Germanium transistor sub

[Jeff Liebermann]

On Sat, 04 Jun 2011 12:57:53 -0400, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

A lot of Grundig radios are almost impossible to locate schematics
for. One radio with his (Transistor) TR-305 model number was for sale
recently on Ebay.

The newest 'TR' series listed in Sams is the TR-17, and date 1965.
There are no YB models listed in Sams, BTW.

I missed that model when searching with Google. This might be it:
<http://www.radiomuseum.org/r/grundig_transistor_305.html>
There's a schematic but the site owner wants $25 for membership.

It uses four AF126 transistors in the AM/FM IF Amplifier stages.

The original is available on eBay:
<http://cgi.ebay.com/380327967522> $9 including shipping from UK.
or
<http://www.dil.nl/PartDetails.aspx?ProductID=AF126> 11 Euros.

As Arfa mentioned, the NTE160 and the AF126 seem to have the same case
(TO-72) but different pinouts. The base and emitter pins are
reversed.





--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Michael A. Terrell]

Ian Field wrote:

"Michael A. Terrell" ?mike.terrell@earthlink.net? wrote in message
news:hsSdnWDRNKWF-XfQnZ2dnUVZ_oudnZ2d@earthlink.com...
?
? Jeff Liebermann wrote:
??
?? On Fri, 3 Jun 2011 17:39:30 -0700 (PDT), klem kedidelhopper
?? ?captainvideo462009@gmail.com? wrote:
??
?? ?I think I've found the transistor that is intermittently failing in my
?? ?Grundig 305 transistor radio.
??
?? Ummm... could you take a 2nd look at the model number? Grundig makes
?? the YB-305, but that's not germanium.
?? ?http://www.universal-radio.com/catalog/portable/yb305.html?
?? Grundig also makes a 3059, but that's tubes:
?? ?http://www.oldradioworld.de/3059.htm?
?
? A lot of Grundig radios are almost impossible to locate schematics
? for. One radio with his (Transistor) TR-305 model number was for sale
? recently on Ebay.

In contrast, most of their TVs had a service sheet stowed in a slot inside
the cabinet.

Until someone removed it. How many of those old TV schematics are
available on line, and for free?

General Electric, Sears-Silvertone and other companies did the same
thing in the US, but they were usually missing whenever I cracked the
case on one.


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

 

[Michael A. Terrell]

Jeff Liebermann wrote:

On Sat, 04 Jun 2011 12:57:53 -0400, "Michael A. Terrell"
?mike.terrell@earthlink.net? wrote:

? A lot of Grundig radios are almost impossible to locate schematics
?for. One radio with his (Transistor) TR-305 model number was for sale
?recently on Ebay.
?
? The newest 'TR' series listed in Sams is the TR-17, and date 1965.
?There are no YB models listed in Sams, BTW.

I missed that model when searching with Google. This might be it:
?http://www.radiomuseum.org/r/grundig_transistor_305.html?
There's a schematic but the site owner wants $25 for membership.

? It uses four AF126 transistors in the AM/FM IF Amplifier stages.

The original is available on eBay:
?http://cgi.ebay.com/380327967522? $9 including shipping from UK.
or
?http://www.dil.nl/PartDetails.aspx?ProductID=AF126? 11 Euros.

As Arfa mentioned, the NTE160 and the AF126 seem to have the same case
(TO-72) but different pinouts. The base and emitter pins are
reversed.

A piece of 'Spaghetti' tubing over the emitter was common in repairs
in the '60s & '70s.


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

 

[Bo-Lennart]

On Jun 4, 2:39 am, klem kedidelhopper <captainvideo462...@gmail.com>
wrote:

I think I've found the transistor that is intermittently failing in my
Grundig 305 transistor radio.It is an AF126. I obtained an NTE 160
which is supposed to replace the AF126. however I installed it and the
radio  does not work at all. I wouldn't think that I would have to do
a complete IF alignment after simply replacing a transistor, that is I
would think that even if the new part detuned the circuit slightly, I
would expect to get something through. Any opinions on this? Thanks,
Lenny

Hi...
I can send You a AF126. You pay the postage, the transistor You can
have for free.

Bo-Lennart Karlsson
Falun, SWEDEN

 

[klem kedidelhopper]

On Jun 5, 5:15 am, Bo-Lennart <bo-lennart.karls...@telia.com> wrote:

On Jun 4, 2:39 am, klem kedidelhopper <captainvideo462...@gmail.com
wrote:

I think I've found the transistor that is intermittently failing in my
Grundig 305 transistor radio.It is an AF126. I obtained an NTE 160
which is supposed to replace the AF126. however I installed it and the
radio  does not work at all. I wouldn't think that I would have to do
a complete IF alignment after simply replacing a transistor, that is I
would think that even if the new part detuned the circuit slightly, I
would expect to get something through. Any opinions on this? Thanks,
Lenny

Hi...
I can send You a AF126. You pay the postage, the transistor You can
have for free.

