Hmmm. OK, so, perhaps help me understand. Lets start with what goes to and from the 5U4's. If you tell me what I should be looking at in terms of components and what the current (pun intended) values are or those in the 5U4 "chain" then perhaps I can understand better what this "design problem" you are referring to is.
Oh, and this is the amp pre any work (big power supply caps have been removed in this image)
Thanks!
Oh, and this is the amp pre any work (big power supply caps have been removed in this image)
Thanks!
This is who designed my SLI-50...
Not sure the statement that he doesn't understand tube equipment really applies?
The Single-Ended Amplifier: Cary's Dennis Had | Stereophile.com
You've got the amp that has the arcing tubes, and many people here are offering a solution. 🙂 🙂 🙂
And this is the tube I'm using...
Winged "C" (SED) 5U4-G Black Plate Rectifier Tubes - www.thetubestore.com
Winged "C" (SED) 5U4-G Black Plate Rectifier Tubes - www.thetubestore.com
The capacitors are much too big for the input of the rectifier - because the enormous capacitor doesn't discharge much from the amplifier load between the 120hz pulses of DC, the conduction angle becomes very short, and the rectifier can only conduct for very short pulses because the capacitor can only charge when the voltage of the cap is lower the the voltage common off the rectifier.
This causes lots of stress in the rectifier because there is nowhere for the current to go except for a small window.
Now if the first capacitor the rectifier sees is small, and preferable followed by even a small choke, the current has somewhere to go because the small capacitor is discharging quickly and has room to accept the charging pulse. The choke can accept charge 90deg later than the cap and therefore helps give the pulse somewhere to go and smooths the supply quite a bit.
Anyway, after the first CR or CL, you can make the filter reservoir as big as you like.
http://www.tubezone.net/pdf/5u4.pdf This data sheet shows that typical capacitor input filter is 40uF
This causes lots of stress in the rectifier because there is nowhere for the current to go except for a small window.
Now if the first capacitor the rectifier sees is small, and preferable followed by even a small choke, the current has somewhere to go because the small capacitor is discharging quickly and has room to accept the charging pulse. The choke can accept charge 90deg later than the cap and therefore helps give the pulse somewhere to go and smooths the supply quite a bit.
Anyway, after the first CR or CL, you can make the filter reservoir as big as you like.
http://www.tubezone.net/pdf/5u4.pdf This data sheet shows that typical capacitor input filter is 40uF
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Thanks 6L6!
So, lets correctly and properly presume that I don't know what to look for. To which pin is what capacitor connected in the rectifier?
As an aside, since I was mistakingly using 5V4's, what if any damage could that have caused?
So, lets correctly and properly presume that I don't know what to look for. To which pin is what capacitor connected in the rectifier?
As an aside, since I was mistakingly using 5V4's, what if any damage could that have caused?
Chris Hornbeck's comments have pretty much nailed it.
I also suspect the "cap craze" had something to do with this faulty design. (bigger is better?)
Before all the planned obsolescence and greedy consumerism made their stains on products, consumer products were designed with collaborated standards of quality in mind, and the proof is clear to see, even today.
Why do you think that vintage products are coveted by so many?
Because they were manufactured the right way, with thoughtful design, distinctive styling, and satisfying performance.
Those manufacturer claims and catch-phrases meant something back then.
Zenith products = "The quality goes in before the name goes on"
RCA Victor = "The most trusted name in sound"
Westinghouse = "You can be sure, if it's Westinghouse"
And the list goes on.....cars, home appliances, clothing, etc., all fought for customer appreciation.
Brand recognition was a top priority to these companies.
But now today, this once-made legacy of quality-by-name is falsely milked by savvy greed-hungry corporations that bought those brand names, and manufacture crap in my opinion.
The LLC (limited liability)designation in modern times now helps to protect these badgers by insuring them from complaints and financial destruction.
LLC in my opinion means Lousy Loser Crap.
Indeed, the once proud tube era reputation, among other products, is now just a marketing tool to keep customers on the hook like some poor fish in a pond.
Dumbing down of society, brainwashing, helps keep the cash flowing.
I also suspect the "cap craze" had something to do with this faulty design. (bigger is better?)
Before all the planned obsolescence and greedy consumerism made their stains on products, consumer products were designed with collaborated standards of quality in mind, and the proof is clear to see, even today.
Why do you think that vintage products are coveted by so many?
Because they were manufactured the right way, with thoughtful design, distinctive styling, and satisfying performance.
