Conference hydra::amiga_v1

    Yup, went through the same thing.  I'd suggest the 8520.  Memory
    Location has them in stock.  If you're desperate and can't find
    one, I think I have a good one lying around somewhere you can have
    until you find one.
    
    They run around $20 and are VERY succeptable to static electricity.
    
    John
    

Thanks John.   I haven't taken it apart yet. What is the full part number
and manufacturer of the 8520?

John    

There has been a lot of talk on USENET about the 8520 going away so this is
probably the most likely place to start looking. As an owner myself,I would
have prefered to see the 1489 go before a bad line spike could make it through
to my more valuable chips. Looks like my next hardware project will be to
put opto-isolation on some of these connectors :^{

hopin' to keep my 1000 alive for a lot longer,

Dick

    Near as I can tell, the 8520 is a CBM chip.  I forgot to ask.. do
    you have a 500 or a 1000?  I was assuming a 500.  If not then my
    diagnosis may be at fault (i.e. 1488/1489 chip is about $1).
    
    

>  have prefered to see the 1489 go before a bad line spike could make it through
> to my more valuable chips. Looks like my next hardware project will be to



Me too.  And I think if it was a spike on the RX data and TX data the 1488/1489
chips would get the hit. But the other control lines (CTS,DTR, DSR, etc..) go
directly to the 8520 chips - no "little" chips in between...


John

RE .4

It's an A500.  I think the 8520 is reasonable, since it is virtually
unprotected on all control lines (DTR, CTS etc).

I tried calling Active (Westboro, Ma) and they had no mention of "8520".

I'll try the memory location...


(This is a *real* bummer. I can't even use the modem. Oh Well, at least the
printer works for now...)


John

I called the Memory Location. They have 8520's in stock at $22.00.

I also called the store where I purchased my Amiga (General Computer Store,
Framingham, Mass). He told me to call D5 Associates in Bedford Mass.

D5 Assoc. is a Commodore repair shop. The also stock all the Amiga custom
chips:

		8520	$18.75
		Paula	 63.00
		Agnes	 50.25
		Denise	 58.90


The guy at Memory Location said the problem is either (80% probability) 8520
or (20%) Paula.

The guy at D5 says 90% 8520, 10% Paula. (I hope Paula's OK!!!)

D5 also said he has heard rumors of FAT AGNUS being $200.00! They will
stock them when availiable.

Anyway, I'll pick up an 8520 and try it.

John

Well, I picked up an 8520 Friday. Drove home, plugged it in, and no go :-(


So I decided I would bring the whole machine to D5 Associates on Saturday.

I must have spent the night dreaming, cause I was up at 7:00 Saturday morning
with my logic probe and a volt meter (crude huh? only equipment I have at home!)

Turned out to be the 1489 RS232 reciever chip - $1.29 at Radio Shack!

Now Amy talks serial again...


John

    This may be late but I make it a habit to always unplug the AC line
    cord from the wall and only plug in the modem to the phone line
    when I want to use it.  This may be a hassel but its cheaper then
    fixing it.  If you don't have a power strip with surge suppresors
    you can pick some up from Radio shack.  Three per power strip will
    do it.  Hot to Gnd, Hot to Neutral, and Neutral to Gnd.  Then replace
    them every year or two.  If you need an indication on how often
    to replace them just observe you house lights while the AC cycles.
    Lots of blinks replace yearly few blinks every two years.  Its
    all guess work.
    
    My two cents
    Alan
    

	Last night I noticed the same problem described in .0.  I was sending
stuff to the modem just fine, but not recieving anything.  Tried another modem.
No change.  Tried a VAX terminal drop (unpluged the cable to the modem, and
pluged it into the null-modem cable comming from the VAX).  That Worked fine!
Tried with the modems.  No good.  Plugged the modems into a VT220.  They're
fine.  Plugged the Amiga back into the VAX.  That still works.

	This is a year and a half old B2000, that worked fine up until last
night.  Any clues?

Thanks,
Mark

    The null modem cable bypasses modem control lines such as
    clear to send, requrest to send, data set ready, and data terminal
    ready.
    These lines may be asserted or something, like data terminal ready
    might be de-asserted.
    tom

Re:.11

	At least DTR is asserted (the modem shows it that way).

Mark

    
    I had a similar problem at a customer site,  the failure was
    (in his case) a RS232 driver/receiver chip that was busted.  The chip
    was working when a VT100 was plugged in but a DMF32 async
    port wasn't.  RS232 should work from 15 volts (+/-) to 5 volts.
    But I saw SOME working at 3 volts.  (out of specs).
    Some will, some won't....  
    
    Being at your place I would get a scope and look at the amplitude
    of the signal.  You would probably see a difference when you plug
    the VT200 and the modem.  Make sure the signals are within spec.

        (On my Amiga I use the DECconnect type to my modem or printer.)
    
    Good luck.