I have a Heathkit IP-27 bench supply that I got at the dump. Its
problem is that the current limiter doesn't work due to a bad
transistor. Unfortunately, the transistor is a germanium one and
replacements are $30!

I found a forum post where the guy had substituted a silicon transistor
(TIP32C) and he said a germanium diode in the base circuit should also
be replaced with a silicon one. My question is: why does the diode need
to be replaced?

Here is the relevant part of the circuit diagram (transistor Q1 & diode D7):
http://imgur.com/a/43wmd

Thanks,
Bob

If the transistor you need is a DTG600, NTE179 is a substitute and is germanium. I have one in stock if you want it. This is a TO-3 style transistor right?

The posted schematic was a bit fuzy, so if I have the part number wrong, please post the correct one.

Dan

On 1/5/2017 11:14 AM, wrote:
If the transistor you need is a DTG600, NTE179 is a substitute and is germanium. I have one in stock if you want it. This is a TO-3 style transistor right?

The posted schematic was a bit fuzy, so if I have the part number wrong, please post the correct one.


The transistor is a DLG600. I remember seeing that the NTE179 was a
substitute, but the NTE179's that I found were just about as expensive.
Especially compared to the $0.48 for the TIP32C.

Thanks just the same.

Bob

On 1/5/2017 12:07 PM, Bob Engelhardt wrote:
The transistor is a DLG600. ...

Oops - D _T_ G, as you said

"Bob Engelhardt" wrote in message
news
On 1/5/2017 12:07 PM, Bob Engelhardt wrote:
The transistor is a DLG600. ...

Oops - D _T_ G, as you said

TBH: I'd strip out the original current limiter circuit and rebuild with one
from a more modern linear PSU.

Its usual practice to use a separate small signal transistor who's B/E
threshold detects the volt drop across the current sense resistor. Its
collector shunts away base current from the pass transistor. If you go that
far - a Darlington pass transistor has a number of advantages.

The B/E threshold is different between silicon and germanium, so you need to
re calculate the current sense resistors. There's various online archives of
test gear schematics - you can probably find a circuit that you can pretty
much copy.

On 1/5/2017 2:39 PM, Benderthe.evilrobot wrote:
TBH: I'd strip out the original current limiter circuit and rebuild with
one from a more modern linear PSU. ...

Too much. I could even live without the limiter, but for a couple of
cheap parts, I'll fix it. But not anything more.

On Thu, 05 Jan 2017 12:07:25 -0500, Bob Engelhardt
wrote:

On 1/5/2017 11:14 AM, wrote:
If the transistor you need is a DTG600, NTE179 is a substitute and is germanium. I have one in stock if you want it. This is a TO-3 style transistor right?

The posted schematic was a bit fuzy, so if I have the part number wrong, please post the correct one.


The transistor is a DLG600. I remember seeing that the NTE179 was a
substitute, but the NTE179's that I found were just about as expensive.
Especially compared to the $0.48 for the TIP32C.

Try eBay for an NTE179:
http://www.ebay.com/sch/i.html?_nkw=nte179
Yep, expensive.

DLG600 is rated at 90V/25A, while the TIP32C at 100V/3A. That would
seem to be a rather poor choice for a substitute.

If you substitute silicon, you'll need to change some component values
to deal with the Vbe change from 0.3v to 0.6v. Probably doubling the
resistance of the 8.2 ohm sense resistor, and changing D7 from
germanium to silicon. Hopefully, the current ranges will remain the
same. The silicon device will have a better gain-bandwidth product,
so a few ferrite beads to keep the power xsistor from oscillating. If
you choose to use a different package, you'll need to do some creative
mounting and heat sinking. The analog series current limiting
transistor will dissipate considerable heat at high loads.

Sounds like too much work. I'll see if can find one in my junk pile.
I've been hoarding germanium devices for years for use in repairs.

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

On 1/5/2017 1:04 PM, Jeff Liebermann wrote:
....
DLG600 is rated at 90V/25A, while the TIP32C at 100V/3A. That would
seem to be a rather poor choice for a substitute.

What you don't know, cause I didn't say, is that the supply is 50v, 1.5A.


If you substitute silicon, you'll need to change some component values
to deal with the Vbe change from 0.3v to 0.6v. Probably doubling the
resistance of the 8.2 ohm sense resistor, and changing D7 from
germanium to silicon. Hopefully, the current ranges will remain the
same. The silicon device will have a better gain-bandwidth product,
so a few ferrite beads to keep the power xsistor from oscillating. If
you choose to use a different package, you'll need to do some creative
mounting and heat sinking. The analog series current limiting
transistor will dissipate considerable heat at high loads.

