Commodore 64 old Breadbin tan style wanted

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Commodore 64 old Breadbin tan style wanted

Postby Gurner on Mon Feb 10, 2014 2:37 pm

Hi,

Mine just died, after only a week out of retirement!

Can pick up in Auckland or post would work too.

Cheers :D
Gurner
 
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Re: Commodore 64 old Breadbin tan style wanted

Postby RonTurner on Mon Feb 10, 2014 3:06 pm

You could keep an eye peeled on TradeMe: *C64, Spectrum & ZX81 Section* also known as the *Vintage Computer Section*

Just wanted to comment that you should check that the power supply is ok, before plugging in your new C64 (when you get it) , they are known as Commodore killers when they go out of tune.

did you get the black screen of death ? (hate that) :x it used to go twenty years ago :!:
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Re: Commodore 64 old Breadbin tan style wanted

Postby Gurner on Mon Feb 10, 2014 4:26 pm

Cheers Ron, how do I check the supply?

The SID is faulty, so only plays one voice and the others intermittently, in odd tones.


RonTurner wrote:You could keep an eye peeled on TradeMe: *C64, Spectrum & ZX81 Section* also known as the *Vintage Computer Section*

Just wanted to comment that you should check that the power supply is ok, before plugging in your new C64 (when you get it) , they are known as Commodore killers when they go out of tune.

did you get the black screen of death ? (hate that) :x it used to go twenty years ago :!:
Gurner
 
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Joined: Tue Aug 06, 2013 11:42 am

Re: Commodore 64 old Breadbin tan style wanted

Postby RonTurner on Mon Feb 10, 2014 5:37 pm

put it under load for a decent amount of time and check the voltages when its hot

here is some useful text about the subject:

If you have some experience with a soldering iron and have a multitmeter,
you can make a tester to safely evaluate a Commodore "black brick" power supply
without risking damage to your computer. You need a 7 pin female DIN connector,
some hookup wire and a couple of lamps to use as an artificial load for the
supply. If you have a junked C64 board laying around, remove the power connector
from it and wire it to a pair of 12 volt car bulbs. I use #1003 12 volt lamps,
one each for the two outputs: +5V and 9VAC. The lamps each draw under one Amp.
An artificial load is recommended to keep a failing supply from damaging your
computer. Connect it to the computer only after tests show it's working OK.
Run the supply with the lamps connected for about half an hour or until the
case of the supply gets warm. Monitor the 5 volt supply with a DC voltmeter to
see if the voltage is too low or (and here is what to really look out for) too
high! It should measure almost exactly 5 volts. Low voltage (4.7VDC or less) will
cause problems like a blank screen and program crashes with the computer. Less
than 4.9 volts usually means the capacitors in the supply are failing. A failing
supply may still read 5 volts if not properly loaded! On the other hand, if the
voltage starts rising, going up past about 5.2 volts (loaded or not), it means
the regulator chip in the supply is failing. Excessive voltage can and will
damage the computer. I've seen bad ones that would always work when cold, then
fail when they warmed up. The lamp on the 5V line will get very bright if the
regulator shorts because the output voltage will rise to about 11 volts. RAM
chips in the computer are "TTL" devices and seem the most sensitive to
overvoltage. Their "absolute maximum rating" is 6 volts. A leaky regulator may
cause the voltage to rise slowly, so you need to monitor it with the voltmeter
as the supply warms up. Also check the 9VAC, which will either be there or not.
Loss of the 9VAC will produce a blank screen on early C64s even though the red
LED is on and the +5 volts is normal. Because the circuitry inside the later
C64C is different, loss of the 9VAC or an open fuse inside the C64C will still
allow the computer to work! However, you will not have sound, the cassette will
not work, and there will be no TOD clock source for the CIA chips, so some
programs may not work. Loss of the 9 volts AC will not damage the computer.That
voltage will never be high or low... it's there or it isn't.
Although you could use large resistors for the tester, I prefer lamps
because they give me a constant visual indication of what's happening. Both
voltages should be nice and steady. If either lamp flickers, goes out, or goes
up in brightness, time for a new supply. Since the brick is potted with epoxy,
it is considered unrepairable. Resistors can be substituted for the lamps, as
follows: a 5 to 8 ohm, 20 watt resistor for the 5 volt line, and a 10 to 15 ohm
20 watt for the 9VAC line. Keep in mind both lamps and resistors will get hot
after a few minutes. Don't set them on any surface like plastic that could be
damaged by heat, or on metal that could cause a short.

