5E3 immediately blows fuse

[bk121]

My first 5E3 build has issues. as soon as power is applied the fuse blows immediately. im suspecting the problem may be a faulty power transformer as it was salvaged from a old failed build. at any rate my electornics knowledge is sub par but ive been reading as much as possible. at any rate id like to see if anyone could confirm my wiring of the transformers just to make sure i did it properly. the transformer is from antique electrical supply and ive attatched the wiring diagram. ive attatched the two green t the heaters at pins 2 and 7. the two yellows at pins 2 and 8 at the rectifier. the two reds at 4 and 6 of the rectifier. the red/yellow ct to ground. clipped the blue. connected black to power and white to white on the power cord. power cord green to ground and black to fuse. I may as well put in my wiring of the ot just to be 100% certain as well since i was confused. Its a mercury ftdo-59. the yellow secondary to the tip of the speaker jack. black/red to pin 3 of 6v6gt closeest to rectifier. blue to pin 3 of 6v6gt closest to output jack. the orange/yllow to standby switch. hopefully somebody can shed some light. ive tripple checked all the other wiring and it appears its correct and really appears as something here would be wired incorrectly as the rest of the crcuit is not recieving any power at all. Ive build a 18 watt kit before and decided to try this one on sourcing my own parts from scratch but really wish i would of stayed on the "kit" track...i appreciate any assistance in advance...

[bbartilson]

I've tripple checked all the other wiring and it appears its correct and really appears as something here would be wired incorrectly as the rest of the crcuit is not recieving any power at all. Ive build a 18 watt kit before and decided to try this one on sourcing my own parts from scratch but really wish i would of stayed on the "kit" track...i appreciate any assistance in advance...

1. Go and buy a box of fuses. If you don't have a variac to bring the power up slowly, you will likely blow a couple before you're done, and that's okay. The fuses are there to protect your circuit (your hard work) Let them do so.

2. Remove ALL of the tubes, make sure standby is off. Try to power the amp. Does the fuse blow?

If yes:

Disconnect the B+ and bias supply secondaries from the circuit. It's okay to let the wires hang in the air, provided they don't touch the chassis or each other. Try again. If fuse still blows, likely you have a bad PT, but it's worth then checking your heater wiring carefully to make sure you haven't accidentally shorted the heater winding someplace. Still I'm not sure a shorted heater winding would be enough to blow the fuse immediately.

If no:

Quadruple check your wiring, or better yet, post some pictures of your build. Posting the pictures before unwiring anything is okay too. Maybe we'll see something you don't.

3. Don't get discouraged. The first question I ask when something is broken - something I got from a Bob Pease book years ago: "Did it ever work?". A new circuit has NEVER worked right. It is a surprise and a joy (even for an old-timer like me) when a circuit works as designed the first time you power it up. It's disappointing when it doesn't - but it should be a lot bigger surprise when it DOES work. Remember that it never has before. With all the help around here, there's no question that it CAN and should at some point.

Get back to us with pics or the result of disconnecting the secondaries, whichever comes first.

-Bill

[stokes]

Maybe I am not reading your post right,but do you have a wire from your OT connected to the standby switch?In describing your OT wiring you state"orange/yellow to standby switch".The rest of your OT connections sound odd to me as well,as the colors you describe arent familiar to me.I see no reason any wire from an OT should be connected to the standby switch,of course,I am assuming the standby switch is breaking the PT's CT to ground.Just FYI there was another poster here some time ago who was having similar troubles with a PT from Antique Elect.Supply.It turned out they had a bad batch of PT's.He went through 3 of them before he ordered from someone else.

[haashole]

Maybe I am not reading your post right,but do you have a wire from your OT connected to the standby switch?
--snip--
I see no reason any wire from an OT should be connected to the standby switch,

I don't choose to do it this way myself, but here is an example of a 5E3 layout with the OT connected to the standby switch:

http://www.ceriatone.com/images/layo...atone_edit.jpg

[bk121]

the ceriatone is the layout that i am using which is why i hooked it up that way. Problem with the output transformer is i couldnt find any documentation on it. Its a mercury ftdo-59

[haashole]

the ceriatone is the layout that i am using which is why i hooked it up that way. Problem with the output transformer is i couldnt find any documentation on it. Its a mercury ftdo-59

You don't have the "one-page" document from Mercury? I'm using a MM FTDO-M, which I think is the same as yours, but with multiple secondaries 4/8/16. But mine doesn't have any multi-colored wires, so my info won't help you.

