Fender ’64 Custom Deluxe Reverb 2018(Feb. 2025) fuse issue?

[Peng1026]

Hi everyone,


just got a very strange issue about the Fender ’64 Custom Deluxe Reverb amp:

Location: Germany. I had bought a brand new one in the local shop and after about five to six hours of non-consecutive use, the fuse blowd (not during the using, it just couldn't be turned on again). I replaced the fuse, and it happend again after several hours playing. Then I returned the amp, and bought another new one on thomann. Today, the fuse of the new one blowed again. Both amps behaved exactly the same, despite being otherwise normal before the fuse blew. I live in a relatively new apartment with a stable electrical system—no voltage issues at all, and all my other devices work perfectly fine, I measured the voltage, and it was a steady 235V. Plus, I'm using a surge protection power strip, so I don't think it's an issue with my power supply.

It’s quite surprising to have this happen repeatedly on brand-new ’64 Customs. The two amps have both serials number starting with CR4207xx, both 2018 (update: Feb. 2025) production. I don't know why I got those NOS twice in Germany (update: ChatGPT gave me a quite wrong answer about the production year, the both amp are actually from Feb. 2025. serial number CR420717 and CR420804) . I'll return the amp, and am not asking for a resolution to this, just wanted to know if anyone get a clue about this?

[GuyBoden]

Don't use the surge protection power strip and see if fuse still blows.

[Peng1026]

Don't use the surge protection power strip and see if fuse still blows.

yes, the second time blowing of the first amp happened during the amp being plugged directly into the wall outlet.

[andrew]

Silly question, I know, but did you check the current rating of the fuses that are in there versus what they’re supposed to be?

[Robermax]

are these supposed to be slow blow fuses?

[Peng1026]

are these supposed to be slow blow fuses?

no, it has a F1A fuse in it.

[nevershouldhavesoldit]

Assuming you have the correct fuse in it (which is probably true, since you bought it new), the two most common causes are a bad power tube and a bad rectifier tube. If one of the power tubes is glowing bright red compared to the other, it’s the culprit.

If the fuse blew immediately or shortly after you turned on the amp, the way to tell which tube is bad (assuming that’s the problem) is easy. With the amp off, remove the power tubes. Put a fresh fuse in, plug it in, and turn it on. If the fuse blows, it’s the rectifier. If it doesn’t, a power tube that’s going bad is the likely cause. But if the fuse blows only after you’ve been playing for a while, a power tube is the probable cause. If it’s not a tube, a bad plate resistor on one of the output tubes is the next likely cause. Sometimes components have to get hot to reveal an early failure or a mechanical break like a poor solder joint.

What’s different about yours is that you say the same thing has happened to two brand new amps. The odds against 2 identical bad tubes, components, or assembly errors in a row in 2 different examples of the same hand wired model are astronomical. Unless you find a bad component, there has to be an issue common to both of them. That means external issues like improper line voltage. You said these amps are NOS. Are you sure the power supplies are correct for your location? Could they have been made for another market with different voltage or frequency? Germany is 230V, 50 Hz IIRC.

[Peng1026]

Assuming you have the correct fuse in it (which is probably true, since you bought it new), the two most common causes are a bad power tube and a bad rectifier tube. If one of the power tubes is glowing bright red compared to the other, it’s the culprit.

If the fuse blew immediately or shortly after you turned on the amp, the way to tell which tube is bad (assuming that’s the problem) is easy. With the amp off, remove the power tubes. Put a fresh fuse in, plug it in, and turn it on. If the fuse blows, it’s the rectifier. If it doesn’t, a power tube that’s going bad is the likely cause. But if the fuse blows only after you’ve been playing for a while, a power tube is the probable cause. If it’s not a tube, a bad plate resistor on one of the output tubes is the next likely cause. Sometimes components have to get hot to reveal an early failure or a mechanical break like a poor solder joint.

What’s different about yours is that you say the same thing has happened to two brand new amps. The odds against 2 identical bad tubes, components, or assembly errors in a row in 2 different examples of the same hand wired model are astronomical. Unless you find a bad component, there has to be an issue common to both of them. That means external issues like improper line voltage. You said these amps are NOS. Are you sure the power supplies are correct for your location? Could they have been made for another market with different voltage or frequency? Germany is 230V, 50 Hz IIRC.

Many thanks for the suggestions. I'm actually quite sure that the power supplies are correct, like i wrote above, i measured a steady 235V at home. I made a mistake about the production year, the both amp are actually from Feb. 2025 (serial number CR420717 and CR420804), ChatGPT had given me a quite wrong answer.

