Delco DS-501 problem

[Gary Tayman]

If any of you have ever messed with car radios, you'll know that Delco
radios used a DS-501 power transistor for nearly every radio, from the first
hybrids right on up into the 1970's. These germanium transistor didn't fail
often, which i probably why replacements are scarce today. In fact the
books I have show replacements as either an SK-3012 or a GE-4. ECG doesn't
have a cross-reference. These things can be expensive, if you can find them
at all.

So -- right now I have a Corvette radio with no sound, and what appears to
be a DS-501 that's bad. Now -- I happen to have a cigar box full of new
power transistors that are that distinctive size and shape of the DS-501.
However I can't seem to determine what they are to see if they
cross-reference. Some of them are gold colored and have "108 6507" on them,
others are silver and say "466 108 6621", and still others are gold and say
"049 6222." Can anyone identify these transistors and tell me if they would
make a compatible substitute for a DS-501?

Of course if they can't be identified, I may try and stick one in just to
see what happens . .. .

[Steven Dinius_]

Gary, you are a service person. Delco/Delphi will send you info a lot easier
than it was when I needed books on the AM stereo equipped 2000 series models
I have...? Go through the parts site at GM or ask a dealer for leads...worth
a shot though maybe you did that already?

Post by Gary Tayman
If any of you have ever messed with car radios, you'll know that Delco
radios used a DS-501 power transistor for nearly every radio, from the first
hybrids right on up into the 1970's. These germanium transistor didn't fail
often, which i probably why replacements are scarce today. In fact the
books I have show replacements as either an SK-3012 or a GE-4. ECG doesn't
have a cross-reference. These things can be expensive, if you can find them
at all.
So -- right now I have a Corvette radio with no sound, and what appears to
be a DS-501 that's bad. Now -- I happen to have a cigar box full of new
power transistors that are that distinctive size and shape of the DS-501.
However I can't seem to determine what they are to see if they
cross-reference. Some of them are gold colored and have "108 6507" on them,
others are silver and say "466 108 6621", and still others are gold and say
"049 6222." Can anyone identify these transistors and tell me if they would
make a compatible substitute for a DS-501?
Of course if they can't be identified, I may try and stick one in just to
see what happens . .. .
--
Gary E. Tayman/Tayman Electrical
Sound Solutions For Classic Cars
http://www.taymanelectrical.com

[Michael A. Terrell]

Post by Steven Dinius_
Gary, you are a service person. Delco/Delphi will send you info a lot easier
than it was when I needed books on the AM stereo equipped 2000 series models
I have...? Go through the parts site at GM or ask a dealer for leads...worth
a shot though maybe you did that already?

No, they won't. The part has been obsolete for almost 30 year, and
Delco is useless when it comes to supplying information on parts that
old. The only way you would get it was if you could find one of the
engineers from the old Kokomo, Indiana plant. I used to see them every
year at the Dayton hamfest, but the last time I was there was 1987. I
used to attend the annual Delco Electronics service school back in the
70s, as well.

[Steven Dinius_]

Post by Michael A. Terrell

Post by Steven Dinius_
Gary, you are a service person. Delco/Delphi will send you info a lot easier
than it was when I needed books on the AM stereo equipped 2000 series models
I have...? Go through the parts site at GM or ask a dealer for leads...worth
a shot though maybe you did that already?

No, they won't. The part has been obsolete for almost 30 year, and
Delco is useless when it comes to supplying information on parts that
old. The only way you would get it was if you could find one of the
engineers from the old Kokomo, Indiana plant. I used to see them every
year at the Dayton hamfest, but the last time I was there was 1987. I
used to attend the annual Delco Electronics service school back in the
70s, as well.
--
?
Michael A. Terrell
Central Florida

Thank you, I stand happily informed.

[Michael A. Terrell]

Post by Gary Tayman
If any of you have ever messed with car radios, you'll know that Delco
radios used a DS-501 power transistor for nearly every radio, from the first
hybrids right on up into the 1970's. These germanium transistor didn't fail
often, which i probably why replacements are scarce today. In fact the
books I have show replacements as either an SK-3012 or a GE-4. ECG doesn't
have a cross-reference. These things can be expensive, if you can find them
at all.
So -- right now I have a Corvette radio with no sound, and what appears to
be a DS-501 that's bad. Now -- I happen to have a cigar box full of new
power transistors that are that distinctive size and shape of the DS-501.
However I can't seem to determine what they are to see if they
cross-reference. Some of them are gold colored and have "108 6507" on them,
others are silver and say "466 108 6621", and still others are gold and say
"049 6222." Can anyone identify these transistors and tell me if they would
make a compatible substitute for a DS-501?
Of course if they can't be identified, I may try and stick one in just to
see what happens . .. .
--
Gary E. Tayman/Tayman Electrical
Sound Solutions For Classic Cars
http://www.taymanelectrical.com

Industry Number : DS501
NTE Device Number: NTE105
T-PNP, GERMANIUM AUDIO PO,TO-36

I think that I still have a couple new ECG-105 transistors.


