sci.electronics.repair@googlegroups.com

Today's topics:

* AM/FM radio troubleshooting - 4 messages, 3 authors
http://groups.google.com/group/sci.electronics.repair/t/9e2ca200c549afdd?hl=en
* Randall RG100G3 powerFET amp - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/57d83a13c4840b3c?hl=en
* Recycling electronic waste. - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/da679f4848b11be7?hl=en
* What happened to my hard drive? - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/5638540b7e458b4e?hl=en
* Fixing a bent usb - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/9f38e546d86013dd?hl=en
* Thermal Imaging Camera - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/1041c79652cb2ae5?hl=en

==============================================================================
TOPIC: AM/FM radio troubleshooting
http://groups.google.com/group/sci.electronics.repair/t/9e2ca200c549afdd?hl=en
==============================================================================

== 1 of 4 ==
Date: Sat, May 21 2011 5:01 pm
From: "Phil Allison"

"John-Del"
"Phil Allison"

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

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

** Then you have not seen everything.

Imbecile.

... Phil

== 2 of 4 ==
Date: Sat, May 21 2011 5:58 pm
From: "Michael A. Terrell"

klem kedidelhopper wrote:
>
> On May 21, 10:05 am, "N_Cook" <dive...@tcp.co.uk> wrote:
> > klem kedidelhopper <captainvideo462...@gmail.com> wrote in message
> >
> > news:d384fa64-4fcf-42c3-b061-1c0a786f3c15@p23g2000vbl.googlegroups.com...
> >
> >
> >
> > > I have a Grundig "Transistor 305" portable radio. It uses germanium
> > > transistors. I've had this thing for over forty years and although I
> > > don't use it often it has been a nice radio. In 1971 I replaced the
> > > transistor in the FM detector circuit and I have had no problems with
> > > it until just recently. Last month I spent three days in the hospital
> > > and I brought the Grundig with me. I noticed that after it was on for
> > > about a half hour it would start to cut out. I turned it off and then
> > > later turned it on again, and after a period of time it happened
> > > again. After several similar episodes I stopped using it. I wondered
> > > about some type of interference from the hospital but that was wishful
> > > thinking. In any case being in no position to test it I decided to
> > > just put it away. Yesterday I put it on the bench and took a look at
> > > it. Sure enough after a brief time it cut out again. I injected a
> > > signal, (my finger on a small screwdriver) onto the wiper of the
> > > volume control and ascertained that there is nothing wrong up to the
> > > speaker. So now I need to get into the IF's and detector. My problem
> > > is my old signal generators are not working and all I can come up with
> > > for 10.7MHZ. is a CW signal out of my MFJ249 SWR meter. The MFJ puts
> > > out a clean signal however it is CW, and it's amplitude is not
> > > adjustable. I don't think that an unmodulated signal would be a
> > > problem in this application but I don't know what the amplitude of the
> > > MFJ is and I would hate to blow up an otherwise good IF amplifier with
> > > an excessive signal. I''m admittedly a bit rusty having not trouble
> > > shot an IF amplifier/detector circuit in many years so does anyone
> > > have a feel for how I might signal trace this radio with what I have
> > > on hand? Thanks very much for any advice. Lenny
> >
> > Any 4 pin Ge transistors in there? if there is then the usual simple fudge
> > is worth a try
>
> Well the AM is not working either when this set fails. And since the
> set uses the same transistors but different coils for each stage that
> doesn't really help me to track this down. I could look at the CW
> signal from the 249 with my 50MHZ. scope or my spectrum analyzer but I
> still don't know what a safe signal amplitude would be. Does anyone
> know what the proper typical amplitude of an IF signal would be so
> that I would be able to simulate this and inject this signal into the
> IF amplifiers and detector stage? BTW except for the outputs, they're
> all 4 pin GE transistors. What do you mean by the "simple fudge"?
> Thanks, Lenny

