• Please review our updated Terms and Rules here

Commodore Pet 2001 Fuse

A

Aristotle

Member
Joined
May 10, 2013
Messages
14
Location
England
Hi new to the forum

I have a Commodore Pet 2001-N, which I suspect is completely fried. I took out the fuse and inside were a few pieces of glass. What fuse do I need to insert?

Many thanks
 
dave_m said:
For a 110V system, a 1.6A slo-blo and for a 220V system a 0.8A slo-blo.
Click to expand...

Dave, first thanks for the reply. I'm in the UK so it will be a 220V system, I can locate the following fuse:

Rated current 0.8 A
Rated voltage 250 VAC/DC
Characteristic (time/current) slow-blow
Breaking capacity 35 A@ 250 VAC
Construction form Glass tube
Dimensions ø x L 5.2 x 20 mm

Would this be suitable? This would actually come from a European supplier - all the slo-blos I can find in the UK appear to 0.5A, 1A, 1.6A or higher.

Appreciate any thoughts.
 
Last edited:
T1A, should be fine, but use a ceramic one. (RS or even Maplins should be ok for this.)

Mains fuses should be higher breaking capacity then 35A as the mains can supply more than 35A & in exceptional circumstances the fuse can continue to arc.

Also have an investigate as to why the fuse went in the first place, it was probably just doing it's job.
 
Yes, as nige says, check the chassis capacitors, and the mainboard for any signs of charing or distress on the diode rectifiers CR1,2,4,and 5 and the voltage regulator devices especially VR3 and VR4. Have you found the PET schematics and board layouts on Zimmers? Check your board top assembly number to make sure you are using the correct drawings as the PET has many variations.

With a little help from the boys on the forum, you will get your classic Commodore working again.

http://zimmers.net/anonftp/pub/cbm/schematics/computers/pet/index.html
 
Thanks - I can get a T1AH ceramic from an eBay dealer. Presumably, this will be okay? Is ceramic more durable? I believe the blown fuse in the fuse cap was glass... there were shards of glass and the the fuse was totally destroyed - I had to hook out the metal end of the fuse from the cap.

I'm yet to clean-up the fuse bits left in the machine part. I will be opening the hood next week and cleaning the circuit board. I will take a good look. I confess I'm a novice at this and will be working carefully and slowly - but may be back for more help, if you are around on the forums.

Thx.
 
Last edited:
Thanks Dave. I will take a look. As I said above, I'm a novice at this and will be working carefully and slowly. I fell in love with the PET when I was a young teenager. After Debbie Harry, the PET was the next thing I longed to have in my bedroom! The closest I got (computer-wise) was a VIC-20. I'm pleased just to have one, even a non-working one, in my study nearly 35 years later! Sad, but true. Are the PET manuals etc online? I had a quick look at Zimmers for these but couldn't find them. I'm sure I will be back to the forums many times before I get this one working. Thx again.
 
Aristotle also check the actual fuse holder itself as I had a merry dance with a pet, as I thought it was the funk enstor line filter or capacitor. The fuse was totally obliterated into small pieces of glass too. It turned out to be the Bakelite fuse holder that was tracking to the chassis putting a dead short across the supply. It had a few ohms resistance and closely you could see the carbon on the side of the holder down to the nut that mounts it.
 
Thank you Pet Rescue. I've already noted that the fuse holder in the PET itself is loose/wobbly (and has old fuse debris inside it). Presumably, the fuse holder should not be moving? I will be checking this very carefully when I open up the PET. The fuse cap - now I've got the end of the old fuse out - looks fine.
 
Aristotle said:
Thank you Pet Rescue. I've already noted that the fuse holder in the PET itself is loose/wobbly (and has old fuse debris inside it). Presumably, the fuse holder should not be moving? I will be checking this very carefully when I open up the PET. The fuse cap - now I've got the end of the old fuse out - looks fine.
Click to expand...

Definitely not moving, it should be nice and firm and has a flat to stop it from turning.
 
Thanks, Pet Rescue. I should point out that the bakelite fuse holder and a rubber washer has come away from the Pet chasis. Clearly this can be re-affixed, no problem. However, I note that protruding from the hole is a metal tube (the same as in the fuse cap) which houses one end of the fuse. Should this tube be recessed in the Pet chasis or does it poke out into the bakelite fuse holder? If the latter, it means a metal tube could potentially touch the metal casing of the Pet - and this alarms me, somewhat.

I'm awaiting my cleaning equipment I've ordered before I left the hood of the Pet to see if there are obvious signs of a short; however, could it be that this fuse holder is something to do with the lights going out on this Pet?

As always, appreciate any help as I have not repaired a Pet before.
 