If you don't have the sheet from Mercury, maybe you can email them for it.

[Bruce / Mission Amps]

the ceriatone is the layout that i am using which is why i hooked it up that way. Problem with the output transformer is i couldnt find any documentation on it. Its a mercury ftdo-59

You might have an old MM OT as the most current art work I have from MM and their FTDO-59 output transformer is this:

Primary side:
Blue... 6V6 plate
Black/Red ... 6V6 plate
White/Orange is the primary center tap (B+)

Secondary side:
The Yellow tubing is over the 8 ohm speaker lead.
The OT's channel mount has a wire soldered to it called the self-lead, which would be the other side of the secondary winding and normally grounded at the speaker jack but not so with these.
Since the speaker jacks are grounded to most metal chassis' and so is the OT's channel mount, there is no need for a ground wire from the OT to the jack.
Not a great idea in my mind but that is the way it is on the MM FTDO-59 OT.

[Bruce / Mission Amps]

Maybe I am not reading your post right,but do you have a wire from your OT connected to the standby switch?In describing your OT wiring you state"orange/yellow to standby switch".The rest of your OT connections sound odd to me as well,as the colors you describe arent familiar to me.I see no reason any wire from an OT should be connected to the standby switch,of course,I am assuming the standby switch is breaking the PT's CT to ground.Just FYI there was another poster here some time ago who was having similar troubles with a PT from Antique Elect.Supply.It turned out they had a bad batch of PT's.He went through 3 of them before he ordered from someone else.

He has it wired right... the standby switch, when closed, is supplying B+ to the OT center tap and the eyelet board's first filter cap and subsequent B+ rail.

There is no reason to wire the standby switch to the center tap of the high voltage secondary.
Don't assume everyone uses a standby switch as you promote.
If you are not careful with the bias supply design and your use of a high-V center tap standby, it is a good way to potentially apply "instant on" B+ to the power tube's plates with near zero bias voltage on their grids ...while the bias supply rail is developing negative voltage and or charging up.

MM has a habit of using odd color wires at random and sometimes I'll get them with different color wires then the first time I ordered them.

[stokes]

"There is no reason to wire the standby switch to the center tap of the high voltage secondary.
Don't assume everyone uses a standby switch as you promote.
If you are not careful with the bias supply design and your use of a high-V center tap standby, it is a good way to potentially apply "instant on" B+ to the power tube's plates with near zero bias voltage on their grids ...while the bias supply rail is developing negative voltage and or charging up."
The original 5E3 has no standby switch.It is also cathode biased,so there is no concern about the bias supply as you describe.His original post doesnt say what he used to build this thing,so I was just asking.One of my first "teachers",was an engineer for RCA way before any of us were even born,advised me to put the standby on the CT as I described.Its been working fine since 1974,so excuse me,but there is no reason not to wire it on the CT in this circuit.So now if you are done "correcting" me,maybe you can back to telling this guy why ,if he has it wired right as you say, he is still blowing fuses,and I'll keep my "ignorant questions" to myself.bk121,I appologize for asking for clarification on that point,but as Bruce pointed out "MM has a habit of using odd color wires at random" we can assume you have it wired right.

[Bruce / Mission Amps]

One of my first "teachers",was an engineer for RCA way before any of us were even born,advised me to put the standby on the CT as I described.Its been working fine since 1974,so excuse me,but there is no reason not to wire it on the CT in this circuit.So now if you are done "correcting" me,maybe you can back to telling this guy why ,if he has it wired right as you say, he is still blowing fuses,and I'll keep my "ignorant questions" to myself.bk121,I appologize for asking for clarification on that point,...

Ha ha... I've read many of your replies and posts... you seem to have a pretty good understanding of vacuum tube electronics but please save the sarcastic remarks for some of the youngsters or novice builders/tweakers. I am not in awe of you.
However, I will debate the issue with you a bit more if you'd like.

If he wired the thing as in his artwork, it should be OK.
His blowing the fuse is something else... possibly a bad power tranny but more likely a dead or partial short from the first filter cap to ground or some other very simply wiring error.
Maybe a solder bridge across lug 3 to 2 on a power tube or plate to filament on a preamp tube socket, a shorted plate to screen or grid inside a bad power tube... or maybe he has a filament lead shorted to ground... etc.
A careful review of the eyelet board and sockets will probably reveal the issue.

