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Heil Ohmega 400 transistors

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Anonymous
July 2, 2004 12:07:10 AM

Archived from groups: rec.audio.tech (More info?)

I need replacement output and output driver transistors for a Heil Ohmega
400 power amp (1970's).
The company no longer has stock, but I spoke with Bob Heil, and he said he
has seen discussions on this amp in this NG. The part #s are proprietary,
and he knows of no cross.
Has anyone repaired this amp?
Anonymous
July 2, 2004 11:41:11 PM

Archived from groups: rec.audio.tech (More info?)

StewieGriffin wrote:
> I need replacement output and output driver transistors for a Heil Ohmega
> 400 power amp (1970's).
> The company no longer has stock, but I spoke with Bob Heil, and he said he
> has seen discussions on this amp in this NG. The part #s are proprietary,
> and he knows of no cross.
> Has anyone repaired this amp?
>
>
Are any of the old transistors good? If so, you may be able to reverse
engineer the spec. If you have a schematic you can make some
assumptions. What's the output topology? What's the rail voltages? Take
the old good devices and use a transistor checker to determine HFE. With
the HFE and the supply rail voltages, you should be in the ballpark spec
wise to find something usable. Post what you know.

Bob



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Anonymous
July 3, 2004 2:27:21 AM

Archived from groups: rec.audio.tech (More info?)

"StewieGriffin" <Stewie@nospam.net> wrote in message
news:KrydnVFEpp0qZXjdRVn-tw@adelphia.com
> I need replacement output and output driver transistors for a Heil
> Ohmega 400 power amp (1970's).
> The company no longer has stock, but I spoke with Bob Heil, and he
> said he has seen discussions on this amp in this NG. The part #s
> are proprietary, and he knows of no cross.
> Has anyone repaired this amp?

Here's an independent opinion in the matter:

http://groups.google.com/groups?selm=8d6b6a60bc43882c36...
Related resources
Can't find your answer ? Ask !
Anonymous
July 3, 2004 10:37:21 AM

Archived from groups: rec.audio.tech (More info?)

In article <40e600a6_2@corp.newsgroups.com>,
Bob Urz <sound@inetnebr.com> wrote:

> StewieGriffin wrote:
> > I need replacement output and output driver transistors for a Heil Ohmega
> > 400 power amp (1970's).
> > The company no longer has stock, but I spoke with Bob Heil, and he said he
> > has seen discussions on this amp in this NG. The part #s are proprietary,
> > and he knows of no cross.
> > Has anyone repaired this amp?
> >
> >
> Are any of the old transistors good? If so, you may be able to reverse
> engineer the spec. If you have a schematic you can make some
> assumptions. What's the output topology? What's the rail voltages? Take
> the old good devices and use a transistor checker to determine HFE. With
> the HFE and the supply rail voltages, you should be in the ballpark spec
> wise to find something usable. Post what you know.

Matching (or exceeding) the original device's HFE isn't enough.

I have seen instances where new (superior) transistors were unstable and
oscillated at high frequency where "originals" did not. The problem is
that new devices frequently have decent gain at a far higher frequency
than older ones. Sometimes the oscillation occurs only when the devices
are being driven with (perfectly ordinary) signals.

I would recommend some careful o'scope work whenever "better" devices
are substituted, but I'd be pretty certain that new devices could be
made to operate in the amplifier somehow.

Isaac
Anonymous
July 3, 2004 1:10:16 PM

Archived from groups: rec.audio.tech (More info?)

