Ok but if the Caps are rated for the extra unloaded voltage there shouldn't be an issue right? I mean usually I try to make amps idiot proof, for example if somebody was to turn the amp on without the power tubes in the caps will be rated for the higher voltage due to a substantially smaller load than normal operating conditions. I do remember reading something about tubes not liking voltage on the plate while the filament isn't on.
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Eli,
The 5V winding does not have a center tap, is this an issue? Can I just pull the B+ from pin 8 like the 5AR4? My reservoir cap value is 50uf and I see on an RCA datasheet 40uf is max, I can't seem to find a datasheet for the Tung-Sols, I am sure 50uf isn't going to shorten the life to much though.
And don't some old Mcintosh's use the 5U4? I bet some people running those would pay a fair amount for the Tung-Sols but I would like to keep some around for future use, maybe sell some on fleapay and keep the rest
I have never used an inrush current limiter, I will look into that thanks for the tip.
The 5V winding does not have a center tap, is this an issue? Can I just pull the B+ from pin 8 like the 5AR4? My reservoir cap value is 50uf and I see on an RCA datasheet 40uf is max, I can't seem to find a datasheet for the Tung-Sols, I am sure 50uf isn't going to shorten the life to much though.
And don't some old Mcintosh's use the 5U4? I bet some people running those would pay a fair amount for the Tung-Sols but I would like to keep some around for future use, maybe sell some on fleapay and keep the rest
I have never used an inrush current limiter, I will look into that thanks for the tip.
The issue is twofold...first, surge voltage on capacitors, tubes, and other components when a 5U4 (or other directly heated rectifier) is used. Second, some tubes ARE sensitive to cathode bombardment when HT is applied before the cathode comes up to temperature. Repeated on-off cycles may be a failure mode for the 5AR4 or 5V4 type tubes, but the delayed warm up saves stress on components downstream from the rectifier.
50uF is right on the edge, if the high voltage secondary winding resistance is high enough they will run OK. (Concern is exceeding the peak current rating on a continuous basis)
No problem with picking the DC off of pin 8, and I would think these would do the job nicely in your application.
Plenty of voltage margin on those caps from what you describe, and the 5U4 will indeed drop a little more than the 5AR4, but lightly loaded as it is likely to be perhaps not the full 20V you were hoping to loose.
I use 5U4 in some of my regulator designs, have had no problems so far with EL34, 6550, etc.
Just measure the voltage at the most vulnerable filter cap during warm up to make sure its voltage rating is not exceeded.
5U4 are tough, I have seen some used at the edge of several of their ratings simultaneously (PIV and max current) and they still seemed to live for quite a while. (As in years)
No problem with picking the DC off of pin 8, and I would think these would do the job nicely in your application.
Plenty of voltage margin on those caps from what you describe, and the 5U4 will indeed drop a little more than the 5AR4, but lightly loaded as it is likely to be perhaps not the full 20V you were hoping to loose.
I use 5U4 in some of my regulator designs, have had no problems so far with EL34, 6550, etc.
Just measure the voltage at the most vulnerable filter cap during warm up to make sure its voltage rating is not exceeded.
5U4 are tough, I have seen some used at the edge of several of their ratings simultaneously (PIV and max current) and they still seemed to live for quite a while. (As in years)
I added 100R 10watt wirewound resistors in series with the plates of the rectifiers because of the low winding resistance on the secondaries, I think the 5U4's will be fine and will try them. They will probably be more reliable then the Russian 5AR4's that are in there now
The 5U4 was the go-to rectifier in the 1950's and early 60's. Virtually every TV set and HiFi that was too hungry for the 5Y3 got a 5U4. Some early color TV's had TWO 5U4's. They were often mounted right in the end bell of the power transformer. I don't remember ever seeing a TV with a 5AR4 in it.
Yes, and so did Scott, Fisher, Pilot and many others. ALL the old guitar amps used a 5U4 or a 5Y3. The 5AR4 didn't come into vogue until the mid 60's. It offered a lower dynamic resistance which improves B+ regulation in a class AB audio amp. The simple change of a rectifier tube gave the stereo manufacturers a few more watts of power for little or no money, and POOF the 5U4 vanished in audio......except in some guitar amps.
In a guitar amp used for blues and some rock music the older 5U4 and 5Y3 tubes along with smallish filter caps provided some B+ sag. This increases the amps sustain, and adds character to the amps "tone."
Take a 20 watt guitar amp, crank it to 11, then add 20 db of excess gain in front of the amp from a stomp box. Then blast a power chord at full tilt. The 20 watt amp attempts to produce 2000 watts, but makes a very distorted 25 watts. The output tubes draw excess current, especially if the tiny OPT is entering saturation. This drags the power supply voltage down which reduces the gain of the entire amp chain. As the chord dies out, the guitar's output drops reducing the overload on the amp, allowing the B+ to build back up slowly, increasing the amps gain. This characteristic alone will keep 5U4's in production for a long while. I know guitar players that will put 5Y3's in an amp that overloads them, or use old worn out 5U4's with brand new 6L6GC's to increase the sag.
Most metal players prefer the "bite" of a 5AR4 (or solid state rectifiers) with a big fat filter cap behind it. They want all of the power all of the time......
