On Sat, 20 Sep 2008 16:14:21 -0700 (PDT), charrid
wrote:

Would anybody who owns Eico model 710 GDO be willing to supply coil
data (diameter, length, No. of turns, wire diameter) so that I could
duplicate the coils?

Yech, tubes. I have several Heathkit grid dip meters, but no Eico.

This may help:
http://www.qsl.net/n4xy/GDO_EICO.html
The photo shows one coil, which should give you an idea as to the
general size and construction of the coil.

The photo of the Eico 710-A looks very much like one of my Heathkits
(buried somewhere). Do you have a 710 or a 710-A. There's a huge
difference.

I bought the coil-less 710 at the fleamarket and
cannot find the coil set. I am mainly interested in the 2.9-7,5 and
7.5-18 MHz ranges. Or maybe a close-up photo with a ruler laying next
to the coils would be enough.
73, Rich OK8RF

Others have suggested cut-n-try which is probably good enough. As
long as the coil looks roughly like the original, it should work.

However, if you wanna do the math, look at the schematic and figure
out the minimum and maximum capacitance on the variable tuning
capacitor. Be sure to include any trimmers or padding capacitors in
the tuned circuit. You know the lowest and highest frequencies from
the dial. Drag out your abacus and plug the numbers into the usual LC
resonant frequency equation. Solve for a value of L that will be
roughly the same at both the high and low ends of the dial. You
probably won't hit the exact value, but it should be close. Lots of
online calculators for the inductance of solenoid wound coils. No
need for an LRC meter as you can just plug it into the grid dip meter
and count the frequency.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Sat, 20 Sep 2008 20:02:57 -0700, Jeff Liebermann
wrote:

This may help:
http://www.qsl.net/n4xy/GDO_EICO.html
The photo shows one coil, which should give you an idea as to the
general size and construction of the coil.

More photos.
http://reviews.ebay.com/Eico-710-Grid-Dip-Meter-Coil-Set-protection-packing_W0QQugidZ10000000001863194?ssPageName=BUYG D:CAT:-1:SEARCH:5
Oh-oh. My Heathkit coils do not have ferrite or iron slugs. The Eico
710 coils apparently do. The coil on the left is obviously broken.

Free manual for the Eico 710:
http://bama.edebris.com/manuals/eico/710/
I'm too lazy to find a DejaVu decompressor, but I expect there are
some instructions and diagrams of the coils in the manual.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Sep 21, 5:11*am, Jeff Liebermann wrote:
On Sat, 20 Sep 2008 20:02:57 -0700, Jeff Liebermann
wrote:

Free manual for the Eico 710:
http://bama.edebris.com/manuals/eico/710/
I'm too lazy to find a DejaVu decompressor, but I expect there are
some instructions and diagrams of the coils in the manual.
....
Jeff, thanks very much for your suggestions and links. I have actually
already downloaded BAMA manual (Dejavu plugin works great on IrfanView
4.20, saves as pdf) and I will get to work calculating the approximate
inductances. The variable C is the only component they don't show the
value for, but I'll take a guess, wind a coil and listen for the
signal. Then with some trial and error I can probably come up with a
couple of coils for the ranges I am interested in. I know the scale
won't be accurate, but in this day of digital readouts it's not
important.

I am fascinated with the number of GDO's shown on N4XY's site - I
remember seeing just Heath, Eico and an old Mullen.

Thanks agn
Rich OK8RF

On Sun, 21 Sep 2008 12:52:35 -0700 (PDT), charrid
wrote:

On Sep 21, 5:11*am, Jeff Liebermann wrote:
On Sat, 20 Sep 2008 20:02:57 -0700, Jeff Liebermann
wrote:

Free manual for the Eico 710:
http://bama.edebris.com/manuals/eico/710/
I'm too lazy to find a DejaVu decompressor, but I expect there are
some instructions and diagrams of the coils in the manual.

Jeff, thanks very much for your suggestions and links. I have actually
already downloaded BAMA manual (Dejavu plugin works great on IrfanView
4.20, saves as pdf)

Duh. I use Irfanview heavily, but have never bothered to download the
DejaVu plugin. Thanks.

and I will get to work calculating the approximate
inductances. The variable C is the only component they don't show the
value for, but I'll take a guess, wind a coil and listen for the
signal.