Isaac Wingfield wrote:

> In article <40e600a6_2@corp.newsgroups.com>,
> Bob Urz <sound@inetnebr.com> wrote:
>
>
>>StewieGriffin wrote:
>>
>>>I need replacement output and output driver transistors for a Heil Ohmega
>>>400 power amp (1970's).
>>>The company no longer has stock, but I spoke with Bob Heil, and he said he
>>>has seen discussions on this amp in this NG. The part #s are proprietary,
>>>and he knows of no cross.
>>>Has anyone repaired this amp?
>>>
>>>
>>
>>Are any of the old transistors good? If so, you may be able to reverse
>>engineer the spec. If you have a schematic you can make some
>>assumptions. What's the output topology? What's the rail voltages? Take
>>the old good devices and use a transistor checker to determine HFE. With
>>the HFE and the supply rail voltages, you should be in the ballpark spec
>>wise to find something usable. Post what you know.
>
>
> Matching (or exceeding) the original device's HFE isn't enough.
>
> I have seen instances where new (superior) transistors were unstable and
> oscillated at high frequency where "originals" did not. The problem is
> that new devices frequently have decent gain at a far higher frequency
> than older ones. Sometimes the oscillation occurs only when the devices
> are being driven with (perfectly ordinary) signals.
>
> I would recommend some careful o'scope work whenever "better" devices
> are substituted, but I'd be pretty certain that new devices could be
> made to operate in the amplifier somehow.
>
> Isaac
True, there is no one step sliver bullet. And many older power
transistors were not known for there exceptional specs.
Scoping the outputs and looking for the oscillation or modulation
on the waveforms is a good idea. Some capacitors may have to be added
to the drivers or such to "slow down" a replacement if that's the case.

Considering the option is a "NO FIX", i think it worth a shot.
The worst case scenario is trying to source some germanium transistors.
Now that's a snipe hunt.

Bob



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Anonymous
July 4, 2004 11:35:23 PM

Archived from groups: rec.audio.tech (More info?)

"Bob Urz" <sound@inetnebr.com> wrote in message
news:40e6be46_5@corp.newsgroups.com...
> The worst case scenario is trying to source some germanium transistors.
> Now that's a snipe hunt.

A 400W power amp with germanium output transistors, do you know of any?

TonyP.
Anonymous
July 4, 2004 11:35:24 PM

Archived from groups: rec.audio.tech (More info?)

TonyP wrote:

> "Bob Urz" <sound@inetnebr.com> wrote in message
> news:40e6be46_5@corp.newsgroups.com...
>
>>The worst case scenario is trying to source some germanium transistors.
>>Now that's a snipe hunt.
>
>
> A 400W power amp with germanium output transistors, do you know of any?
>
> TonyP.
>
>
Did i say OUTPUTS? Some earlier Phase linear amps used a germanium
transistor in its pre driver stages as i recall. They also used some
shitty slow Delco To-3 outputs in some models.
It all comes down to ID'ing the parts.

Bob




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Anonymous
July 4, 2004 11:35:25 PM

Archived from groups: rec.audio.tech (More info?)

Bob Urz <sound@inetnebr.com> wrote:


> TonyP wrote:

>> "Bob Urz" <sound@inetnebr.com> wrote in message
>> news:40e6be46_5@corp.newsgroups.com...
>>
>>>The worst case scenario is trying to source some germanium transistors.
>>>Now that's a snipe hunt.
>>
>>
>> A 400W power amp with germanium output transistors, do you know of any?
>>
>> TonyP.
>>
>>
> Did i say OUTPUTS? Some earlier Phase linear amps used a germanium
> transistor in its pre driver stages as i recall. They also used some
> shitty slow Delco To-3 outputs in some models.
> It all comes down to ID'ing the parts.

At the time, those triple diffused NPN's were considered quite fast.
Anonymous
July 5, 2004 10:31:01 PM

Archived from groups: rec.audio.tech (More info?)

"Bob Urz" <sound@inetnebr.com> wrote in message
news:40e82679$1_3@corp.newsgroups.com...
> TonyP wrote:
> > A 400W power amp with germanium output transistors, do you know of any?
> > TonyP.
> >
> Did i say OUTPUTS?

The OP did IIRC.

TonyP.
Anonymous
July 5, 2004 10:31:02 PM

Archived from groups: rec.audio.tech (More info?)