Most 5U4's will outlive a 5AR4 and they will generally survive a sparking out. Once you see fireworks inside a 5AR4, it's usually toast. Ditto the 5Y3's in old Fender Bandmasters (made for a 5U4). You see sparks every time you turn the amp on, but the tube lives for a year or two.
I have not found this necessary in many applications, but it is always the safest route to take. I have built some cathode follower output stages where this was a necessity. I just add two extra windings to an Antek toroidal power transformer for the heater supplies.
If you want to make a full wave bridge with 4 damper tubes you will need two isolated windings for two of the heaters since the H/K ratings will be violated if all 4 heaters are tied together.
Thanks Tubelab! I will be digging them out soon and give them a whirl in both my guitar amps and stereo amps.
Got it thanks. Most of the amps I built the 5V heater windings are rated for 3A. I am unsure of my Fender Deluxe Reverb Reissue, I know the vintage ones were rated for 3A but I can't find any specs for the stock Fender transformer in the reissues.
Firstly thanks for a host of info regarding guitar amps and power supplies, although it is not my prime interest.
Just to add that one must not forget the tolerance on electrolytic capacitors. I'm to lazy to go look now (see time of morning - bed still waiting!) but I recall something like +10% to -30%, or is it the other way round? I have measured 40µF caps to be >50µF, etc.
Just to add that one must not forget the tolerance on electrolytic capacitors. I'm to lazy to go look now (see time of morning - bed still waiting!) but I recall something like +10% to -30%, or is it the other way round? I have measured 40µF caps to be >50µF, etc.
I have seen some as bad as +80%/-20%, I have seen 47uF Panasonics as high as 65uF.
I had been tinkering with an idea I call the Sagulator. The Sagulation knob goes from loose, to tight. In other words from worse than unregulated to tightly regulated. It is still a work in progress, and I don't even have a lab right now, so I can't say when work will resume.
I started off with a simple mosfet regulator with adjustable unregulation, I also made one of the typical "VVA" devices that adjusts the B+ or screen voltage on the output tubes. All of that stuff evolved into a programmable power supply with enough smarts not to let the user blow up the amp. There also a bunch more programmable features in the works.
Dear friend you represent a big part of the history of the common things that is the first fact that people forget. Your description transport me to the deep inside the part of those dirty devices, where people mix the poverty with the entertainment. Now probably there are not one of them, people and tube tvs.
There are people here and everywhere with an incredible hearing capacity that they can distinguish the difference in sound of valves compared with solid state rectifying.
IOT:
Finally after of question you, I got the transformers, ongaku clones from one member from Cyprus that he offer by swap list, at the end they result very thin laminations and their weight more more than 10kilos each, I am painting them and I started to build my fake ongaku.
I will use the original one first design with four 5AR4, but against my volunteer because an internal voice said this is one more bottle of snake oil.
Anyway the Chassis holes, the space there is ready for them, finally I will investigate later replacing with the new CREE diodes that somebody else, friends, members and common sense people's recommend nowadays.
I just replace my tired DX4 with a new EX4 in my Mauhorns and with this and the new amp.
Ready for start to listen Class A SE without NFB.
Further listening testes I hope to contribute for get a GZ34 mullard metal base.
A best regards for you gentlemen
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I actually have no idea what the difference in sound sounds like. I'm familiar with the by the book concept of how silicon diodes add noise though. For my curiousity, at what point can there be no difference in sound? Would an SE amp with a stabilized, filtered, and regulated power supply sound different?
I'm curious of the actual difference between the two types of devices. Many people take one side or the other and I don't particularly care for their kool aid.
I'm curious of the actual difference between the two types of devices. Many people take one side or the other and I don't particularly care for their kool aid.
So the CL-90 inrush current limiter was mentioned to slow the B+ rise down when using directly heated rectifiers. Can someone explain how this works to me
Isn't the purpose of these devices to limit current not voltage? Starting at time 0 when the rectifier starts to put out voltage the other tubes are not conducting so the only load is the power supply capacitors, the current they draw is proportional to time, voltage, and capacitance. This current is what the CL-90 will limit by it's cold/high resistive state, but the current is caused by the voltage and amount of capacitance right?
So how does it limit the voltage?
I am not saying anybody who recommended the CL-90 is wrong, and I am not doubting the CL-90 wouldn't work because you guys know your sh*t far better than I. I am just not understanding what is happing and would like some explanation whether it be in layman's terms or in a mathematical equation or both.
-Thanks
Isn't the purpose of these devices to limit current not voltage? Starting at time 0 when the rectifier starts to put out voltage the other tubes are not conducting so the only load is the power supply capacitors, the current they draw is proportional to time, voltage, and capacitance. This current is what the CL-90 will limit by it's cold/high resistive state, but the current is caused by the voltage and amount of capacitance right?
So how does it limit the voltage?
I am not saying anybody who recommended the CL-90 is wrong, and I am not doubting the CL-90 wouldn't work because you guys know your sh*t far better than I. I am just not understanding what is happing and would like some explanation whether it be in layman's terms or in a mathematical equation or both.
-Thanks
So the CL-90 inrush current limiter was mentioned to slow the B+ rise down when using directly heated rectifiers. Can someone explain how this works to me
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jeff
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