Bo-Lennart Karlsson
Falun, SWEDEN

Hi, What do you think the postage to the US will be? Thanks, Lenny

 

[Ian Field]

"isw" <isw@witzend.com> wrote in message
news:isw-5D78C0.22221803062011@[216.168.3.50]...

In article
d10f76b7-c0f3-4318-9388-4cdf52de224c@v31g2000vbs.googlegroups.com>,
klem kedidelhopper <captainvideo462009@gmail.com> wrote:

I think I've found the transistor that is intermittently failing in my
Grundig 305 transistor radio.It is an AF126. I obtained an NTE 160
which is supposed to replace the AF126. however I installed it and the
radio does not work at all. I wouldn't think that I would have to do
a complete IF alignment after simply replacing a transistor, that is I
would think that even if the new part detuned the circuit slightly, I
would expect to get something through. Any opinions on this?

From the subject, you say the original transistor is a Ge device.

There's a very good chance that the "replacement" is actually a Si one.
You can check this by measuring the forward conduction drop of the B-E
junction -- a Ge one will be about half that of Si.

If the replacement is, in fact, a Si device, you still might be able to
get good performance from it by adjusting the bias point.

There seems to be a consensus of opinion that the OP has indeed selected a
suitable Ge replacement, however I suspect that even if a Si part had been
fitted the consequenses wouldn't be as serious as it not working at all.

Any sort of decent quality radio would have automatic bias common emitter
stages, the base bias is set by a voltage divider - that and the value of
the emitter resistor determine the collector current.

The self compensating nature of the circuit would tend to ensure a
relatively small reduction in collector current, the main problem I can
think of is that AGC is often fed at the bottom of the base bias divider, so
using a transistor with a higher Vbe may have a similar effect to a large
AGC control voltage - very low gain maybe, but totally inoperative;
doubtful.

 

[William Sommerwerck]

"Ian Field" <gangprobing.alien@ntlworld.com> wrote in message
news:40QGp.906$fQ4.736@newsfe16.ams2...

Any sort of decent quality radio would have automatic bias common emitter
stages, the base bias is set by a voltage divider - that and the value of
the emitter resistor determine the collector current.

The self compensating nature of the circuit would tend to ensure a
relatively small reduction in collector current, the main problem I can
think of is that AGC is often fed at the bottom of the base bias divider,
so using a transistor with a higher Vbe may have a similar effect to a
large AGC control voltage - very low gain maybe, but totally inoperative;
doubtful.

This isn't quite the way I learned it in school.

The kind of bias you're describing tends to keep collector current constant
with beta variations. Vbe is taken into account in the design. I don't think
a circuit intended for 0.2 to 0.3 volts would work with a transistor needing
0.6 to 0.7 volts.

 

[Ian Field]

"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message
news:isgiiu$jpq$1@dont-email.me...

"Ian Field" <gangprobing.alien@ntlworld.com> wrote in message
news:40QGp.906$fQ4.736@newsfe16.ams2...

Any sort of decent quality radio would have automatic bias common emitter
stages, the base bias is set by a voltage divider - that and the value of
the emitter resistor determine the collector current.

The self compensating nature of the circuit would tend to ensure a
relatively small reduction in collector current, the main problem I can
think of is that AGC is often fed at the bottom of the base bias divider,
so using a transistor with a higher Vbe may have a similar effect to a
large AGC control voltage - very low gain maybe, but totally inoperative;
doubtful.

This isn't quite the way I learned it in school.

The kind of bias you're describing tends to keep collector current
constant
with beta variations. Vbe is taken into account in the design. I don't
think
a circuit intended for 0.2 to 0.3 volts would work with a transistor
needing
0.6 to 0.7 volts.

Collector current does fall, but there is also a corresponding fall in
emitter current wich reduces the emitter resistor volt drop - which goes
some way to compensating the higher Vbe.

So it doesn't result in the transistor being completely cut off - as would
happen if the emitter went straight to ground without an emitter resistor.