In article <40e911cf$0$25461$afc38c87@news.optusnet.com.au>,
TonyP@optus.net.com.au says...
>
> "Bob Urz" <sound@inetnebr.com> wrote in message
> news:40e82679$1_3@corp.newsgroups.com...
> > TonyP wrote:
> > > A 400W power amp with germanium output transistors, do you know of any?
> > > TonyP.
> > >
> > Did i say OUTPUTS?
>
> The OP did IIRC.
>
> TonyP.
>
>
>
The OP said:

> Subject: Heil Ohmega 400 transistors
> From: StewieGriffin <Stewie@nospam.net>
> Newsgroups: rec.audio.tech

> I need replacement output and output driver transistors for a Heil Ohmega
> 400 power amp (1970's).
> The company no longer has stock, but I spoke with Bob Heil, and he said he
> has seen discussions on this amp in this NG. The part #s are proprietary,
> and he knows of no cross.
> Has anyone repaired this amp?

I think Bob Urz was the first mention of germanium transistors in
particular.

Bob said:

---SNIP---

> Considering the option is a "NO FIX", i think it worth a shot.
> The worst case scenario is trying to source some germanium transistors.
> Now that's a snipe hunt.

> Bob

I hated those proprietary electronics designers. They liked to make
small mods to a component/module, contract with a builder, and all
purchases had to go through them. Couldn't even get parts direct from
the mfr. that made them without authorization from the builder.

Ken B
Anonymous
July 5, 2004 10:31:12 PM

Archived from groups: rec.audio.tech (More info?)

I wonder what it was that made silicon win out over germanium in solid state
technology. Back in the '60s, we used to see a lot of germanium transistors.
Germanium has a lower p-n drop (0.2 volts vs. 0.6 for silicon) which could
theoretically reduce power dissipation. In the late '70s and early '80s,
there was a rectifier company that was making germanium rectifiers for power
supplies because they were more efficient.

So, what are the properties of silicon that make it superior to germanium?
Easier to fabricate?
More reliable?
Higher power/current capability?
Less temperature sensitive?
cheaper/more plentiful?
Anonymous
July 5, 2004 11:44:36 PM

Archived from groups: rec.audio.tech (More info?)

In article <Q7hGc.12672$Xq4.404@nwrddc02.gnilink.net>,
Karl Uppiano <karl_uppiano@verizon.net> wrote:

>I wonder what it was that made silicon win out over germanium in solid state
>technology. Back in the '60s, we used to see a lot of germanium transistors.
>Germanium has a lower p-n drop (0.2 volts vs. 0.6 for silicon) which could
>theoretically reduce power dissipation. In the late '70s and early '80s,
>there was a rectifier company that was making germanium rectifiers for power
>supplies because they were more efficient.
>
>So, what are the properties of silicon that make it superior to germanium?
>Easier to fabricate?
>More reliable?
>Higher power/current capability?
>Less temperature sensitive?
>cheaper/more plentiful?

http://www.ti.com/corp/docs/company/history/siltranspro...
gives one look at the question - it's a 1954 press release about
silicon transistors.

"Higher power", "less temperature-sensitive", and "cheaper" seem to be
the high points. I believe that "more reliable", "lower reverse
leakage" and "capable of operating at higher voltages" also come into
it.

These days, the popular solutions for rectifiers requiring low forward
voltage drop seems to be to use either Schottky diodes (roughly half
the forward drop of grown-junction silicon, I believe), or synchronous
switched rectification using MOSFETs or IGBTs.

--
Dave Platt <dplatt@radagast.org> AE6EO
Hosting the 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!
Anonymous
July 5, 2004 11:52:37 PM

Archived from groups: rec.audio.tech (More info?)