There is no calibration in the circuit - the current limit is picked by
rotating a pot until the current is limited where you want it.
Hopefully this will be able to account for the different device. There
was a poster who did this, so I'm probably OK.

I will mount it, isolated, to the steel frame. And at 1.5A that
"should" be enough sinking.

Sounds like too much work. I'll see if can find one in my junk pile.
I've been hoarding germanium devices for years for use in repairs.


My order is in, but thanks anyhow.

Bob

On Thu, 05 Jan 2017 10:04:58 -0800, Jeff Liebermann
wrote:

On Thu, 05 Jan 2017 12:07:25 -0500, Bob Engelhardt
wrote:

On 1/5/2017 11:14 AM, wrote:
If the transistor you need is a DTG600, NTE179 is a substitute and is germanium. I have one in stock if you want it. This is a TO-3 style transistor right?

The posted schematic was a bit fuzy, so if I have the part number wrong, please post the correct one.


The transistor is a DLG600. I remember seeing that the NTE179 was a
substitute, but the NTE179's that I found were just about as expensive.
Especially compared to the $0.48 for the TIP32C.

Try eBay for an NTE179:
http://www.ebay.com/sch/i.html?_nkw=nte179
Yep, expensive.

DLG600 is rated at 90V/25A, while the TIP32C at 100V/3A. That would
seem to be a rather poor choice for a substitute.

If you substitute silicon, you'll need to change some component values
to deal with the Vbe change from 0.3v to 0.6v. Probably doubling the
resistance of the 8.2 ohm sense resistor, and changing D7 from
germanium to silicon. Hopefully, the current ranges will remain the
same. The silicon device will have a better gain-bandwidth product,
so a few ferrite beads to keep the power xsistor from oscillating. If
you choose to use a different package, you'll need to do some creative
mounting and heat sinking. The analog series current limiting
transistor will dissipate considerable heat at high loads.

Sounds like too much work. I'll see if can find one in my junk pile.
I've been hoarding germanium devices for years for use in repairs.

I have not heard about germanium in years. When I played around with old
tube stuff in the 60s - 70s, I remember germanium diodes were fairly
common. I never ran across a germanium transistor.

Reading this thread made me question what germanium really is, and I
read the following article (good article). I know it was used to make
the FIRST semiconductors, I never knew much more about it.
It appears it's a costly elemental material.

Here are a few clips from that article.

[quote]

From:
https://en.wikipedia.org/wiki/Germanium

Germanium "metal" (isolated germanium) is used as a semiconductor in
transistors and various other electronic devices. Historically, the
first decade of semiconductor electronics was based entirely on
germanium. Today, the amount of germanium produced for semiconductor
electronics is one fiftieth the amount of ultra-high purity silicon
produced for the same. Presently, the major end uses are fibre-optic
systems, infrared optics, solar cell applications, and light-emitting
diodes (LEDs). Germanium compounds are also used for polymerization
catalysts and have most recently found use in the production of
nanowires. This element forms a large number of organometallic
compounds, such as tetraethylgermane, useful in organometallic
chemistry.

-
Germanium differs from silicon in that the supply is limited by the
availability of exploitable sources, while the supply of silicon is
limited only by production capacity since silicon comes from ordinary
sand and quartz. While silicon could be bought in 1998 for less than $10
per kg, the price of germanium was almost $800 per kg.

[End Quote]

wrote in message
...
On Thu, 05 Jan 2017 10:04:58 -0800, Jeff Liebermann
wrote:

On Thu, 05 Jan 2017 12:07:25 -0500, Bob Engelhardt
wrote:

On 1/5/2017 11:14 AM, wrote:
If the transistor you need is a DTG600, NTE179 is a substitute and is
germanium. I have one in stock if you want it. This is a TO-3 style
transistor right?

The posted schematic was a bit fuzy, so if I have the part number
wrong, please post the correct one.


The transistor is a DLG600. I remember seeing that the NTE179 was a
substitute, but the NTE179's that I found were just about as expensive.
Especially compared to the $0.48 for the TIP32C.

Try eBay for an NTE179:
http://www.ebay.com/sch/i.html?_nkw=nte179
Yep, expensive.

DLG600 is rated at 90V/25A, while the TIP32C at 100V/3A. That would
seem to be a rather poor choice for a substitute.

