From Newsgroup: comp.sys.cbm

Hi!

In 1986 I got a C64, which I had connected to a TV set. The C64 later broke down and I got a new one on the warranty. Last year, I bought an old C128, which I also connected to a TV set. These computers all have in common that
as the computer heats up after it has been turned on, the channel that it transmits on increases until after a while it stabilizes somewhere between channel 36 and 37. It seems to be different from computer to computer how
much the channel increases until it stabilizes. Some computers change
channels so much so that if you let the TV stay at the original channel,
after a while you can't read the text on the screen and only hear noise. I
find it a bit annoying that I have to fine tune the TV channel on the TV set until the computer has become heated up and the channel has stabilized. This problem has occurred with several different TV sets so it is not a problem
with the TV set. It has also occurred with all C64/C128 computers I have
tested with so it seems like it is a general problem. However, when I in the 80s mentioned this problem to other C64 users, they didn't recognize the problem. I find this very strange since I have had it with all my C64s/C128s (except for my newest C128 since I have only had that connected to a monitor
so I don't know if the problem occurs when connecting it to a TV set). Is
this really a general problem or have I only had extremely bad luck with all
my C64s/C128s (the latter seems pretty improbable I think)?

/Christian (change "combort" to "comhem" in my e-mail address if responding
via e-mail)


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From Newsgroup: comp.sys.cbm

In 1986 I got a C64, which I had connected to a TV set. The C64 later

broke

down and I got a new one on the warranty. Last year, I bought an old C128, which I also connected to a TV set. These computers all have in common

that

as the computer heats up after it has been turned on, the channel that it transmits on increases until after a while it stabilizes somewhere between channel 36 and 37. It seems to be different from computer to computer how much the channel increases until it stabilizes. Some computers change channels so much so that if you let the TV stay at the original channel, after a while you can't read the text on the screen and only hear noise. I find it a bit annoying that I have to fine tune the TV channel on the TV

set

until the computer has become heated up and the channel has stabilized.

This

problem has occurred with several different TV sets so it is not a problem with the TV set. It has also occurred with all C64/C128 computers I have tested with so it seems like it is a general problem. However, when I in

the

80s mentioned this problem to other C64 users, they didn't recognize the problem. I find this very strange since I have had it with all my

C64s/C128s

(except for my newest C128 since I have only had that connected to a

monitor

so I don't know if the problem occurs when connecting it to a TV set). Is this really a general problem or have I only had extremely bad luck with

all

my C64s/C128s (the latter seems pretty improbable I think)?

The problem is caused by the cheap RF modulator used inside the C64/C128.
It's design doesn't make any attempt to keep the output frequency constant.

I can think of a couple of explanations why other C64 users didn't
experience the problems your described:
1. They used the video output instead of the RF modulator (which gives a
better picture quality as well);
2. They used a TV set with a (better) AFC feature, which keeps the set automatically tuned even when the output frequency of the RF modulator (slightly) drifts;
3. They kept their C64 running 24/7;
4. I read somewhere that early C64 models used a better RF modulator.


--
Peter van Merkerk
peter.van.merkerk(at)dse.nl


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From Newsgroup: comp.sys.cbm

Christian Johansson wrote:

These computers all
have in common that as the computer heats up after it has been turned
on, the channel that it transmits on increases until after a while it stabilizes somewhere between channel 36 and 37.

That's very strange, I never had this problem, not even slightly. And from
1986 to 2003 I used about 8 different C64s, none of them showed that
behaviour.

/Steppe


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From Newsgroup: comp.sys.cbm

Thank you for your response.

1. No, they used the RF output.

2. No, I don't think this is the explanation either. I have had the same problem with three TV sets: one from 1973, one from 1985 and one from 2001.
The one from 2001 should at least have a good AFC feature I think.

3. No, they didn't keep their C64s running all the time so this is not the explanation either.

4. Almost all my friends had an old "breadbin" C64 while I have only used
C64C and C128 so this could possibly be at least a part of the explanation.

/Christian


"Peter van Merkerk" <merkerk@deadspam.com> skrev i meddelandet news:benfuc$76h1e$1@ID-133164.news.uni-berlin.de...

In 1986 I got a C64, which I had connected to a TV set. The C64 later

broke

down and I got a new one on the warranty. Last year, I bought an old

C128,

which I also connected to a TV set. These computers all have in common

that

as the computer heats up after it has been turned on, the channel that

it

transmits on increases until after a while it stabilizes somewhere

between

channel 36 and 37. It seems to be different from computer to computer

how

much the channel increases until it stabilizes. Some computers change channels so much so that if you let the TV stay at the original channel, after a while you can't read the text on the screen and only hear noise.

I

find it a bit annoying that I have to fine tune the TV channel on the TV

set

until the computer has become heated up and the channel has stabilized.

This

problem has occurred with several different TV sets so it is not a

problem

with the TV set. It has also occurred with all C64/C128 computers I have tested with so it seems like it is a general problem. However, when I in

the

80s mentioned this problem to other C64 users, they didn't recognize the problem. I find this very strange since I have had it with all my

C64s/C128s

(except for my newest C128 since I have only had that connected to a

monitor

so I don't know if the problem occurs when connecting it to a TV set).

Is

this really a general problem or have I only had extremely bad luck with

all

my C64s/C128s (the latter seems pretty improbable I think)?

The problem is caused by the cheap RF modulator used inside the C64/C128. It's design doesn't make any attempt to keep the output frequency

constant.

I can think of a couple of explanations why other C64 users didn't
experience the problems your described:
1. They used the video output instead of the RF modulator (which gives a better picture quality as well);
2. They used a TV set with a (better) AFC feature, which keeps the set automatically tuned even when the output frequency of the RF modulator (slightly) drifts;
3. They kept their C64 running 24/7;
4. I read somewhere that early C64 models used a better RF modulator.

--
Peter van Merkerk
peter.van.merkerk(at)dse.nl

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