Those manufacturer claims and catch-phrases meant something back then.
Zenith products = "The quality goes in before the name goes on"
RCA Victor = "The most trusted name in sound"
Westinghouse = "You can be sure, if it's Westinghouse"
And the list goes on.....cars, home appliances, clothing, etc., all fought for customer appreciation.
Brand recognition was a top priority to these companies.
But now today, this once-made legacy of quality-by-name is falsely milked by savvy greed-hungry corporations that bought those brand names, and manufacture crap in my opinion.
The LLC (limited liability)designation in modern times now helps to protect these badgers by insuring them from complaints and financial destruction.
LLC in my opinion means Lousy Loser Crap.
Indeed, the once proud tube era reputation, among other products, is now just a marketing tool to keep customers on the hook like some poor fish in a pond.
Dumbing down of society, brainwashing, helps keep the cash flowing.
From this - 5U4G Emission Labs Data Sheet
(Emphasis mine)
"When studying the graph, you will see a dotted line, on the right upper side. It looks like a corner of the graph is cut off here. This cut off piece will be larger when the first capacitor is larger. So now, it is specified for a first capacitor of 10uF in this graph. The best way to prevent problems, is not the maximum value capacitors, and use simply a bit higher transformer voltage and larger chokes to get the required result. This will not give less efficiency of the rectifier circuit ! It will however make any type of rectifier tube last longer. Even the opposite effect can be seen, when people over-rate the first capacitor in an attempt to get lowest possible hum. In several cases, over-rating the capacitor will even increase the total hum of the amplifier. Elementary design rules say, you stabilize a high voltage with a large choke, and low voltage with a large capacitor. With maximum value capacitors, the capacitor charge pulses get extremely high, causing hum field radiation into the pre-amplifier wiring and tubes. These charge pulses have a kind of "bad sounding" wave shape, and smallest hum field radiation from this, can become audible if strayed into the pre-amp circuit anywhere. Two design notes for this are at the end of this data sheet. When designing your own circuit, you should really read those notes."
"Note 2) To prevent large charge current peaks, the first capacitor (C1) should NOT be larger than 40uF. If the input capacitor is too large, this will result in heavy AC charge current through this capacitor. This is not good for the rectifier tube, and also not for the capacitor lifetime. The AC capacitor current peaks may cause hum radiation into the preamplifier. With the given C-L-C values in table, the rectifier circuit will work best. For filtering, with oversized components, you will have best results by increasing the choke. Do not oversize capacitor C1, this may increase hum. You can choose the choke large as you want. This will have better results with high voltage rectification."
"Note 3) Rectifier tubes may under no circumstance carry larger current peaks as what they are designed for. The current peaks are mainly a function of: power supply DC load, first capacitor and transformer copper resistance. The copper resistance for 5U4G and 5Z3 may not be smaller than 170 Ohms. This is very important to check, and too low copper resistance may damage the rectifier, no matter what brand or construction. Use a small series resistor if the copper resistance of the used transformer is too low. If you scroll further down this data sheet., there is a link to a table with historical information about this, for several rectifier types, not only 5U4G."
(Emphasis mine)
"When studying the graph, you will see a dotted line, on the right upper side. It looks like a corner of the graph is cut off here. This cut off piece will be larger when the first capacitor is larger. So now, it is specified for a first capacitor of 10uF in this graph. The best way to prevent problems, is not the maximum value capacitors, and use simply a bit higher transformer voltage and larger chokes to get the required result. This will not give less efficiency of the rectifier circuit ! It will however make any type of rectifier tube last longer. Even the opposite effect can be seen, when people over-rate the first capacitor in an attempt to get lowest possible hum. In several cases, over-rating the capacitor will even increase the total hum of the amplifier. Elementary design rules say, you stabilize a high voltage with a large choke, and low voltage with a large capacitor. With maximum value capacitors, the capacitor charge pulses get extremely high, causing hum field radiation into the pre-amplifier wiring and tubes. These charge pulses have a kind of "bad sounding" wave shape, and smallest hum field radiation from this, can become audible if strayed into the pre-amp circuit anywhere. Two design notes for this are at the end of this data sheet. When designing your own circuit, you should really read those notes."
