2SD2385 + 2SB1556 Transistors

[fruittool]

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

[Dave Platt]

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 <dpl...@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]

"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

[N_Cook]

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

Any external giveaways as yo piracy?

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

[fruittool]

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

[chuck]

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

[William Sommerwerck]

> 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.

[Michael A. Terrell]

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

[William Sommerwerck]

>> 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]

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

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

[fruittool]

'Phil Allison[_2_ Wrote:
> ;2949783']

>
> ** 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?

N_Cook;2949784 Wrote:
>
>
> Any external giveaways as yo piracy?
>
>

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

Regards




--
fruittool

[Phil Allison]

"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]

"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]

"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]

"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

[Cydrome Leader]

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

[Gareth Magennis]

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

Particularly if they ship from China, Hong Kong etc.



Gareth.

[Phil Allison]

"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]

'Phil Allison[_2_ Wrote:
> ;2950038']"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


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 suppliers
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 know
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 quality
and has a uk landline number unlike the other site with it's 020
number.

What do you guys think?

Thanks,
Ant




--
fruittool

[Gareth Magennis]

>
> 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.

[jurb...@gmail.com]

Will wonders never cease ? This place actually has a datasheet ! (they failed me so much I no longer bother, but at the end it said "PDF" so I got it)

http://www.datasheetcatalog.org/datasheet/toshiba/3250.pdf

If you really cannot get them you can make Darlingtons, but I don't recommend it. However when you look at the internal diagram you see the the EB junction on a meter is not going to read like a Darlington because of the 100 ihm resistor across the EB junction of the output. You would only see the drop of the driver EB junction. Depending on your meter it might read 0.100 higher, but will not read 1.2 volts as you might expect.

You are not ordering a million of these things, if the right part is a bit more expensive it is worth it. Like someone said B & D, but then I don't know where you are. If not in the US, dealing internationally can be a PITA.

J

[Phil Allison]

"fruittool"

> To me, the pictures look genuine,

** But you are an utter idiot.




.... Phil

[Phil Allison]

<jurb...@gmail.com>

http://www.datasheetcatalog.org/datasheet/toshiba/3250.pdf


** Shame the schem in the above omits the reverse diode across the C and E
terminals.

Easiest way to pick a power darlington with an ohm meter.


.... Phil

[jurb...@gmail.com]

Actually it might not have one, there is no law.

With two resistors, a DVM and a 12 volt supply you can measure the hfe quite easily.

That 100 ohm resistor is much more important, otherwise the Icex of the first transistor at the very least will always be applied to the base of the second transistor. The Ice leakage numbers for the whole device would look like germanium.

J

[Phil Allison]

<jurb...@gmail.com>

> Actually it might not have one, there is no law.

** Every darlington power transistor made has a reverse diode from C to E -
it is part if the structure of the chip.

All power mosfets have a similar diode.

> With two resistors, a DVM and a 12 volt supply you can measure the hfe
> quite easily.

** But you gotta be real quick or the device will cook.

> That 100 ohm resistor is much more important, otherwise the Icex of the
> first transistor at the very least will always be applied to the base of
> the second transistor. The Ice leakage numbers for the whole device would
> look like germanium.

** Hogwash.

The 100ohm resistor is there to improve the switch off speed of the power
transistor plus increase the breakdown voltage a little.

Leakage current in the driver transistor is only a few microamps, at most, a
current level the output device can barely amplify at all.


.... Phil

[Sofa Slug]

http://www.pacparts.com/part.cfm