Heathkit ETI-7040 Manual Wanted Universal Counter 175 MHz

ICM7226AIJL

counter/driver

scratches

FR = Frequency Ratio ? My guess , corroded switch contacts

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.

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David
dgminala at mediacombb dot net

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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.

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 .............

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

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

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

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

John :-#)#

--
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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 are: 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 .............

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.

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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.

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 .............

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.

Neil S.

Thanks John.. as that seemed to be my only option, I made the purchase.. so I may have the manual by the end of the week.

BTW, they send manuals by USPS ($5 for this purchase), which I prefer, and they also accept PayPal so it's a fairly easy checkout, and the checkout system accepted "not published" for the phone number entry. FWIW, using PayPal may be preferrable for some folks, so one isn't giving credit card info to various online sellers.

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