"Note 2) To prevent large charge current peaks, the first capacitor (C1) should NOT be larger than 40uF. If the input capacitor is too large, this will result in heavy AC charge current through this capacitor. This is not good for the rectifier tube, and also not for the capacitor lifetime. The AC capacitor current peaks may cause hum radiation into the preamplifier. With the given C-L-C values in table, the rectifier circuit will work best. For filtering, with oversized components, you will have best results by increasing the choke. Do not oversize capacitor C1, this may increase hum. You can choose the choke large as you want. This will have better results with high voltage rectification."
"Note 3) Rectifier tubes may under no circumstance carry larger current peaks as what they are designed for. The current peaks are mainly a function of: power supply DC load, first capacitor and transformer copper resistance. The copper resistance for 5U4G and 5Z3 may not be smaller than 170 Ohms. This is very important to check, and too low copper resistance may damage the rectifier, no matter what brand or construction. Use a small series resistor if the copper resistance of the used transformer is too low. If you scroll further down this data sheet., there is a link to a table with historical information about this, for several rectifier types, not only 5U4G."
Here is a full breakdown of the caps as they sit in the circuit. The only caps that have a higher rating are the two electrolytics at 47uf...
...I mean draw the schematic from what you see. Start at the transformer, to the rectifier sockets, to the various things in the PSU, to where the PSU connects to the audio circuitry.
I read through that article from Dennis Had, and am not impressed.
He sounds like a kid that played with amps at a young age and never had proper schooling on electronics.
Then delved into marketing his stuff to unwary customers.
Not one mention of formal education in electronic design, no mention of schools, no proof of certification, nothing.
Just some guy working as an investment banker, looking for suckers in the home entertainment crowd to make him more money.
Greed - typical of today's world.
It's not much different than the chinese buying up the old established brand names that once held proud reputations, and now relying on those reputations to sell the modern junk they produce.
Read the "about us" websites these companies have....
They all mention how they "came a long way" and evolved from the status they built.... yeah, sure, RCA today isn't one bit attached to when it was RCA Victor.
Or Zenith, or Crosley, or Emerson, or Sylvania, etc etc.....
They all make crap now.
You can't believe what these companies tell you.
For instance, Bell and Howell used to make quality cameras, projectors, etc.
The asian company that bought the brand name now states "the name you trusted for over 50 years" - and that cracks me up.
People need to wake up and realize the "once was" was.... and isn't, today.
Gotcha. Thanks for the link to Emission Labs!
I shall attempt to do so.
It seems that a lot of the comments have to do with large caps. There are none other than the big 1200uf power caps??? So, trying to figure out if there are no big caps, then what do the caps have to do with arching as if they are bigger than 40, they cause a problem?
Also, does anyone know what this is? It's connected to the only cap I did not replace...
I shall attempt to do so.
It seems that a lot of the comments have to do with large caps. There are none other than the big 1200uf power caps??? So, trying to figure out if there are no big caps, then what do the caps have to do with arching as if they are bigger than 40, they cause a problem?
Also, does anyone know what this is? It's connected to the only cap I did not replace...
Thank you for the generalization and painting myself and others as "ignorant consumers" Appreciate it. Does not however help solve the problem at hand. I'll let Leica and Hasselblad know that I made a bad decision on purchasing them a long time ago because I am clueless. And, I could be wrong, but making tube amps at a time when they were a niche market, doesn't exactly look like a cash cow compared to investment banking. Your premise might be a bit "off"...
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Dual 5AR4 rectifiers with 1000uF input capacitors were not totally uncommon in the 1980s and later. I have worked on several pairs of early Quicksilver 8417 amps with 800 - 1000uF input capacitors. These particular amps were built when new Mullard 5AR4 were still readily available, current production types don't seem to survive for long in these amps.
I don't think it was a good idea, but the manufacturers got away with it for some period of time apparently.
To the OP I would look for a very rugged pair of 5U4 like the GE or RCA, and I would install 1N4007 diodes in series with the plates which may or may not help in the arcing problem (should help with hot starts I'd think)
Hopefully people have noticed the standby switch in negative side of the supply - the Cary schematic is not particularly clear. I'm not convinced this is the safest way to do it. (I'm also not a fan of the standby switch)
I don't think it was a good idea, but the manufacturers got away with it for some period of time apparently.
To the OP I would look for a very rugged pair of 5U4 like the GE or RCA, and I would install 1N4007 diodes in series with the plates which may or may not help in the arcing problem (should help with hot starts I'd think)
Hopefully people have noticed the standby switch in negative side of the supply - the Cary schematic is not particularly clear. I'm not convinced this is the safest way to do it. (I'm also not a fan of the standby switch)