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

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

== 3 of 4 ==
Date: Sat, May 21 2011 8:52 pm
From: klem kedidelhopper

On May 21, 8:58 pm, "Michael A. Terrell" <mike.terr...@earthlink.net>
wrote:
> klem kedidelhopper wrote:
>
> > On May 21, 10:05 am, "N_Cook" <dive...@tcp.co.uk> wrote:
> > > klem kedidelhopper <captainvideo462...@gmail.com> wrote in message
>
> > >news:d384fa64-4fcf-42c3-b061-1c0a786f3c15@p23g2000vbl.googlegroups.com...
>
> > > > I have a Grundig "Transistor 305" portable radio. It uses germanium
> > > > transistors. I've had this thing for over forty years and although I
> > > > don't use it often it has been a nice radio. In 1971 I replaced the
> > > > transistor in the FM detector circuit and I have had no problems with
> > > > it until just recently.  Last month I spent three days in the hospital
> > > > and I brought the Grundig with me. I noticed that after it was on for
> > > > about a half hour it would start to cut out. I turned it off and then
> > > > later turned it on again, and after a period of time it happened
> > > > again. After several similar episodes I stopped using it. I wondered
> > > > about some type of interference from the hospital but that was wishful
> > > > thinking. In any case being in no position to test it I decided to
> > > > just put it away. Yesterday I put it on the bench and took a look at
> > > > it. Sure enough after a brief time it cut out again. I injected a
> > > > signal, (my finger on a small screwdriver) onto the wiper of the
> > > > volume control and ascertained that there is nothing wrong up to the
> > > > speaker. So now I need to get into the IF's and detector. My problem
> > > > is my old signal generators are not working and all I can come up with
> > > > for 10.7MHZ. is a CW signal out of my MFJ249 SWR meter. The MFJ puts
> > > > out a clean signal however it is CW, and it's amplitude is not
> > > > adjustable. I don't think that an unmodulated signal would be a
> > > > problem in this application but I don't know what the amplitude of the
> > > > MFJ is and I would hate to blow up an otherwise good IF amplifier with
> > > > an excessive signal. I''m admittedly a bit rusty having not trouble
> > > > shot an IF amplifier/detector circuit in many years so does anyone
> > > > have a feel for how I might signal trace this radio with what I have
> > > > on hand?  Thanks very much for any advice. Lenny
>
> > > Any 4 pin Ge transistors in there? if there is then the usual simple fudge
> > > is worth a try
>
> > Well the AM is not working either when this set fails. And since the
> > set uses the same transistors but different coils for each stage that
> > doesn't really help me to track this down. I could look at the CW
> > signal from the 249 with my 50MHZ. scope or my spectrum analyzer but I
> > still don't know what a safe signal amplitude would be. Does anyone
> > know what the proper typical amplitude of an IF signal would be so
> > that I would be able to simulate this and inject this signal into the
> > IF amplifiers and detector stage? BTW except for the outputs, they're
> > all 4 pin GE transistors. What do you mean by the "simple fudge"?
> > Thanks, Lenny
>
>   Check the collector voltages on the IF and mixer stage.  Use at least
> a 1 meg resistor between the probe and the transistor to keep from
> disturbing the circuit.  I saw a lot of this in old germanium transistor
> car radios.  Noise induced into the circuit would momentarily restore
> the transistor enough to work for a while, but of there was zero
> collector voltage, one of the IF transformers was open.  If it was high,
> the transistor was bad.  I troubleshot those radios and repaired most of
> them in under five minutes with that simple method. :)
>
> --
> It's easy to think outside the box, when you have a cutting torch.

