I have a Pac with a low 6M* line, when I piggyback a 74LS86 (IIRC, whatever
chip generates that signal) on it, it's fine, but taking it off, the game
'bogs down', sometimes, but plays with no glitches but somtimes the music
slows down speeds up, etc. Looks like low TTL levels measured at Pin 1 on
the z80 sync buss card. When I say piggyback, I put my logic comparator on
it and it raises the levels by about .4V

Do folks just slap some HC chips in the circuit or is there a better classic
way to fix this? Course I could just solder a duplicate chip on top I guess.
I suppose something else tied to that line may be pulling it down but I
haven't gotten that far yet. Replacing the crappy sync buss single wipe
socket may help of course.

Ideas? Does anyone talk fairly serious tech here or should I take all this
to sci.electronics.repair?

--
"Quality is the enemy of production."
Homepage - http://members.cox.net/rcbullock/ 'It's lamer than Spaeth's!'
** Replies to rcbullock '"AT"" cox.net ** Sorry, I detest spam.

"Robert Bullock" wrote in message
news:YEn3e.59$Iq6.35@okepread01...
I have a Pac with a low 6M* line, when I piggyback a 74LS86 (IIRC,
whatever
chip generates that signal) on it, it's fine, but taking it off, the game
'bogs down', sometimes, but plays with no glitches but somtimes the music
slows down speeds up, etc. Looks like low TTL levels measured at Pin 1 on
the z80 sync buss card. When I say piggyback, I put my logic comparator on
it and it raises the levels by about .4V

Do folks just slap some HC chips in the circuit or is there a better
classic
way to fix this? Course I could just solder a duplicate chip on top I
guess.
I suppose something else tied to that line may be pulling it down but I
haven't gotten that far yet. Replacing the crappy sync buss single wipe
socket may help of course.

Ideas? Does anyone talk fairly serious tech here or should I take all this
to sci.electronics.repair?


You've either got a weak chip driving the bus, or something is pulling it
down. Try replacing the chip driving first and see where that gets you.

No Robert, we are all beneath you and you must take your genius knowledge to
a higher level.

Thomas

"Robert Bullock" wrote in message
news:YEn3e.59$Iq6.35@okepread01...
I have a Pac with a low 6M* line, when I piggyback a 74LS86 (IIRC, whatever
chip generates that signal) on it, it's fine, but taking it off, the game
'bogs down', sometimes, but plays with no glitches but somtimes the music
slows down speeds up, etc. Looks like low TTL levels measured at Pin 1 on
the z80 sync buss card. When I say piggyback, I put my logic comparator on
it and it raises the levels by about .4V

Do folks just slap some HC chips in the circuit or is there a better
classic way to fix this? Course I could just solder a duplicate chip on
top I guess. I suppose something else tied to that line may be pulling it
down but I haven't gotten that far yet. Replacing the crappy sync buss
single wipe socket may help of course.

Ideas? Does anyone talk fairly serious tech here or should I take all this
to sci.electronics.repair?

--
"Quality is the enemy of production."
Homepage - http://members.cox.net/rcbullock/ 'It's lamer than Spaeth's!'
** Replies to rcbullock '"AT"" cox.net ** Sorry, I detest spam.

You cound try an HC, definitely more source/sink current punch, but
your switching time may degrade and you'd see some glitching taking
place. You may try a 74S86 instead. Still twice more punch than the LS,
but with better propagation delays.

Course we don't talk narly well as dem dere sci-ty folk. Us being all
out in thu hills I rec-on. ;-)

- Craig



Robert Bullock wrote:
I have a Pac with a low 6M* line, when I piggyback a 74LS86 (IIRC,
whatever
chip generates that signal) on it, it's fine, but taking it off, the
game
'bogs down', sometimes, but plays with no glitches but somtimes the
music
slows down speeds up, etc. Looks like low TTL levels measured at Pin
1 on
the z80 sync buss card. When I say piggyback, I put my logic
comparator on
it and it raises the levels by about .4V

Do folks just slap some HC chips in the circuit or is there a better
classic
way to fix this? Course I could just solder a duplicate chip on top I
guess.
I suppose something else tied to that line may be pulling it down but
I
haven't gotten that far yet. Replacing the crappy sync buss single
wipe
socket may help of course.

Ideas? Does anyone talk fairly serious tech here or should I take all
this
to sci.electronics.repair?

--
"Quality is the enemy of production."
Homepage - http://members.cox.net/rcbullock/ 'It's lamer than
Spaeth's!'
** Replies to rcbullock '"AT"" cox.net ** Sorry, I detest spam.

According to the schematic, the source of that signal is the 74LS368 chip
near the crystal. I've seen that chip fail before. It's not all that
difficult to find, so I recommend replacing it.

Then again, the 74LS86 chip that's also connected to that line (as an input)
could perhaps be loading down that signal, and may need replacement,
instead. But that too is an easy-to-get chip.