Ken B wrote:
> In article <40e911cf$0$25461$afc38c87@news.optusnet.com.au>,
> TonyP@optus.net.com.au says...
>
>>"Bob Urz" <sound@inetnebr.com> wrote in message
>>news:40e82679$1_3@corp.newsgroups.com...
>>
>>>TonyP wrote:
>>>
>>>>A 400W power amp with germanium output transistors, do you know of any?
>>>>TonyP.
>>>>
>>>
>>>Did i say OUTPUTS?
>>
>>The OP did IIRC.
>>
>>TonyP.
>>
>>
>>
>
> The OP said:
>
>
>>Subject: Heil Ohmega 400 transistors
>>From: StewieGriffin <Stewie@nospam.net>
>>Newsgroups: rec.audio.tech
>
>
>>I need replacement output and output driver transistors for a Heil Ohmega
>>400 power amp (1970's).
>>The company no longer has stock, but I spoke with Bob Heil, and he said he
>>has seen discussions on this amp in this NG. The part #s are proprietary,
>>and he knows of no cross.
>>Has anyone repaired this amp?
>
>
> I think Bob Urz was the first mention of germanium transistors in
> particular.
>
Just a note: i cannot say that this amp has or uses germanium
transistors. I just remember trying to source them to fix some earlier
high power Phase linears of a similar vintage. So, its just something
to look out for. Especially since no one seems to have any information
on this amp. And the Phase amps used them as a bias transistor or such,
not outputs. I do remember some early to mid 60's hi-fi amps
that had some though. As i recall, the output devices were relatively
leaky and did not have a high voltage breakdown. Of course that was 60's
fabrication and technology.

Bob



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Anonymous
July 6, 2004 6:08:59 AM

Archived from groups: rec.audio.tech (More info?)

> http://www.ti.com/corp/docs/company/history/siltranspro...
> gives one look at the question - it's a 1954 press release about
> silicon transistors.

Interesting link. I enjoyed the term "triode transistor". They were still
thinking in terms of vacuum tubes in those days, weren't they?
Anonymous
July 6, 2004 9:24:34 AM

Archived from groups: rec.audio.tech (More info?)

On Tue, 06 Jul 2004 02:08:59 GMT, "Karl Uppiano"
<karl_uppiano@verizon.net> wrote:

>> http://www.ti.com/corp/docs/company/history/siltranspro...
>> gives one look at the question - it's a 1954 press release about
>> silicon transistors.
>
>Interesting link. I enjoyed the term "triode transistor". They were still
>thinking in terms of vacuum tubes in those days, weren't they?

Nope, they were thinking in terms of correct semantics. A transistor
has three electrodes, hence it *is* a triode, just like its vacuum
tube predecessor. The term was later dropped because almost all
transistors are triodes, hence there isn't the need for additional
descriptors thatyou have with vacuum tubes.
--

Stewart Pinkerton | Music is Art - Audio is Engineering
Anonymous
July 6, 2004 9:28:12 AM

Archived from groups: rec.audio.tech (More info?)

On Mon, 05 Jul 2004 18:31:12 GMT, "Karl Uppiano"
<karl_uppiano@verizon.net> wrote:

>I wonder what it was that made silicon win out over germanium in solid state
>technology. Back in the '60s, we used to see a lot of germanium transistors.
>Germanium has a lower p-n drop (0.2 volts vs. 0.6 for silicon) which could
>theoretically reduce power dissipation. In the late '70s and early '80s,
>there was a rectifier company that was making germanium rectifiers for power
>supplies because they were more efficient.
>
>So, what are the properties of silicon that make it superior to germanium?
>Easier to fabricate?
>More reliable?
>Higher power/current capability?
>Less temperature sensitive?
>cheaper/more plentiful?

All of the above! :-)

Principally however, it was the max junction temperature of about 200
degrees Celsius, rather than the 85 of germanium, which made the
difference. As we used to say in the '60s, geraniums wilt! If you need
a high efficiency diode, you'd now use a Schottky, which combines low
forward drop with high temperature capability.
--

Stewart Pinkerton | Music is Art - Audio is Engineering
Anonymous
July 6, 2004 12:18:12 PM

Archived from groups: rec.audio.tech (More info?)

"Stewart Pinkerton" <patent3@dircon.co.uk> wrote in message
news:uldke05eon8vkg0180cvgo6kbpl25h5j5a@4ax.com...
> On Tue, 06 Jul 2004 02:08:59 GMT, "Karl Uppiano"
> <karl_uppiano@verizon.net> wrote:
>
> >> http://www.ti.com/corp/docs/company/history/siltranspro...
> >> gives one look at the question - it's a 1954 press release about
> >> silicon transistors.
> >
> >Interesting link. I enjoyed the term "triode transistor". They were still
> >thinking in terms of vacuum tubes in those days, weren't they?
>
> Nope, they were thinking in terms of correct semantics. A transistor
> has three electrodes, hence it *is* a triode, just like its vacuum
> tube predecessor. The term was later dropped because almost all
> transistors are triodes, hence there isn't the need for additional
> descriptors thatyou have with vacuum tubes.

