Re: Bogen amp, 8417 tubes blow up, the whole story

[Choky]

****ty xpost.
I'm writin' from RecAudioTubes-where we also know and have SS amps,but we
are not so bloody pompous and too bloody smart.
stay in peace with your precious SS amps.
(point is that man wants to make something with own hands and brain,not just
to find 50W for 45 bucks.

--
Choky
Prodanovic Aleksandar
YU


"Precious Pup" > wrote in message
...
>
>
> Michael Floyd wrote:
> >
> > Very interesting and amusing story - I actually enjoyed reading it,
> > but...
> >
> > ...I don't agree with your approach...
>
> Nor I.
>
> "George R. Gonzalez" > wrote:
> > >I aquired this Bogen PA amplifier, 50 watts out allegedly, pair of
8417's
> > >for output.
> > >...
> > >I go to order some new ones, and no matter where I look, they're
pricey--
> > >$50-80 each.
> > >...
> > >Any ideas out there how this could have ever worked right?
>
> Yes, throw it in the garbage and go to the store and get a new amp for
quite cheap. For even cheaper, get a
> good cheap used solid state amp off ebay or a garage sale. You'll save
yourself money, time, and
> aggravation. I'll bet you can get a dollar/watt, or thereabouts, for new
if you do just a little shopping.

[Don Lancaster]

Precious Pup wrote:
>
> Michael Floyd wrote:
> >
> > Very interesting and amusing story - I actually enjoyed reading it,
> > but...
> >
> > ...I don't agree with your approach...
>
> Nor I.
>
> "George R. Gonzalez" > wrote:
> > >I aquired this Bogen PA amplifier, 50 watts out allegedly, pair of 8417's
> > >for output.
> > >...
> > >I go to order some new ones, and no matter where I look, they're pricey--
> > >$50-80 each.
> > >...
> > >Any ideas out there how this could have ever worked right?
>
> Yes, throw it in the garbage and go to the store and get a new amp for quite cheap. For even cheaper, get a
> good cheap used solid state amp off ebay or a garage sale. You'll save yourself money, time, and
> aggravation. I'll bet you can get a dollar/watt, or thereabouts, for new if you do just a little shopping.

If you really want that vacuum tube sound, you can get it simply by
using barbed wire to conntect the speakers of an ordinary solid state
amp.

Full details at http://www.tinaja.com/glib/marcia.pdf

--
Many thanks,

Don Lancaster
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
voice: (928)428-4073 email: fax 847-574-1462

Please visit my GURU's LAIR web site at http://www.tinaja.com

[Chuck Harris]

Geeze Don!

When you're get sick with the SARS, and have that high fever,
you really should put your laptop away, and give writing
a much needed rest.

-Chuck, WA3UQV

Don Lancaster wrote:

> If you really want that vacuum tube sound, you can get it simply by
> using barbed wire to conntect the speakers of an ordinary solid state
> amp.
>
> Full details at http://www.tinaja.com/glib/marcia.pdf
>

[weisselk]

People seem to have a very limited historical understanding of things.
Look at a Bogen catalogue from the period this amp was produced. The
price of a MO 100a was something like $445, wholesale, in the mid
60's. This puts it on a par, pricewise, with comparable Mac amps.
Which now go for very big money. But Bogen was selling to industry, by
and large. So go figure the value ratio of build quality, design etc.
I sold an Audio Matiere amp two years ago that was a piece of garbage
compared to most Bogen stuff I've seen. It cost only $5400. What a
deal. You cannot imagine how badly that thing was designed. An A list
component, of course. Just a big joke.

George still has not said whether he recapped this amp, or just tried
to redesign it on the fly.

Jonathan

[Shiva]

"Jon Elson" > wrote in message
...
>
>
> George R. Gonzalez wrote:
>
> >Sometimes you wonder how some products ever made it out of the design
lab.
> >
> >Sometimes there's so much wrong, you wonder if the item is a joke.
> >
> >Someday I may relate the story of the no-name amplifier, but today's
story
> >is from a quite respected company, Bogen.
> >
> Respected? By who? They made a lot of public address gear, and a lot of
it
> went up in smoke. I can't be sure, but I think I know someone who
wrestled
> with this same amp, or maybe all their tube stuff was designed like this.
> Very low-budget design, to produce a unit that barely met very low specs,
> but absolutely couldn't be made cheaper, and to hell with the user.
>
> After looking inside some of their stuff, **I** certainly never respected
> the brand.
>

