2SD2385 + 2SB1556 Transistors

fruittool · Oct 25, 2012

I've just been done on ebay. Both output transistors on a Kenwood A-9
amplifier had blown. Ordered the pair from ebay, installed them
working, great. Turned it off to put it back together and noticed th
heatsink was really hot on the repaired side. I found that the bas
voltage on both transistors was low. Swapped both transistors from th
good side to the repaired side and its now fine. Put the new ones in th
good side the and now the good side has got hot and all the voltage
have dropped the same as they did when they were on the repaired side.

Does anyone know where i can get a genuine pair of these transistors a
a reasonable price

--
fruittool

Dave Platt · Oct 25, 2012

I've just been done on ebay. Both output transistors on a Kenwood A-97
amplifier had blown. Ordered the pair from ebay, installed them,
working, great. Turned it off to put it back together and noticed the
heatsink was really hot on the repaired side. I found that the base
voltage on both transistors was low. Swapped both transistors from the
good side to the repaired side and its now fine. Put the new ones in the
good side the and now the good side has got hot and all the voltages
have dropped the same as they did when they were on the repaired side.

Does anyone know where i can get a genuine pair of these transistors at
a reasonable price?

What was the base-to-emitter voltage on the questionable transistors,
when the amp is idling? How does it compare to the working parts?

These parts (when genuine) seem to be Darlingstons, not just single
transistors. You may have been sold a pair of mislabeled standard
transistors instead - this would probably result in over-biasing and a
high idle current.

Or, possibly they're genuine parts, but have a higher beta than the
ones for which the amp was spec'ed? The beta bin would be a
one-character A, B, or C, possibly stamped on the lower left corner of
the plastic. If that's the case, they might work OK with some
adjustment to the idle/bias settings.

TIP142/TIP147 *might* be acceptable substitutes although their gain
seems lower.

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Phil Allison · Oct 26, 2012

"Dave Platt"

These parts (when genuine) seem to be Darlingstons, not just single
transistors.

You may have been sold a pair of mislabeled standard
transistors instead - this would probably result in over-biasing and a
high idle current.

** For sure.

Or, possibly they're genuine parts, but have a higher beta than the
ones for which the amp was spec'ed?

** Nonsense.

Output transistors are typically biased with a voltage that varies with the
temperature of the heatsink.

TIP142/TIP147 *might* be acceptable substitutes although their gain
seems lower.

** The fact they have a Vce of 100V as compared to the originals with 140V
is far more of a worry.

The BDV65C and BDV64C darlington pair is closer at 120V Vce.

The OP can measure the +/- DC rails see if the total is more than 120V.

..... Phil

fruittool · Oct 26, 2012

Dave Platt;2949536 Wrote:

I've just been done on ebay. Both output transistors on a Kenwood A-97-
amplifier had blown. Ordered the pair from ebay, installed them,
working, great. Turned it off to put it back together and noticed the
heatsink was really hot on the repaired side. I found that the base
voltage on both transistors was low. Swapped both transistors from the
good side to the repaired side and its now fine. Put the new ones i
the
good side the and now the good side has got hot and all the voltages
have dropped the same as they did when they were on the repaired side.

Does anyone know where i can get a genuine pair of these transistors at
a reasonable price?-

What was the base-to-emitter voltage on the questionable transistors,
when the amp is idling? How does it compare to the working parts?

These parts (when genuine) seem to be Darlingstons, not just single
transistors. You may have been sold a pair of mislabeled standard
transistors instead - this would probably result in over-biasing and a
high idle current.

Or, possibly they're genuine parts, but have a higher beta than the
ones for which the amp was spec'ed? The beta bin would be a
one-character A, B, or C, possibly stamped on the lower left corner of
the plastic. If that's the case, they might work OK with some
adjustment to the idle/bias settings.

TIP142/TIP147 *might* be acceptable substitutes although their gain
seems lower.

The design uses an STK350-030 ic to drive the output transistors
According to the service manual, at idle, the output from the driver i
to each transistor base should be around 1.2 volts. These new ones ar
causing that voltage to drop to around 0.6 - 0.8v, and this is with th
bias adjustment full up.
I tried using one of the new ones with an old complimentary one from th
good side and this caused a massive imbalance in the idle bias 1.4v fo
the good one and 0.6 for the suspect one. Can i assume from thes
voltages that the replacement's are not darlingtons? 0.6v is right for
single transistor and 1.2v (approximately double) for a darlington?

