This model is a factory assembled model, and wasn't available as a kit,
AFAICT.

Dual counter A-B, single 8-digit LED display (7-segment LED green or red
digits).

Input A 5Hz-175MHz
Input B 5Hz-2MHz

The Input B doesn't show a count when a signal is applied.

The Input A section seems to operate as it should.

I've seen that the actual circuit section for Input B does have an output
signal which is connected to the main board at J103.
I can also see that the counter/display IC is getting good signals at the
correct pins.. input A and B, and control.

Some repairs were made by previous owner, it seems, such as replacement of
the original Frequency Counter/Timer display driver U20, with an ICM7226AIJL
(high reliability ceramic).

I first assumed that someone may have applied over-voltage(s) to the input
channels, and smoked the counter/display driver IC, but I've seen random
numbers displayed as I probed around the area of IC18 and the counter/driver
IC, which indicates that the unit can display readings for Input B (no
signal applied to Input A), but the displayed count is incorrect and
inconsistent.

An Intersil ICM7226A/B application/datasheet was included with the counter
unit, and found to be installed in the unit.

The ICM7226 is capable of 2 inputs A & B, and up to 100MHz as a
multi-function (frequency/period) counter and 8 digit display driver.

http://www.nostalgickitscentral.com/...hkit_test.html

The the counter/driver IC, and a circuit IC U18 CD74HCT86E (quad 2-input
Exclusive-OR), and possibly one other support IC may have been replaced.

There was evidence of what appears to be probe-skid-type, or tool scratches
on the bottom of the board in the area of the input circuitry section of
Input A.

The majority of the ICs are Hitachi, and a couple are Motorola and RCA
devices.

A third BNC input connector located on the rear panel is labeled TOTALIZE.

Another aspect that I'm unsure of is one of the functions.. there is a
selection of FR as one of the unit's functions, and since there is already
one marked FREQ, I think FR represents something else.

The other functions a

PER (period)

TI (time interval?)

TOTAL (totalize)

CHK (check display and indicators)


wb_wildbill-AT-yah-oh-oh.com

--
Cheers,
WB
..............

Wild_Bill wrote in message
...
This model is a factory assembled model, and wasn't available as a kit,
AFAICT.

Dual counter A-B, single 8-digit LED display (7-segment LED green or red
digits).

Input A 5Hz-175MHz
Input B 5Hz-2MHz

The Input B doesn't show a count when a signal is applied.

The Input A section seems to operate as it should.

I've seen that the actual circuit section for Input B does have an output
signal which is connected to the main board at J103.
I can also see that the counter/display IC is getting good signals at the
correct pins.. input A and B, and control.

Some repairs were made by previous owner, it seems, such as replacement of
the original Frequency Counter/Timer display driver U20, with an
ICM7226AIJL
(high reliability ceramic).

I first assumed that someone may have applied over-voltage(s) to the input
channels, and smoked the counter/display driver IC, but I've seen random
numbers displayed as I probed around the area of IC18 and the
counter/driver
IC, which indicates that the unit can display readings for Input B (no
signal applied to Input A), but the displayed count is incorrect and
inconsistent.

An Intersil ICM7226A/B application/datasheet was included with the counter
unit, and found to be installed in the unit.

The ICM7226 is capable of 2 inputs A & B, and up to 100MHz as a
multi-function (frequency/period) counter and 8 digit display driver.

http://www.nostalgickitscentral.com/...hkit_test.html

The the counter/driver IC, and a circuit IC U18 CD74HCT86E (quad 2-input
Exclusive-OR), and possibly one other support IC may have been replaced.

There was evidence of what appears to be probe-skid-type, or tool
scratches
on the bottom of the board in the area of the input circuitry section of
Input A.

The majority of the ICs are Hitachi, and a couple are Motorola and RCA
devices.

A third BNC input connector located on the rear panel is labeled TOTALIZE.

Another aspect that I'm unsure of is one of the functions.. there is a
selection of FR as one of the unit's functions, and since there is already
one marked FREQ, I think FR represents something else.