Well shheeet, John, if **you** don't respect it, it must indeed be trash!
And, John? there could be two reasons why you "[know] someone who [has]
wrestled with an amp like this": 1. the design sux. 2. the guy's an
idiot. Something makes me wann'a bet on the latter, 'coz I'm not the
brightest bulb in the tree, and I've had no problems doin' Bogens.
Budget-built? Sure. Unreliable? Hey, i'd love to see how modern toob amps
will fare in 40 yrs...
> >
> >
> Jon
>

[Shiva]

"George R. Gonzalez" > wrote in message
news:hYTPa.43358$N7.5224@sccrnsc03...
> I seem to have stirred up a lot of controversy here. Let me summarize the
> responses:
>
>
> (A) You're right in adding the "missing" snubbers, missing fuses, missing
> bias controls, missing bias filters, missing bias test points, missing
bias
> set points, especially since the amp
> is acting up, even after replacing capacitors, looking it over... etc.
>
> (B) This Bogen amplifier is a part of our honorable tube heritage, the
> ancient designers never made any design compromises, you should be flogged
> for even hinting of any possibility of cutting-corners by the engineers,
or
> suggesting
> that the amplifier could be improved with a few modern components and
> techniques.
>
> (C) Bogen made high-quality stuff that lasted forever.
>
> (D) Bogen made some stuff that was marginal, that blew tubes a lot.
>
> ---
>
> In other words, all over the spectrum, and a lot more heat than
> illumination.
>
> I'll readily concede that all of the above may be true, although not all
for
> the same
> amplifier model.
>
> But as my viewpoint is mainly an engineering one, I see this more as
> a challenge to tame, not as a historical artifact that should be preserved
> and worshiped as-is.
>
> You all, are of course are entitiled to differ and to treat your
amplifiers
> as you see fit.
>
>
>
> Regards,
>
>
> George
>


Once again, George, an interestin' take on things you've got there. You've
got some conflicting (in your eyes) replies, and thus think that the replies
offered "a lot more heat then illumination" (you punster, you...) let me
try to make sense of this for you, shall i? (I shall)
The people who suggested it was fine to add all the crapola to the amp may
have felt "hey, it's not my amp, if the guy wants to play Will E Coyote, let
him". perfectly valid. You paid for the thing, you can turn it into
anything your heart desires, it's *yours*.
No one reply which i have read implied that the amp you got was "A part of
history [attempt at bitin' sarcasm & bull**** snipped]" and, thus, should be
preserved. Dude! The things are common coz they didn't **** the bed in
their youth & got tossed - no one will miss your Bogen. And, ads far as
"using modern techniques"? Hard as i try, can't think of a single thing
you've mentioned that was not known when the amp was built. Or, do you
really think Bogen was unfamiliar with bias pots, snubbers & filter caps?
What the people were politely tryin' to tell you (since you approach this
from an engineering perspective) was that instead of finding the problem you
chose to redesign the amp. Well, that's fine, but if you really want to
play engineer, why not find the actual *cause* of the problem first (after
all, the sucker worked for years without all them new-fangled techniques
like snubbers), and *then* try to improve on the design? In other words, if
you can't even *fix* the foolish thing, perhaps you're not quite yet in a
position to mod it? With all respect to your engineerin' prowess...

[RonSonic]

On Sun, 13 Jul 2003 00:37:15 GMT, "Shiva" > wrote:

>
>"Jon Elson" > wrote in message
...
>>
>>
>> George R. Gonzalez wrote:
>>
>> >Sometimes you wonder how some products ever made it out of the design
>lab.
>> >
>> >Sometimes there's so much wrong, you wonder if the item is a joke.
>> >
>> >Someday I may relate the story of the no-name amplifier, but today's
>story
>> >is from a quite respected company, Bogen.
>> >
>> Respected? By who? They made a lot of public address gear, and a lot of
>it
>> went up in smoke. I can't be sure, but I think I know someone who
>wrestled
>> with this same amp, or maybe all their tube stuff was designed like this.
>> Very low-budget design, to produce a unit that barely met very low specs,
>> but absolutely couldn't be made cheaper, and to hell with the user.
>>
>> After looking inside some of their stuff, **I** certainly never respected
>> the brand.
>>
>
>Well shheeet, John, if **you** don't respect it, it must indeed be trash!
>And, John? there could be two reasons why you "[know] someone who [has]
>wrestled with an amp like this": 1. the design sux. 2. the guy's an
>idiot. Something makes me wann'a bet on the latter, 'coz I'm not the
>brightest bulb in the tree, and I've had no problems doin' Bogens.
>Budget-built? Sure. Unreliable? Hey, i'd love to see how modern toob amps
>will fare in 40 yrs...

We know how well the modern SS amps hold up.