The transistors numbers you listed sound like old Burroughs part numbers
from some of their early '70s mini computers.

BTW, the JEDEC number for the DS501 was 2N441

[Gary Tayman]

Although I appreciate all the replies, it seems everyone has it backwards.
I know what a DS-501 is, what I don't know is what those other types are and
if they would make a suitable replacement.

I don't like the idea of putting in used transistors, especially germanium,
but at this point that may be the case. I get umpteen Delco radios for
conversion and the old DS-501's get tossed. I think I got another one
today; I'll have to pull it and try it in this set. However I'd still like
to know if my cigar box full of new 108's will work. BTW, there is a 108
that will substitute for some silicon type, but I don't believe this is
correct. The similar types with the 049 number shows the replacement being
a zener diode!
--
Gary E. Tayman/Tayman Electrical
Sound Solutions For Classic Cars
http://www.taymanelectrical.com

Post by Michael A. Terrell

Post by Gary Tayman
If any of you have ever messed with car radios, you'll know that Delco
radios used a DS-501 power transistor for nearly every radio, from the first
hybrids right on up into the 1970's. These germanium transistor didn't fail
often, which i probably why replacements are scarce today. In fact the
books I have show replacements as either an SK-3012 or a GE-4. ECG doesn't
have a cross-reference. These things can be expensive, if you can find them
at all.
So -- right now I have a Corvette radio with no sound, and what appears to
be a DS-501 that's bad. Now -- I happen to have a cigar box full of new
power transistors that are that distinctive size and shape of the DS-501.
However I can't seem to determine what they are to see if they
cross-reference. Some of them are gold colored and have "108 6507" on them,
others are silver and say "466 108 6621", and still others are gold and say
"049 6222." Can anyone identify these transistors and tell me if they would
make a compatible substitute for a DS-501?
Of course if they can't be identified, I may try and stick one in just to
see what happens . .. .
--
Gary E. Tayman/Tayman Electrical
Sound Solutions For Classic Cars
http://www.taymanelectrical.com

Industry Number : DS501
NTE Device Number: NTE105
T-PNP, GERMANIUM AUDIO PO,TO-36
I think that I still have a couple new ECG-105 transistors.
The transistors numbers you listed sound like old Burroughs part numbers
from some of their early '70s mini computers.
BTW, the JEDEC number for the DS501 was 2N441
--
?
Michael A. Terrell
Central Florida

[John Byrns]

Post by Gary Tayman
If any of you have ever messed with car radios, you'll know that Delco
radios used a DS-501 power transistor for nearly every radio, from the first
hybrids right on up into the 1970's. These germanium transistor didn't fail
often, which i probably why replacements are scarce today.

"Didn't fail often"!? I bought a new car in the fall of 1967 which had
one of those in the radio and it died within two weeks, the only
transistor failure I have ever experienced in a car radio I owned. The
dealer wanted the radio for several weeks to fix it, the replacement I
installed lasted as long as I had the car.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/

[Mark Oppat]

Gary,
I have several of these type output xsistors too. One is labelled 501 I
think if you still need some.
Mark Oppat

Post by Gary Tayman
If any of you have ever messed with car radios, you'll know that Delco
radios used a DS-501 power transistor for nearly every radio, from the first
hybrids right on up into the 1970's. These germanium transistor didn't fail
often, which i probably why replacements are scarce today. In fact the
books I have show replacements as either an SK-3012 or a GE-4. ECG doesn't
have a cross-reference. These things can be expensive, if you can find them
at all.
So -- right now I have a Corvette radio with no sound, and what appears to
be a DS-501 that's bad. Now -- I happen to have a cigar box full of new
power transistors that are that distinctive size and shape of the DS-501.
However I can't seem to determine what they are to see if they
cross-reference. Some of them are gold colored and have "108 6507" on them,
others are silver and say "466 108 6621", and still others are gold and say
"049 6222." Can anyone identify these transistors and tell me if they would
make a compatible substitute for a DS-501?
Of course if they can't be identified, I may try and stick one in just to
see what happens . .. .
--
Gary E. Tayman/Tayman Electrical
Sound Solutions For Classic Cars
http://www.taymanelectrical.com

[Gary Tayman]

Mark,

I might take you up on that offer, however I'm still trying to figure out
what I've got here.

