Germanium transistor sub

  • Thread starter klem kedidelhopper
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klem kedidelhopper

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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" <captainvideo462009@gmail.com> wrote in message
news:d10f76b7-c0f3-4318-9388-4cdf52de224c@v31g2000vbs.googlegroups.com...
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
Click to expand...
AF126 and NTE160, appear to have different pinouts ?

http://english.electronica-pt.com/db/cross-reference.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
<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?
Click to expand...
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.
Click to expand...

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.
 
Inasmuch as the NTE device is spec'd for this sort of application, it seems
very strange you don't get something out of it.

It IS possible you have the leads reversed. I'm sure anyone in this group
will confirm that one can make the same mistake over and over and over and
not catch it. Make sure the E and B leads aren't touching.

The next step is to confirm that the replacement transistor is actually
good, regardless of the ohmeter readings. Check the bias. Are the voltages
correct? Or is the transistor saturated or cut off?

If the bias is correct, put a 'scope and input and output, and see what's
there.

You might also build a simple amplifier using a GE Transistor Handbook
circuit, and see whether or not it works.

Barring some weird mistake on your part, I'm going to go with Sherlock and
state that, as we've eliminated all the impossible stuff, the only thing
logically remaining is that you have a bad transistor.
 
On 6/4/2011 8:49 AM, William Sommerwerck wrote:
Barring some weird mistake on your part, I'm going to go with Sherlock and
state that, as we've eliminated all the impossible stuff, the only thing
logically remaining is that you have a bad transistor.
Click to expand...
Or the obvious, the transistor wasn't at fault to begin with.

Jeff


--
"Everything from Crackers to Coffins"
 
On Jun 4, 5:59 am, "Michael A. Terrell" <mike.terr...@earthlink.net>
wrote:
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.
Click to expand...
Yes I am aware of the reversal of emitter and base leads between the
two types. I was very careful with that. I triple checked the
connections each time I removed the 160 and then re installed it. The
radio does in fact work intermittently as it did before each time the
old transistor is installed back in the radio so at this point I can
still get back to square one, thankfully, (as long as the foil doesn't
start lifting from the phenolic board). The ohmmeter confirms the
original as well as the 160 as being a PNP Ge transistor too.There is
somewhat of a difference in reverse ohmmeter readings between the 160
and the AF126 but I would have suspected that from germaniums,
especially one old one and one new one anyway. Although it really
shouldn't be necessary I did a search for an AF126 but the only thing
that came up were some old spec sheets. I think that this one sadly is
long gone. I did initially try the 160 in the circuit with the metal
can lead disconnected. I didn't think that this would make any
difference because when troubleshooting the chassis originally I was
looking for "whiskers" as suggested to me before as possibly being the
case. So I had lifted all the can shields from all the transistors
and that didn't make any difference. The radio still worked
intermittently. So I did finally solder the can lead on the 160 on but
it still did not work, I don't want to touch the alignment because I'm
just not convinced that this is where the problem is. I know that
NTE's don't always work in the particular application but I wonder if
perhaps this is whats going on here. I just can't help wondering if
I'm missing something else though. If anyone has any further thoughts
on this I would be most sincerely grateful. Lenny
 
Jeffrey Angus wrote:
On 6/4/2011 8:49 AM, William Sommerwerck wrote:

Barring some weird mistake on your part, I'm going to go with Sherlock
and
state that, as we've eliminated all the impossible stuff, the only thing
logically remaining is that you have a bad transistor.


Or the obvious, the transistor wasn't at fault to begin with.

Jeff


Which is where I would start :)
Click to expand...


Jamie
 
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.
Click to expand...
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 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
 
klem kedidelhopper wrote:
On Jun 4, 5:59 am, "Michael A. Terrell" <mike.terr...@earthlink.net
wrote:
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.

Yes I am aware of the reversal of emitter and base leads between the
two types. I was very careful with that. I triple checked the
connections each time I removed the 160 and then re installed it. The
radio does in fact work intermittently as it did before each time the
old transistor is installed back in the radio so at this point I can
still get back to square one, thankfully, (as long as the foil doesn't
start lifting from the phenolic board). The ohmmeter confirms the
original as well as the 160 as being a PNP Ge transistor too.There is
somewhat of a difference in reverse ohmmeter readings between the 160
and the AF126 but I would have suspected that from germaniums,
especially one old one and one new one anyway. Although it really
shouldn't be necessary I did a search for an AF126 but the only thing
that came up were some old spec sheets. I think that this one sadly is
long gone. I did initially try the 160 in the circuit with the metal
can lead disconnected. I didn't think that this would make any
difference because when troubleshooting the chassis originally I was
looking for "whiskers" as suggested to me before as possibly being the
case. So I had lifted all the can shields from all the transistors
and that didn't make any difference. The radio still worked
intermittently. So I did finally solder the can lead on the 160 on but
it still did not work, I don't want to touch the alignment because I'm
just not convinced that this is where the problem is. I know that
NTE's don't always work in the particular application but I wonder if
perhaps this is whats going on here. I just can't help wondering if
I'm missing something else though. If anyone has any further thoughts
on this I would be most sincerely grateful. Lenny
Click to expand...


