In every possible way. They have lower ESR, their faster, they have no paste electrolyte to dry out so last forever, they are tighter tolerance, they don't drift as they age, if subjected to high voltage spikes they self heal instead of shorting out. Look at a spec sheet for the specifics.
Most of the plate resistors get hot so they get a workout. They typically drift up to ~110k, which is OK. Indication to replace them is a hiss or frying bacon type sounds. If they get a hairline crack, they will make a *pop* type sound. Chopsticking will usually reveal a cracked CC.
Agreed ^
I have used 1A slow fuses in my AB763 (similar power usage). Maybe get a 1A and a 2A, and if the 1A blows swap to the 2A.
I go to my local Ace hardware or other small parts store. Usually they’ll have enough selection to find something that works.
Try Rob's site. Look under *Amp Protection Mods*.
Thanks LLC. Maybe it's me...I tried for 30 minutes to dig out any info on fusing the high voltage secondary leads on the PT, I think it's just not there. https://robrobinette.com/Generic_Tube_Amp_Mods.htm#Protection_Mods
Blue Bill, I remember having the same problem finding info on the fuse ratings when I built my AB763 kit.
It's there... this from Rob's 5F6A mods site:
) I did see those, but in my overwhelmed state, at midnight last night, I dismissed them as pertaining to different amps than the DR, and therefore, perhaps not correct for it. It looks like the money paragraph is:
For those guys, rig a non-destructive bracket to existing screw and just use thermal compound. TIP: Heat sinks can be harvested off old dead computer CPU. They work great. Many have 12vDC fans integrated into them, which is even nicer and which solves the fan-mounting issue in one fell swoop. I always install a bypass switch on the fan, for those times that my amps went to the studio for recording, and where a fan noise is unacceptable.
Interesting disagreement over capacitors. Not picking a side, but here's a tiny sliver of data to throw into the discussion...
Agree that a rebias will be in order, but is probably in order anyway. The significant advantage of using the GZ34 is that the filament load is 1.1 amp less than a 5U4. That 1.1 amp lower strain on your 50 year old main transformer is a significant lessening of filament winding load. Since the heat between all secondary windings is quickly shared inside the transformer, ANY reduction in any secondary load is good for the lifespan of all secondary windings. Cool transformers live longer.
Keep in mind that the GZ34/5AR4 is an indirectly heated cathode, whereas the 5U4 family is a direclty heated cathode. That's also a good benefit in this case generally beneficial to component logevity, due to the slightly gentler rise to operational B+. Going the other way, (changing from GZ34 to 5U4 and similar) not so much...
In my experience, there are three other mods that are good investments in OEM transformer longevity. In my practice, I always add these three. All are undoable and do not affect the vintage vibe of the amp.
1. A small cooling fan mounted to the primary transformer. It can be powered by a wall wart or even from a small rectified source from the filament circuit itself, if sufficient headroom is present. If you swap to a GZ34, you just gained 1.1 amp headroom. You can invest 100 (or less) of that in powering a quiet 12vDC computer CPU fan. The cooling provided will reap transformer life benefits far in excess of the >100ma load the fan imposes.
2. I add a heat sink - attached directly to the bell of the transformer. Epoxy+ thermal compound is your friend, unless you are an absolute purist and cannot see your way clear to remove the varnish drippings from your transformer bell.
3. I always include a bucking transformer for amplifiers in this age range or older. This is built into a standard 2 gang box and stuck in the back of the amp. This simple tool reduces primary transformer input voltage to about 115VAC, which helps restore plate voltages to something a little more normal. Primary dropping like this will also bring your tube filament voltage back into reasonable range. This is almost universally ignored by guitar amp guys, but it is an improvement that will gain benefits for tube longevity - if you have an amp that is already pushing the filaments beyond their "best" range.
These are all minor improvements. Some guys overlook or dismiss them. They are not sexy like speaker swaps, tone stack, feedback mods, special PIO caps, grain oriented magic wire, mystery tibetan salt crystals, , and so forth. But they are easy to accomplish and are all good performance and safety measures - ESPECIALLY if you are going to be driving a vintage amp hard for regular shows. (Something I personally did my entire active career as a player. I never blew a vintage amp so modified in 30+ years of gigging them this way)
Finally, speaking of speakers, I FULLY agree with TubeDude - definitely replace that speaker. IME, this is just not a great match for a Deluxe, and EV units are very heavy too. I've been down this road of these large voice coil high performance PA style speakers in small tube amps. Besides the JBL D123, I've had poor results with this particular path, and FWIW I have about fifty or sixty of these types hanging on my speaker wall of fame/shame. The lower power "primative" types just seem to work better in Deluxes.
You got the proper pronoun. lol.
Chances are your PT is rated for less than 150mA and the amp will use less than that. The main point is to protect the PT wire from heating to the point of failure or melting the enamel insulation. You don't want nuisance tripping so you want a value large enough to avoid metal fatigue of the fuse yet small enough to trip when needed. I assume most of the time the circuit will have a catastrophic failure. It won't just slowly heat up. The diode will fail short or the tube will fail short to the heater. Maybe others will opine differently but I would think 500mA of fast or slow blow fusing would suffice. Either will trip with the *event*.