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

== 4 of 4 ==
Date: Sat, May 21 2011 9:38 pm
From: "Michael A. Terrell"

klem kedidelhopper wrote:
>
> On May 21, 8:58 pm, "Michael A. Terrell" <mike.terr...@earthlink.net>
> wrote:
> > klem kedidelhopper wrote:
> >
> > > On May 21, 10:05 am, "N_Cook" <dive...@tcp.co.uk> wrote:
> > > > klem kedidelhopper <captainvideo462...@gmail.com> wrote in message
> >
> > > >news:d384fa64-4fcf-42c3-b061-1c0a786f3c15@p23g2000vbl.googlegroups.com...
> >
> > > > > I have a Grundig "Transistor 305" portable radio. It uses germanium
> > > > > transistors. I've had this thing for over forty years and although I
> > > > > don't use it often it has been a nice radio. In 1971 I replaced the
> > > > > transistor in the FM detector circuit and I have had no problems with
> > > > > it until just recently. Last month I spent three days in the hospital
> > > > > and I brought the Grundig with me. I noticed that after it was on for
> > > > > about a half hour it would start to cut out. I turned it off and then
> > > > > later turned it on again, and after a period of time it happened
> > > > > again. After several similar episodes I stopped using it. I wondered
> > > > > about some type of interference from the hospital but that was wishful
> > > > > thinking. In any case being in no position to test it I decided to
> > > > > just put it away. Yesterday I put it on the bench and took a look at
> > > > > it. Sure enough after a brief time it cut out again. I injected a
> > > > > signal, (my finger on a small screwdriver) onto the wiper of the
> > > > > volume control and ascertained that there is nothing wrong up to the
> > > > > speaker. So now I need to get into the IF's and detector. My problem
> > > > > is my old signal generators are not working and all I can come up with
> > > > > for 10.7MHZ. is a CW signal out of my MFJ249 SWR meter. The MFJ puts
> > > > > out a clean signal however it is CW, and it's amplitude is not
> > > > > adjustable. I don't think that an unmodulated signal would be a
> > > > > problem in this application but I don't know what the amplitude of the
> > > > > MFJ is and I would hate to blow up an otherwise good IF amplifier with
> > > > > an excessive signal. I''m admittedly a bit rusty having not trouble
> > > > > shot an IF amplifier/detector circuit in many years so does anyone
> > > > > have a feel for how I might signal trace this radio with what I have
> > > > > on hand? Thanks very much for any advice. Lenny
> >
> > > > Any 4 pin Ge transistors in there? if there is then the usual simple fudge
> > > > is worth a try
> >
> > > Well the AM is not working either when this set fails. And since the
> > > set uses the same transistors but different coils for each stage that
> > > doesn't really help me to track this down. I could look at the CW
> > > signal from the 249 with my 50MHZ. scope or my spectrum analyzer but I
> > > still don't know what a safe signal amplitude would be. Does anyone
> > > know what the proper typical amplitude of an IF signal would be so
> > > that I would be able to simulate this and inject this signal into the
> > > IF amplifiers and detector stage? BTW except for the outputs, they're
> > > all 4 pin GE transistors. What do you mean by the "simple fudge"?
> > > Thanks, Lenny
> >
> > Check the collector voltages on the IF and mixer stage. Use at least
> > a 1 meg resistor between the probe and the transistor to keep from
> > disturbing the circuit. I saw a lot of this in old germanium transistor
> > car radios. Noise induced into the circuit would momentarily restore
> > the transistor enough to work for a while, but of there was zero
> > collector voltage, one of the IF transformers was open. If it was high,
> > the transistor was bad. I troubleshot those radios and repaired most of
> > them in under five minutes with that simple method. :)
>
> The IF's are AF124,and 126. And to answer a previous question I did
> use cold spray on everything but the detector, which is inside a can.

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

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

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

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

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

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

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

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

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

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

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

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

==============================================================================
TOPIC: Randall RG100G3 powerFET amp
http://groups.google.com/group/sci.electronics.repair/t/57d83a13c4840b3c?hl=en
==============================================================================

== 1 of 1 ==
Date: Sat, May 21 2011 5:08 pm
From: "Phil Allison"

"Nutcase Kook"
>
> Off centre hole is 0.3mm displaced vertically. No first rank manufacturer
> would have that amount of engineering departure from the industry TOP3
> dimensions
>

** Think you at clutching at straws instead of getting the amp fixed.

That FET has been working fine in the amp for many years - so it is not
likely to be a fake or dud.

