Location of Standby switch - before B+1 or after????

[Structo]

Tony, are you sure about that?

My D'Lite has the balancing resistors and the caps bleed off in a matter of seconds since those resistors do go to ground.

Or are you talking about something else?

Since the D'Lite has the standby switch before the big caps, the whole PS filter bleeds down.

I can see if you have the big caps first you would have to close the standby switch to effectively drain the rest of the caps.

[butwhatif]

We should change the thread subject to 101 ways to wire a standby switch!! LOL


Tony VVT[/quote]

Amen, or move this thread to the garage talk venue, don't have a clue what it has to do with D discussion, unless carling somehow sounds better than a-b because my girl says so due to the thicker cryo silver plating in od mode at temps over 70 deg C lofl2x

[tictac]

is there a particular reason why you want to keep voltage on the choke or the sag resistor when in standby..

No, it's just that it's the only way to wire the circuit using a single pole on/off/on...

tictac - change that drawing to show where the OT gets it's B+ - there is no point in having a standby if the plates have full power on them.

But the plates don't have "full power" on them, if the screen is shut off [0 Volts] the tube cannot conduct current regardless of whether the OT primary has voltage present on it. Most Fender amp have this type of standby and I've never heard of anyone complaining about "that lousy Fender style standby" it works fine.

The Traynor type standby which lifts the center tap of the Secondary of the PT leaves the entire B+ rail connected to the primary but it too works because current can't flow in the pre & power amp.

[talbany]

What is in question I think is not the B+ but whether the main caps should be on the hot or cold side of standby for #124. Your #124 schemo in the files section shows OT plate caps on the hot side, B+ on the cold side, and the original hand drawn drawing shows it all on the cold side. I seem to remember Funk once saying that HAD put his main caps on the hot side like your drawing, but I trust my memory about as far as i can heave a 100 watt head

I think we can all agree that there are quite a few different ways to wire a Standby switch..I think a few old timers including myself have just sort of picked up on Fenders method a Benchmark amp like the Twin and it made perfect sense and everything else seems wrong..As far as how 124 was done here is an easy to read layout to a Twin same method as 124.. Rectifier to B+1 to standby switch to choke & CT...Have a nice day..

Tony, are you sure about that?

My D'Lite has the balancing resistors and the caps bleed off in a matter of seconds since those resistors do go to ground.

Tom don't know about you bro but I've been zapped by a few Blackface Fenders in my day that should have bled out..On paper your right the balancing resistors should discharge.. I'll tell my feet that the next time they are flapping in the wind.. LOL!!!

Tony VVT
(Your not officially considered a real man until you've been zapped by a Twin)

No, it's just that it's the only way to wire the circuit using a single pole on/off/on...

Try this!

[heisthl]

Most Fender amp have this type of standby and I've never heard of anyone complaining about "that lousy Fender style standby" it works fine.

Please point me to even one Fender schematic that has B+ on the OT in standby mode.

[Tubetastic]

I wonder if this is a good time to ask a question on Standby Switches that has been niggling me since reading it...

In one of Kevin O'Connors books he says a Standby isn't really necessary - unless it is for Higher Voltage/Power amps. IIRC, he said in Sweden they had Fender remove Standby switches.


Anyway, I'd be interested in the Opinion of the Amp builders on here on that Standby not necessary comment - I know about Cathode stripping. Thoughts?

[talbany]

Much of this argument depends on how the Stby is wired of coarse.. If it is wired say like a BF Twin when you power up the amp in Standby by charging the B+1 first and the filaments helps limit the amount of in-rush current placed on the transformer...It is also healthier for the cathode to be heated before applying the high voltage to the plates( Primary function).. As well as keeping the tubes warm while idle for extended periods of time..It's not as critical for amps with Tube rectifiers since they require a short warm up time before the high voltage is applied to the plates..Although most old tube jockeys still advise installing one..There are Pros and cons to everything.. To me this is the main purpose of a Stby..



Tony VVT

[heisthl]

http://www.peavey.com/support/technotes ... pter_6.pdf
likes the use of "screen" standby

[talbany]

Henry..
Cool Read!! Thanks...



Tony

[Tubetastic]

Thanks, Tony.


Interesting link, Henry. I was ignorant to "Cathode Poisoning".

[Chad]

Thanks for the link Henry , Very interesting info their for sure. Anyone know anything about the "inrush current limiters” That Peavey is talking about or what components it consists of. Thanks , Chad

[butwhatif]

Inrush limiters were used especially in some hi power solid state amps which, when turned on, draw a lot of current to charge the dc surge caps. One in particular was the Crest 9001, which was capable of 6600w at 2 ohms. Anyone who ever used a Crest 8001 will attest to the 20A breakers they typically tripped several times at start up , because they didn't have adequate inrush protection.

[Structo]

Yeah, my D'Lite drains the caps pretty quick.
In under a minute the voltage is down to a safe level.

But I do like to verify it on the caps with a meter before diving in.

I suppose if you don't follow a safety regiment, that one time you don't measure for voltage, you're gonna get knocked on your ass.

[tictac]

Please point me to even one Fender schematic that has B+ on the OT in standby mode.

You are correct, what I was thinking when I wrote that was the first filter cap on most Fenders is before the standby and the first filter cap is what filters the plates so the plates are connected before the standby.

The reality is: first filter cap is before the standby the plates are connected after the standby...I Stand Corrected

In the drawing I posted I wanted to be able to switch between a choke and the resistor (Robben Ford Mod) using a single pole on/off/on switch; the only way to get it done is if the plates are wired before the standby. With the switch in the middle standby the amp is indeed in standby even with voltage on the plates...

[talbany]

Yeah, my D'Lite drains the caps pretty quick.
In under a minute the voltage is down to a safe level.

But I do like to verify it on the caps with a meter before diving in.

I suppose if you don't follow a safety regiment, that one time you don't measure for voltage, you're gonna get knocked on your ass.
Very Happy
_________________

Tom yeah that's a funny thing for example if I just fired it up and apply the first charge 90% of the time you have to zap em before you go back in.. (This relates to the Fender/Dlite PS plates now)..After that if I only have the amp on for a few minutes say to do some voicing/tweaking they drain out.. If it's out of the cab and don't give it time to bleed bleed down and the amps been on for say 20 minutes it's a 50/50 proposition...That's been my experience... The one time you say yeah there drained ZAP!! I always snap them regardless...Especially if no one is around..(Maybe someone here with more experience with PS can shed some light on why this is)...The Dumble Precision PS w 220k bleeders on each stage drains quickly every time..


Tony VVT