The other functions a

PER (period)

TI (time interval?)

TOTAL (totalize)

CHK (check display and indicators)


wb_wildbill-AT-yah-oh-oh.com

--
Cheers,
WB
.............



FR = Frequency Ratio ?
My guess , corroded switch contacts

Thank you Nigel.. frequency ratio would likely be a function of a universal
counter with 2 inputs.

There is no selector switch to select between Input A and Input B, which I
think is what you were suggesting.
That may seem odd (to me too).. that's where a manual would be handy, to see
what the actual operating procedures are like.

I forgot to mench, something that you generally include, which would be the
age of the instrument.. probably from about 1988.

--
Cheers,
WB
..............


"N_Cook" wrote in message
...

FR = Frequency Ratio ?
My guess , corroded switch contacts

Wild_Bill wrote:
This model is a factory assembled model, and wasn't available as a
kit, AFAICT.

Dual counter A-B, single 8-digit LED display (7-segment LED green or
red digits).

Input A 5Hz-175MHz
Input B 5Hz-2MHz

The Input B doesn't show a count when a signal is applied.

The Input A section seems to operate as it should.

I've seen that the actual circuit section for Input B does have an
output signal which is connected to the main board at J103.
I can also see that the counter/display IC is getting good signals at
the correct pins.. input A and B, and control.

Some repairs were made by previous owner, it seems, such as
replacement of the original Frequency Counter/Timer display driver
U20, with an ICM7226AIJL (high reliability ceramic).

I first assumed that someone may have applied over-voltage(s) to the
input channels, and smoked the counter/display driver IC, but I've
seen random numbers displayed as I probed around the area of IC18 and
the counter/driver IC, which indicates that the unit can display
readings for Input B (no signal applied to Input A), but the
displayed count is incorrect and inconsistent.

An Intersil ICM7226A/B application/datasheet was included with the
counter unit, and found to be installed in the unit.

The ICM7226 is capable of 2 inputs A & B, and up to 100MHz as a
multi-function (frequency/period) counter and 8 digit display driver.

http://www.nostalgickitscentral.com/...hkit_test.html

The the counter/driver IC, and a circuit IC U18 CD74HCT86E (quad
2-input Exclusive-OR), and possibly one other support IC may have
been replaced.
There was evidence of what appears to be probe-skid-type, or tool
scratches on the bottom of the board in the area of the input
circuitry section of Input A.

The majority of the ICs are Hitachi, and a couple are Motorola and RCA
devices.

A third BNC input connector located on the rear panel is labeled
TOTALIZE.
Another aspect that I'm unsure of is one of the functions.. there is a
selection of FR as one of the unit's functions, and since there is
already one marked FREQ, I think FR represents something else.

The other functions a

PER (period)

TI (time interval?)

TOTAL (totalize)

CHK (check display and indicators)


wb_wildbill-AT-yah-oh-oh.com

Do you have a copy of the schematic that you can post somewhere on the web
so we can take a look at the circuitry? Otherwise, it's just a shot in the
dark.

--
David
dgminala at mediacombb dot net

I appreciate your offer to assist, David, but nothing came with the unit,
other than the Intersil ICM7226 counter/driver datasheet.

--
Cheers,
WB
..............


"Dave M" wrote in message
...

Do you have a copy of the schematic that you can post somewhere on the web
so we can take a look at the circuitry? Otherwise, it's just a shot in
the dark.

--
David
dgminala at mediacombb dot net

On Jan 1, 8:01*am, "Wild_Bill" wrote:
This model is a factory assembled model, and wasn't available as a kit,
AFAICT.

Dual counter A-B, single 8-digit LED display (7-segment LED green or red
digits).

Input A 5Hz-175MHz
Input B 5Hz-2MHz

The Input B doesn't show a count when a signal is applied.

The Input A section seems to operate as it should.

I've seen that the actual circuit section for Input B does have an output
signal which is connected to the main board at J103.
I can also see that the counter/display IC is getting good signals at the
correct pins.. input A and B, and control.