..... Phil

==============================================================================
TOPIC: Recycling electronic waste.
http://groups.google.com/group/sci.electronics.repair/t/da679f4848b11be7?hl=en
==============================================================================

== 1 of 1 ==
Date: Sat, May 21 2011 5:43 pm
From: "Michael A. Terrell"

Ian Field wrote:
>
> "Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
> news:_7ydnWbbjM-APUjQnZ2dnUVZ_sGdnZ2d@earthlink.com...
> >
> > Ian Field wrote:
> >>
> >> "Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
> >> news:bKWdnfIcsI7U8UjQnZ2dnUVZ_smdnZ2d@earthlink.com...
> >> >
> >> > Ian Field wrote:
> >> >>
> >> >> "b" <reverend_rogers@yahoo.com> wrote in message
> >> >> news:058eb586-4a80-4d09-a7dc-3d5213dc7010@x3g2000yqj.googlegroups.com...
> >> >> On May 17, 10:28 pm, "Ian Field" <gangprobing.al...@ntlworld.com>
> >> >> wrote:
> >> >> > Taking your e-waste to the council tip doesn't allways mean it will
> >> >> > be
> >> >> > recycled in a lawful manner!
> >> >> >
> >> >> > http://www.bbc.co.uk/iplayer/episode/b0116gw0/Panorama_Track_My_Trash/
> >> >>
> >> >> this video by artist chris jordan has some extremely disturbing points
> >> >> on the shameful wastefulness of the so-called developed world:
> >> >>
> >> >> What I'd like to know is how to make some of the scrap PCs come my
> >> >> way.
> >> >>
> >> >> Firstly I could probably find something better than I've got.
> >> >>
> >> >> Secondly I could aquire more HDDs to store all the stuff I download.
> >> >>
> >> >> Thirdly I could make some cash refurbishing and selling any surplus.
> >> >
> >> >
> >> > Tell people you know that you'll take their old computers and wipe
> >> > any personal information from the hard drives. Then ask them to tell
> >> > others about you. Be careful, or you'll get so many you won't have
> >> > room for them.
> >>
> >> Most of the people I know want money for their old computer.
> >
> >
> > I know people like that, too, but I know about 25X as many who just
> > want them out of their way.
> >
> >
> >> Recently I found a Next brand all in one flat screen jobbie in the
> >> bin room, it was all on a single PCB with row upon row of burst
> >> electrolytics - but I scored a 250Gb laptop style HDD and a couple
> >> of 1Gb PC2 sticks, didn't have anything I could test the Celeron
> >> CPU in though.
> >
> >
> > I picked up a working Dell Insperion 531S w/512 MB of RAM and two
> > good LCD monitors for free a fewweeks ago. Not only were they given to
> > me, but the woman insisted on loading them in my truck for me. So far,
> > she's given me about 20 computers and 30 monitors. :)
>
> Scored a hit on freecycle today.

I picked up 7 19" gateway LCD monitors on Craig's list that only
needed a few electrolytics in the power supplies. One had a damaged
panel, and another had a damaged case, so that left six repairable 19"
monitors. :)

> Someone emailed with "a few" computers - some working, some not. Turned out
> to be a garage full.
>
> Its times like this not having a car is a PITA, I turned up on the
> motorcycle expecting to make a few trips, anyway with a bit of negotiation
> he started loading his car - and somewhat more enthusiastically when I
> offered to take all he wanted rid of, and not just pick the best bits and
> leave him with the rubbish.