Aristotle could you take pic of the fuse holder?
I can't quite picture what you mean, inside the fuse holder is the metal tube that holds one end of the fuse but it is normally set in the holder.
The holder itself should stick proud of the chassis unless it's sheared like they do. You should not be able to touch the tube.

Here is one that's available on ebay http://www.ebay.co.uk/itm/Fuse-Holder-Panel-Mount-250V-10A-20mm-/261206987426?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item3cd12652a2
 
I will take pictures tomorrow and post. What you call the fuse holder I'm calling the fuse cap (which has a small groove to turn it). The cap, in my terminology, is inserted into a plastic/bakelite stub that is affixed to the metal chasis near the on/off rocker. The fuse cap, of course, is inserted and turned into the stub. This stub has come away from the chassis. So I have two parts - the fuse cap and the fuse stub. On the pet I have a hole in the chassis over which the stub and washer should be attached. Inside this hole is the metal tube, similar to the one in the fuse cap. Hence, my question above. This metal tube is able protrude through the hole (and into the stub once affixed) or should it be recessed in chassis and the fuse bridge the gap over the metal chassis.
 
Aristotle we'll get there what I'm calling the fuse holder is the Bakelite body which is attached to the chassis with the nut and washer. The end cap is what you are calling the fuse cap. Now what happens is that the fuse holder (Bakelite body) can break which is why I think you have two parts. The end cap with the slot for locking/unlocking(fuse cap) should fit into the fuse holder (Bakelite body) which is shouldered and should be proud of the chassis by 10mm or so. The fuse holder (Bakelite body) has a metal cap inside it that connects to the bottom of the fuse and should be in the lower part of the fuse holder (Bakelite body) which you should not be able to physically touch (as it could be live!)

Confused you will be a picture will definitely help! :D

fuse 2.jpg
 
Last edited:
Pet Rescue here is the photo:

Pet Fuse.jpg

My concern: the metal tube is quite loose - and as you can see in the photo it is touching the metal chassis. My original question was: should this tube protrude into the holder? I believe you state that it does protrude into the lower part of the fuse holder. In which case, this metal tube is spanning the metal chassis. What stops it from actually touching the metal chassis? I note the fuse holder is flanged at the lower end - presumably this is sufficient to lift the metal tube above the metal chassis and stop it from touching it?

It appears the fuse holder was glued to the chassis. Is this correct? The only thing I can't relate to in your reply is your mention of a "nut".

Finally, I lifted the lid. And apart from dust at the back by the ports (image 1), I can see no obvious signs of damage in here. Photos below.

Image 1.jpgImage 2.jpgImage 3.jpg

I note the heavy duty electrics are at the back on the left... what if there is a loose connection in here? Is it possible to get inside, if required?
 
Last edited:
Hi Aristotle just as I thought, your fuse body has split in two thus allowing the inside tube to be exposed.
On your photo the fuse holder should be attached to the rest of the Bakelite that is inside the chassis.
Yours is in three pieces instead of two. You should only have a fuse body and a fuse cap.
You need a new panel mount fuse like the one in my posting( the ebay link).
That could be why your fuse obliterated as the live metal tube isn't being insulated by the Bakelite.
It's touching the chassis!

fuse holder.jpg

To get to the rest of the fuse inside you may need move the transformer assembly if you do:-
Then I find it easier to take the mainboard out making a note of the plug positions of the cables.
Disconnect the earth wires at the back of the chassis near the transformer, the undo the four nuts underneath the chassis that hold the transformer to
the chassis. (cut the cable ties on the large capacitor if you want more room)
Note two wires(brown if I remember rightly) are still soldered to the transformer to the monitor so be careful when moving the transformer assembly.
The cables to the fuse holder are soldered so you'll need to get the iron out!:D
Don't forget to make a note of the cables to which parts of the fuse holder they go.
 
Last edited:
Okay - I now know what I need to do. Just one last question - at least for now. You say "To get to the rest of the fuse inside you need to unscrew the two screws on the back that hold the switch and fuse assembly." On the back of where? I can find no screws on the back panel near the switch and fuse - or are these inside the chassis?
 
Sorry Aristotle I've altered the text as I have realised you have an older model not the one with a separate switch and fuse assembly.
Yours only has cut outs for separate switch and fuse.

This is the newer type:-

pet4032b.jpg
 
Pet Rescue, it all makes sense now! I will probably enter radio silence for a bit as I need to order fuses, fuse mounts (and, yes, a soldering iron :D). However, I may well be in contact again after the "operation" has been performed.

Thank you for giving your time and advice on, what must be, a very niche topic! I will be REALLY pleased IF I can get this Pet working again.

Over and out, for now.
 
You must log in or register to reply here.
Back
Top