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Sprague 716P Orange Drop, 200V & 400V Where to Buy ?

being unemployed sometimes we have to give up the simple pleasures to get by... I think a big bowl of butter pecan or rocky road would do wonders for my morale right now. I may have to go check into that :scratch2:
 
Bluelobster said:
Good question Jay!
You are right that a cap may only see the potential across the grid in operation but because a higher voltage as referenced to ground, as you pointed out, is there, it is done as a safety factor especially if you miswired or something shorted to ground it would help prevent catastrophic failure when powered on.
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Correct me if i am wrong... But didn't the OEM's put smaller caps in this equipment j have been fooling with all the time?
 
I typically see 400v on coupling (say in integrateds), and 200v in tone amp sections. Sometimes though you will see ceramics in tone circuits and I imagine they are rated at 1000, or more.:yuck:
 
jaymanaa said:
Help out the fat dumb kid here. I see lots of 400v coupling caps in old gear, but if you measure "across" the cap in operation, the voltage can be a lot less. The "potential" to ground is that high maybe, but they aren't going to ground, they are going to grids. I've always wondered about this, and now seems like the time to ask. Thanks, Jay:yes:
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It is often true that once the equipment is “up and running”, the voltage across the capacitor may be much less than the rated voltage. However, it is often the case that at startup through the time when the equipment reaches the “up and running” state, the voltage across the capacitor may be much greater. The capacitor needs to be rated to handle the peak voltage.

jaymanaa said:
Do this experiment; when she's up and running, stick a meter lead on each side of those caps and see how much voltage is actually there. I'm curious to know.:scratch2:
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Try this experiment; stick a meter across the capacitor and then turn on the equipment. What is the peak voltage you read?
 
tcdriver said:
Try this experiment; stick a meter across the capacitor and then turn on the equipment. What is the peak voltage you read?
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I'd like to see those results as well. The only thing I could see raising voltage at start up would be resistors not resisting due to no load on the until warm up occurs (approx. 11 seconds).
 
Jay,
I will be sure to take those measurements. I am not so sure what will happen during start up though because I will mostly likely have a thermistor on each leg of the incoming ac. The schematic shows very low voltage in that area it does have me a bit perplexed
 
jaymanaa said:
I'd like to see those results as well. The only thing I could see raising voltage at start up would be resistors not resisting due to no load on the until warm up occurs (approx. 11 seconds).
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Depending on circuit design, tubes not conducting can cause voltage across caps to soar to near full B+ until the tube warms up. Typical situation might be a cap coupling the plate of a driver tube to the grid of a final esp if fixed bias and SS power supplies are used
 
jaymanaa said:
My drug of choice is Extreme Moose Tracks covered with microwaved hershy's hot fudge. Way better than sex or audio.:drool:
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Put it on a bed of corn flakes and you're cooking with gas. It's better than audio, anyway. And costs less than sex...
 
This is one of the more educational threads.
Physical size of caps also matters, especially in integrated amps.

Does anyone know if some vendors staggered voltage ratings on output coupling caps for a reason? I've never gotten a definitive answer. The voltage across coupling caps in a push-pull pair certainly does vary, and some are quick to use four duplicates, but these original designers often did things for a reason.

Just wondering . . .
 
IF....physical size of the caps are of major importance?
Do the caps have to be Sprague Orange Drops?
I've found that Mallory 150 caps come in a physically smaller package than Sprague Orange Drops, for the same exact values.

Steve
 
gearhound said:
IF....physical size of the caps are of major importance?
Do the caps have to be Sprague Orange Drops?
I've found that Mallory 150 caps come in a physically smaller package than Sprague Orange Drops, for the same exact values.

Steve
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The M150's are metalized polyester, while 715P and 716P are polypropylene. Polypropylene has about an order of magnitude lower DA and DF than polyester making them a more "ideal" capacitor.
 
The thing I'm getting at is cost and availability. Check epay on say Vitamin Q 200v oil caps, they are much cheaper, and 100v are cheaper still. The 400v are the ones that command big money, and if a simple mod (say delay on HT) will allow me to run 100v couplers, I'm for it, especially on custom built amps. I look at it like using compactrons instead of EL34s and such.
 
O but 716 orange drops sound so good in vintage gear and the cost is low. Antique Supply is where i got mine.
 
jaymanaa said:
The thing I'm getting at is cost and availability. Check epay on say Vitamin Q 200v oil caps, they are much cheaper, and 100v are cheaper still. The 400v are the ones that command big money, and if a simple mod (say delay on HT) will allow me to run 100v couplers, I'm for it, especially on custom built amps. I look at it like using compactrons instead of EL34s and such.
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Not to belabor the issue but...We now enter the realm of failure mode, probability, consequences and design philosophy. While a soft-start or HT delay may indeed prevent excessive voltage from appearing across a cap, this is under ideal conditions. What happens if a tube fails to light up for whatever reason? What if you accidentaly pull a tube while the amp is powered up? What if you forget to install a tube in the first place? What is the probability of any of these fault situations occurring? What are the consequences of the fault? Will a cap fail? If it does, will it just cause bad sound or will it take out an expensive final or worse yet, a tough to replace custom OPT?

My own personal philosophy is to assume the worst case is probable and go from there because tube equipment is not mainstream and therefore worth extra measures that enhance reliability. In the case of coupling caps, I generally use the highest voltage avail that will fit properly but also consistent with function.
 
Steve O said:
Not to belabor the issue but...We now enter the realm of failure mode, probability, consequences and design philosophy. While a soft-start or HT delay may indeed prevent excessive voltage from appearing across a cap, this is under ideal conditions. What happens if a tube fails to light up for whatever reason? What if you accidentaly pull a tube while the amp is powered up? What if you forget to install a tube in the first place? What is the probability of any of these fault situations occurring? What are the consequences of the fault? Will a cap fail? If it does, will it just cause bad sound or will it take out an expensive final or worse yet, a tough to replace custom OPT?

My own personal philosophy is to assume the worst case is probable and go from there because tube equipment is not mainstream and therefore worth extra measures that enhance reliability. In the case of coupling caps, I generally use the highest voltage avail that will fit properly but also consistent with function.
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please define "HT delay".:scratch2:
 
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