[nevershouldhavesoldit]

Many thanks for the suggestions. I'm actually quite sure that the power supplies are correct, like i wrote above, i measured a steady 235V at home. I made a mistake about the production year, the both amp are actually from Feb. 2025 (serial number CR420717 and CR420804), ChatGPT had given me a quite wrong answer.

There has to be an indication of the line voltage for which the amp was built somewhere on the chassis. If voltage is too low, the amp may draw too much current. So if your line voltage fluctuates at times (which is common - it’s almost never a steady value over time), a temporary drop could go low enough to pop a fuse. But if you’re running 235 and the amp was built for Germany, it should be fine. I don’t know of any country with higher line domestic voltage than that, so this is probably not the problem..

It’s just hard to believe that 2 fresh identical amps have the same exact internal problem. I haven’t read or heard that there’s a production problem with the Custom Shop Princetons.

[Peng1026]

There has to be an indication of the line voltage for which the amp was built somewhere on the chassis. If voltage is too low, the amp may draw too much current. So if your line voltage fluctuates at times (which is common - it’s almost never a steady value over time), a temporary drop could go low enough to pop a fuse. But if you’re running 235 and the amp was built for Germany, it should be fine. I don’t know of any country with higher line domestic voltage than that, so this is probably not the problem..

It’s just hard to believe that 2 fresh identical amps have the same exact internal problem. I haven’t read or heard that there’s a production problem with the Custom Shop Princetons.

thanks again for the informations. I made a photo of the amp (the first picture, I don't know why the picture ist upside down... sorry for that), the voltage is 230V, seems that nothing wrong I did.

If there were a problem with my household power supply, how could I verify it—considering that the voltage I measured has been consistently stable at around 235V, and none of my other devices, regardless of their power consumption, have ever had any issues?
Both of these amps were manufactured in February 2025. Could this possibly be a batch-related quality issue, or maybe something specific to the EU version's power transformer?
I also noticed that the 120V U.S. version uses an F2A fuse (the second picture), whereas the 230V EU version uses an F1A fuse . Could that be relevant?

[GuyBoden]

Have you tested the amp in another location/building?

[nevershouldhavesoldit]

thanks again for the informations. I made a photo of the amp (the first picture, I don't know why the picture ist upside down... sorry for that), the voltage is 230V, seems that nothing b wrong I did.

If there were a problem with my household power supply, how could I verify it—considering that the voltage I measured has been consistently stable at around 235V, and none of my other devices, regardless of their power consumption, have ever had any issues?
Both of these amps were manufactured in February 2025. Could this possibly be a batch-related quality issue, or maybe something specific to the EU version's power transformer?
I also noticed that the 120V U.S. version uses an F2A fuse (the second picture), whereas the 230V EU version uses an F1A fuse . Could that be relevant?

Wow - this one’s a puzzle! The 1A fuse is correct. Wattage equals voltage times current. You’re running at twice the voltage over there, so the amp pulls half as much current to make the same power.

You’d think we’d have heard about if there were a bad batch. I suspect they don’t sell a lot of this model given its price. But if even half a dozen blow fuses, I’d expect to see web posts about it. I suspect that a bad batch of tubes is more likely than bad transformers. But Fender uses a lot of those tubes in a lot of amps, and there’s not a rash of tube failure reports in ‘25 Fender amps.

I’d get a fresh pack of fuses, take off the back panel so you can watch the output tubes, and see if one glows a lot brighter than the other as you play through it (and especially just before the fuse blows. If one gets bright cherry red, it’s bad and probably the cause.

But if it’s not a power tube, the only way you can test the rectifier tube yourself is to pull the 6V6s, power it on, and leave it for 24 hours or more to see if the fuse blows. If that doesn’t happen, I’d return it and find another amp. At that price, there are many fine options.

[swampguide]

I have a 6 year old Deluxe Reverb Reissue that recently started blowing fuses after the amp was running for a while. It turned out to be the rectifier tube. If you take out the rectifier tube and you see small white flakes inside it, the tube is likely bad. If you (gently) shake the tube the flakes will be loose inside the tube. Here's a link to a video by the amp repairman "Psionic" where he describes this issue.

Good luck!

[Peng1026]

Wow - this one’s a puzzle! The 1A fuse is correct. Wattage equals voltage times current. You’re running at twice the voltage over there, so the amp pulls half as much current to make the same power.

You’d think we’d have heard about if there were a bad batch. I suspect they don’t sell a lot of this model given its price. But if even half a dozen blow fuses, I’d expect to see web posts about it. I suspect that a bad batch of tubes is more likely than bad transformers. But Fender uses a lot of those tubes in a lot of amps, and there’s not a rash of tube failure reports in ‘25 Fender amps.