That's what I was getting at. They hadn't gotten around to realizing yet
that transistors were only going to have three legs for the next 50-odd
years. Unlike tubes, n-odes weren't going to be much of a distinguishing
factor.

Once we really got into it, we started referring to them by polarity and
type (e.g., NPN vs. PNP, BJT vs. FET, JFET vs. MOSFET, even a short flurry
of activity with UJTs, an odd bird that was hyped up all over Electronics
Illustrated, but that I don't see much of any more). I have only seen a few
dual-gate MOSFETS, which were four-terminal devices (tetrodes, I guess),
used as multipliers in superhet detectors. Oh, and those dual-emitter things
used in TTL logic gates.
Anonymous
July 6, 2004 1:36:34 PM

Archived from groups: rec.audio.tech (More info?)

On Tue, 06 Jul 2004 08:18:12 GMT, "Karl Uppiano"
<karl_uppiano@verizon.net> wrote:

>
>"Stewart Pinkerton" <patent3@dircon.co.uk> wrote in message
>news:uldke05eon8vkg0180cvgo6kbpl25h5j5a@4ax.com...
>> On Tue, 06 Jul 2004 02:08:59 GMT, "Karl Uppiano"
>> <karl_uppiano@verizon.net> wrote:
>>
>> >> http://www.ti.com/corp/docs/company/history/siltranspro...
>> >> gives one look at the question - it's a 1954 press release about
>> >> silicon transistors.
>> >
>> >Interesting link. I enjoyed the term "triode transistor". They were still
>> >thinking in terms of vacuum tubes in those days, weren't they?
>>
>> Nope, they were thinking in terms of correct semantics. A transistor
>> has three electrodes, hence it *is* a triode, just like its vacuum
>> tube predecessor. The term was later dropped because almost all
>> transistors are triodes, hence there isn't the need for additional
>> descriptors thatyou have with vacuum tubes.
>
>That's what I was getting at. They hadn't gotten around to realizing yet
>that transistors were only going to have three legs for the next 50-odd
>years. Unlike tubes, n-odes weren't going to be much of a distinguishing
>factor.
>
>Once we really got into it, we started referring to them by polarity and
>type (e.g., NPN vs. PNP, BJT vs. FET, JFET vs. MOSFET, even a short flurry
>of activity with UJTs, an odd bird that was hyped up all over Electronics
>Illustrated, but that I don't see much of any more). I have only seen a few
>dual-gate MOSFETS, which were four-terminal devices (tetrodes, I guess),
>used as multipliers in superhet detectors. Oh, and those dual-emitter things
>used in TTL logic gates.
>

This is all good stuff apart from the tetrode comparison. In fact a
JFET is a pretty good match for a tetrode - it just doesn't need the
fourth terminal, which in the tetrode is really for mopping up lost
electrons that otherwise float around under certain anode voltage
conditions.

d
Pearce Consulting
http://www.pearce.uk.com
Anonymous
July 7, 2004 7:50:47 AM

Archived from groups: rec.audio.tech (More info?)

