Weekend Project Thread
- Thread starter Alonzo
- Start date
Grainger49
New member
Alonzo,
I know only one thing about a grid choke. It replaces a resistor from grid (or outer lead of grid stopper resistor) to ground. I never put them in my Paramours. It is pretty full already. Take a look:
http://www.bottlehead.com/smf/index.php/topic,1185.0.html
I pretty much got nothing!
I know only one thing about a grid choke. It replaces a resistor from grid (or outer lead of grid stopper resistor) to ground. I never put them in my Paramours. It is pretty full already. Take a look:
http://www.bottlehead.com/smf/index.php/topic,1185.0.html
I pretty much got nothing!
Grid chokes are a double edged sword. They can give a really great improvement in the sense of dynamics, but they are susceptible to hum pickup. So they don't work in every setup. I would suggest connecting them and rotating and otherwise moving them around for lowest noise pickup before committing to a location on the chassis.
Alonzo
Member
Thanks Doc,
Is this a spot where higher value is better? Mike's BCP-16's or equivalent? I have some room to the front of my chassis, will long leads also pick up hum or is it a function of the windings in a magnetic field?
Grainger, that definitely is a blivit. You do need a taller base, there's always more iron, bigger caps....
Is this a spot where higher value is better? Mike's BCP-16's or equivalent? I have some room to the front of my chassis, will long leads also pick up hum or is it a function of the windings in a magnetic field?
Grainger, that definitely is a blivit. You do need a taller base, there's always more iron, bigger caps....
Sorry folks -- still in the midst of a sea of boxes, unpacking and dealing with a wrenched back on top of it all.
Here's a pretty basic primer on line rated caps that hits most of the high points:
http://www.justradios.com/safetytips.html
I hope that gives folks enough info to make a decision on whether they want to continue with their current caps or switch to something a bit more safe. It's not that your typical poly film cap won't work across the line, it is a question of when and how it will fail -- especially those of you who live in places where electrical storms are frequent and intense, or nearer to power plants and large substations where large voltage spikes can happen.
Me, I'd just do it for peace of mind.
Thanks, and happy reading,
Jim
Here's a pretty basic primer on line rated caps that hits most of the high points:
http://www.justradios.com/safetytips.html
I hope that gives folks enough info to make a decision on whether they want to continue with their current caps or switch to something a bit more safe. It's not that your typical poly film cap won't work across the line, it is a question of when and how it will fail -- especially those of you who live in places where electrical storms are frequent and intense, or nearer to power plants and large substations where large voltage spikes can happen.
Me, I'd just do it for peace of mind.
Thanks, and happy reading,
Jim
Alonzo
Member
Thanks Jim, interesting read. Even though I'm not the safest person in the world, I wouldn't want to start any fires. I took a couple of pages of reading to find my caps weren't recommended for "across the line" applications, they really should put the safety information in the front. Luckily Vishay makes other caps that will fit my situation.
Alonzo,
No problem -- it's just one of those things not many folks know or talk about but it is good practice especially for us diy types.
I will probably try this on whatever amp ends up at my bedside table as the only nearby electrical outlet also has hardwired into it, the two dimmable halogen reading lights my wife had installed on each side of the bed. I have very little room to work with here so I'm going to have to come up with a very clever, compact outlet strip and filter setup for my headphone rig. I've got some ideas but no shop in place to make it happen yet.
-- Jim
No problem -- it's just one of those things not many folks know or talk about but it is good practice especially for us diy types.
I will probably try this on whatever amp ends up at my bedside table as the only nearby electrical outlet also has hardwired into it, the two dimmable halogen reading lights my wife had installed on each side of the bed. I have very little room to work with here so I'm going to have to come up with a very clever, compact outlet strip and filter setup for my headphone rig. I've got some ideas but no shop in place to make it happen yet.
-- Jim
Alonzo - count me as a grid choke fan! I have them in my Quickie now. Been back and forth between Paul's very well designed CCS and the chokes, and I think the chokes will stay in this time. I think it may because I listen to digital. If you are analog then the CCS may be 'cleaner' and better.
Alonzo
Member
Eric,
I've been in that corner before...I think everyone visits there now and then.
John, what are you playing your SR-45 into, I"m playing my 45 into horns, so I"m trying to determine what will improve, I have a hard time defining "dynamics". Did the sound stage expand, or more depth to voices and instruments? These chokes are probably a month or so away, I've got to get onto Mike's build list, in the meantime I'm adding BCP-15s hopefully soon.
