anymore. I bought it as a kit from the RCA distributor at the
time, Bruno NY in Manhattan and built it when I was 17. It still works
great. I use an Energiser for the ohmmeter but I really do worry about
the battery leaking. I've been meaning to replace the battery with a
little isolated DC supply for a long time but just have never gotten
to it. Lenny

Phil:

I've seen an intermittant 2AG fuse twice, Drove me nuts the first
time. By intermittant, I mean it would open in circuit, but would
test OK with an ohmmeter.

On May 22, 8:42*pm, "Ron D." wrote:
Phil:

I've seen an intermittant 2AG fuse twice, *Drove me nuts the first
time. *By intermittant, I mean it would open in circuit, but would
test OK with an ohmmeter.


I mean 3AG fuse.

"Ron D."

I've seen an intermittant 2AG fuse twice, Drove me nuts the first
time. By intermittant, I mean it would open in circuit, but would
test OK with an ohmmeter.

** Yep.

Typically, the fuse wire has come loose at one end - or was never soldered
in the first place.

It looks fine and has continuity due to light pressure contact alone.

When the wire heats under load, it opens and closes.




...... Phil

On Fri, 20 May 2011 15:21:01 -0700, klem kedidelhopper wrote:

I have a Grundig "Transistor 305" portable radio. It uses germanium
transistors. I've had this thing for over forty years and although I
don't use it often it has been a nice radio. In 1971 I replaced the
transistor in the FM detector circuit and I have had no problems with it
until just recently. Last month I spent three days in the hospital and
I brought the Grundig with me. I noticed that after it was on for about
a half hour it would start to cut out. I turned it off and then later
turned it on again, and after a period of time it happened again. After
several similar episodes I stopped using it. I wondered about some type
of interference from the hospital but that was wishful thinking. In any
case being in no position to test it I decided to just put it away.
Yesterday I put it on the bench and took a look at it. Sure enough after
a brief time it cut out again. I injected a signal, (my finger on a
small screwdriver) onto the wiper of the volume control and ascertained
that there is nothing wrong up to the speaker. So now I need to get into
the IF's and detector. My problem is my old signal generators are not
working and all I can come up with for 10.7MHZ. is a CW signal out of my
MFJ249 SWR meter. The MFJ puts out a clean signal however it is CW, and
it's amplitude is not adjustable. I don't think that an unmodulated
signal would be a problem in this application but I don't know what the
amplitude of the MFJ is and I would hate to blow up an otherwise good IF
amplifier with an excessive signal. I''m admittedly a bit rusty having
not trouble shot an IF amplifier/detector circuit in many years so does
anyone have a feel for how I might signal trace this radio with what I
have on hand? Thanks very much for any advice. Lenny

Start with the first RF amp. It's probably a superhet so there will be a
455 osc and mixer. After that a couple rf amps and the the detector.

Google a superhetrodyne receiver. This one uses ICs but the basics are the
same

http://www.seekic.com/uploadfile/ic-...7173226815.gif

Should give you some insight as to where the signal is being lost in the
path.

--
Live Fast Die Young, Leave A Pretty Corpse

On May 22, 6:41*pm, Meat Plow wrote:


Start with the first RF amp. It's probably a superhet so there will be a
455 osc and mixer. After that a couple rf amps and the the detector.

Google a superhetrodyne receiver. This one uses ICs but the basics are the
same

http://www.seekic.com/uploadfile/ic-...7173226815.gif

Should give you some insight as to where the signal is being lost in the
path.

How do you tune the radio in that schematic?

"spamtrap1888"

http://www.seekic.com/uploadfile/ic-...7173226815.gif


How do you tune the radio in that schematic?


** Like any receiver that uses a crystal oscillator.

By swapping the crystal.

Ask anyone with a RC model.



...... Phil

On May 23, 2:10*am, "Phil Allison" wrote:
"spamtrap1888"



http://www.seekic.com/uploadfile/ic-...7173226815.gif

How do you tune the radio in that schematic?

** Like any receiver that uses a crystal oscillator.

* *By swapping the crystal.

* *Ask anyone with a RC model.

..... *Phil

Well we all knew that you were off your rails Phil, but now we know
just what it was that drove you nuts. An intermittent fuse. No TWO
intermittent fuses. Possibly if not the most, then one of the most
simple components known to electronics techs. I sincerely hope they
weren't "chemical" fuses. I guess you must have slept through that
class huh? Maybe that can happen to "2AG" fuses, dunno.....Lenny

"klem kedidelhopper"


** Lenny,

it would be an act of kindness to simply put a bullet in your head.

I sincerely feel sorry for anyone whose life or well being you are able to
influence - cos it must be life of pure hell for them putting up with a
lunatic like you.

Calling you as six toed, banjo plucking retard was such a masterful piece of
understatement.

Cos all you really are is a piece of ****ing garbage.



..... Phil

On May 23, 10:09*am, "Phil Allison" wrote:
"klem kedidelhopper"

** Lenny,

it would be an act of kindness to simply put a bullet in your head.

I sincerely feel sorry for anyone whose life or well being you are able to
influence *- cos it must be life of pure hell for them putting up with a
lunatic like you.

Calling you as six toed, banjo plucking retard was such a masterful piece of
understatement.

Cos all you really are is a piece of ****ing garbage.

.... *Phil

So eloquently put Phil! But then I'd expect nothing less from you.
Lenny

On May 22, 11:10*pm, "Phil Allison" wrote:
"spamtrap1888"



http://www.seekic.com/uploadfile/ic-...7173226815.gif

How do you tune the radio in that schematic?