I’d get a fresh pack of fuses, take off the back panel so you can watch the output tubes, and see if one glows a lot brighter than the other as you play through it (and especially just before the fuse blows. If one gets bright cherry red, it’s bad and probably the cause.

But if it’s not a power tube, the only way you can test the rectifier tube yourself is to pull the 6V6s, power it on, and leave it for 24 hours or more to see if the fuse blows. If that doesn’t happen, I’d return it and find another amp. At that price, there are many fine options.

I did the first part you said, I see a way brighter 5AR4 than the two 6V6GTs. The 6V6s are rather same bright. Is that the problem?

[nevershouldhavesoldit]

I did the first part you said, I see a way brighter 5AR4 than the two 6V6GTs. The 6V6s are rather same bright. Is that the problem?

It’s not a “rule”, but I don’t recall seeing a rectifier tube that was grossly brighter than any output tubes. Swapping in a new one would tell you if this is a problem - if the new one is not that bright, the tube is probably bad. But unless you have one in another amp, you’ll have to buy one to find out. The proper way to check it is to use a tube tester or measure its output voltage (which is the B+ voltage across the output tubes).

The classic signs of rectifier tube weakness include bluish / purplish flashes or coloration between elements, intermittent noises like scratching or hum, whitish flakes inside, and microphonics when you tap it with a nonconductive stick (chopstick, dowel, etc). Replacing it is a hit or miss approach to diagnosis. I don’t like throwing parts or money at an undiagnosed problem and hoping it’ll go away. If the tube shows any visible or audible signs of weakness, I’d replace it.

It’s not uncommon for a little corrosion to build up on the pin connectors in the tube socket, especially if they’ve opened up a bit over time and let the pins get loose. But that’s almost impossible in a fresh new amp. I suppose a socket could come out of the box with loose pin connectors. Remove the rectifier tube and pay attention to how much force is needed. If it slips out with very little resistance, the pin connectors in the socket could have been insufficiently crimped when made. If that’s the case (which is unlikely), Google how to tighten tube socket pin connectors - it’s easy.

I’ve only seen one amp with loose tubes out of the box. I bought one of the first Blues Deluxes, and the output tubes kept falling out. They didn’t come with tube retainers back then, but neither did other Fender amps with upside down chassis and no other tube ever fell out on me.

[GuyBoden]

I've used Solid State Tube Rectifiers, they're inexpensive for a test, less sag, so sound good too:
TAD Solid State Rectifier – Musikhaus Thomann

[nevershouldhavesoldit]

I've used Solid State Tube Rectifiers, they're inexpensive for a test, less sag, so sound good too:
TAD Solid State Rectifier – Musikhaus Thomann

SS rectifiers like that put out 10 to 20% higher B+ voltage than a 5AR4. If the amp is biased at its maximum, this can damage output tubes, plate resistors, PS filter caps etc if they’re at all marginal. Since we don’t know what’s wrong with the amp and it could be a single small item like a plate resistor that might be burned up by the higher voltage, I wouldn’t do that. Swapping parts is already a poor substitute for proper diagnostics.

[Sam Sherry]

SS rectifiers like that put out 10 to 20% higher B+ voltage than a 5AR4. If the amp is biased at its maximum, this can damage output tubes, plate resistors, PS filter caps etc if they’re at all marginal. Since we don’t know what’s wrong with the amp and it could be a single small item like a plate resistor that might be burned up by the higher voltage, I wouldn’t do that. Swapping parts is already a poor substitute for proper diagnostics.

No argument.

Ted Weber's "Copper Cap" SS rectifier line provide the same drop as the analogous vacuum rectifier. Here's the WZ34 (= ss 5AR4).

As a bonus there's no draw on the filament power supply, which is really handy if you want to run 6L6s in a 6V6 amp without overloading the power transformer.

[andrew]

I’m going to play Captain Obvious here and state that working in tube amps is very dangerous if you are not properly trained and potentially lethal. Seriously.

Take it to an experienced technician. If it’s brand new, repair costs should be covered under warranty.

[GuyBoden]

SS rectifiers like that put out 10 to 20% higher B+ voltage than a 5AR4. If the amp is biased at its maximum, this can damage output tubes, plate resistors, PS filter caps etc if they’re at all marginal. Since we don’t know what’s wrong with the amp and it could be a single small item like a plate resistor that might be burned up by the higher voltage, I wouldn’t do that. Swapping parts is already a poor substitute for proper diagnostics.

If you're not competent with high voltage electrical equipment, then I suggest taking the Amp back to the shop.

Guy Boden BEng(Hon)

[nevershouldhavesoldit]

If you're not competent with high voltage electrical equipment, then I suggest taking the Amp back to the shop.