I've been in that corner before...I think everyone visits there now and then.
John, what are you playing your SR-45 into, I"m playing my 45 into horns, so I"m trying to determine what will improve, I have a hard time defining "dynamics". Did the sound stage expand, or more depth to voices and instruments? These chokes are probably a month or so away, I've got to get onto Mike's build list, in the meantime I'm adding BCP-15s hopefully soon.
Grainger49
New member
I thought it was my corner.
2wo
Active member
Alonzo, I use the SR-45 mostly with Hornshoppe horns. The grid chokes Give more of a sense of attack and make the amp seem more powerful and alive. It did not change the tone much. The sound stage did not change in size so much as the space it conveys seems more solid and real. I can hear more of the room in which the recording was made...John
4
4krow
Guest
"IN THIS CORNNNER, IS JAHNNN, THE SOLDER KING(SHOUTING/APPLAUSE). AND, IN THIS CORNER,-, THE RETURNING-BURNNNN CHAMP! GGGRAINGER! THE BOTTLEHEAD SMASHHHER! ( BOOO! 'YER A BUM! {SORRY, IT'S NOT YER HOME TOWN}). JUDGING TONIGHT WILL BE KKKROWWWW...."I DON'T WANNA SEE ANY COLD JOINTS-HOT LEADS OR BURNING BELOW THE BELT. GENTLEMEN, START YOUR IRONS."
Somebody make it stop.....
Somebody make it stop.....
Grainger49
New member
I thought I was the Corner Sitting Champ. Just ask my Mom.
Alonzo
Member
John,
My Frugel horns are a similar design so it seems that the chokes will be good for me also. Will give it a try once I have chokes and have fixed the amp.
I've committed a triple sin, I've killed 3 1940 45 tubes for some reason I can't fathom. While playing the amp and breaking in, about 45 - 1 hour in, one channel will die. I thought it was a bad solder joint opening when heated so, I re-wet pins 1 and 4, looked for shorts and started again. About an hour or so later, tube #2 didn't work. So me, being dumb, took a layer apart to check solder joints, checked voltages on the heaters, plugged in a new tube and a short time later, another tube bites the dust.
So after 3 tube failures I decide to take the amp down for repairs but I can't see any thing wrong. I measure 2.9 volts AC on the heaters, the transformer is rated for 5v CT 3A, I'm running the 45 heaters in series with no CT, each measures out at 2.9 volts.
This has happened on the same side, the side extended from the heater wiring. I'm thinking of replacing the wiring due to a heat induced short, just to see if that's it, but I don't see any obvious causes. Does anyone have any ideas?? Oh yeah, tested it with some 2a3's and they played fine...
I'm at a loss, please help...
My Frugel horns are a similar design so it seems that the chokes will be good for me also. Will give it a try once I have chokes and have fixed the amp.
I've committed a triple sin, I've killed 3 1940 45 tubes for some reason I can't fathom. While playing the amp and breaking in, about 45 - 1 hour in, one channel will die. I thought it was a bad solder joint opening when heated so, I re-wet pins 1 and 4, looked for shorts and started again. About an hour or so later, tube #2 didn't work. So me, being dumb, took a layer apart to check solder joints, checked voltages on the heaters, plugged in a new tube and a short time later, another tube bites the dust.
So after 3 tube failures I decide to take the amp down for repairs but I can't see any thing wrong. I measure 2.9 volts AC on the heaters, the transformer is rated for 5v CT 3A, I'm running the 45 heaters in series with no CT, each measures out at 2.9 volts.
This has happened on the same side, the side extended from the heater wiring. I'm thinking of replacing the wiring due to a heat induced short, just to see if that's it, but I don't see any obvious causes. Does anyone have any ideas?? Oh yeah, tested it with some 2a3's and they played fine...
I'm at a loss, please help...
2.9V is a 16% overvoltage. That is quite high, most of the old texts say the filament voltage should stay within +/- 5%, i.e., 2.375 to 2.625V. So that might be at least part of the problem. However, if it keeps happening on only one channel it might be that something else that is isolated to that side is causing the problem. That fact that it doesn't happen for 45 minutes tends to indicate that it is either a thermal issue or maybe it is in fact that the tubes just tend to die after 45 minutes from the filament overvoltage. I'd suggest using a resistor in the filament supply to get the voltage closer to 2.5V and using an expendable tube like a worn 45 to see if it holds up over time.