Code: Select all
        9VAC -----7           6----- 9VAC

      ground -----3             1----- ground

         +5VDC -----5         4----- +5VDC or no connection
                         2----- ground

RonTurner
 
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Re: Commodore 64 old Breadbin tan style wanted

Postby Gurner on Mon Feb 10, 2014 7:52 pm

Thanks for the info, Ron.

Far out, the C64s seem to be quite prone to issues.
My various retro gaming consoles seem to be fairly bullet-proof with the exception on the NES's connector.
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Re: Commodore 64 old Breadbin tan style wanted

Postby RonTurner on Mon Feb 10, 2014 8:07 pm

You can call me Gav.

often those ol consoles have fewer components.

They are old, components age, capacitors pop and sizzle like frying eggs, its not uncommon, they just need TLC just like you cant expect an old car to keep going without changing the oil and adjusting the timing.

I got hold of a PCI cooling fan to add to one of the ports of my C64 as extra cooling for a start, and there is a good PSU overload protection circuit that can be found at the lemon64 forum, (im not exactly sure of the link) but its good insurance.

Not long ago I got hold of the famed Dolphin DOS (loads a disk in 5 seconds) but my big clunker 1541 is playing up (typical) but the ROM upgrade on its own is fanastic, it makes use of the function keys for instant directory etc.

Originally Commodore where going to make the disk drive load through the expansion port but due to a bug in one of there custom chips they
had to use the serial port, hence the worlds slowest disk drive loading (typically not much faster than a cassette tape), Dolphin DOS addresses
this problem.

Yup its a two step forwards, *boom \!/ one step backwards battle , but thats half the fun :wink:
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Re: Commodore 64 old Breadbin tan style wanted

Postby mrad01 on Mon Feb 10, 2014 9:17 pm

The C64 can be a bit of a bitch - but it pretty much all starts with the PSU fluctuating and killing chips. If you can get a stable PSU - and keep it stable as Gav suggests, you should be good.

I had a bit of a nightmare time with my C64s for a while, but once you figure the PSU is the start of all your issues, you can manage it.

Enjoy.
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Re: Commodore 64 old Breadbin tan style wanted

Postby Gibsaw on Tue Feb 11, 2014 12:30 pm

It does strike me as possible to "unpot" the PSU with some heat. Yet to try it though.

Although everything I've read seems to suggest that removing the epoxy brick from the casing, throwing it in the bin, and replacing the PSU with a better design seems to be the most sensible repair. :D
"dsakey" on trademe. Apple II's are my thing.
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Re: Commodore 64 old Breadbin tan style wanted

Postby Gurner on Wed Feb 12, 2014 9:17 am

Is it possible to just buy a brand new PSU with the same ratings off the shelf from Jaycar or similar?


Gibsaw wrote:It does strike me as possible to "unpot" the PSU with some heat. Yet to try it though.

Although everything I've read seems to suggest that removing the epoxy brick from the casing, throwing it in the bin, and replacing the PSU with a better design seems to be the most sensible repair. :D
Gurner
 
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Re: Commodore 64 old Breadbin tan style wanted

Postby RonTurner on Wed Feb 12, 2014 12:34 pm

Gut an old PSU and fit two wall warts ,one 5v DC and one 9v AC
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Re: Commodore 64 old Breadbin tan style wanted

Postby Gibsaw on Tue Feb 25, 2014 12:41 pm

RonTurner wrote:Gut an old PSU and fit two wall warts ,one 5v DC and one 9v AC

This definitely seems the most common approach. Safe (ish) and modular.

Don't skimp on the wall warts though. Many of them are garbage. Especially modern cellphone chargers.
"dsakey" on trademe. Apple II's are my thing.
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Re: Commodore 64 old Breadbin tan style wanted

Postby Gurner on Thu Feb 27, 2014 7:35 pm

Got another C64, please disregard this want ad. :)
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