 

[Michael A. Terrell]

Ian Field wrote:

"isw" <isw@witzend.com> wrote in message
news:isw-5D78C0.22221803062011@[216.168.3.50]...
In article
d10f76b7-c0f3-4318-9388-4cdf52de224c@v31g2000vbs.googlegroups.com>,
klem kedidelhopper <captainvideo462009@gmail.com> wrote:

I think I've found the transistor that is intermittently failing in my
Grundig 305 transistor radio.It is an AF126. I obtained an NTE 160
which is supposed to replace the AF126. however I installed it and the
radio does not work at all. I wouldn't think that I would have to do
a complete IF alignment after simply replacing a transistor, that is I
would think that even if the new part detuned the circuit slightly, I
would expect to get something through. Any opinions on this?

From the subject, you say the original transistor is a Ge device.

There's a very good chance that the "replacement" is actually a Si one.
You can check this by measuring the forward conduction drop of the B-E
junction -- a Ge one will be about half that of Si.

If the replacement is, in fact, a Si device, you still might be able to
get good performance from it by adjusting the bias point.

There seems to be a consensus of opinion that the OP has indeed selected a
suitable Ge replacement, however I suspect that even if a Si part had been
fitted the consequenses wouldn't be as serious as it not working at all.

Any sort of decent quality radio would have automatic bias common emitter
stages, the base bias is set by a voltage divider - that and the value of
the emitter resistor determine the collector current.

The 'Emmiter resistor in similar radios is nothing more than the DC
rsesistance of the AM & FM IF transformer primaries in series.

The self compensating nature of the circuit would tend to ensure a
relatively small reduction in collector current, the main problem I can
think of is that AGC is often fed at the bottom of the base bias divider, so
using a transistor with a higher Vbe may have a similar effect to a large
AGC control voltage - very low gain maybe, but totally inoperative;
doubtful.

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

 

[mloo55]

If the radio is intermitent it does not mean that necessarily the
transistor, i think of one probable cause is the variable capacitor
besides if the transistor you mentioned is part of the if section
then you may check with another radio tuning a frequency so produces
an harmonics in the good radio so you know the mixer stage is working
then you can inyect a signal with your finger in the base of the first
if transistor and a radio station should be heard. Have you tried to
resolder all points and verify all paths are in god condition. Hope it
can help.
rgds

On Jun 4, 2:39 am, klem kedidelhopper <captainvideo462...@gmail.com
wrote:

I think I've found the transistor that is intermittently failing in my
Grundig 305 transistor radio.It is an AF126. I obtained an NTE 160
which is supposed to replace the AF126. however I installed it and the
radio  does not work at all. I wouldn't think that I would have to do
a complete IF alignment after simply replacing a transistor, that is I
would think that even if the new part detuned the circuit slightly, I
would expect to get something through. Any opinions on this? Thanks,
Lenny

Hi...
I can send You a AF126. You pay the postage, the transistor You can
have for free.

Bo-Lennart Karlsson
Falun, SWEDEN

Hi, What do you think the postage to the US will be? Thanks, Lenny- Hide quoted text -

- Show quoted text -

 

[Archon]

On 6/7/2011 5:47 PM, klem kedidelhopper wrote:

On Jun 6, 9:37 pm, mloo55<mloo1...@gmail.com> wrote:
If the radio is intermitent it does not mean that necessarily the
transistor, i think of one probable cause is the variable capacitor
besides if the transistor you mentioned is part of the if section
then you may check with another radio tuning a frequency so produces
an harmonics in the good radio so you know the mixer stage is working
then you can inyect a signal with your finger in the base of the first
if transistor and a radio station should be heard. Have you tried to
resolder all points and verify all paths are in god condition. Hope it
can help.
rgds



On Jun 4, 2:39 am, klem kedidelhopper<captainvideo462...@gmail.com
wrote:

I think I've found the transistor that is intermittently failing in my
Grundig 305 transistor radio.It is an AF126. I obtained an NTE 160
which is supposed to replace the AF126. however I installed it and the
radio does not work at all. I wouldn't think that I would have to do
a complete IF alignment after simply replacing a transistor, that is I
would think that even if the new part detuned the circuit slightly, I
would expect to get something through. Any opinions on this? Thanks,
Lenny

Hi...
I can send You a AF126. You pay the postage, the transistor You can
have for free.