That will work as long as you don't accidentally land on a
sub-harmonic. Methinks a frequency counter might be more useful than
tuning around the bands looking for the signal.

If you have a capitance meter or bridge, it might be possible to
measure the value of the tuning capacitor.

Then with some trial and error I can probably come up with a
couple of coils for the ranges I am interested in. I know the scale
won't be accurate, but in this day of digital readouts it's not
important.

Chuckle. A few months ago, I won a used HP something universal
counter on eBay because I wanted the extra digits of resolution.
However, that was for period and event counting, not frequency.

I am fascinated with the number of GDO's shown on N4XY's site - I
remember seeing just Heath, Eico and an old Mullen.

Search Google for "base dip oscillator" and "gate dip oscillator".
There are a few designers that couldn't find the grid pin on the
semiconductor devices. My Heathkit HD-1250 calls it a "solid-state
dip meter".

I don't know if this will help, but the HD-1250 looks very much like
the Eico (other than the tube versus the xistor). Here's a table of
coil values for it assembled from various parts of the manual:

MHZ uH
L1 1.6 - 3.4 171 red
L2 3.2 - 6.6 41.1 orn
L3 6.3 - 13 10.2 yel
L4 12.5 - 26 2.62 grn
L5 25 - 51 0.72 blu
L6 48 - 100 0.196 vio
L7 100 - 250 ???? brn

As usual, no value on the tuning capacitor in the manual, but it can
be calculated from the above data.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Sep 22, 2:15*am, Jeff Liebermann wrote:
On Sun, 21 Sep 2008 12:52:35 -0700 (PDT), charrid
wrote:

sub-harmonic. *Methinks a frequency counter might be more useful than
tuning around the bands looking for the signal.

Which brings me to another one of my boat anchors - GR-1192B freq.
counter which worked fine for 20 years just stopped counting. I am
trying to find a manual on the Manual exchange group but so far no
reply. No BAMA record, either. I know the new counters are cheap and
tenth in size, but the neon display tubes look so nice...

Just got mail from K7ITM offering to supply the Eico coil info. Thanks
for the Heath data.

Rich OK8RF

On Sun, 21 Sep 2008 22:25:33 -0700 (PDT), charrid
wrote:

On Sep 22, 2:15*am, Jeff Liebermann wrote:
On Sun, 21 Sep 2008 12:52:35 -0700 (PDT), charrid
wrote:

sub-harmonic. *Methinks a frequency counter might be more useful than
tuning around the bands looking for the signal.

Which brings me to another one of my boat anchors - GR-1192B freq.
counter which worked fine for 20 years just stopped counting.

Nixie tubes. Ah... nostalgia. I've got several boxes with Nixie
tubes (HP5248M, HP5246L, and some home made junk). I think I paid
more for the printed manuals than for the counters and downconverters.
The usual problem with ancient hardware are the electrolytic
cazapitors. If you have an ESR meter, test them to see if they have
"dried out". If everything looks like it's working (display lights up
and digits change when thrashing the buttons), then it might be the
time base oscillator or dividers. Try an external time base
oscillator in case the crystal has quit.

I am
trying to find a manual on the Manual exchange group but so far no
reply. No BAMA record, either. I know the new counters are cheap and
tenth in size, but the neon display tubes look so nice...

Photo of the counter at bottom of page:
http://www.k5cm.com/k1ggiFMTMethod.htm

General Radio morphed into GenRad and was bought by Teradyne. The
test equipment division went to IET Labs:
http://www.ietlabs.com/Genrad/index.html
The have a few manuals online:
http://www.ietlabs.com/pdf/Manuals/index.html
but not the GR1192B. Send them email as I'm sure they have a printed
copy in the archives that only needs to be scanned. Maybe just the
schematic and block diagram.

I make it a habit of buying or downloading the manual for literally
every piece of test equipment that I use. I find myself repairing the
old equipment all too often:
http://802.11junk.com/jeffl/pics/home/slides/lab.html
Note: It's a lab, not a museum.