Some repairs were made by previous owner, it seems, such as replacement of
the original Frequency Counter/Timer display driver U20, with an ICM7226AIJL
(high reliability ceramic).

I first assumed that someone may have applied over-voltage(s) to the input
channels, and smoked the counter/display driver IC, but I've seen random
numbers displayed as I probed around the area of IC18 and the counter/driver
IC, which indicates that the unit can display readings for Input B (no
signal applied to Input A), but the displayed count is incorrect and
inconsistent.

An Intersil ICM7226A/B application/datasheet was included with the counter
unit, and found to be installed in the unit.

The ICM7226 is capable of 2 inputs A & B, and up to 100MHz as a
multi-function (frequency/period) counter and 8 digit display driver.

http://www.nostalgickitscentral.com/...hkit_test.html

The the counter/driver IC, and a circuit IC U18 CD74HCT86E (quad 2-input
Exclusive-OR), and possibly one other support IC may have been replaced.

There was evidence of what appears to be probe-skid-type, or tool scratches
on the bottom of the board in the area of the input circuitry section of
Input A.

The majority of the ICs are Hitachi, and a couple are Motorola and RCA
devices.

A third BNC input connector located on the rear panel is labeled TOTALIZE..

Another aspect that I'm unsure of is one of the functions.. there is a
selection of FR as one of the unit's functions, and since there is already
one marked FREQ, I think FR represents something else.

The other functions a

PER (period)

TI (time interval?)

TOTAL (totalize)

CHK (check display and indicators)

wb_wildbill-AT-yah-oh-oh.com

--
Cheers,
WB
.............

My incination would be to closely examine the soldering, both rework
and original. If that looks good, then apply the same signal of about
1 kHz sine to both inputs and compare the signal at the A and B input
pins on the counter chip with a good 'scope. Vary the input level and
see that the processed signals remain identical. If the signals are
identical, then the two input channels are probably okay and the
problem lies in the the control circuitry or the counter chip. Since
you see operation when probing, that suggested the counter chip is
good, but thre is a fault in it's control due to some sort of poor
connection such as solder, a dirty switch as N. Cook suggests, or even
'lead rot' on one or more DIP packages.

Neil S.

Thanks Neil.. my suspicion is as you suggested, as I've seen waveforms
present at the 2 inputs of the counter IC with signal generator inputs at
Input A & B, and that perhaps one of a couple of other ICs may be the
culprit.

In numerical order, just before the ICM7226 counter IC there a
U18 quad 2-input Exclusive-OR
U19 HD74LS74AP dual D-type positive edge triggered F-flops with reset and
clear

Of course, there are numerous other signals to the counter IC that are
essential for proper operation, where I believe a schematic would be most
helpful.
There is a Test Point pin TP1 beside U18, for example.

The only obvious non-factory soldering is around the input area of the Input
A circuit components, where it appears that some resistor leads were lifted
to check their values.
The soldering under the sockets for the 2 newer ICs (U18 and counter IC U20)
looks identical to the rest of the wave-soldered factory assembly
connections, although oddly enough those 2 ICs are the only ones with
sockets.

FWIW, I wouldn't claim that it's not possible for me to be fooled, but I've
seen a lot of soldering and hand soldering generally always has certain
characteristics that differ from factory connections, such as inconsistent
amounts of solder applied to some pads and several other traits.

--
Cheers,
WB
..............


"nesesu" wrote in message
...

My incination would be to closely examine the soldering, both rework
and original. If that looks good, then apply the same signal of about
1 kHz sine to both inputs and compare the signal at the A and B input
pins on the counter chip with a good 'scope. Vary the input level and
see that the processed signals remain identical. If the signals are
identical, then the two input channels are probably okay and the
problem lies in the the control circuitry or the counter chip. Since
you see operation when probing, that suggested the counter chip is
good, but thre is a fault in it's control due to some sort of poor
connection such as solder, a dirty switch as N. Cook suggests, or even
'lead rot' on one or more DIP packages.

Neil S.

