Wanted: schematic for KROHN-HITE MODEL 440-A Oscillator

[Engineer[_2_]]

Hi, Vacuumlanders,
Does anyone have the schematic for the vintage tube-based KROHN-HITE
MODEL 440-A Oscillator that they could scan and send me, or point to a
link (I haven't found one.) It's bigger than some boatanchors!
Mind has just died - no oscillation (but it was working.) I have
found a dead 6H6 tube (double-diode, heater open circuit - it may not
be critical and I could replace it with a 6AL5 with a base adapter);
also found a low emission 6AU5 (beam power tube) - it seems to be a B+
regulator but I still seem to have good B+. All 6SL7's test OK to
"good"; I subbed the worst one but still no oscillation. All other
tubes test OK to "good+". Now I'm stuck! I'm blind w/o a schematic on
this one.
Thanks for all replies.
Cheers,
Roger
PS. email address shown is fake (anti-spam.) Kindly use analogdino at
(ta-boy) rogers dot(ty as they) com(e), suitably decoded. Tks.
PPS. Also posted on RAR+P and sci.electronic.repair as group readers
differ but do overlap. I hope no-one is offended.

[Patrick Turner]

On Jan 31, 4:54*am, Engineer > wrote:
> Hi, Vacuumlanders,
> Does anyone have the schematic for the vintage tube-based KROHN-HITE
> MODEL 440-A Oscillator that they could scan and send me, or point to a
> link (I haven't found one.) *It's bigger than some boatanchors!
> Mind has just died - no oscillation (but it was working.) *I have
> found a dead 6H6 tube (double-diode, heater open circuit - it may not
> be critical and I could replace it with a 6AL5 with a base adapter);
> also found a low emission 6AU5 (beam power tube) - it seems to be a B+
> regulator but I still seem to have good B+. *All 6SL7's test OK to
> "good"; I subbed the worst one but still no oscillation. All other
> tubes test OK to "good+". *Now I'm stuck! I'm blind w/o a schematic on
> this one.
> Thanks for all replies.
> Cheers,
> Roger
> PS. *email address shown is fake (anti-spam.) *Kindly use analogdino at
> (ta-boy) rogers dot(ty as they) com(e), suitably decoded. *Tks.
> PPS. Also posted on RAR+P and sci.electronic.repair as group readers
> differ but do overlap. I hope no-one is offended.

If one does a Google search for your oscillator, not much comes up
except references to its use in measuring amps THD.

When tube gear dies here what I do is trace the schematic if I cannot
find one online or in an old book.

All true analog electronic enthusiasts should be capable of
maintaining their gear themselves and/or be capable of designing and
building whatever they want including oscillators, oscilloscopes, volt
meters, filters, etc, etc, etc.

Tubed test gear IS ALWAYS much more simply constructed than something
using chips and a wave form fabricator.
Nobody need build all their own test gear but one should be able to
fix a fault after analysis without any data fairly easy. Test gear I
have sometimes does fail like all electronic things and the tubed test
gear i have is the most easily fixed. I had an all solid state Labtech
oscilliscope made in the early 1990s and it worked well for a few
years but slowly functions vanished and it became way too difficult to
service, so out the ****ing thing went to the bin.
I found other simpler better 'scopes. My solid state function
generator also finally developed so many faults it too was binned to
cut my losses. I use a 1kHz wein bridge sine wave oscillator I made
myself with only 1 opamp and a discrete transistor amp within and it
is fixable easily because its simple, and THD < 0.002%, OK for tube
amps. I have 3 other wein bridge oscillators, with special circuits to
stop the amplitude bounce. Two are tubed, and dead easy to service.

I am planning another using 4 x 3gang radio tuning gangs for the R&C
wein bridge networks. Most WB oscilators with tuning caps are limited
in their lowest F to 20Hz which is bad, and one wants to get to 4Hz at
least, so if C max is increased from 400pF to say 2,400pF, then F
could reach down to the 4Hz. But old man time prevents me using a few
of the box fulls of tuning caps I have accumulated. Oiled up and
cleaned, the tuning gangs offer better F spread and more reliable and
stable operation than most pots.

I often get tube gear here to repair, service or upgrade and rarely
can I find any schematic so I take the time to draw the schematic.
Just this week I had a pair of Quad 40 amps, and a pair of 100W Ming
Da amps with 6SN7, 300B and 845, plus the Ming Da preamp which has 2A3
for HT diodes, 6SN7&6DJ8 for signal amping as well as EL34&6SN7 for B+
reg.
It does not take long to draw a schematic and prove you have it done
right and then you come to know just how the thing works all the
better, and where to look if something dies, or a voltage at an
electrode looks wrong while probing around for what you expect to
find.

Please get busy.

I have a couple of VTVM which were in very poor condition when they
were donated to me.
When one looks at the specs of these old bits of junk they are
impressive compared to a DVMM but the DVMM has a digital readout which
is so much more handy than peering at a dial and picking out which
dial scale to read and what the reading is. DVMM are MORE ACCURATE,
but of course a DVMM cannot accurately read ac volts above about 2kHz
which is a PIA when measuring an F response, or the Z of a speaker for
the whole AF range.
The schematics are very complex with so many switches. I got the
meters moving OK and put in new batteries but the measurements are
nonsensical and the meter readings silly. I will have to think long
and hard to find which of the ancient old parts are faulty.

I have to work for a living and I don't have all the time i'd like to
fix nice old junk. If you are retired, there's no excuse; jus' do it.
It stops Alzimer's disease.

Patrick Turner.

[GRe]

"Engineer" > wrote in message
...
> Hi, Vacuumlanders,
> Does anyone have the schematic for the vintage tube-based KROHN-HITE
> MODEL 440-A Oscillator that they could scan and send me, or point to a
> link (I haven't found one.)
[...]



There's a "Kron-Hite 440A (R) Operating & Maintenanca Manual" on e-Bay, item
# 370280895805

Rgds, Gio

[Engineer[_2_]]

On Feb 1, 3:02*am, "GRe" > wrote:
> "Engineer" > wrote in message
>
> ...> Hi, Vacuumlanders,
> > Does anyone have the schematic for the vintage tube-based KROHN-HITE
> > MODEL 440-A Oscillator that they could scan and send me, or point to a
> > link (I haven't found one.)
>
> [...]
>
> There's a "Kron-Hite 440A (R) Operating & Maintenanca Manual" on e-Bay, item
> # 370280895805
>
> Rgds, Gio

Great! thanks! I've bought it! $10 plus shipping.
Cheers,
Roger

[Watt? Me worry?]

> It stops Alzimer's disease.
>
> Patrick Turner


Hi RATs!

Yes, this hobby is a great place to burn off time, whenever
possible :)

No, Alz is not quite that cooperative. Friend lost his wife last year.
She had the chair of the medical research department at their
University.

Disease is easy to diss. Living thru it is a bit less galant ;)

Happy Ears!

Al Marcy