Just got mail from K7ITM offering to supply the Eico coil info. Thanks
for the Heath data.

Cool. One question. Is the frequency range of the Eico the same as
the Heathkit ranges that I listed? I'm curious.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Sep 22, 8:37*am, Jeff Liebermann wrote:
On Sun, 21 Sep 2008 22:25:33 -0700 (PDT), charrid
wrote:

"dried out". *If everything looks like it's working (display lights up
and digits change when thrashing the buttons), then it might be the
time base oscillator or dividers. *Try an external time base
oscillator in case the crystal has quit. *

Power supply was also my first thought, but Nixies light up and if I
try hard, I can change some digits. Time base fault sounds like a
good bet. Thanks for the hint.

Photo of the counter at bottom of page:
http://www.k5cm.com/k1ggiFMTMethod.htm

I have already emailed k5cm asking if he has the manual

The have a few manuals online:
http://www.ietlabs.com/pdf/Manuals/index.html
but not the GR1192B. *Send them email as I'm sure they have a printed
copy in the archives that only needs to be scanned. *Maybe just the
schematic and block diagram.

I did get to ietlabs site in my first searches. Never thought of
mailing them for a scan, though. I'll give them a try.


old equipment all too often:
http://802.11junk.com/jeffl/pics/home/slides/lab.html
Note: *It's a lab, not a museum.

I don't think 20-30 year old HP's are at all museum pieces - they are
still in their prime.

Cool. *One question. *Is the frequency range of the Eico the same as
the Heathkit ranges that I listed? *I'm curious.

Eico 710 has 8 coils starting below AM BC band:
L1 0.4 - 0.7
L2 0.7-1.38
L3 1.38-2.9
L3 2.9-7.5
L4 7.5-18
L5 18-42
L6 42-100
L7 100-250

Rich, OK8RF

--
Jeff Liebermann * *
150 Felker St #D * *http://www.LearnByDestroying.com
Santa Cruz CA 95060http://802.11junk.com
Skype: JeffLiebermann * * AE6KS * *831-336-2558

Jeff Liebermann wrote:

...
Others have suggested cut-n-try which is probably good enough. As
long as the coil looks roughly like the original, it should work.
...


Yeah, working as a software engineer and finding I get the most money
from convincing those "with money" that I am worth "some of their money"
has made me aware of the value of reverse engineering--whether software
or hardware--it works!

But, if you have built enough "old box tube xmitters", you can almost
guess the dia./turns/and-caps wink Heck, bet I could come up with a
circuit using the same coils, using a fet, and saving the cost of the
filament power! Indeed, if the tube uses an octal socket, in his current
GDO, why not replace the tube with a fet(s)?

Regards,
JS

On Sat, 20 Sep 2008 21:27:20 -0700, John Smith
wrote:

Jeff Liebermann wrote:
...
Others have suggested cut-n-try which is probably good enough. As
long as the coil looks roughly like the original, it should work.
...

Yeah, working as a software engineer and finding I get the most money
from convincing those "with money" that I am worth "some of their money"
has made me aware of the value of reverse engineering--whether software
or hardware--it works!

The very first think I did when starting a new product, was to do a
"survey" of the competitions products. If possible, some were
purchased, dissected, reverse engineered, and on one occasion, cloned.
No need to reinvent the wheel when the competition has done it for
you.

But, if you have built enough "old box tube xmitters", you can almost
guess the dia./turns/and-caps wink Heck, bet I could come up with a
circuit using the same coils, using a fet, and saving the cost of the
filament power! Indeed, if the tube uses an octal socket, in his current
GDO, why not replace the tube with a fet(s)?

Because the typical FET as a much higher transconductance (typically
about 30 millisiemens versus 5 millisiemens) and a much wider
frequency response, that you'll probably spend considerable time
stabilizing the oscillator. It's not easy to build a tunable
oscillator that operates over such a wide frequency range. Also, the
grid and gate currents are quite different. It can be done because
there are FET grid dip oscillators available. However, if you compare
schematics, they are sufficiently different to require a rebuild.

It's also criminal sacrilege to despoil such a vintage boat anchor.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558