Bo-Lennart Karlsson
Falun, SWEDEN

Hi, What do you think the postage to the US will be? Thanks, Lenny- Hide quoted text -

- Show quoted text -

Well the odd thing is that the radio always starts out working
perfectly. It will run consistently for anywhere from ten minutes to
sometimes two hours. It seemed that at first operating it at low
volume settings may have precipitated the problem but now I'm not so
sure about that. However once the intermittent condition begins it
continues until the unit is shut off for a period of time. After that
the period of time it takes for the intermittent condition to start
again after a subsequent power on is directly proportional to the time
the radio has been off. I managed to measure all transistor voltages
during an "OK" period. I then took similar voltage readings during
failure. As expected all voltages on all transistors were affected,
however the voltages measured at the terminals of this particular
transistor in question are all the same, (about 3.0volts) when the
failure condition occurs. It was for this reason i suspected this
transistor, (as improbable as this may seem), of developing what looks
like a "dynamic" b e c short. Lenny
Cracked volume control pot

JC

 

[klem kedidelhopper]

On Jun 6, 9:37 pm, mloo55 <mloo1...@gmail.com> wrote:

If the radio is intermitent it does not mean that necessarily the
transistor, i think of one probable cause is the variable capacitor
besides if the transistor you  mentioned is part of the if section
then you may check with another radio tuning a frequency so produces
an harmonics in the good radio so you know the mixer stage is working
then you can inyect a signal with your finger in the base of the first
if transistor and a radio station should be heard. Have you tried to
resolder all points and verify all paths are in god condition. Hope it
can help.
rgds



On Jun 4, 2:39 am, klem kedidelhopper <captainvideo462...@gmail.com
wrote:

I think I've found the transistor that is intermittently failing in my
Grundig 305 transistor radio.It is an AF126. I obtained an NTE 160
which is supposed to replace the AF126. however I installed it and the
radio  does not work at all. I wouldn't think that I would have to do
a complete IF alignment after simply replacing a transistor, that is I
would think that even if the new part detuned the circuit slightly, I
would expect to get something through. Any opinions on this? Thanks,
Lenny

Hi...
I can send You a AF126. You pay the postage, the transistor You can
have for free.

Bo-Lennart Karlsson
Falun, SWEDEN

Hi, What do you think the postage to the US will be? Thanks, Lenny- Hide quoted text -

- Show quoted text -

Well the odd thing is that the radio always starts out working
perfectly. It will run consistently for anywhere from ten minutes to
sometimes two hours. It seemed that at first operating it at low
volume settings may have precipitated the problem but now I'm not so
sure about that. However once the intermittent condition begins it
continues until the unit is shut off for a period of time. After that
the period of time it takes for the intermittent condition to start
again after a subsequent power on is directly proportional to the time
the radio has been off. I managed to measure all transistor voltages
during an "OK" period. I then took similar voltage readings during
failure. As expected all voltages on all transistors were affected,
however the voltages measured at the terminals of this particular
transistor in question are all the same, (about 3.0volts) when the
failure condition occurs. It was for this reason i suspected this
transistor, (as improbable as this may seem), of developing what looks
like a "dynamic" b e c short. Lenny

 

[N_Cook]

klem kedidelhopper <captainvideo462009@gmail.com> wrote in message
news:be9c9271-8923-48e1-8bb2-f29b4cd156f8@ct4g2000vbb.googlegroups.com...
On Jun 6, 9:37 pm, mloo55 <mloo1...@gmail.com> wrote:

If the radio is intermitent it does not mean that necessarily the
transistor, i think of one probable cause is the variable capacitor
besides if the transistor you mentioned is part of the if section
then you may check with another radio tuning a frequency so produces
an harmonics in the good radio so you know the mixer stage is working
then you can inyect a signal with your finger in the base of the first
if transistor and a radio station should be heard. Have you tried to
resolder all points and verify all paths are in god condition. Hope it
can help.
rgds



On Jun 4, 2:39 am, klem kedidelhopper <captainvideo462...@gmail.com
wrote:

I think I've found the transistor that is intermittently failing in
my
Grundig 305 transistor radio.It is an AF126. I obtained an NTE 160
which is supposed to replace the AF126. however I installed it and
the
radio does not work at all. I wouldn't think that I would have to do
a complete IF alignment after simply replacing a transistor, that is
I
would think that even if the new part detuned the circuit slightly,
I
would expect to get something through. Any opinions on this? Thanks,
Lenny

Hi...
I can send You a AF126. You pay the postage, the transistor You can
have for free.

