Cassette I/O Board Q104 ?

[john]

Anybody have the standard part number for this?

It's Heathkit part 417-897.  Manual describes it as 'Selected FET'.

-John

[Joseph Travis]

The H8-5 Service manual shows it as a selected 3686.  I believe it may be a 2N3686.

Regards,

Joe

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[norberto.collado koyado.com]

It will be nice to check an H8-5 original board to find out the manufacturer number.

 

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[john]

I'm repairing an original board and the component is marked with the Heathkit part number (417-897) .  That was the first thing I checked.  No idea why Heathkit tried to impose their own part numbers rather than use the standard manufacturer numbers like everybody else on the planet.  But then they decided to ditch the S-100 bus, so that tells you something.

Thanks Joe,  I'll try a 2N3686

-John

[norberto.collado koyado.com]

Jameco has several N-Channel MOSFET 3-pins that you could try…

 

https://www.jameco.com/shop/KeywordSearchResultView?langId=-1&storeId=10001&catalogId=10001&search_type_c=jamecoall&freeText=n+channel+mosfet

 

Norberto

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[Dave McGuire]

On 1/30/23 01:05, 'john' via SEBHC wrote:
> No idea why Heathkit tried to impose their own part numbers rather than
> use the standard manufacturer numbers like everybody else on the
> planet.  But then they decided to ditch the S-100 bus, so that tells you
> something.

House numbers are extremely common in the industry; rare is the
company that doesn't use them. As frustrating as it can be for the rest
of us, there are many reasons for it.

"Selected" components is one common reason; components that need to
be qualified by one specification or another, like selecting a standard
type of transistor for low leakage, for example.

Another common reason is to add metadata like a specific
manufacturer. If it's determined that a 74LS74 from National
Semiconductor doesn't work properly in a circuit, but a 74LS74 from
Texas Instruments does, a house number can specify "a Texas Instruments
74LS74".

House-numbered components are more common than not, industry-wide,
and have been for decades.

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA

[John Crane]

Maybe in the larger consumer electronics industry - but not hobby micros from the 70's.

MITS didn't do it, neither did IMSAI, Processor Tech, SWTPC....

I have found ' house numbers' in HP calculators, but those were custom chips.

-J

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[Dave McGuire]

True, hobby companies (who were largely staffed/started by hobbyists)
did it less. One presumes Heath was planning for (and got) larger
production volumes, where this becomes more important. The other
companies you mention were arguably a small fraction of the size of Heath.

HP uses house numbers for everything, custom or not, whether they're
printed on the component or not. Look at the service manual for any HP
test instrument.

-Dave

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[Douglas Miller]

Also, recall that Heath did more than just computers, and started doing
that a long time before micro computers.

[Geo Monroe]

Companies use their own part numbers for a couple of reasons. They would keep a supply of parts in their own inventory. If they source different parts that are pin for pin and functionally compatible they can record them in their inventory under one part number for example. I have worked for companies that maintained parts in stock locally.