4A 125V or 7A 125V SLO BLO fuse ------------------------ F301

[jalexquijano]

After fully checking the parts i need to order from my supplier as replacements for my 1990 Fender the Twin aka Red Knob, i found out that there is a mistake on the rear faceplate of the amp as it states that the value of the Fuse is 7A 125V while on the manufacturer list shows as 4A 125. Does anyone know the correct values for these fuses???

[xtian]

Mains fuse? Must be 4A.

[Tom Phillips]

Interesting. I have seen the fuse rating discrepancies in the Fender service information but never ran across a mislabeled back panel silkscreen.
I agree with the 4A Slo-Blo rating. That amp also has a 5A Slo-Blo internal fuse in series with the panel mounted fuse.

Edit: I take that back. I found the attached photo in my records showing the 7A mains fuse label on a 1990 version of "The Twin." This amp also used a 10A Slo-Blo internal fuse. I suspect that Fender had a nuisance fuse blowing problem and therefore upped the fuse value. The service information and the operator's manual have several different values listed. I find 4A SB, 7A SB and 8A SB specified for the external fuse and 5A SB, 8A SB and 10A SB specified for the internal fuse in various places in the literature. If it was my amp I would start with a 4A external fuse and see if it exhibited any nuisance blowing.

[jalexquijano]

Mine states the same at the rear 7A 125V!!! But the parts list state 4A 125? Whats the worst it could happen if i slide a 4A there? Actually it has a slo blo fuse but it does not describes the value! The amp is working!

[Tom Phillips]

Mine states the same at the rear 7A 125V!!! But the parts list state 4A 125? Whats the worst it could happen if i slide a 4A there? Actually it has a slo blo fuse but it does not describes the value! The amp is working!

I'm sticking with my statement from post #3 "If it was my amp I would start with a 4A external fuse and see if it exhibited any nuisance blowing" and "I suspect that Fender had a nuisance fuse blowing problem and therefore upped the fuse value." The Fender changes were a progression over the production life of the amp model and, as is common in this industry, they didn't carefully update the documentation. You wrote "7A 125V!!!" 7A may merit one exclamation point but certainly not three. It's just not that big of a deal. Just start with a 4 or 5 A fuse and make sure it is a Slo-Blo type. Or, since the amp is working, there isn't really a problem. However, since you said "Actually it has a slo blo fuse but it does not describes the value!" I assume that you can't find the Amp value on the existing fuse. If that's the case then it will give you peace of mind to buy a new known value fuse or get out a magnifying glass and maybe you will find the marking on your fuse.