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Hi Guys my friend ---{who lives overseas}--- finally wrote back about his amp that was blowing rectifier tubes.This is what he said: "Even the factory guys did not know how to fix this issue, the Cary amp is their CAD 2A3 AMP SE. It was a standard design, but there is no schematic available. Right now I'm listing through these amp as we communicate to each other. I don't know how long the rectifier tube will last!? Apart from a big flash when switching the amp ON it works fine, until the rectifier tube blows."
It would be a great big help to him if someone could just provide him with a schematic of his Cary CAD 2A3 AMP SE. At least that way he could compare the capacitance on his first filter cap and see if Cary is keeping up with their infamous use of too much capacitance in the first filter cap! Oh yeah my friend wants to know if switching to the Shuguang 274B would be a smart move both sonically and for longer tube life? TIA to all those who choose to help my friend and I resolve his problem.
Finally the CD below is a recording of two incredible guitarists playing what I've come to believe is some of the most beautiful guitar music I've ever heard! Check out Jano, Mori from their Krushevo CD at the link below...
I'm listening to: Krushevo by Vlatko Stefanovski + Moroslav Tadic
Thetubeguy1954 (Tom Scata)
Central Florida Audio Society -- SETriodes Group -- Space Coast Audio Society
Full-range/Wide-range Drivers --- Front & Back-Loaded Horns --- High Sensitivity Speakers
Edits: 12/23/16Follow Ups:
"At least that way he could compare the capacitance on his first filter cap and see if Cary is keeping up with their infamous use of too much capacitance in the first filter cap!"He doesn't need a schematic.
What he needs to do is look at the first cap and tell us what value it is.
If it's to big for the rectifier tube then he needs to decrease it's value.
The schematic above shows a 1200uf cap right after the rectifier tube.
The link below for the CAD 2a3 SE manual shows that 2 1200uf caps are used in the power supply.
If we put 2 and 2 together I think it's safe to say Cary is keeping up with their infamous use of too much capacitance in the first filter cap but the guy with the amp can know for sure just by looking.
Have him look. If he doesn't know how to tell what comes after what, instruct him.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 12/24/16 12/24/16
Tre'
Thanks so much for this input. I'm going to send my friend a link to your post and see if it helps him.
I'm listening to: Elixir by Fourplay
Thetubeguy1954 (Tom Scata)
Central Florida Audio Society -- SETriodes Group -- Space Coast Audio Society
Full-range/Wide-range Drivers --- Front & Back-Loaded Horns --- High Sensitivity Speakers
I believe that the CV378/53KU shown in the schematic is same as the GZ-37. Several decades ago I owned a Quicksilver KT88 amp which also had a huge first cap in the PS. The GZ-37 is an extremely robust rectifier and the only one I found that could last in the Quicksilver. I would recommend that the OP try a GZ-37. Sadly, they are no longer $16 which is why I recommended the 5V3/5AU4.
If the amp were mine, I would put the most robust indestructible rectifier I could find in the amp. The 274B is exactly the opposite of that. Blow $10 and buy a 5AU4 or 5V3A on epay. These tubes were intended to power all the tubes in a color TV including the picture tube. If a 5AU4 fails then there is a serious problem with the amp.
The 5AU4 makes the GZ34/5AR4 look like a toy.
Can the 5 VAC winding on the unit's power trafo safely energize the brute's filament? It does draw 3.75 A.
Eli D.
Yes, it does draw 750mA more current than the 5U4GB. I know what some here on AA do is to check the rectifier winding under load and assume that if there is > 5V then they are OK. My own feeling is that if 750mA is a strain on the power transformer then that's not a very robust piece of equipment and not worth the thousands that it costs.I bought an infrared thermometer on Amazon for less than $20. Another test one can do is to use the infrared thermometer to check the temp of the power transformer with a 5U4GB after the unit is fully warmed up and then do the same with the 5AU4 to see if there is an appreciable difference.
In the end though, there is either something wrong with the amp if 5U4GBs rectifiers are failing or the user is using 5U4G or 274B rectifiers which can't handle the current.
Edits: 12/24/16
Darned tootin something is wrong with the amp. It's the ABUSE Cary subjects vacuum rectifiers to. :> (( In a nutshell, highly defective design.
If the unit's owner lacks the know how needed about PSU design, then that party should send the amp to Sachs, Samra, etc. for a complete going over.
Eli D.
Kinda sly, but really if your friend insists on using his amp that blows up rectifiers don't be surprised if the amp blows up next. Determining the value of the first capacitor in the filter supply is easy. It is just a matter of tracing the capacitor that is hooked up to pin 8 of the rectifier socket. Sometimes the center tap off the 5 volt filament circuit is used for the B+ tap but not often as most transformers do not have a 5vct. If the pin8 tap is going to a choke then the value of the following capacitor is less problematic but still should not be more than a 100 or maybe 200 uf.
Hi DAK!
If you look back at most of the past posts of mine, you'll see that I almost always post what I'm listening to! I do this because I love it when I'm exposed to music that I previously didn't know about, but loved it when I heard it. I'm hoping others might follow my example and post the music they're listening to as well. I do it it here and most all the other audio sites I visit. I mentioned this recording ---{ instead of just listening as I'm listening to (whatever) }--- only because of how much I loved the music and the quality of the recording!
As far as the Cary amp goes, my friend is having the rectifier problem I described and needs help resolving the problem. So I appreciate your input and will definitely pass it on to him. Thank-You...
I'm listening to: From Me To You by Tom Coster
Thetubeguy1954 (Tom Scata)
Central Florida Audio Society -- SETriodes Group -- Space Coast Audio Society
Full-range/Wide-range Drivers --- Front & Back-Loaded Horns --- High Sensitivity Speakers
And thank you for passing on your music. It is so hard finding good music nowadays. happy holidays!
No problem DAK! Life is too short and music too precious to waste time arguing about petty things. Don't you agree?
I'm listening to: Trust by Graus & Bronzwaer
Thetubeguy1954 (Tom Scata)
Central Florida Audio Society -- SETriodes Group -- Space Coast Audio Society
Full-range/Wide-range Drivers --- Front & Back-Loaded Horns --- High Sensitivity Speakers
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