"Don Pearce" <donald@pearce.uk.com> wrote in message
news:D 1pke0hagivdqq1m8519uaa4j9sauoj7nr@4ax.com...
> On Tue, 06 Jul 2004 08:18:12 GMT, "Karl Uppiano"
> <karl_uppiano@verizon.net> wrote:
>
> >
> >"Stewart Pinkerton" <patent3@dircon.co.uk> wrote in message
> >news:uldke05eon8vkg0180cvgo6kbpl25h5j5a@4ax.com...
> >> On Tue, 06 Jul 2004 02:08:59 GMT, "Karl Uppiano"
> >> <karl_uppiano@verizon.net> wrote:
> >>
> >> >> http://www.ti.com/corp/docs/company/history/siltranspro...
> >> >> gives one look at the question - it's a 1954 press release about
> >> >> silicon transistors.
> >> >
> >> >Interesting link. I enjoyed the term "triode transistor". They were
still
> >> >thinking in terms of vacuum tubes in those days, weren't they?
> >>
> >> Nope, they were thinking in terms of correct semantics. A transistor
> >> has three electrodes, hence it *is* a triode, just like its vacuum
> >> tube predecessor. The term was later dropped because almost all
> >> transistors are triodes, hence there isn't the need for additional
> >> descriptors thatyou have with vacuum tubes.
> >
> >That's what I was getting at. They hadn't gotten around to realizing yet
> >that transistors were only going to have three legs for the next 50-odd
> >years. Unlike tubes, n-odes weren't going to be much of a distinguishing
> >factor.
> >
> >Once we really got into it, we started referring to them by polarity and
> >type (e.g., NPN vs. PNP, BJT vs. FET, JFET vs. MOSFET, even a short
flurry
> >of activity with UJTs, an odd bird that was hyped up all over Electronics
> >Illustrated, but that I don't see much of any more). I have only seen a
few
> >dual-gate MOSFETS, which were four-terminal devices (tetrodes, I guess),
> >used as multipliers in superhet detectors. Oh, and those dual-emitter
things
> >used in TTL logic gates.
> >
>
> This is all good stuff apart from the tetrode comparison. In fact a
> JFET is a pretty good match for a tetrode - it just doesn't need the
> fourth terminal, which in the tetrode is really for mopping up lost
> electrons that otherwise float around under certain anode voltage
> conditions.
>
> d
> Pearce Consulting
> http://www.pearce.uk.com

I agree JFETs are 3-terminal devices that have tetrode tube-like
characteristics, but tetra means four, which is where the tube got it's
name. So it depends if you go by behavior or by semantics. What to choose,
what to choose...
July 9, 2004 11:00:53 AM

Archived from groups: rec.audio.tech (More info?)

On Tue, 06 Jul 2004 08:18:12 GMT, Karl Uppiano wrote:


> Once we really got into it, we started referring to them by polarity and
> type (e.g., NPN vs. PNP, BJT vs. FET, JFET vs. MOSFET, even a short flurry
> of activity with UJTs, an odd bird that was hyped up all over Electronics
> Illustrated, but that I don't see much of any more). I have only seen a few
> dual-gate MOSFETS, which were four-terminal devices (tetrodes, I guess),
> used as multipliers in superhet detectors. Oh, and those dual-emitter things
> used in TTL logic gates.

In the integrated-circuit world, multiple emitter and multiple collector
devices are very common (especially in older processes), since it's so easy
to make them. I used to regularly build devices with five or six emitters
or collectors. Functionally, multiple emitter/collector devices are
generally the same as the same number of individual transistors in
parallel, but the combined device often takes considerably less space on an
IC.

-- Mike --
Anonymous
July 9, 2004 10:37:56 PM

Archived from groups: rec.audio.tech (More info?)

In article <1akkfraparket.17vwoqv3xzwta.dlg@40tude.net>,
Mike <mike@nospam.com> wrote:

>In the integrated-circuit world, multiple emitter and multiple collector
>devices are very common (especially in older processes), since it's so easy
>to make them. I used to regularly build devices with five or six emitters
>or collectors. Functionally, multiple emitter/collector devices are
>generally the same as the same number of individual transistors in
>parallel, but the combined device often takes considerably less space on an
>IC.

Multiple-emitter transistors, with built-in ballast resistors
connected to each emitter, are also used for RF applications. The
parallelism and internal ballasting make the transistors quite a bit
more rugged, and able to survive heavy or mismatched loads (e.g.
shorted or open outputs) than would be the case for a single-emitter
transistor having the same current-drive capacity.

--
Dave Platt <dplatt@radagast.org> AE6EO
Hosting the 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!
!