Guy Boden BEng(Hon)

That's always great advice, and I was remiss in not including it. Anyone who is at all uncertain or lacks the knowledge, skill, experience, and tools to work on an amplifier safely should not attempt to do so. Most disasters occur because of inexperience, overconfidence, or some combination of the two.

But all we're talking about here is looking at the tubes in place, inserting or removing tubes, and tapping the rectifier with a chopstick. These solid state replacements for tube rectifiers are built on tube bases, so they replace the tube by plugging into the same socket. The chassis does not have to be removed from the cabinet or opened up.

The only potentially dicey thing I suggested is tightening the tube pin connectors in the socket if the tube pins are loose in them. To do this, you need to discharge the power supply caps and check with a meter to be sure they're at zero potential. There are warnings about this in every instructional web page, book, and article I've ever seen about it.

[rpjazzguitar]

The OP indicated that the fuse didn't blow while he was using the amp. Rather, he implied, that the amp couldn't be turned on again and the problem turned out to be the fuse. Or did I misunderstand him? There was some ambiguity in the description.

So, what would put a surge of power through the fuse when the amp is being turned off, or just sitting there? Or what could break a fuse, mechanically?

All of this is just for fun. The right thing to do is return the amp or get it serviced under the warranty.

[nevershouldhavesoldit]

The OP indicated that the fuse didn't blow while he was using the amp. Rather, he implied, that the amp couldn't be turned on again and the problem turned out to be the fuse. Or did I misunderstand him? There was some ambiguity in the description.

So, what would put a surge of power through the fuse when the amp is being turned off, or just sitting there? Or what could break a fuse, mechanically?

All of this is just for fun. The right thing to do is return the amp or get it serviced under the warranty.

You understood it the same way I did. He said

after about five to six hours of non-consecutive use, the fuse blowd (not during the using, it just couldn't be turned on again). I replaced the fuse, and it happend again after several hours playing.

But you interpreted it to mean that the fuse blew when he turned it off. I’d bet dollars to donuts that it blew when he tried to turn it back on. I also agree with you that it’s a warranty issue, but only if it’s a covered failure. I don’t think the warranty covers tubes. So if it’s a bad rectifier or output tube, he’s on his own unless the dealer has really good customer service. That’s why I suggested checking for bad tubes first.

If a power tube failed and took out another component like a plate resistor, I don’t think the warranty will cover that either. Some really good dealers will pick it up to keep customers happy, but he could also get a repair bill.

The exact same failure in two brand new HW amps like that is really odd. Getting a bad tube or component is uncommon in one amp. The exact same problem in two is just really suspicious. I’d return it for a refund, but I’m not entirely convinced it was the amplifiers.

[rpjazzguitar]

You understood it the same way I did. He said



But you interpreted it to mean that the fuse blew when he turned it off. I’d bet dollars to donuts that it blew when he tried to turn it back on. I also agree with you that it’s a warranty issue, but only if it’s a covered failure. I don’t think the warranty covers tubes. So if it’s a bad rectifier or output tube, he’s on his own unless the dealer has really good customer service. That’s why I suggested checking for bad tubes first.

If a power tube failed and took out another component like a plate resistor, I don’t think the warranty will cover that either. Some really good dealers will pick it up to keep customers happy, but he could also get a repair bill.

The exact same failure in two brand new HW amps like that is really odd. Getting a bad tube or component is uncommon in one amp. The exact same problem in two is just really suspicious. I’d return it for a refund, but I’m not entirely convinced it was the amplifiers.

Great points and I claim no expertise. But, he replaced the fuse, turned the amp on successfully and then it happened again. Does that mean he turned it off and could not turn it on again?

I should have realized, when I posted, that the turning-on was probably when the fuse blew. But OTOH, the turning-off fits the facts, if it's true that the same thing happened again (ie it didn't blow while he was using it).

No comments yet about the standby switch, if it matters.

[nevershouldhavesoldit]

Great points and I claim no expertise. But, he replaced the fuse, turned the amp on successfully and then it happened again. Does that mean he turned it off and could not turn it on again?

I should have realized, when I posted, that the turning-on was probably when the fuse blew. But OTOH, the turning-off fits the facts, if it's true that the same thing happened again (ie it didn't blow while he was using it).

No comments yet about the standby switch, if it matters.

As he said, “it just couldn’t be turned on again”. He made no mention of the standby switch, but I overlooked that because I keep thinking of a Princeton (which has no standby) instead of a Deluxe. Mea culpa! If an output tube did this, the fuse would have blown when the standby was switched on because it controls B+ voltage to the output tubes. If it blew when powered up with the standby switch on standby, it would be the rectifier tube if the problem is a tube.