Bo-Lennart Karlsson
Falun, SWEDEN

Hi, What do you think the postage to the US will be? Thanks, Lenny- Hide
quoted text -

- Show quoted text -

Well the odd thing is that the radio always starts out working
perfectly. It will run consistently for anywhere from ten minutes to
sometimes two hours. It seemed that at first operating it at low
volume settings may have precipitated the problem but now I'm not so
sure about that. However once the intermittent condition begins it
continues until the unit is shut off for a period of time. After that
the period of time it takes for the intermittent condition to start
again after a subsequent power on is directly proportional to the time
the radio has been off. I managed to measure all transistor voltages
during an "OK" period. I then took similar voltage readings during
failure. As expected all voltages on all transistors were affected,
however the voltages measured at the terminals of this particular
transistor in question are all the same, (about 3.0volts) when the
failure condition occurs. It was for this reason i suspected this
transistor, (as improbable as this may seem), of developing what looks
like a "dynamic" b e c short. Lenny

++++

In that case look for C problems

 

[spamtrap1888]

On Jun 7, 4:40 pm, Archon <Chipbee40_Spa...@yahoo.com> wrote:

On 6/7/2011 5:47 PM, klem kedidelhopper wrote:

On Jun 6, 9:37 pm, mloo55<mloo1...@gmail.com>  wrote:
If the radio is intermitent it does not mean that necessarily the
transistor, i think of one probable cause is the variable capacitor
besides if the transistor you  mentioned is part of the if section
then you may check with another radio tuning a frequency so produces
an harmonics in the good radio so you know the mixer stage is working
then you can inyect a signal with your finger in the base of the first
if transistor and a radio station should be heard. Have you tried to
resolder all points and verify all paths are in god condition. Hope it
can help.
rgds

On Jun 4, 2:39 am, klem kedidelhopper<captainvideo462...@gmail.com
wrote:

I think I've found the transistor that is intermittently failing in my
Grundig 305 transistor radio.It is an AF126. I obtained an NTE 160
which is supposed to replace the AF126. however I installed it and the
radio  does not work at all. I wouldn't think that I would have to do
a complete IF alignment after simply replacing a transistor, that is I
would think that even if the new part detuned the circuit slightly, I
would expect to get something through. Any opinions on this? Thanks,
Lenny

Hi...
I can send You a AF126. You pay the postage, the transistor You can
have for free.

Bo-Lennart Karlsson
Falun, SWEDEN

Hi, What do you think the postage to the US will be? Thanks, Lenny- Hide quoted text -

- Show quoted text -

Well the odd thing is that the radio always starts out working
perfectly. It will run consistently for anywhere from ten minutes to
sometimes two hours. It seemed that at first operating it at low
volume settings may have precipitated the problem but now I'm not so
sure about that. However once the intermittent condition begins it
continues until the unit is shut off for a period of time. After that
the period of time it takes for the intermittent condition to start
again after a subsequent power on is directly proportional to the time
the radio has been off. I managed to measure all transistor voltages
during an "OK" period. I then took similar voltage readings during
failure. As expected all voltages on all transistors were affected,
however the voltages measured at the terminals of this particular
transistor in question are all the same, (about 3.0volts) when the
failure condition occurs. It was for this reason i suspected this
transistor, (as improbable as this may seem), of developing what looks
like a "dynamic" b e c short. Lenny

Cracked volume control pot

In that case he could temporarily replace the pot with two resistors,
right? And see if the circuit goes intermittent.

 

[William Sommerwerck]

In that case he could temporarily replace the pot with two
resistors, right? And see if the circuit goes intermittent.

Because it always starts out working, and this is definitely
consistent. I really feel that this is an active component problem.

Maybe, maybe not. (I'm inclined to agree "yes, it is", when you say that the
transistor has the same voltage on all terminals.) But you really need to
put a 'scope on the unit, and step through it.

 

[Arfa Daily]

"klem kedidelhopper" <captainvideo462009@gmail.com> wrote in message
news:b5798536-8983-4504-94cc-de83dfebe476@k13g2000vbv.googlegroups.com...

On Jun 8, 10:51 am, spamtrap1888 <spamtrap1...@gmail.com> wrote:
On Jun 7, 4:40 pm, Archon <Chipbee40_Spa...@yahoo.com> wrote:



On 6/7/2011 5:47 PM, klem kedidelhopper wrote:

On Jun 6, 9:37 pm, mloo55<mloo1...@gmail.com> wrote:
If the radio is intermitent it does not mean that necessarily the
transistor, i think of one probable cause is the variable capacitor
besides if the transistor you mentioned is part of the if section
then you may check with another radio tuning a frequency so produces
an harmonics in the good radio so you know the mixer stage is
working
then you can inyect a signal with your finger in the base of the
first
if transistor and a radio station should be heard. Have you tried to
resolder all points and verify all paths are in god condition. Hope
it
can help.
rgds

On Jun 4, 2:39 am, klem
kedidelhopper<captainvideo462...@gmail.com
wrote:

I think I've found the transistor that is intermittently failing
in my
Grundig 305 transistor radio.It is an AF126. I obtained an NTE
160
which is supposed to replace the AF126. however I installed it
and the
radio does not work at all. I wouldn't think that I would have
to do
a complete IF alignment after simply replacing a transistor, that
is I
would think that even if the new part detuned the circuit
slightly, I
would expect to get something through. Any opinions on this?
Thanks,
Lenny

Hi...
I can send You a AF126. You pay the postage, the transistor You
can
have for free.

