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

"klem kedidelhopper" wrote in message
...
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

AF126 and NTE160, appear to have different pinouts ?

http://english.electronica-pt.com/db....php?ref=AF126

and

http://www.nteinc.com/specs/100to199/pdf/nte160.pdf

Arfa

Even if the transistor's output capacitance was far-enough "off" to
significantly detune the IF, you'd still get something. *

Are you certain you installed the NTE 160 with the leads in the right
positions?

What happens when you put the old transistor back?

You should also check the transistor with a diode-safe ohmeter.

* I assume the designer would take the base-collector capacitance into
account when designing the IF transformers. You'd want the latter to have
significantly higher capacitance so that swapping transistors wouldn't cause
a big shift in tuning.

In article
,
klem kedidelhopper 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.

Isaac

isw wrote:

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.


There is a 100% chance that you're wrong:

http://www.nteinc.com/specs/100to199/pdf/nte160.pdf


This link was also posted in the original thread: AM/FM radio
troubleshooting


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

"isw" wrote in message
]...
In article
,
klem kedidelhopper 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.

"Ian Field" wrote in message
...

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.

"William Sommerwerck" wrote in message
...
"Ian Field" wrote in message
...

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.

Ian Field wrote:

"isw" wrote in message
]...
In article
,
klem kedidelhopper 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.

On Fri, 3 Jun 2011 17:39:30 -0700 (PDT), klem kedidelhopper
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

Perhaps if you disclosed the correct model number, and possibly which
xsistor you're replacing, we can find a schematic, and determine if
your NTE substitute is appropriate?


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

Jeff Liebermann wrote:

On Fri, 3 Jun 2011 17:39:30 -0700 (PDT), klem kedidelhopper
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.

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

It uses four AF126 transistors in the AM/FM IF Amplifier stages. Sams
shows the collector voltages at 0, because each collector goes to ground
through the primary of each pair of IF transformers. A modern meter
will still show some voltage at the collector, but a VTVM used by Sams
would barely make the needle move. The schematic shows between 4 - 6
ohms to ground from each collector.


Perhaps if you disclosed the correct model number, and possibly which
xsistor you're replacing, we can find a schematic, and determine if
your NTE substitute is appropriate?


He said it was AF126, which does cross to ECG/NTE 160.


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

On Jun 4, 12:57*pm, "Michael A. Terrell"
wrote:
Jeff Liebermann wrote:

On Fri, 3 Jun 2011 17:39:30 -0700 (PDT), klem kedidelhopper
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.

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

* It uses four AF126 transistors in the AM/FM IF Amplifier stages. *Sams
shows the collector voltages at 0, because each collector goes to ground
through the primary of each pair of IF transformers. *A modern meter
will still show some voltage at the collector, but a VTVM used by Sams
would barely make the needle move. *The schematic shows between 4 - 6
ohms to ground from each collector.

Perhaps if you disclosed the correct model number, and possibly which
xsistor you're replacing, we can find a schematic, and determine if
your NTE substitute is appropriate?

* *He said it was AF126, which does cross to ECG/NTE 160.

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

A lot of good information guys. I'm sorry I didn't include it in this
new post but the radio model is "Transistor 305".It was given to me
around 1970 and it wasn't new then so I'm guessing a bit here. It is
late 60's vintage I think. And I do have a schematic and foil side
board layout too.I did buy two of these 160's. (I wasn't going to open
the second if I didn't have to as they were 5.50 apiece) but maybe
this one is bad. I didn't think I'd have to touch the alignment either
Michael. Just figured that it would work even somewhat.Lenny.

klem kedidelhopper wrote:

On Jun 4, 12:57 pm, "Michael A. Terrell"
wrote:
Jeff Liebermann wrote:

On Fri, 3 Jun 2011 17:39:30 -0700 (PDT), klem kedidelhopper
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.

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

It uses four AF126 transistors in the AM/FM IF Amplifier stages. Sams
shows the collector voltages at 0, because each collector goes to ground
through the primary of each pair of IF transformers. A modern meter
will still show some voltage at the collector, but a VTVM used by Sams
would barely make the needle move. The schematic shows between 4 - 6
ohms to ground from each collector.

Perhaps if you disclosed the correct model number, and possibly which
xsistor you're replacing, we can find a schematic, and determine if
your NTE substitute is appropriate?

He said it was AF126, which does cross to ECG/NTE 160.


A lot of good information guys. I'm sorry I didn't include it in this
new post but the radio model is "Transistor 305".It was given to me
around 1970 and it wasn't new then so I'm guessing a bit here. It is
late 60's vintage I think. And I do have a schematic and foil side
board layout too.I did buy two of these 160's. (I wasn't going to open
the second if I didn't have to as they were 5.50 apiece) but maybe
this one is bad. I didn't think I'd have to touch the alignment either
Michael. Just figured that it would work even somewhat.Lenny.


When it isn't working, check the signal at the collector of each IF
amp with your scope. Any shop scope will display an AM IF. If it
disappears at some stage, find out why. If it is missing at the mixer
output, check continuity on the first IF transformer.


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

A lot of good information guys. I'm sorry I didn't include it in this
new post but the radio model is "Transistor 305".It was given to me
around 1970 and it wasn't new then so I'm guessing a bit here. It is
late 60's vintage I think. And I do have a schematic and foil side
board layout too.I did buy two of these 160's. (I wasn't going to open
the second if I didn't have to as they were 5.50 apiece) but maybe
this one is bad. I didn't think I'd have to touch the alignment either
Michael. Just figured that it would work even somewhat.

As I said, you should have been getting something, even if the IF alignment
wasn't spot-on.

$5.50? Ouch!

Be careful handling the device. Transistors can be damaged by static
electricity. When opening the box, after -- uh -- discharging myself, I'd
dump the transistor onto a piece of aluminum foil, then roll up the
transistor in the foil until I was ready to insert it.

"Michael A. Terrell" wrote in message
...

Jeff Liebermann wrote:

On Fri, 3 Jun 2011 17:39:30 -0700 (PDT), klem kedidelhopper
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.

Ian Field wrote:

"Michael A. Terrell" ? wrote in message
...
?
? Jeff Liebermann wrote:
??
?? On Fri, 3 Jun 2011 17:39:30 -0700 (PDT), klem kedidelhopper
?? ? 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/catal...le/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.

On Jun 4, 2:39*am, klem kedidelhopper
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

On Jun 5, 5:15*am, Bo-Lennart wrote:
On Jun 4, 2:39*am, klem kedidelhopper
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

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
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 -