Once again: Check the Collector voltage. That will show if the
transistor is properly biased, and if it is a good transistor. If it
isn't in the ballpark of a similar radio, look for the cause. Shorted
capacitors in IF cans was a common failure, but well below bad &
intermittent transistors.

I serviced hundreds, if not over a thousand transistor radios in the
'60s & early '70s. I never saw a radio that needed alignment after
replacing a transistor, unless someone had played with it. Some were
poorly aligned from the factory, but those were generally the ones that
sold for less than $20 new.

--
It's easy to think outside the box, when you have a cutting torch.
 
"klem kedidelhopper" <captainvideo462009@gmail.com> wrote in message
news:11632d85-0489-4943-8953-c49e6d28aaba@j28g2000vbp.googlegroups.com...
On Jun 4, 5:59 am, "Michael A. Terrell" <mike.terr...@earthlink.net
wrote:
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.

Yes I am aware of the reversal of emitter and base leads between the
two types. I was very careful with that. I triple checked the
connections each time I removed the 160 and then re installed it. The
radio does in fact work intermittently as it did before each time the
old transistor is installed back in the radio so at this point I can
still get back to square one, thankfully, (as long as the foil doesn't
start lifting from the phenolic board). The ohmmeter confirms the
original as well as the 160 as being a PNP Ge transistor too.There is
somewhat of a difference in reverse ohmmeter readings between the 160
and the AF126 but I would have suspected that from germaniums,
especially one old one and one new one anyway. Although it really
shouldn't be necessary I did a search for an AF126 but the only thing
that came up were some old spec sheets. I think that this one sadly is
long gone. I did initially try the 160 in the circuit with the metal
can lead disconnected. I didn't think that this would make any
difference because when troubleshooting the chassis originally I was
looking for "whiskers" as suggested to me before as possibly being the
case. So I had lifted all the can shields from all the transistors
and that didn't make any difference. The radio still worked
intermittently. So I did finally solder the can lead on the 160 on but
it still did not work, I don't want to touch the alignment because I'm
just not convinced that this is where the problem is. I know that
NTE's don't always work in the particular application but I wonder if
perhaps this is whats going on here. I just can't help wondering if
I'm missing something else though. If anyone has any further thoughts
on this I would be most sincerely grateful. Lenny
Click to expand...
OK. Let's apply a little genuine fault-finding here. When the radio goes
off, does it stay off, or does it come back on as soon as you bring any test
gear near it ? If it stays off, then you need to split the circuit down at
the mixer. When it's working, use a 'scope to check the level of the local
oscillator. Look at its frequency, and watch it move as you tune from the
top to the bottom of the band. When it goes off, recheck. If the LO signal
is still there, and of the same amplitude and frequency as it was before,
then the problem is south of that point in the IF or detector stages. If
anything has changed with the LO signal, then the problem is north of there.
The LO / mixer might well be all the same stage. It was very common to use
self oscillating mixers back in the days of Ge transistors. It was also
common to use a winding on the ferrite rod as part of the L for the
oscillator. Been a long time now, but I seem to recall them being called
Reinartz (sp?) oscillators ?? As a slight aside, when a radio 'dies' like
this, the AM IF stages can often be checked as being basically functional,
with a screwdriver and a finger. Touching the base legs of the IF
transistors will often result in some local AM station being picked up
'thinly'. Again, it's been a long time, but I seem to recall that
intermittent faults like this often came down to those polyester silver foil
and clear plastic cylindrical caps (they used to be made by a company called
Suflex) and intermittent high value resistors. If the radio uses any of that
type of cap in the LO / mixer/ RF stages, then when it goes off, just give
each one that you can get at, a gentle squeeze with a pair of long-nosed
pliers.

Arfa
 
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
Click to expand...
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?
Click to expand...

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, 6:07 am, klem kedidelhopper <captainvideo462...@gmail.com>
wrote:
On Jun 4, 5:59 am, "Michael A. Terrell" <mike.terr...@earthlink.net
wrote:

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.

Yes I am aware of the reversal of emitter and base leads between the
two types. I was very careful with that. I triple checked the
connections each time I removed the 160 and then re installed it.
Click to expand...
I'm having a hard time picturing how one would swap B and C. Is the
substitute mounted high above the board?

To see if the AF160 is good or not, and to make sure the NTE is a
match: could you call a community college or tech hs to see if they
had a curve tracer you could use? Then you could compare to those spec
sheets you downloaded.
 
klem kedidelhopper wrote:
On Jun 4, 12:57 pm, "Michael A. Terrell" <mike.terr...@earthlink.net
wrote:
Jeff Liebermann wrote:

On Fri, 3 Jun 2011 17:39:30 -0700 (PDT), klem kedidelhopper
captainvideo462...@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.

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.
Click to expand...