Bo-Lennart Karlsson
Falun, SWEDEN

Hi, What do you think the postage to the US will be? Thanks, Lenny-
Hide quoted text -

- Show quoted text -

Well the odd thing is that the radio always starts out working
perfectly. It will run consistently for anywhere from ten minutes to
sometimes two hours. It seemed that at first operating it at low
volume settings may have precipitated the problem but now I'm not so
sure about that. However once the intermittent condition begins it
continues until the unit is shut off for a period of time. After that
the period of time it takes for the intermittent condition to start
again after a subsequent power on is directly proportional to the
time
the radio has been off. I managed to measure all transistor voltages
during an "OK" period. I then took similar voltage readings during
failure. As expected all voltages on all transistors were affected,
however the voltages measured at the terminals of this particular
transistor in question are all the same, (about 3.0volts) when the
failure condition occurs. It was for this reason i suspected this
transistor, (as improbable as this may seem), of developing what
looks
like a "dynamic" b e c short. Lenny

Cracked volume control pot

In that case he could temporarily replace the pot with two resistors,
right? And see if the circuit goes intermittent.

Because it always starts out working, and this is definitely
consistent. I really feel that this is an active component problem.
Lenny

If you have the schematics for the radio, then it should be no problem
figuring out what is going wrong. There really can't be very much that could
cause all three terminals of the transistor to assume the same voltage.
Something amiss with the emitter return maybe ? If the base is biased with
respect to ground, and the emitter is returned to ground, then you must
measure a difference between the base and emitter, equivalent to a germanium
P-N junction drop. If the emitter return goes open, then you might well read
(almost) the same voltage at the emitter and base, and possibly the
collector too.

Arfa

 

[Michael A. Terrell]

Arfa Daily wrote:

"klem kedidelhopper" <captainvideo462009@gmail.com> wrote in message
news:b5798536-8983-4504-94cc-de83dfebe476@k13g2000vbv.googlegroups.com...
On Jun 8, 10:51 am, spamtrap1888 <spamtrap1...@gmail.com> wrote:
On Jun 7, 4:40 pm, Archon <Chipbee40_Spa...@yahoo.com> wrote:



On 6/7/2011 5:47 PM, klem kedidelhopper wrote:

On Jun 6, 9:37 pm, mloo55<mloo1...@gmail.com> wrote:
If the radio is intermitent it does not mean that necessarily the
transistor, i think of one probable cause is the variable capacitor
besides if the transistor you mentioned is part of the if section
then you may check with another radio tuning a frequency so produces
an harmonics in the good radio so you know the mixer stage is
working
then you can inyect a signal with your finger in the base of the
first
if transistor and a radio station should be heard. Have you tried to
resolder all points and verify all paths are in god condition. Hope
it
can help.
rgds

On Jun 4, 2:39 am, klem
kedidelhopper<captainvideo462...@gmail.com
wrote:

I think I've found the transistor that is intermittently failing
in my
Grundig 305 transistor radio.It is an AF126. I obtained an NTE
160
which is supposed to replace the AF126. however I installed it
and the
radio does not work at all. I wouldn't think that I would have
to do
a complete IF alignment after simply replacing a transistor, that
is I
would think that even if the new part detuned the circuit
slightly, I
would expect to get something through. Any opinions on this?
Thanks,
Lenny

Hi...
I can send You a AF126. You pay the postage, the transistor You
can
have for free.

Bo-Lennart Karlsson
Falun, SWEDEN

Hi, What do you think the postage to the US will be? Thanks, Lenny-
Hide quoted text -

- Show quoted text -

Well the odd thing is that the radio always starts out working
perfectly. It will run consistently for anywhere from ten minutes to
sometimes two hours. It seemed that at first operating it at low
volume settings may have precipitated the problem but now I'm not so
sure about that. However once the intermittent condition begins it
continues until the unit is shut off for a period of time. After that
the period of time it takes for the intermittent condition to start
again after a subsequent power on is directly proportional to the
time
the radio has been off. I managed to measure all transistor voltages
during an "OK" period. I then took similar voltage readings during
failure. As expected all voltages on all transistors were affected,
however the voltages measured at the terminals of this particular
transistor in question are all the same, (about 3.0volts) when the
failure condition occurs. It was for this reason i suspected this
transistor, (as improbable as this may seem), of developing what
looks
like a "dynamic" b e c short. Lenny

Cracked volume control pot

In that case he could temporarily replace the pot with two resistors,
right? And see if the circuit goes intermittent.

