6581 SID 8580 Swap
Brian S
in place of the 8580 SID?
The reason I'm asking is because I recently tried this swap (taking the 6581
from a recently acquired old 64). It didn't sound right in the 64C so I
swapped it back to the old (original) 64, but still didn't sound right. I
used the Sanxion (Thalamus) tape loading tune for testing. It sounded 90% OK
but certain parts seemed missing.
Could this swap have damaged the 6581 SID? If so, I would like to apologise
to the C64/SID community in advance!
Brian
Lyndon Amsdon
Hmm, AFAIK they used differnet voltages. I think it was 9v and 12v. The
older SID chips sound better anyway as the filters are nicer and some
sounds are really faint on the newer chips. There are patchs out there
though. You may have broken it, I'm not sure. Unlikely.
Cameron Kaiser
>Is it OK to put a 6581 (from an old 64) SID chip into a 64C (later version)
>in place of the 8580 SID?
No! The voltages are very different! It does certainly sound like some
portion of the chip has been fried. :-(
--
Cameron Kaiser * cka...@stockholm.ptloma.edu * posting with a Commodore 128
personal page: http://www.armory.com/~spectre/
** Computer Workshops: games, productivity software and more for C64/128! **
** http://www.armory.com/~spectre/cwi/ **
Brian S
"Cameron Kaiser" <cka...@stockholm.ptloma.edu> wrote in message
news:3afea19c$0$37304$45be...@newscene.com...
Pekka "Pihti" Takala
I have successfully installed a 8580 chip to 6581 socket. Works fine.
I just raised the pin 28 of the 8580 (9 volt in 8580, 12v in 6581) up
and connected it to the 12 v rail on the c128 with one 3.7 volt
zenerdiode. It lowers the voltage enough for 8580 to work. Finally, i
put right size capacitors to the c128 that originally had the 6581, and
got it working fine. Because the voltage is lower than 9 v (actually
about 8.3-8.5 v), it does not get so hot as does in original 64, and i
think it will live longer. All other pins are compatible on a 6581 and
8580, you just must ensure that the chip gets correct voltage. If you
put a 6581 to place of 8580, you need to make a internal psu for it
since you need to give the 6581 12v. I suggest that you use a rectifier
connected to 9 vac and then some big electrolytic capacitors.
Suggested PSU: ________
| 7812 |
9 VAC --->|---| ________
|in| | | out -
9 VAC --->|---*--- | --------------- > to sid 12v pin, 28
| | | | |-
100 uF = | 10uF = + 1k |
+100 nF | |+100nF| | |
GND ---------------------------------
the + sign is a 1 k resitor. The diodes can be almost any type, 1n4148
should do fine. The 100 uf capacitor is needed to reduce rippel before
7812 regulator. The 10 uf capacitor in output is for filtering. The 100
nf capacitors are connected parallel to electrolytic capacitors and they
reduce noise. The resistor is there also because it makes a little load
to 7812 and it also helps to make the voltage stable. Then a shielded
cable is connected to sid pin 28. Connect the shield of the cable to the
ground. This is needed because the audio gets done from the 12 v and if
it is noisy, the audio sounds garbled also. And the 6581 sounds garbled
also on a standard c64c.
I think your 6581 is OK.
--
*Pekka "Pihti" Takala *pekka....@pp.inet.fi
*asm sw developer *home: +358-6-8311341
*cellular: +358-40-5670465
Brian S
"Pekka "Pihti" Takala" <pekka....@pp.inet.fi> wrote in message
news:3B000564...@pp.inet.fi...
So it's not quite the straight swap that I thought it was! Thanks for all
the info.
>
> I think your 6581 is OK.
I'm not so sure. I had only tested it with a couple of tunes before doing
the swap, so it may have already been faulty. I will be getting hold of
another old 64 soon, so I can do a comparison check.
Cameron Kaiser
>I have successfully installed a 8580 chip to 6581 socket. Works fine.
>I just raised the pin 28 of the 8580 (9 volt in 8580, 12v in 6581) up
:
>cable is connected to sid pin 28. Connect the shield of the cable to the
>ground. This is needed because the audio gets done from the 12 v and if
>it is noisy, the audio sounds garbled also. And the 6581 sounds garbled
>also on a standard c64c.
But this isn't really a simple chip swap. :-P
Overdoc
Lyndon Amsdon schrieb in Nachricht ...