Regard

--
fruittool

N_Cook · Oct 26, 2012

fruittool <fruittool.acf52c8@diybanter.com> wrote in message
news:fruittool.acf52c8@diybanter.com...

I've just been done on ebay. Both output transistors on a Kenwood A-97
amplifier had blown. Ordered the pair from ebay, installed them,
working, great. Turned it off to put it back together and noticed the
heatsink was really hot on the repaired side. I found that the base
voltage on both transistors was low. Swapped both transistors from the
good side to the repaired side and its now fine. Put the new ones in the
good side the and now the good side has got hot and all the voltages
have dropped the same as they did when they were on the repaired side.

Does anyone know where i can get a genuine pair of these transistors at
a reasonable price?

--
fruittool

Any external giveaways as yo piracy?

ground surface ?
smudged printing or looks as though logo was stamped with a potatoe die?

chuck · Oct 26, 2012

On Thu, 25 Oct 2012 20:06:24 +0000, fruittool
<fruittool.acf52c8@diybanter.com> wrote:

I've just been done on ebay. Both output transistors on a Kenwood A-97
amplifier had blown. Ordered the pair from ebay, installed them,
working, great. Turned it off to put it back together and noticed the
heatsink was really hot on the repaired side. I found that the base
voltage on both transistors was low. Swapped both transistors from the
good side to the repaired side and its now fine. Put the new ones in the
good side the and now the good side has got hot and all the voltages
have dropped the same as they did when they were on the repaired side.

Does anyone know where i can get a genuine pair of these transistors at
a reasonable price?

http://www.bdent.com/ only carries genuine semiconductor
manufacturer's lines. Chuck

William Sommerwerck · Oct 26, 2012

one from the good side and this caused a massive imbalance
in the idle bias 1.4v for the good one and 0.6 for the suspect one.
Can I assume from these voltages that the replacements are not
Darlingtons? 0.6v is right for a single transistor and 1.2v
(approximately double) for a Darlington?

It sounds as if these aren't Darlingtons.

Do you have a way to measure the current gain? It should be at least 1000 --
probably higher.

Michael A. Terrell · Oct 26, 2012

William Sommerwerck wrote:

I tried using one of the new ones with an old complimentary [sic]
one from the good side and this caused a massive imbalance
in the idle bias 1.4v for the good one and 0.6 for the suspect one.
Can I assume from these voltages that the replacements are not
Darlingtons? 0.6v is right for a single transistor and 1.2v
(approximately double) for a Darlington?

It sounds as if these aren't Darlingtons.

Do you have a way to measure the current gain? It should be at least 1000 --
probably higher.

Pull one of the new transistors and check it with an ohm meter. If it
tests like a single transistor, it is.

fruittool · Oct 26, 2012

'Phil Allison[_2_ Wrote:

** The fact they have a Vce of 100V as compared to the originals wit
140V
is far more of a worry.

The BDV65C and BDV64C darlington pair is closer at 120V Vce.

The OP can measure the +/- DC rails see if the total is more than 120V.

I had this same concern, each rail is 52V. Your suggested parts see
closer but, would i have to change both pairs to keep the response o
both channels identical?

N_Cook;2949784 Wrote:

Any external giveaways as yo piracy?

On first examination there's nothing particularly suspect but, afte
checking what the proper markings would be, it turns out the gai
classification (A, B or C) is missing on one and is the letter 'O' o
the other. Another giveaway is the LOT number, it should be one numbe
for the last digit of the year and one letter 'A' for January to 'L' fo
December. Both have three numbers and no letters.

Regard

--
fruittool

William Sommerwerck · Oct 26, 2012

Do you have a way to measure the current gain?
It should be at least 1000 -- probably higher.

Pull one of the new transistors and check it with an
ohmeter. If it tests like a single transistor, it is.

I assume you're referring to the base-emitter junction.

petrus bitbyter · Oct 26, 2012

"fruittool" <fruittool.ad04fe8@diybanter.com> schreef in bericht
news:fruittool.ad04fe8@diybanter.com...

Dave Platt;2949536 Wrote:
I've just been done on ebay. Both output transistors on a Kenwood A-97-
amplifier had blown. Ordered the pair from ebay, installed them,
working, great. Turned it off to put it back together and noticed the
heatsink was really hot on the repaired side. I found that the base
voltage on both transistors was low. Swapped both transistors from the
good side to the repaired side and its now fine. Put the new ones in
the
good side the and now the good side has got hot and all the voltages
have dropped the same as they did when they were on the repaired side.