Because it always starts out working, and this is definitely
consistent. I really feel that this is an active component problem.
Lenny

If you have the schematics for the radio, then it should be no problem
figuring out what is going wrong. There really can't be very much that could
cause all three terminals of the transistor to assume the same voltage.
Something amiss with the emitter return maybe ? If the base is biased with
respect to ground, and the emitter is returned to ground, then you must
measure a difference between the base and emitter, equivalent to a germanium
P-N junction drop. If the emitter return goes open, then you might well read
(almost) the same voltage at the emitter and base, and possibly the
collector too.

It's a PNP transistor. The emitter has the highest voltage, so it is
something opening in the collector path to ground. When it opens, the
base voltage rises because the transistor is no longer biased properly.

Arfa

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

 

[klem kedidelhopper]

On Jun 8, 10:51 am, spamtrap1888 <spamtrap1...@gmail.com> wrote:

On Jun 7, 4:40 pm, Archon <Chipbee40_Spa...@yahoo.com> wrote:



On 6/7/2011 5:47 PM, klem kedidelhopper wrote:

On Jun 6, 9:37 pm, mloo55<mloo1...@gmail.com>  wrote:
If the radio is intermitent it does not mean that necessarily the
transistor, i think of one probable cause is the variable capacitor
besides if the transistor you  mentioned is part of the if section
then you may check with another radio tuning a frequency so produces
an harmonics in the good radio so you know the mixer stage is working
then you can inyect a signal with your finger in the base of the first
if transistor and a radio station should be heard. Have you tried to
resolder all points and verify all paths are in god condition. Hope it
can help.
rgds

On Jun 4, 2:39 am, klem kedidelhopper<captainvideo462...@gmail.com
wrote:

I think I've found the transistor that is intermittently failing in my
Grundig 305 transistor radio.It is an AF126. I obtained an NTE 160
which is supposed to replace the AF126. however I installed it and the
radio  does not work at all. I wouldn't think that I would have to do
a complete IF alignment after simply replacing a transistor, that is I
would think that even if the new part detuned the circuit slightly, I
would expect to get something through. Any opinions on this? Thanks,
Lenny

Hi...
I can send You a AF126. You pay the postage, the transistor You can
have for free.

Bo-Lennart Karlsson
Falun, SWEDEN

Hi, What do you think the postage to the US will be? Thanks, Lenny- Hide quoted text -

- Show quoted text -

Well the odd thing is that the radio always starts out working
perfectly. It will run consistently for anywhere from ten minutes to
sometimes two hours. It seemed that at first operating it at low
volume settings may have precipitated the problem but now I'm not so
sure about that. However once the intermittent condition begins it
continues until the unit is shut off for a period of time. After that
the period of time it takes for the intermittent condition to start
again after a subsequent power on is directly proportional to the time
the radio has been off. I managed to measure all transistor voltages
during an "OK" period. I then took similar voltage readings during
failure. As expected all voltages on all transistors were affected,
however the voltages measured at the terminals of this particular
transistor in question are all the same, (about 3.0volts) when the
failure condition occurs. It was for this reason i suspected this
transistor, (as improbable as this may seem), of developing what looks
like a "dynamic" b e c short. Lenny

Cracked volume control pot

In that case he could temporarily replace the pot with two resistors,
right? And see if the circuit goes intermittent.

Because it always starts out working, and this is definitely
consistent. I really feel that this is an active component problem.
Lenny

 

[Arfa Daily]

"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
news:eKednQUNp631gG3QnZ2dnUVZ_oudnZ2d@earthlink.com...

Arfa Daily wrote:

"klem kedidelhopper" <captainvideo462009@gmail.com> wrote in message
news:b5798536-8983-4504-94cc-de83dfebe476@k13g2000vbv.googlegroups.com...
On Jun 8, 10:51 am, spamtrap1888 <spamtrap1...@gmail.com> wrote:
On Jun 7, 4:40 pm, Archon <Chipbee40_Spa...@yahoo.com> wrote:



On 6/7/2011 5:47 PM, klem kedidelhopper wrote:

On Jun 6, 9:37 pm, mloo55<mloo1...@gmail.com> wrote:
If the radio is intermitent it does not mean that necessarily the
transistor, i think of one probable cause is the variable
capacitor
besides if the transistor you mentioned is part of the if
section
then you may check with another radio tuning a frequency so
produces
an harmonics in the good radio so you know the mixer stage is
working
then you can inyect a signal with your finger in the base of the
first
if transistor and a radio station should be heard. Have you tried
to
resolder all points and verify all paths are in god condition.
Hope
it
can help.
rgds

On Jun 4, 2:39 am, klem
kedidelhopper<captainvideo462...@gmail.com
wrote:

I think I've found the transistor that is intermittently
failing
in my
Grundig 305 transistor radio.It is an AF126. I obtained an NTE
160
which is supposed to replace the AF126. however I installed it
and the
radio does not work at all. I wouldn't think that I would
have
to do
a complete IF alignment after simply replacing a transistor,
that
is I
would think that even if the new part detuned the circuit
slightly, I
would expect to get something through. Any opinions on this?
Thanks,
Lenny

Hi...
I can send You a AF126. You pay the postage, the transistor You
can
have for free.

Bo-Lennart Karlsson
Falun, SWEDEN

Hi, What do you think the postage to the US will be? Thanks,
Lenny-
Hide quoted text -

- Show quoted text -

Well the odd thing is that the radio always starts out working
perfectly. It will run consistently for anywhere from ten minutes
to
sometimes two hours. It seemed that at first operating it at low
volume settings may have precipitated the problem but now I'm not
so
sure about that. However once the intermittent condition begins it
continues until the unit is shut off for a period of time. After
that
the period of time it takes for the intermittent condition to
start
again after a subsequent power on is directly proportional to the
time
the radio has been off. I managed to measure all transistor
voltages
during an "OK" period. I then took similar voltage readings during
failure. As expected all voltages on all transistors were
affected,
however the voltages measured at the terminals of this particular
transistor in question are all the same, (about 3.0volts) when the
failure condition occurs. It was for this reason i suspected this
transistor, (as improbable as this may seem), of developing what
looks
like a "dynamic" b e c short. Lenny

Cracked volume control pot

In that case he could temporarily replace the pot with two resistors,
right? And see if the circuit goes intermittent.

Because it always starts out working, and this is definitely
consistent. I really feel that this is an active component problem.
Lenny

If you have the schematics for the radio, then it should be no problem
figuring out what is going wrong. There really can't be very much that
could
cause all three terminals of the transistor to assume the same voltage.
Something amiss with the emitter return maybe ? If the base is biased
with
respect to ground, and the emitter is returned to ground, then you must
measure a difference between the base and emitter, equivalent to a
germanium
P-N junction drop. If the emitter return goes open, then you might well
read
(almost) the same voltage at the emitter and base, and possibly the
collector too.


It's a PNP transistor. The emitter has the highest voltage, so it is
something opening in the collector path to ground. When it opens, the
base voltage rises because the transistor is no longer biased properly.

I haven't got a copy of the circuit to hand, but I'm not sure that I
understand what you're saying. A PNP circuit is just the same as an NPN
circuit, but with the battery upside down. Ground is ground and bias is
bias, applied between the base and emitter. Doesn't matter whether it's a
PNP or an NPN transistor, the ground reference is just the opposite pole of
the battery. The emitter having the "highest voltage" is basically an
arbitrary term as that voltage could be 'higher' in a positive or negative
direction, depending on where you are taking to be your measurement
reference. Things get a little more complicated to get your head around,
where the circuit is powered the 'conventional' way up, but the transistors
are in upside down. Maybe that's what you're saying here ?

Arfa

 

[William Sommerwerck]

It's a PNP transistor. The emitter has the highest voltage, so it is
something opening in the collector path to ground. When it opens, the
base voltage rises because the transistor is no longer biased properly.

I haven't got a copy of the circuit to hand, but I'm not sure that I
understand what you're saying. A PNP circuit is just the same as an NPN
circuit, but with the battery upside down. Ground is ground and bias is
bias, applied between the base and emitter. Doesn't matter whether it's a
PNP or an NPN transistor, the ground reference is just the opposite pole
of
the battery. The emitter having the "highest voltage" is basically an
arbitrary term as that voltage could be 'higher' in a positive or negative
direction, depending on where you are taking to be your measurement
reference. Things get a little more complicated to get your head around,
where the circuit is powered the 'conventional' way up, but the
transistors
are in upside down. Maybe that's what you're saying here ?

I was going to demur, too.

In a junction transistor, the EB junction is forward-biased, the BC junction
reverse-biased. The EB junction can be correctly biased even if the
collector is dangling. I don't see how opening the collector's path to its
intended voltage source would alter the base voltage.