Those Bogens ran for decades with little or no maintenance. Just fix the thing
and it'll be fine. Any competent tech should have no problem with one of those.

Ron

[Jimmy]

"Shiva" > wrote in message
...
>
> "George R. Gonzalez" > wrote in message
> news:hYTPa.43358$N7.5224@sccrnsc03...
> > I seem to have stirred up a lot of controversy here. Let me summarize
the
> > responses:
> >
> >
> > (A) You're right in adding the "missing" snubbers, missing fuses,
missing
> > bias controls, missing bias filters, missing bias test points, missing
> bias
> > set points, especially since the amp
> > is acting up, even after replacing capacitors, looking it over... etc.
> >
> > (B) This Bogen amplifier is a part of our honorable tube heritage, the
> > ancient designers never made any design compromises, you should be
flogged
> > for even hinting of any possibility of cutting-corners by the engineers,
> or
> > suggesting
> > that the amplifier could be improved with a few modern components and
> > techniques.
> >
> > (C) Bogen made high-quality stuff that lasted forever.
> >
> > (D) Bogen made some stuff that was marginal, that blew tubes a lot.
> >
> > ---
> >
> > In other words, all over the spectrum, and a lot more heat than
> > illumination.
> >
> > I'll readily concede that all of the above may be true, although not all
> for
> > the same
> > amplifier model.
> >
> > But as my viewpoint is mainly an engineering one, I see this more as
> > a challenge to tame, not as a historical artifact that should be
preserved
> > and worshiped as-is.
> >
> > You all, are of course are entitiled to differ and to treat your
> amplifiers
> > as you see fit.
> >
> >
> >
> > Regards,
> >
> >
> > George
> >
>
>
Occasionally one of these amps used to come into my shop with the output
tubes crispy fried. Usually this waas because the grid coupling caps were
shorted. replace these with 600 volt units. Also check other associated
componets for "doneness". Also be prepared to lay out much bucks for
replacement tubes. I wouldnt think an engineer would have much trouble
replacing these with something a little more economical, 6550's should be a
good choice I think.

[George R. Gonzalez]

"Jimmy" > wrote in message
. com...



> Occasionally one of these amps used to come into my shop with the output
> tubes crispy fried. Usually this waas because the grid coupling caps were
> shorted.

Shorted? Really? I see about onne shorted capacitor out of maybe 200 leaky
ones.



>replace these with 600 volt units.

I did replace all the caps-- they were the pink Renee Witherspoon plastic
kind,
of which about 99.5% I've encountered have been very leaky. The capacitors,
not the actresses.

> I wouldnt think an engineer would have much trouble
> replacing these with something a little more economical, 6550's should be
a
> good choice I think.

If they were just about any tube other than 8417's, then there are lots of
possible alternatives.
For example the 6L6, 6550, 7207, 6DQ6 series have roughly similar
characteristics.

But the 8417 was one of the highest-tech tubes made, with an incomparable
gm of 23,000! I don't know of any similar tubes.

This high a gm means that if we plugged in 6550's, the overall gain would go
down
more than 10DB, probably much more than the driver tube could make up.

Short of patching on one more preamp stage, I don't think plugging in any
other
tube type would work. Oh, and these tubes are being run at 625 volts, a bit
above
typical tube levels.


Regards,

George

[Shiva]

"Jimmy" > wrote in message
. com...
>
> "Shiva" > wrote in message
> ...
> >
> > "George R. Gonzalez" > wrote in message
> > news:hYTPa.43358$N7.5224@sccrnsc03...
> > > I seem to have stirred up a lot of controversy here. Let me summarize
> the
> > > responses:
> > >
> > >
> > > (A) You're right in adding the "missing" snubbers, missing fuses,
> missing
> > > bias controls, missing bias filters, missing bias test points, missing
> > bias
> > > set points, especially since the amp
> > > is acting up, even after replacing capacitors, looking it over...
etc.
> > >
> > > (B) This Bogen amplifier is a part of our honorable tube heritage, the
> > > ancient designers never made any design compromises, you should be
> flogged
> > > for even hinting of any possibility of cutting-corners by the
engineers,
> > or
> > > suggesting
> > > that the amplifier could be improved with a few modern components and
> > > techniques.
> > >
> > > (C) Bogen made high-quality stuff that lasted forever.
> > >
> > > (D) Bogen made some stuff that was marginal, that blew tubes a lot.
> > >
> > > ---
> > >
> > > In other words, all over the spectrum, and a lot more heat than
> > > illumination.
> > >
> > > I'll readily concede that all of the above may be true, although not
all
> > for
> > > the same
> > > amplifier model.
> > >
> > > But as my viewpoint is mainly an engineering one, I see this more as
> > > a challenge to tame, not as a historical artifact that should be
> preserved
> > > and worshiped as-is.
> > >
> > > You all, are of course are entitiled to differ and to treat your
> > amplifiers
> > > as you see fit.
> > >
> > >
> > >
> > > Regards,
> > >
> > >
> > > George
> > >
> >
> >
> Occasionally one of these amps used to come into my shop with the output
> tubes crispy fried. Usually this waas because the grid coupling caps were
> shorted. replace these with 600 volt units. Also check other associated
> componets for "doneness". Also be prepared to lay out much bucks for
> replacement tubes. I wouldnt think an engineer would have much trouble
> replacing these with something a little more economical, 6550's should be
a
> good choice I think.
>
>