It seems a few years ago I needed one, and was able to cross-reference some
of the transistors in this box as being a suitable replacement. But that
was well, years ago.

I gave you the short story, now here's the long story:

Yesterday I had somebody drive down here from Ocala with a Corvette radio,
asking if I could fix it. With him looking over my shoulder, I put it on
the bench and got perfect audio right up to the base of the DS-501. I got
around 12 volts at the base, a 0.2 drop at the emitter, and zero at the
collector (normal would be 1.5v). As for other components that are related,
there is a bias adjustment in the emitter circuit (verified the rheostat is
fine), an electrolytic which is one third of an FP can -- which somebody
substituted with a new one but left the other two FP's intact, and a
three-legged cap that goes to emitter-base-ground. With the caps removed
and the bias adjusted anywhere, I get the same thing.

I pulled the transistor and tested it. Now -- is it just me, or does anyone
else have problems checking germaniums? Silicon I can tell right away, but
germaniums are screwy. I tried a digital meter, the numbers just flopped
around in meaningless fashion. I tried it on a VTVM, and it appears to be
shorted emitter to collector both ways (but wouldn't I get 12 volts at the
speaker?). I checked it with a VOM, and it showed OPEN collector!

So, with the fellow still at my shoulder, I went through my books to
cross-reference the DS-501. The GE book shows GE-4, the SK book shows
SK-3012, and the EGC book didn't show anything. I've got an ECG software on
the computer which doesn't recognize the number. I'll admit I didn't check
for NTE, but I was using older manuals because they would be more prone to
show this obsolete type.

At this point I was not interested in trying to mail-order a replacement,
but to check my cigar box of power transistors to see which of those
"buttons" will also cross reference to a GE-4 or SK-3012, remembering I had
been successful before. One type cross-references to a silicon (I didn't
check to see if it's round or some other configuration to verify if I'm on
the right track); the other crosses to a zener, which is obviously
erroneous. That's as far as I was able to get.

I did find, in the box, another DS-501, but it's used. Still it's worth a
try. I checked it with the meters, they show the exact same thing. I put
it in the radio, I get the exact same result. So, do I suspect two bad
transistors with the exact same problem or could it be something else in the
circuit even though it all appears good? Testing, or subbing, an "unknown"
at this point would be useless, but if I determined that they are indeed
similar I could try this. The solution? I just received a Delco radio for
conversion -- when I remove the DS-501 I'll try it in this radio.
--
Gary E. Tayman/Tayman Electrical
Sound Solutions For Classic Cars
http://www.taymanelectrical.com

Post by Mark Oppat
Gary,
I have several of these type output xsistors too. One is labelled 501 I
think if you still need some.
Mark Oppat

Post by Gary Tayman
If any of you have ever messed with car radios, you'll know that Delco
radios used a DS-501 power transistor for nearly every radio, from the

first

Post by Gary Tayman
hybrids right on up into the 1970's. These germanium transistor didn't

fail

Post by Gary Tayman
often, which i probably why replacements are scarce today. In fact the
books I have show replacements as either an SK-3012 or a GE-4. ECG

doesn't

Post by Gary Tayman
have a cross-reference. These things can be expensive, if you can find

them

Post by Gary Tayman
at all.
So -- right now I have a Corvette radio with no sound, and what appears to
be a DS-501 that's bad. Now -- I happen to have a cigar box full of new
power transistors that are that distinctive size and shape of the DS-501.
However I can't seem to determine what they are to see if they
cross-reference. Some of them are gold colored and have "108 6507" on

them,

Post by Gary Tayman
others are silver and say "466 108 6621", and still others are gold and

say

Post by Gary Tayman
"049 6222." Can anyone identify these transistors and tell me if they

would

Post by Gary Tayman
make a compatible substitute for a DS-501?
Of course if they can't be identified, I may try and stick one in just to
see what happens . .. .
--
Gary E. Tayman/Tayman Electrical
Sound Solutions For Classic Cars
http://www.taymanelectrical.com

[John Byrns]

Post by Gary Tayman
Mark,
I might take you up on that offer, however I'm still trying to figure out
what I've got here.
It seems a few years ago I needed one, and was able to cross-reference some
of the transistors in this box as being a suitable replacement. But that
was well, years ago.
Yesterday I had somebody drive down here from Ocala with a Corvette radio,
asking if I could fix it. With him looking over my shoulder, I put it on
the bench and got perfect audio right up to the base of the DS-501. I got
around 12 volts at the base, a 0.2 drop at the emitter, and zero at the
collector (normal would be 1.5v).