I got a phone call a couple days ago from a local thrift store that
said they have a truckload of 'computer stuff' for me to pick up early
Monday morning. They had called one of my usually pickup sites to see
who took their 'computer stuff'. Now, I need to unload the truck from
two stops on Friday. I've started doing 'triage' on the tailgate to
separate the obvious junk from the items that may work, or be worth
fixing. If something is too old to fool with, or missing too many parts
I grab a cordless drill and dismantle it outside. Then I use a
paintbrush or portable air compressor to remove most of the dust
bunnies. If something is covered in Nicotine or may have bugs, it goes
in the garage instead of the shop.

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

==============================================================================
TOPIC: What happened to my hard drive?
http://groups.google.com/group/sci.electronics.repair/t/5638540b7e458b4e?hl=en
==============================================================================

== 1 of 1 ==
Date: Sat, May 21 2011 5:52 pm
From: "Michael A. Terrell"

mike wrote:
>
> On May 20, 1:17 pm, "Michael A. Terrell" <mike.terr...@earthlink.net>
> wrote:
> > Shaun wrote:
> >
> > > It's a 40 Gb drive, very old technology. Just throw it out
> > > and buy a new drive. You'll probably get a 500 Gb for $30
> > > some dollars.
> > >
> > That kind of defeats the reason for having a REPAIR newsgroup.
> >
> Just a follow-up on the drive - whatever happened to it, neither the
> electronics nor the recording-media part of it work any more. After
> careful inspection, there are no problems with bent pins, or other
> physical problems apparent. I suppose I might have an intermittent
> IDE cable which only acted up maybe a couple of times during the
> dozens of cyclings of various programs and test runs, but the cables
> on there are the kink with an extra gizmo to pull the cable lose from
> the plug without stressing the cable-to-plug connection. Anyway,
> thanks to all for the suggestions, I was successful at least in
> learning a bit more about how hard drives work.

You may have some cracked solder joints on the controller board on
the drive, or other problems. Some repairs are beyond the average tech,
because they don't have the right tools available. You need good
magnification and a steady hand to resolder some ultra fine pitch ICs,
and most people can't do it even with the right tools. I keep dead
drives on hand to swap boards and sometimes repair a controller board,
but I worked in electronics manufacturing where it was part of my job to
do that level of work. Just keep studying electronics and you may be
surprised at what you can learn. :)

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

==============================================================================
TOPIC: Fixing a bent usb
http://groups.google.com/group/sci.electronics.repair/t/9f38e546d86013dd?hl=en
==============================================================================

== 1 of 1 ==
Date: Sat, May 21 2011 7:59 pm
From: vjp2.at@at.BioStrategist.dot.dot.com

Too many times I've thrown out a bent USB..
what if I really needed it? how likely would I be to repair it?
Any kits?

Usually happens with memory, but I just dropped and messed up a modem

- = -
Vasos Panagiotopoulos, Columbia'81+, Reagan, Mozart, Pindus, BioStrategist
http://www.panix.com/~vjp2/vasos.htm
---{Nothing herein constitutes advice. Everything fully disclaimed.}---
[Homeland Security means private firearms not lazy obstructive guards]
[Urb sprawl confounds terror] [Phooey on GUI: Windows for subprime Bimbos]

==============================================================================
TOPIC: Thermal Imaging Camera
http://groups.google.com/group/sci.electronics.repair/t/1041c79652cb2ae5?hl=en
==============================================================================

== 1 of 1 ==
Date: Sat, May 21 2011 11:15 pm
From: vjp2.at@at.BioStrategist.dot.dot.com

Very cool for leak detection and finding gaps in insulation
but way overpriced.. the bulk of the value is in the software.

Ditto doppler flow meters - same hardware as a sonic studfinder, the work is
in the software..

- = -
Vasos Panagiotopoulos, Columbia'81+, Reagan, Mozart, Pindus, BioStrategist
http://www.panix.com/~vjp2/vasos.htm
---{Nothing herein constitutes advice. Everything fully disclaimed.}---
[Homeland Security means private firearms not lazy obstructive guards]
[Urb sprawl confounds terror] [Phooey on GUI: Windows for subprime Bimbos]

==============================================================================

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