** Like any receiver that uses a crystal oscillator.

* *By swapping the crystal.

* *Ask anyone with a RC model.

..... *Phil

So meatplow's proffered schematic is even more spectacularly
inappropriate to the OP's situation -- trouble shooting a nine-
transistor AM-FM radio from 1970. Which, as I recall, likely used a
variable capacitor for tuning.

Googling shows a schematic of the Transistor 305 is available for
purchase on radiomuseum.org

On Sun, 22 May 2011 21:53:33 -0700, spamtrap1888 wrote:

On May 22, 6:41Â*pm, Meat Plow wrote:


Start with the first RF amp. It's probably a superhet so there will be
a 455 osc and mixer. After that a couple rf amps and the the detector.

Google a superhetrodyne receiver. This one uses ICs but the basics are
the same

http://www.seekic.com/uploadfile/ic-...7173226815.gif

Should give you some insight as to where the signal is being lost in
the path.

How do you tune the radio in that schematic

Tune as in select a frequency? Maybe by mind control? It's just a crude
example, not meant to be a service diagram.


--
Live Fast Die Young, Leave A Pretty Corpse

On Mon, 23 May 2011 08:00:04 -0700, spamtrap1888 wrote:

On May 22, 11:10Â*pm, "Phil Allison" wrote:
"spamtrap1888"



http://www.seekic.com/uploadfile/ic-...7173226815.gif

How do you tune the radio in that schematic?

** Like any receiver that uses a crystal oscillator.

Â* Â*By swapping the crystal.

Â* Â*Ask anyone with a RC model.

..... Â*Phil

So meatplow's proffered schematic is even more spectacularly
inappropriate to the OP's situation -- trouble shooting a nine-
transistor AM-FM radio from 1970. Which, as I recall, likely used a
variable capacitor for tuning.

Googling shows a schematic of the Transistor 305 is available for
purchase on radiomuseum.org

I'd call it a crude example not a ****ing service manual. As I said when
I posted the image link. Here's a more relevant schematic for ****wits
like you. I apologize but I sometimes forget there are idiots of your ilk
that need to be spoon fed and use a drool cup.

http://transistorhistory.50webs.com/lafay4.gif



--
Live Fast Die Young, Leave A Pretty Corpse

On May 23, 11:00*am, spamtrap1888 wrote:
On May 22, 11:10*pm, "Phil Allison" wrote:

"spamtrap1888"

http://www.seekic.com/uploadfile/ic-...7173226815.gif

How do you tune the radio in that schematic?

** Like any receiver that uses a crystal oscillator.

* *By swapping the crystal.

* *Ask anyone with a RC model.

..... *Phil

So meatplow's proffered schematic is even more spectacularly
inappropriate to the OP's situation -- trouble shooting a nine-
transistor AM-FM radio from 1970. Which, as I recall, likely used a
variable capacitor for tuning.

Googling shows a schematic of the Transistor 305 is available for
purchase on radiomuseum.org

I actually have the book with this radio. It has a schematic but comes
up somewhat short when it comes to voltages and waveforms. And the
intermittent nature of the problem makes it so hard to troubleshoot.
The other night it played on my bench for over ten hours. It never
failed and sounded fine. I finally went over and tuned the FM to a few
other stations and they seemed to sound OK. I then switched to AM and
although I did hear some stations, it being late evening I would have
expected to hear much more. But I wasn't sure about this as the shop
is in the basement. I tuned the AM between 550KHZ and 1600KHZ at which
point the radio suddenly quit. The tuning capacitor is not the issue.
And the switches don't appear to be noisy either. The scenario about
tuning the AM and the set quitting seems a bit of a stretch to be a
coincidence but then I just don't know. Anyone have any theories on if
this might be a small clue here? Thanks for following this thread,
Lenny

On May 25, 7:37*am, klem kedidelhopper
wrote:
On May 23, 11:00*am, spamtrap1888 wrote:





On May 22, 11:10*pm, "Phil Allison" wrote:

"spamtrap1888"

http://www.seekic.com/uploadfile/ic-...7173226815.gif

How do you tune the radio in that schematic?

** Like any receiver that uses a crystal oscillator.

* *By swapping the crystal.

* *Ask anyone with a RC model.

..... *Phil

So meatplow's proffered schematic is even more spectacularly
inappropriate to the OP's situation -- trouble shooting a nine-
transistor AM-FM radio from 1970. Which, as I recall, likely used a
variable capacitor for tuning.

Googling shows a schematic of the Transistor 305 is available for
purchase on radiomuseum.org

I actually have the book with this radio. It has a schematic but comes
up somewhat short when it comes to voltages and waveforms. And the
intermittent nature of the problem makes it so hard to troubleshoot.
The other night it played on my bench for over ten hours. It never
failed and sounded fine. I finally went over and tuned the FM to a few
other stations and they seemed to sound OK. I then switched to AM and
although I did hear some stations, it being late evening I would have
expected to hear much more. But I wasn't sure about this as the shop
is in the basement. I tuned the AM between 550KHZ and 1600KHZ at which
point the radio suddenly quit. The tuning capacitor is not the issue.
And the switches don't appear to be noisy either. The scenario about
tuning the AM and the set quitting seems a bit of a stretch to be a
coincidence but then I just don't know. Anyone have any theories on if
this might be a small clue here? Thanks for following this thread,
Lenny- Hide quoted text -

- Show quoted text -

Put a scope on the output of the mixer and keep it there until the
radio dies, and see if that first stage still is working. Do this one
stage at a time until you find which stage is the problem. Have you
tried heating the radio to induce the failure, you don't mention
trying that?