If you substitute silicon, you'll need to change some component values
to deal with the Vbe change from 0.3v to 0.6v. Probably doubling the
resistance of the 8.2 ohm sense resistor, and changing D7 from
germanium to silicon. Hopefully, the current ranges will remain the
same. The silicon device will have a better gain-bandwidth product,
so a few ferrite beads to keep the power xsistor from oscillating. If
you choose to use a different package, you'll need to do some creative
mounting and heat sinking. The analog series current limiting
transistor will dissipate considerable heat at high loads.

Sounds like too much work. I'll see if can find one in my junk pile.
I've been hoarding germanium devices for years for use in repairs.

I have not heard about germanium in years. When I played around with old
tube stuff in the 60s - 70s, I remember germanium diodes were fairly
common. I never ran across a germanium transistor.

Reading this thread made me question what germanium really is, and I
read the following article (good article). I know it was used to make
the FIRST semiconductors, I never knew much more about it.
It appears it's a costly elemental material.

Apparently it was refined from flue dust where a specific type of coal was
used.

Not difficult to see how it might be hard to come by nowadays.

On Sun, 29 Jan 2017 15:01:02 -0600, wrote:

I have not heard about germanium in years. When I played around with old
tube stuff in the 60s - 70s, I remember germanium diodes were fairly
common. I never ran across a germanium transistor.

Germanium transistors were very common in the 1960's. For example, I
was selling all germanium Motorola pagers and partly germanium mobile
radios at the time. All of the old vibrator power supply to
transistor conversions used germanium power transistors. Most of the
AM car radios were germanium.

Germanium is not dead today. There are SiGe devices that use the best
properties of both materials to good advantage.
https://en.wikipedia.org/wiki/Silicon-germanium

Germanium is also the preferred material for Infrared lenses.
http://www.iiviinfrared.com/Optical-Materials/ge.html

While silicon could be bought in 1998 for less than $10
per kg, the price of germanium was almost $800 per kg.

Yep. Germanium is expensive. Price at the end of 2015 was $1,760/kg
($800/lb):
https://minerals.usgs.gov/minerals/pubs/commodity/germanium/mcs-2016-germa.pdf

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

On 1/5/2017 10:02 AM, Bob Engelhardt wrote:
I have a Heathkit IP-27 bench supply that I got at the dump. Its
problem is that the current limiter doesn't work due to a bad
transistor. Unfortunately, the transistor is a germanium one and
replacements are $30!

I found a forum post where the guy had substituted a silicon transistor
(TIP32C) and he said a germanium diode in the base circuit should also
be replaced with a silicon one.


My question is: why does the diode need
to be replaced?

Because the current limiting is partially determined by the
relationship between the voltage drops of the diode (0.3V) and the
emitter / base junction of the transistor.
If you change only the transistor to (0.6V) you will probably never
develop enough voltage on the transistor to start it conducting.

Mikek



Here is the relevant part of the circuit diagram (transistor Q1 & diode
D7):
http://imgur.com/a/43wmd

Thanks,
Bob


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On 1/5/2017 11:38 AM, amdx wrote:
....
My question is: why does the diode need
to be replaced?

Because the current limiting is partially determined by the
relationship between the voltage drops of the diode (0.3V) and the
emitter / base junction of the transistor.
If you change only the transistor to (0.6V) you will probably never
develop enough voltage on the transistor to start it conducting.

Mikek

Ah! That makes perfect sense. Thank you.

On 2017/01/05 8:38 AM, amdx wrote:
On 1/5/2017 10:02 AM, Bob Engelhardt wrote:
I have a Heathkit IP-27 bench supply that I got at the dump. Its
problem is that the current limiter doesn't work due to a bad
transistor. Unfortunately, the transistor is a germanium one and
replacements are $30!

I found a forum post where the guy had substituted a silicon transistor
(TIP32C) and he said a germanium diode in the base circuit should also
be replaced with a silicon one.


My question is: why does the diode need
to be replaced?

Because the current limiting is partially determined by the
relationship between the voltage drops of the diode (0.3V) and the
emitter / base junction of the transistor.
If you change only the transistor to (0.6V) you will probably never
develop enough voltage on the transistor to start it conducting.

Mikek


Mikek, would replacing the germanium diode with a silicon one fix the
voltage drop you speak of?