Could it be a bad insulator causing a collector to ground short? A short
in the output trnasformer might also cause this.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/

[Brenda Ann]

Post by John Byrns

Post by Gary Tayman
Mark,
I might take you up on that offer, however I'm still trying to figure out
what I've got here.
It seems a few years ago I needed one, and was able to cross-reference some
of the transistors in this box as being a suitable replacement. But that
was well, years ago.
Yesterday I had somebody drive down here from Ocala with a Corvette radio,
asking if I could fix it. With him looking over my shoulder, I put it on
the bench and got perfect audio right up to the base of the DS-501. I got
around 12 volts at the base, a 0.2 drop at the emitter, and zero at the
collector (normal would be 1.5v).

Could it be a bad insulator causing a collector to ground short? A short
in the output trnasformer might also cause this.

PNP transistor.. base should be negative in relation to the emitter. Perhaps
a high C-E leakage?

[Michael A. Terrell]

Post by Brenda Ann
PNP transistor.. base should be negative in relation to the emitter. Perhaps
a high C-E leakage?

The DS501 was a very leaky Germanium transistor and prone to thermal
runaway. When they went bake the took out the emitter fuse resistor.
I've replaced hundreds of both.

[Jim Mueller]

Post by Gary Tayman
If any of you have ever messed with car radios, you'll know that Delco
radios used a DS-501 power transistor for nearly every radio, from the first
hybrids right on up into the 1970's. These germanium transistor didn't fail
often, which i probably why replacements are scarce today. In fact the
books I have show replacements as either an SK-3012 or a GE-4. ECG doesn't
have a cross-reference. These things can be expensive, if you can find them
at all.
So -- right now I have a Corvette radio with no sound, and what appears to
be a DS-501 that's bad. Now -- I happen to have a cigar box full of new
power transistors that are that distinctive size and shape of the DS-501.
However I can't seem to determine what they are to see if they
cross-reference. Some of them are gold colored and have "108 6507" on them,
others are silver and say "466 108 6621", and still others are gold and say
"049 6222." Can anyone identify these transistors and tell me if they would
make a compatible substitute for a DS-501?
Of course if they can't be identified, I may try and stick one in just to
see what happens . .. .

Gary,

Those sound like somebody's in-house part numbers. You may never find out
what they "really" are. That doesn't mean you can't use them.

The first thing to do is find out if they are NPN or PNP. Your multimeter
can take care of that. Then you need to know if they are silicon or
germanium. Your multimeter will tell you that, too. If you have an
analog meter, measure the forward "resistance" of one of the junctions
(B-E or B-C always use the same one for consistency although it probably
won't matter) on power transistors that you know are germanium and
silicon. Note what the "resistance" of each kind is. Then test your
unknowns. It should be pretty obvious which they are. If you use a
digital meter, use the diode test range. A germanium transistor will test
around 0.2 to 0.3 V and a silicon one will be about 0.6 to 0.7 V.

Knowing the gain would be nice but power transistors run at too high
current to be accurately tested by small transistor testers or DMMs.

What you may need to know now is how fast they are. Some car radios put
the output transistor in a feedback circuit and use its slow response as
they main frequency compensation. If you substitute a faster transistor,
it may oscillate or be marginally stable.

The output transistor in the radio in my '67 Valiant died and I had to try
several old transistors to find one that would work right. In this radio
the symptom of an inappropriate type was a brief oscillation when the set
was turned on or off.

Also, it is possible for some other part to be the cause of the failure.
It was in my case. Many years before, one of the small audio transistors
(an early plastic case silicon unit) became intermittant, a common problem
for early plastic semiconductors. When it opened, it upset the bias on
the output transistor and caused it to draw a lot of current (the emitter
resistor got red hot!). Although it continued to work after the problem
transistor was replaced, apparently it had been damaged and had developed
high leakage. The feedback circuit adjusted the bias to correct for this
and it worked but eventually it got bad enough that there was no more
correction range and it stopped working. At this point Iceo was around
300 mA!

So in your case, probably all you can do is determine if they are the
right polarity and material and give them a try; and be sure something
else didn't fry the original one.