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.
Click to expand...
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" <mike.terrell@earthlink.net> wrote in message
news:Ts2dnZGS7M-0wnfQnZ2dnUVZ_oydnZ2d@earthlink.com...
klem kedidelhopper wrote:

On Jun 4, 5:59 am, "Michael A. Terrell" <mike.terr...@earthlink.net
wrote:
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.

Yes I am aware of the reversal of emitter and base leads between the
two types. I was very careful with that. I triple checked the
connections each time I removed the 160 and then re installed it. The
radio does in fact work intermittently as it did before each time the
old transistor is installed back in the radio so at this point I can
still get back to square one, thankfully, (as long as the foil doesn't
start lifting from the phenolic board). The ohmmeter confirms the
original as well as the 160 as being a PNP Ge transistor too.There is
somewhat of a difference in reverse ohmmeter readings between the 160
and the AF126 but I would have suspected that from germaniums,
especially one old one and one new one anyway. Although it really
shouldn't be necessary I did a search for an AF126 but the only thing
that came up were some old spec sheets. I think that this one sadly is
long gone. I did initially try the 160 in the circuit with the metal
can lead disconnected. I didn't think that this would make any
difference because when troubleshooting the chassis originally I was
looking for "whiskers" as suggested to me before as possibly being the
case. So I had lifted all the can shields from all the transistors
and that didn't make any difference. The radio still worked
intermittently. So I did finally solder the can lead on the 160 on but
it still did not work, I don't want to touch the alignment because I'm
just not convinced that this is where the problem is. I know that
NTE's don't always work in the particular application but I wonder if
perhaps this is whats going on here. I just can't help wondering if
I'm missing something else though. If anyone has any further thoughts
on this I would be most sincerely grateful. Lenny



Once again: Check the Collector voltage. That will show if the
transistor is properly biased, and if it is a good transistor. If it
isn't in the ballpark of a similar radio, look for the cause. Shorted
capacitors in IF cans was a common failure, but well below bad &
intermittent transistors.

I serviced hundreds, if not over a thousand transistor radios in the
'60s & early '70s. I never saw a radio that needed alignment after
replacing a transistor,
Click to expand...
I've even got away with replacing transistors in UHF tuners most times I
attempted it.
 
"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.
Click to expand...

In contrast, most of their TVs had a service sheet stowed in a slot inside
the cabinet.
 
Ian Field wrote:
"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
news:Ts2dnZGS7M-0wnfQnZ2dnUVZ_oydnZ2d@earthlink.com...

klem kedidelhopper wrote:

On Jun 4, 5:59 am, "Michael A. Terrell" <mike.terr...@earthlink.net
wrote:
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.

Yes I am aware of the reversal of emitter and base leads between the
two types. I was very careful with that. I triple checked the
connections each time I removed the 160 and then re installed it. The
radio does in fact work intermittently as it did before each time the
old transistor is installed back in the radio so at this point I can
still get back to square one, thankfully, (as long as the foil doesn't
start lifting from the phenolic board). The ohmmeter confirms the
original as well as the 160 as being a PNP Ge transistor too.There is
somewhat of a difference in reverse ohmmeter readings between the 160
and the AF126 but I would have suspected that from germaniums,
especially one old one and one new one anyway. Although it really
shouldn't be necessary I did a search for an AF126 but the only thing
that came up were some old spec sheets. I think that this one sadly is
long gone. I did initially try the 160 in the circuit with the metal
can lead disconnected. I didn't think that this would make any
difference because when troubleshooting the chassis originally I was
looking for "whiskers" as suggested to me before as possibly being the
case. So I had lifted all the can shields from all the transistors
and that didn't make any difference. The radio still worked
intermittently. So I did finally solder the can lead on the 160 on but
it still did not work, I don't want to touch the alignment because I'm
just not convinced that this is where the problem is. I know that
NTE's don't always work in the particular application but I wonder if
perhaps this is whats going on here. I just can't help wondering if
I'm missing something else though. If anyone has any further thoughts
on this I would be most sincerely grateful. Lenny



Once again: Check the Collector voltage. That will show if the
transistor is properly biased, and if it is a good transistor. If it
isn't in the ballpark of a similar radio, look for the cause. Shorted
capacitors in IF cans was a common failure, but well below bad &
intermittent transistors.

I serviced hundreds, if not over a thousand transistor radios in the
'60s & early '70s. I never saw a radio that needed alignment after
replacing a transistor,

I've even got away with replacing transistors in UHF tuners most times I
attempted it.
Click to expand...

I did it all the time in CATV converters where the L.O. was at 1.1
GHz. You had to bend the leads exactly like the original.




--
It's easy to think outside the box, when you have a cutting torch.
 
On Jun 4, 12:57 pm, "Michael A. Terrell" <mike.terr...@earthlink.net>
wrote:
Jeff Liebermann wrote:

On Fri, 3 Jun 2011 17:39:30 -0700 (PDT), klem kedidelhopper
captainvideo462...@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.

   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.
Click to expand...
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.
 
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