John :-#)#



Here is the relevant part of the circuit diagram (transistor Q1 & diode
D7):
http://imgur.com/a/43wmd

Thanks,
Bob



--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

On 1/5/2017 4:14 PM, John Robertson wrote:
On 2017/01/05 8:38 AM, amdx wrote:
On 1/5/2017 10:02 AM, Bob Engelhardt wrote:
I have a Heathkit IP-27 bench supply that I got at the dump. Its
problem is that the current limiter doesn't work due to a bad
transistor. Unfortunately, the transistor is a germanium one and
replacements are $30!

I found a forum post where the guy had substituted a silicon transistor
(TIP32C) and he said a germanium diode in the base circuit should also
be replaced with a silicon one.


My question is: why does the diode need
to be replaced?

Because the current limiting is partially determined by the
relationship between the voltage drops of the diode (0.3V) and the
emitter / base junction of the transistor.
If you change only the transistor to (0.6V) you will probably never
develop enough voltage on the transistor to start it conducting.

Mikek


Mikek, would replacing the germanium diode with a silicon one fix the
voltage drop you speak of?

John :-#)#


There are twenty regulars here that could give you all the details
with the math, I'm not one of them.
If it were me, I'd change both diode and transistor to silicon and see
how it works. I think it will.
Mikek





Here is the relevant part of the circuit diagram (transistor Q1 & diode
D7):
http://imgur.com/a/43wmd

Thanks,
Bob





---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

"amdx" wrote in message
news
On 1/5/2017 4:14 PM, John Robertson wrote:
On 2017/01/05 8:38 AM, amdx wrote:
On 1/5/2017 10:02 AM, Bob Engelhardt wrote:
I have a Heathkit IP-27 bench supply that I got at the dump. Its
problem is that the current limiter doesn't work due to a bad
transistor. Unfortunately, the transistor is a germanium one and
replacements are $30!

I found a forum post where the guy had substituted a silicon transistor
(TIP32C) and he said a germanium diode in the base circuit should also
be replaced with a silicon one.


My question is: why does the diode need
to be replaced?

Because the current limiting is partially determined by the
relationship between the voltage drops of the diode (0.3V) and the
emitter / base junction of the transistor.
If you change only the transistor to (0.6V) you will probably never
develop enough voltage on the transistor to start it conducting.

Mikek


Mikek, would replacing the germanium diode with a silicon one fix the
voltage drop you speak of?

John :-#)#


There are twenty regulars here that could give you all the details with
the math, I'm not one of them.
If it were me, I'd change both diode and transistor to silicon and see
how it works. I think it will.

It looks like the diode generates a reference voltage - that needs to be
kept in step with the Vbe of the new transistor.

The silicon transistor still needs more Vbe to get it conducting, so I
suspect the sense resistors will also need some adjustment.

In article ,
says...

I have a Heathkit IP-27 bench supply that I got at the dump. Its
problem is that the current limiter doesn't work due to a bad
transistor. Unfortunately, the transistor is a germanium one and
replacements are $30!

I found a forum post where the guy had substituted a silicon transistor
(TIP32C) and he said a germanium diode in the base circuit should also
be replaced with a silicon one. My question is: why does the diode need
to be replaced?

Here is the relevant part of the circuit diagram (transistor Q1 & diode D7):
http://imgur.com/a/43wmd

Thanks,
Bob

Without looking, I would say the diode is a form of temperature
compensation and the material of the 2 devices should be the same.
That would be true if they are mounted on the same heat sink.

"Ralph Mowery" wrote in message
.net...
In article ,
says...

I have a Heathkit IP-27 bench supply that I got at the dump. Its
problem is that the current limiter doesn't work due to a bad
transistor. Unfortunately, the transistor is a germanium one and
replacements are $30!

I found a forum post where the guy had substituted a silicon transistor
(TIP32C) and he said a germanium diode in the base circuit should also
be replaced with a silicon one. My question is: why does the diode need
to be replaced?

Here is the relevant part of the circuit diagram (transistor Q1 & diode
D7):
http://imgur.com/a/43wmd

Thanks,
Bob

Without looking, I would say the diode is a form of temperature
compensation and the material of the 2 devices should be the same.
That would be true if they are mounted on the same heat sink.

It looks like a very simplistic version of the current limiting circuit. The
diode Vf is pretty much a reference voltage generator that the sense
resistor volt drop is compared to - the fact that the diode also provides
dome degree of temp-comp, is probably incidental.

On 1/5/2017 2:44 PM, Benderthe.evilrobot wrote:
...- the fact that the diode also
provides dome degree of temp-comp, is probably incidental.

Yeah - the diode and transistor are very thermally independent.