On Jan 1, 4:38*pm, "Wild_Bill" wrote:
Thanks Neil.. my suspicion is as you suggested, as I've seen waveforms
present at the 2 inputs of the counter IC with signal generator inputs at
Input A & *B, and that perhaps one of a couple of other ICs may be the
culprit.

In numerical order, just before the ICM7226 counter IC there a
U18 quad 2-input Exclusive-OR
U19 HD74LS74AP dual D-type positive edge triggered F-flops with reset and
clear

Of course, there are numerous other signals to the counter IC that are
essential for proper operation, where I believe a schematic would be most
helpful.
There is a Test Point pin TP1 beside U18, for example.

The only obvious non-factory soldering is around the input area of the Input
A circuit components, where it appears that some resistor leads were lifted
to check their values.
The soldering under the sockets for the 2 newer ICs (U18 and counter IC U20)
looks identical to the rest of the wave-soldered factory assembly
connections, although oddly enough those 2 ICs are the only ones with
sockets.

FWIW, I wouldn't claim that it's not possible for me to be fooled, but I've
seen a lot of soldering and hand soldering generally always has certain
characteristics that differ from factory connections, such as inconsistent
amounts of solder applied to some pads and several other traits.

--
Cheers,
WB
.............

"nesesu" wrote in message

...

My incination would be to closely examine the soldering, both rework
and original. If that looks good, then apply the same signal of about
1 kHz sine to both inputs and compare the signal at the A and B input
pins on the counter chip with a good 'scope. Vary the input level and
see that the processed signals remain identical. If the signals are
identical, then the two input channels are probably okay and the
problem lies in the the control circuitry or the counter chip. Since
you see operation when probing, that suggested the counter chip is
good, but thre is a fault in it's control due to some sort of poor
connection such as solder, a dirty switch as N. Cook suggests, or even
'lead rot' on one or more DIP packages.

Neil S.

This data sheet looks like it gives enough information to trace
through the operating parameters of the chip in your application.
Heath was known to utilize the 'typical application' circuits of the
manufacturers, so I would not be surprised to find the data sheet
fairly close to the circuit you have. This also explains the various
functions of the controls.
http://www.electroniccircuits.gr/files/ICM7226.pdf

Neil S.

Thanks again, Neil. You're correct that the datasheet shows all the details
of the operation of the counter/display IC.. and going thru the complete set
of I/O signals will likely show if the IC is functional.

I'd still like to have a manual and schematic to see what the recommended
uses or limitations of the counter are, and to confirm that the correct
parts are present.

BTW, the unit was factory built, manufactured in Japan, so the so the design
and features could be nearly identical or similar to counters of other brand
names.

The 80s were around the time when a lot of U.S. domestic test equipment
manufacturers started selling imported models.. Leader, BK Precision etc.
Browsing catalogs back then, it was common to see numerous brand models that
were nearly identical except for cosmetic differences.. front panel, knob
styles etc.

--
Cheers,
WB
..............


"nesesu" wrote in message
...

This data sheet looks like it gives enough information to trace
through the operating parameters of the chip in your application.
Heath was known to utilize the 'typical application' circuits of the
manufacturers, so I would not be surprised to find the data sheet
fairly close to the circuit you have. This also explains the various
functions of the controls.
http://www.electroniccircuits.gr/files/ICM7226.pdf

Neil S.

Wild_Bill wrote:
This model is a factory assembled model, and wasn't available as a kit,
AFAICT.

Dual counter A-B, single 8-digit LED display (7-segment LED green or red
digits).

Input A 5Hz-175MHz
Input B 5Hz-2MHz

The Input B doesn't show a count when a signal is applied.

The Input A section seems to operate as it should.
...

These folks claim to have a copy for sale @ $22USD (not bad if original):

http://www.vintagemanuals.com/manual...model=ETI-7040

However these folks don't have a download schematic (pity) although they
do have a lot of older Heathkit info:

http://www.vintage-radio.info/heathkit/

John :-#)#

--
(Please post followups or tech enquiries to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."