Does anyone know where i can get a genuine pair of these transistors at
a reasonable price?-

What was the base-to-emitter voltage on the questionable transistors,
when the amp is idling? How does it compare to the working parts?

These parts (when genuine) seem to be Darlingstons, not just single
transistors. You may have been sold a pair of mislabeled standard
transistors instead - this would probably result in over-biasing and a
high idle current.

Or, possibly they're genuine parts, but have a higher beta than the
ones for which the amp was spec'ed? The beta bin would be a
one-character A, B, or C, possibly stamped on the lower left corner of
the plastic. If that's the case, they might work OK with some
adjustment to the idle/bias settings.

TIP142/TIP147 *might* be acceptable substitutes although their gain
seems lower.

The design uses an STK350-030 ic to drive the output transistors.
According to the service manual, at idle, the output from the driver ic
to each transistor base should be around 1.2 volts. These new ones are
causing that voltage to drop to around 0.6 - 0.8v, and this is with the
bias adjustment full up.
I tried using one of the new ones with an old complimentary one from the
good side and this caused a massive imbalance in the idle bias 1.4v for
the good one and 0.6 for the suspect one. Can i assume from these
voltages that the replacement's are not darlingtons? 0.6v is right for a
single transistor and 1.2v (approximately double) for a darlington?

Regards

--
fruittool

No doubt you were sent single transistors instead of Darlingtons. The latter
have two diode drops Vbe so 1.2V-1.4V instead of 0.6V-0.7V. If you did not
find out already you could check using the diode tester of a common
unimeter.

petrus bitbyter

Phil Allison · Oct 26, 2012

"fruittool"

'Phil Allison

** The fact they have a Vce of 100V as compared to the originals with
140V is far more of a worry.

The BDV65C and BDV64C darlington pair is closer at 120V Vce.

The OP can measure the +/- DC rails see if the total is more than 120V.

I had this same concern, each rail is 52V. Your suggested parts seem
closer but, would i have to change both pairs to keep the response of
both channels identical?

** LOL - err, no.

You really are a babe in the woods.....

..... Phil

Phil Allison · Oct 26, 2012

"fruittool"

TIP142/TIP147 *might* be acceptable substitutes although their gain
seems lower.

The design uses an STK350-030 ic to drive the output transistors.
According to the service manual, at idle, the output from the driver ic
to each transistor base should be around 1.2 volts. These new ones are
causing that voltage to drop to around 0.6 - 0.8v, and this is with the
bias adjustment full up.

** That will only make the transistors you have get very hot.

I tried using one of the new ones with an old complimentary one from the
good side and this caused a massive imbalance in the idle bias 1.4v for
the good one and 0.6 for the suspect one. Can i assume from these
voltages that the replacement's are not darlingtons? 0.6v is right for a
single transistor and 1.2v (approximately double) for a darlington?

** Yep.

Non darlington devices in that amp will not only run hot but deliver much
less that full output power into a load.

The fact is you simply have NO driver transistors unless darlingtons are
fitted.

..... Phil

Phil Allison · Oct 26, 2012

"William Sommerwanker"

Pull one of the new transistors and check it with an
ohmeter. If it tests like a single transistor, it is.

I assume you're referring to the base-emitter junction.

** Darlington power transistors all have inbuilt diodes from collector to
emitter - a very rare thing among regular transistors.

The base emitter junction will also read higher than usual on an ohmmeter,
the difference being more obvious with an analogue type on the ohms x1 range
than with a DMM on "diode test".

..... Phil

Phil Allison · Oct 26, 2012

"William Sommerwanker"

It sounds as if these aren't Darlingtons.

Do you have a way to measure the current gain? It should be at least
1000 --
probably higher.

** Most transistor checkers will not read correctly with power darlingtons.

.... Phil

Gareth Magennis · Oct 26, 2012

"Cydrome Leader" <presence@MUNGEpanix.com> wrote in message
news:k6eu9m$dri$1@reader1.panix.com...

N_Cook <diverse@tcp.co.uk> wrote:
fruittool <fruittool.acf52c8@diybanter.com> wrote in message
news:fruittool.acf52c8@diybanter.com...

