C128/128D wanted

[saehn]

Does anyone have some extra 128 hardware they'd be willing to sell? What I'd really like is a 128D with JiffyDOS. Barring that, I'd be happy with a 128 flat with 64k VDC upgrade and JiffyDOS. The JiffyDOS isn't essential, I can do that... but I'd rather get one complete and working! Thanks.

[Marcel]

I have a c128, recently I turned it on, but after a few hours it got blocked. I have a 1581 and 1571 drive units, and mps801 printer. Because there is no local service in Colombia, I cannot do anything with that. If you cover the cost of shipping, and give any contribution (via paypal, bank wire or western union wire) I give you my C128, including some books and magazines (commodore gazette). marcelcorzo@yahoo.com.

[saehn]

Thank you Marcel, that's very nice of you. But the shipping from Colombia would be pretty high, especially since as you noted the computer isn't 100% working right now. I hoping to get one from the US or Canada. Sorry, I should have specified that originally.

[Blacklord]

Blocked ?

[Kyllon]

I have a 128 if you like, doesn't have 64kvdc or jiffy dos.  I was going to put in a serviant rom in it however

[saehn]

Thanks Kyllon, but I'm going to hold out for one that at least has the 64k upgrade. I appreciate the offer though!

[SmallCleverDinosaur]

Have you seen this device?

 

It's essentially a "plug and play" 64K upgrade for the VDC. No soldering required. Designed by Chip Level Designs (CLD) back in the days, it's now being sold brand new as a replica by alee650 on ebay here.

[saehn]

Have you seen this device?

 

It's essentially a "plug and play" 64K upgrade for the VDC. No soldering required. Designed by Chip Level Designs (CLD) back in the days, it's now being sold brand new as a replica by alee650 on ebay here.

Thanks, yes, I've seen that device and have given it some thought. My only concern is that a flat 128 + VDC from UK might turn out to cost more than a 128D. Still thinking about it, though. I have a few more leads and there's always eBay (although the one there now isn't fully tested).

My whole reason for wanting to get a new-to-me 128D is that my current flat 128 (v/64k VDC & JiffyDOS) has a buzz that accompanies its sound output. I can hear sounds and music, but the buzz is constant. I know that it's the computer because the monitor works fine with my C64C, no buzzing. I've tried swapping out the SID, no luck. I think I even tried a different power supply. I've asked around and haven't found any other answer that's within my admittedly limited repair abilities.

[megabit]

I can hear sounds and music, but the buzz is constant. I know that it's the computer because the monitor works fine with my C64C, no buzzing.

I'm assuming that you used the same video cable on your C64. That is the first thing I would check (bad ground connection).

Next is to replace coupling capacitor C85, it's an electrolytic 10uF 16v radial lead. It's located at the top right handed edge of the 80 column chip area. The capacitor is probably  shorted.

Dan...

[saehn]

Hm, I'm pretty comfortable with replacing a capacitor... does this look like a good source? Only thing I'm not sure of is whether to get polar/non-polar. I suppose I can just wait and match whatever is in the 128 now.

http://www.westfloridacomponents.com/NP011/10uF+16V+Non+Polar+Radial+Electrolytic+Capacitors.html

However, I'm not so sure what you mean about the checking the ground connection. Do you mean where the ground lead on the video port connects to the circuit board? BTW I've tried other cables, same result.

Thanks for the advice!

[Andrew Wiskow]

Charles Gutman of 8-bit designs is quite adept at doing the 64K VDC upgrade on flat 128s.  You can e-mail him at shifty_butch@hotmail.com to find out what he's currently charging (he's in California).  He's done the upgrade on a couple 128s for me in the past, and he did a great job.

[megabit]

However, I'm not so sure what you mean about the checking the ground connection. Do you mean where the ground lead on the video port connects to the circuit board? BTW I've tried other cables, same result.

Then it's not the cable.

Hm, I'm pretty comfortable with replacing a capacitor... does this look like a good source? Only thing I'm not sure of is whether to get polar/non-polar. I suppose I can just wait and match whatever is in the 128 now.

In this case it does not matter, polar or non-polar is OK.

Dan...

[saehn]

In this case it does not matter, polar or non-polar is OK.

Hm, I tried this and while it didn't help, it didn't seem to hurt either. Only difference is now that there's a slightly different random character pattern at start up.  I found a 10uf 16v electrolytic cap in one of those Radio Shack grab bags. It was axial, not radial, but I don't think that should matter. It was polar and I aligned the legs with what was on the board. It's also much larger in size than the original cap.

Any other suggestions, Dan?

[megabit]

The only thing left is the +12 volt supply.
I don't want to get too deep into this because I don't know what you skills are.

Do you have a volt meter?

Would you be comfortable with jumping a capacitor from the 12 volt regulator output to ground?

Do you have a schematic of the C128?

Dan...

[saehn]

The only thing left is the +12 volt supply. I don't want to get too deep into this because I don't know what your skills are. Do you have a volt meter?

Yes

Would you be comfortable with jumping a capacitor from the 12 volt regulator output to ground?

I think so, I was comfortable soldering that cap into place. I guess it would just depend on the type of connection.

Do you have a schematic of the C128?

Yes

[saehn]

Getting my schematics from here:

http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/c128/index.html

[retrobazar]

I'd like to sell a Commodore C128 boxed, with Jiffydos in each modes (128 and 64) and Basic 8.0. With original power supply + 3 original manuals + Basic 8.0 Floppy +  composite AV cable + original kernal eproms. Conditions: Computer 9/10 - Box 7/10 - Manuals 9/10 . All tested and in fully working order. I'm from Italy. 

[megabit]

Getting my schematics from here:

The schematic we are using is 310378-1-left.

The 12V regulator (U59) is a rectangle shaped IC with a metal tab on it. It's located on the right side of the board next to U7, also by joystick port 2.

Measure the input and output voltage. There are three leads on the IC. As you're looking down at the regulator, the lead on the right is the input and the lead on the left is the output. The center lead is ground.

With the computer turned on, connect the ground lead of your volt meter to the ground plane of the PC Board. Best place is somewhere around the outside edge of the board. Put the positive lead of the volt meter on the input pin of the regulator and measure the voltage, should be between +18 and +20 vdc. Next measure the output, should be +12 vdc +/- 5%.

Dan...

[saehn]

With the computer turned on, connect the ground lead of your volt meter to the ground plane of the PC Board. Best place is somewhere around the outside edge of the board. Put the positive lead of the volt meter on the input pin of the regulator and measure the voltage, should be between +18 and +20 vdc. Next measure the output, should be +12 vdc +/- 5%.

Thanks very much for this assistance, Dan.

I'm getting 14.2 on the right lead (input) and 10.3 on the left lead (output).

[megabit]

I'm getting 14.2 on the right lead (input) and 10.3 on the left lead (output).

Not good!

De-solder the input pin of the regulator and measure the voltage on the PC board where you pulled the input lead. See if the voltage jumps to greater than 19 vdc. If so, the replace the regulator.

If not, look at the two 1 amp. Diodes (1N4001) (CR10 & CR11). See if they are burned, if so, then replace them. If not, then replace C104 (220uF 50v radial) and C105 (330uF 50v radial). You might as well replace the diodes at the same time. They're cheap.

Dan...