>Hmm, AFAIK they used differnet voltages. I think it was 9v and 12v.
Yes, but the 6581 needs 12V and the 8520 needs 9V.
So I think running the 6581 on a lower voltage ( 9V instead of 12V ) will
prevent it from working, but will not damage it.
As far as I know chips can only be fried by using too much voltage on them
or shorting input/output pins.
Or am I wrong in assuming this ?
Overdoc
Spiro Trikaliotis
On Mon, 14 May 2001 22:35:36 GMT, Overdoc wrote:
>So I think running the 6581 on a lower voltage ( 9V instead of 12V ) will
>prevent it from working, but will not damage it.
>As far as I know chips can only be fried by using too much voltage on them
>or shorting input/output pins.
>Or am I wrong in assuming this ?
Well, in general, you're right, but...
With the power supply, giving a lower voltage should not do any damage
(as is the case with the 6581). Anyway, you could get in trouble if
you have too low voltages on input pins.
Think of the following. Suppose you have a power supply of 5 V. Now,
you have ranges in which you suppose an input signal is a logical zero
(let's say, for example, 0 V to 0.8 V), and a range in which you
assume you have a logical one (for example, 2.4 V to 5 V). You can see
that there is a range in which nothing is defined (in our example, 0.8
V to 2.4 V). This range should not be too long on the chip, only for
changings from zero to one or vice versa.
Now, at least with CMOS, the internal schematic of a gate is that you
have two transistors working in a push-pull way ("Gegentaktverstärker"
in German), that is (in this case), exactly one of both is assumed to
be leading. Anyway, in this undefined zone, it can occur that both are
leading. In normal operation, this should only occur for a very short
time. Anyway, if you give, for example, a voltage of 1.5 V to such an
CMOS input, you can damage your device because the current running
through the transistors can be too much for the device. Then, CMOS has
the problem that it can start to oscillate in such a case, exceeding
it's maximum limit.
I'm not sure if these problems are there with other logic families
(and I'm not sure if it's true with today's CMOS chips), but these
problems were there when starting CMOS (the Motorola MC40xx series,
especially the so-called 'A'-series).
To make a long story short, you cannot be sure that low voltages can't
do any harm on your device.
Spiro.
Pekka "Pihti" Takala
>
> Pekka \"Pihti\" Takala <pekka....@pp.inet.fi> writes:
>
> >I have successfully installed a 8580 chip to 6581 socket. Works fine.
> >I just raised the pin 28 of the 8580 (9 volt in 8580, 12v in 6581) up
> :
> >cable is connected to sid pin 28. Connect the shield of the cable to the
> >ground. This is needed because the audio gets done from the 12 v and if
> >it is noisy, the audio sounds garbled also. And the 6581 sounds garbled
> >also on a standard c64c.
>
> But this isn't really a simple chip swap. :-P
Agreed. The different supply voltage and capacitors make the differense.
So a sid exchange is not just a chip change, you must also ensure
correct voltage and correct filter caps. a 12 v sid to c64c that has
originally a 8580, is a pain because there is originally no 12 v rails.
The 8580 to 6581 socket is easy: put a 3.7 v zener from 12 v rail and
the raised pin. Then you change the caps, and voilá you have a 8580
upgraded computer. At least on c128, this is easy.
>
> --
> Cameron Kaiser * cka...@stockholm.ptloma.edu * posting with a Commodore 128
> personal page: http://www.armory.com/~spectre/
> ** Computer Workshops: games, productivity software and more for C64/128! **
> ** http://www.armory.com/~spectre/cwi/ **
--
Brian S
SID) in the more modern 64C case. So I've swapped the complete circuit
boards. The old board fits easily in the new case and vice versa. The most
technical thing I had to to was extend the wires for the LED power
indicator. That'll do me!
--
Brian
"Pekka "Pihti" Takala" <pekka....@pp.inet.fi> wrote in message
news:3B01C1F5...@pp.inet.fi...
>
> Agreed. The different supply voltage and capacitors make the differense.
> So a sid exchange is not just a chip change, you must also ensure
> correct voltage and correct filter caps. a 12 v sid to c64c that has
> originally a 8580, is a pain because there is originally no 12 v rails.
> The 8580 to 6581 socket is easy: put a 3.7 v zener from 12 v rail and
> the raised pin. Then you change the caps, and voilá you have a 8580
> upgraded computer. At least on c128, this is easy.
>
> --