"Craig Yarbrough" bravely wrote to "All" (01 Apr 05 21:32:54)
--- on the heady topic of " TECH: Fix for Low TTL levels? HC chips?"


74HC is not 100% compatible with TTL because of the smaller fan-out, and
74S draws a lot more current so that LS might not drive it properly. The
better replacement is HCT if either LS or ALS was not available, but the
74LS86 is a very common logic ic.


CY From: "Craig Yarbrough"
CY Xref: aeinews rec.games.video.arcade.collecting:73830

CY You cound try an HC, definitely more source/sink current punch, but
CY your switching time may degrade and you'd see some glitching taking
CY place. You may try a 74S86 instead. Still twice more punch than the
CY LS, but with better propagation delays.

CY Course we don't talk narly well as dem dere sci-ty folk. Us being all
CY out in thu hills I rec-on. ;-)

CY - Craig

.... I lurk quietly and carry a big OFF/ON switch.

Ya know, some folks just take everything as an insult. Hard talk of tech not
specific to arcade games is a bit outside the realm of day to day RGVAC, and
might be more appropos to sci.* groups. Especially general digital
electronics questions.

Let's face it, a the signal tends to degrade around here for many reasons
that will be obvious to regular readers.

You too Thomas; if you want to wrongly take what I say as insult, it
wouldn't be the first time.

What I should have said was :

"Does anyone talk fairly serious tech here ANYMORE or should I take all this
to sci.electronics.repair?"

Spaeth's down to one line responses, and I haven't seen K. Layton, Bob
Roberts, Randy Fromm, etc. post in a while.

'Sall I'm sayin'.

And, I'm a sub-genius, just below par in the 130 IQ range. Usually the top
couple of percent on standardized tests. 30 on my ACT, 34 in the Science
section. Some days I feel smarter than others. For the record. Genius is a
strong term. "Needs to apply himself more" would be an accurate statement.


"Craig Yarbrough" wrote in message
oups.com...

Course we don't talk narly well as dem dere sci-ty folk. Us being all
out in thu hills I rec-on. ;-)

Ok Rob, no offense meant or taken. I'd tell you to look for the ;-)
because it usually indicates a tongue-in-cheek response. But whatever.

If I see posts like yours I usually take the time to help out. It's the
least I can do after all the help I've received from the NG over the
past few years. If I make a lame attempt to inject some humor, just
ignore it and move on.

Cheers!

- Craig


Robert Bullock wrote:
Ya know, some folks just take everything as an insult. Hard talk of
tech not
specific to arcade games is a bit outside the realm of day to day
RGVAC, and
might be more appropos to sci.* groups. Especially general digital
electronics questions.

Let's face it, a the signal tends to degrade around here for many
reasons
that will be obvious to regular readers.

You too Thomas; if you want to wrongly take what I say as insult, it
wouldn't be the first time.

What I should have said was :

"Does anyone talk fairly serious tech here ANYMORE or should I take
all this
to sci.electronics.repair?"

Spaeth's down to one line responses, and I haven't seen K. Layton,
Bob
Roberts, Randy Fromm, etc. post in a while.

'Sall I'm sayin'.

And, I'm a sub-genius, just below par in the 130 IQ range. Usually
the top
couple of percent on standardized tests. 30 on my ACT, 34 in the
Science
section. Some days I feel smarter than others. For the record. Genius
is a
strong term. "Needs to apply himself more" would be an accurate
statement.


"Craig Yarbrough" wrote in message
oups.com...

Course we don't talk narly well as dem dere sci-ty folk. Us being
all
out in thu hills I rec-on. ;-)

I'm just giving you a hard time Robert, no harm intended. That's the bad
thing about message boards, it doesn't relay the emotion behind the words.

Thomas

"Robert Bullock" wrote in message
news:i6z3e.236$Iq6.124@okepread01...
Ya know, some folks just take everything as an insult. Hard talk of tech
not specific to arcade games is a bit outside the realm of day to day
RGVAC, and might be more appropos to sci.* groups. Especially general
digital electronics questions.

Let's face it, a the signal tends to degrade around here for many reasons
that will be obvious to regular readers.

You too Thomas; if you want to wrongly take what I say as insult, it
wouldn't be the first time.

What I should have said was :

"Does anyone talk fairly serious tech here ANYMORE or should I take all
this
to sci.electronics.repair?"

Spaeth's down to one line responses, and I haven't seen K. Layton, Bob
Roberts, Randy Fromm, etc. post in a while.

'Sall I'm sayin'.

And, I'm a sub-genius, just below par in the 130 IQ range. Usually the top
couple of percent on standardized tests. 30 on my ACT, 34 in the Science
section. Some days I feel smarter than others. For the record. Genius is a
strong term. "Needs to apply himself more" would be an accurate statement.


"Craig Yarbrough" wrote in message
oups.com...

Course we don't talk narly well as dem dere sci-ty folk. Us being all
out in thu hills I rec-on. ;-)