Have 4 used ones - came out of a working amp, look like crap, but all worked
& the amp pulled rated power. Offers?

[Tim Williams]

"opcom" > wrote in message
...
> ... and put 6GH8's in the driver sockets, with mods.

Ack, GH8.. half of mine are all crackley or don't work at all.. :^)

Tim, listening to Frankenhouse with a 6U8

--
In the immortal words of Ned Flanders: "No foot longs!"
Website @ http://webpages.charter.net/dawill/tmoranwms

[George R. Gonzalez]

"opcom" > wrote in message
...
> My Bogen MO-200 came with no tubes. (basically eight 8417's, driving two
parallel connected transformers for 200W)
>
> 8417 are expensive. I modified the bias supply for 50V, and put an
adjustment for each tube, and stuck 6550's in it. 6CA7's also work fine. I
split the amp into two 100W channels and put 6GH8's in the driver sockets,
with mods.
>
> Mine does have a 1.0uF/100V plastic cap from filament to ground. too new
to be original. Never thought about it.

Aha! Finally, some corroberation and vindication for my
amplifier-desecration.

Some late-breaking info, I just know you were all waiting breathlessly for
this-- The two power-supply filter
capacitors turned out to be a bit down in capacity, about 30% down. I
suspect this contributed to the
problems. Still, it's a pretty marginal design that depends on capacitors
at exactly 100% strength.
And they were tiny to begin with-- two 40uf's in series! Plenty of room for
bigger ones, but noooo,
Bogen saved every penny they could. Maybe they were burdened with the cost
of the rather large output
trannies and had to pinch pennies in other places? Just a random surmise.


Regards,

George

[N. Thornton]

> > I aquired this Bogen PA amplifier, 50 watts out allegedly, pair of 8417's
> > for output.
> >
> > Nicely built, heavy-duty transformers.


Hi. If this thing is using 600v HT to put 50w out, your transformer
ratio is going to be miles out for any more common type of tube. As is
the HT of course. I would not be surprised if it made a mess and/or
shat itself if you put different tubes in and rebiased.

But I'm not familiar with any of those US tube numbers, and havent
actually tried it, so who knows.


Regards, NT

[Max Holubitsky]

The 6550 is an American tube, released in late 1954 by Tung-Sol, of
Newark NJ.
The KT-88 was released a couple years later, by GEC of the UK, and is
similar to the Tung-Sol 6550, but has some improved specifications, and
looks different. The 6550A was introduced in the early 1970s, but GE of
the USA, and improves upon the specifications of the original 6550 to
the point where it is equivalent to the KT-88.

Most of the 6550 tubes on the market today, are 6550A equivalents, and
can be interchanged freely with the KT-88.

"N. Thornton" wrote:

> 6550 is what we know as KT88 - for any other non US reader.
>
> Regards, NT

[Patrick Turner]

Max Holubitsky wrote:

> The 6550 is an American tube, released in late 1954 by Tung-Sol, of
> Newark NJ.
> The KT-88 was released a couple years later, by GEC of the UK, and is
> similar to the Tung-Sol 6550, but has some improved specifications, and
> looks different. The 6550A was introduced in the early 1970s, but GE of
> the USA, and improves upon the specifications of the original 6550 to
> the point where it is equivalent to the KT-88.
>
> Most of the 6550 tubes on the market today, are 6550A equivalents, and
> can be interchanged freely with the KT-88.

And afaik, after testing, EH 6550, EH KT88, Sovtek 6550, and Sovtek KT88
now have identical electrode structure within, and the same electrical
properties,
and only the cosmetics of the glass envelope and lettering is different.

Patrick Turner.

>
>
> "N. Thornton" wrote:
>
> > 6550 is what we know as KT88 - for any other non US reader.
> >
> > Regards, NT