I've just been done on ebay. Both output transistors on a Kenwood A-97
amplifier had blown. Ordered the pair from ebay, installed them,
working, great. Turned it off to put it back together and noticed the
heatsink was really hot on the repaired side. I found that the base
voltage on both transistors was low. Swapped both transistors from the
good side to the repaired side and its now fine. Put the new ones in the
good side the and now the good side has got hot and all the voltages
have dropped the same as they did when they were on the repaired side.

Does anyone know where i can get a genuine pair of these transistors at
a reasonable price?

--
fruittool

Any external giveaways as yo piracy?

ground surface ?
smudged printing or looks as though logo was stamped with a potatoe die?

off ebay is a good clue they're not legit.

Particularly if they ship from China, Hong Kong etc.

Gareth.

Cydrome Leader · Oct 26, 2012

N_Cook <diverse@tcp.co.uk> wrote:

fruittool <fruittool.acf52c8@diybanter.com> wrote in message
news:fruittool.acf52c8@diybanter.com...

I've just been done on ebay. Both output transistors on a Kenwood A-97
amplifier had blown. Ordered the pair from ebay, installed them,
working, great. Turned it off to put it back together and noticed the
heatsink was really hot on the repaired side. I found that the base
voltage on both transistors was low. Swapped both transistors from the
good side to the repaired side and its now fine. Put the new ones in the
good side the and now the good side has got hot and all the voltages
have dropped the same as they did when they were on the repaired side.

Does anyone know where i can get a genuine pair of these transistors at
a reasonable price?

--
fruittool

Any external giveaways as yo piracy?

ground surface ?
smudged printing or looks as though logo was stamped with a potatoe die?

off ebay is a good clue they're not legit.

Phil Allison · Oct 26, 2012

"Gareth Magennis"

"Cydrome Leader"

off ebay is a good clue they're not legit.

Particularly if they ship from China, Hong Kong etc.

** The only offer I see on Ebay for the 2SD2385/2SB1556 pair is from a UK
dealer called "elmassari" in Surrey.

He has a big range of spares for sale at low prices and some of it must be
fakes.

..... Phil

fruittool · Oct 27, 2012

'Phil Allison[_2_ Wrote:

"Gareth Magennis"-
"Cydrome Leader"
-
off ebay is a good clue they're not legit.
-

Particularly if they ship from China, Hong Kong etc.
-

** The only offer I see on Ebay for the 2SD2385/2SB1556 pair is from
UK
dealer called "elmassari" in Surrey.

He has a big range of spares for sale at low prices and some of it mus
be
fakes.

..... Phil

That's the one but the package is labeled 'ELECTRONIC COMPONENTS
SEMICONDUCTORS, PARTS, TRANSISTORS, INVERTERS, TRANSFORMERS | DALBANI
(http://www.nikko-electronics.co.uk) and 'electronic component supplier
and distributors, Nikko Electronics for semiconductors, transistors
capacitors all major brands of spare and replacement parts
(http://www.dalbani.co.uk).

I found 'CHS - replacement remote controls, instruction manuals, audio
video accessories, electronic components & spare parts
(http://www.chsinteractive.co.uk/) to have what i need. Anybody kno
anything about them?

'2Sd2385' (http://tinyurl.com/8jsbwsf)
and
'2Sb1556' (http://tinyurl.com/9vxgkkd)

To me, the pictures look genuine, the site looks a reasonable qualit
and has a uk landline number unlike the other site with it's 02
number.

What do you guys think?

Thanks,
An

--
fruittool

Gareth Magennis · Oct 27, 2012

I found 'CHS - replacement remote controls, instruction manuals, audio &
video accessories, electronic components & spare parts'
(http://www.chsinteractive.co.uk/) to have what i need. Anybody know
anything about them?

Yes, Charles Hyde, I seem to recall, used to sell Tascam and other spares -
I bought some from them.
They were always ridiculously expensive, but they would definitely not
knowingly be dealing with pirated parts.

Gareth.

2SD2385 + 2SB1556 Transistors

fruittool

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Dave Platt

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Phil Allison

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fruittool

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N_Cook

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chuck

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William Sommerwerck

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Michael A. Terrell

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fruittool

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William Sommerwerck

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petrus bitbyter

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Phil Allison

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Phil Allison

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Phil Allison

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Phil Allison

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Gareth Magennis

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Cydrome Leader

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Phil Allison

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fruittool

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