I find the standby switch on the 5E3 circuit to be very useful myself but you are correct it is not mandatory and not quite so important in cathode biased power amps.
Now, he could move the OT's primary center tap wire to the eyelet board
(right at the first filter cap's + lead eyelet) and the B+ breaking standby switch would still work correctly.
Regardless, I think he probably has the standby switch wired correctly and moving it to the center tap is not going to fix anything.... unless while moving the wires around he fixes a short that he has not yet discovered.

But I really do not see any reason to use a power transformer's high voltage secondary center tap as the lead for a standby switch unless the actual switch in question has a low voltage rating, or if just desired and the amp is cathode biased.

Why? I'll repeat myself again.
In a fixed biased amp, breaking the H-V secondary center tap also kills the bias supply voltage so, with the wrong rectifier, like a 5Y3, 5U4 (directly heated cathodes) or solid state diodes, the B+ ramps up VERY fast or instantly while the power tubes have virtually no bias voltage yet.
Cathode biased amps do take a few moments to develop bias voltage too but the current through the power tube is limited by the cathode resistor.
Fixed bias amps have no such luxury.
I don't know if you didn't see what I was talking about or didn't understand that in my previous reply.

As far as you RCA engineer's opinion, well, it might mean the world to you but it is, like mine, just an opinion!
So, explain to us the virtues of this PT H-V center tap standby switch method you promote. Possibly you have some insight that I do not and I can learn something too. It wouldn't be the first time

My opinion is based on what I now know and my experiences over the years.

I got my first taste of vacuum tube construction in around 1963 when I was about 12 years old and built my first vacuum tube Ham Radio Heathkit.
My uncle, also an electronic engineer from WWII, was an old time Ham Op and full time TV-Radio repair man for more then 46 years and I spent many hours with him as a young boy and throughout my teenage years before he passed away.
Going to his house was a like a trip to Oz or at least the Wizard's house

Anyhow, I do have MANY years of working with high voltage power supplies in the real tube amp world and in my 57 years of existence on planet Earth, I've seen and worked on little, pip squeak 1-3 watt tube amps to hundreds of audio watts plus QRO, high powered two way radio land-mobile service vacuum tube equipment with fairly big to extremely HIGH +5KV power supplies, plus seeing hundreds and hundreds of other audio tube amplifiers in various states of operation or mis-repair.
Yet, to be honest, I'm the first to admit I still don't know anywhere near as much as many here. But I do have a lot of real hands on experience.

With some of this in mind, do you think there is any reason that very very few manufacturers use(d) a standby switch in the H-V center tap secondary?
Will it work? Of course it will.
Is it the best way?
I say not really and in some instances I think it can be a disadvantage.
I know Pete Traynor did this but off hand, but without any head scratching and digging around, that is one of the only bona fide amp companys I can think of that used a standby switch with the hi-v secondary center tap.
However, even though they did it, I still think it is not the best way to do it. So, if your RCA engineer actually told you this is the correct way to install a high voltage standby switch, I think his opinion is wrong... not dead wrong, just not fully thought out.
It is merely another way to do it, but I think it is potentially an inferior way to do it.

[stokes]

Not looking for an argument or debate here at all,nor do I ask for your "awe".Our backgrounds and age are quite similar,so I am equally in lack of awe as well.You fired the first shot after I asked for clarification on his description,I fired back,excuse me.I fully understand your concern about the bias issue,but as I pointed out it has no bearing here,this is a cathode biased amp.You know as well as I do when that standby circuit can and cant be used,so lets not re-hash that.Dont know why,but its not the first time I've sensed some animosity from you to one of my replies,but I was merely asking for clarification on his description,obviously that bothered you for some reason,sorry,but I like to be clear before offering a solution.Oh,and by the way,I dont know when I said I was promoting this standby method,just said I used it in this circuit,I dont "promote" anything.So I'll just stop here since this is getting us no closer to helping this guy.Carry on,I'll sit back and learn.

[bk121]

Well id like to thank everyone for their assistance so far. Fortianately for us novices when we see two old timers go at it, we actually can learn quite a bit. Ive looked at quite a bit of layouts and builds before i decided to take on this venture and theres quite a bit of differences in most of them deviating from the original. i went with the layout i choose since it seemed the easiest to follow and as far as the board layout looked very similar to the original. ive lso had success on a previous build form the same vendor, but for all newbies out there like me i would recommend gettign a kit as i think the money ive saved in sourcing my own parts was spent on shipping and handling fees on buying parts i somehow "overlooked".

Back to my build. ive taken all the advice here and put it to work. Bruce was right, i did have a few miswires and loose solder joints when i really dug into the amp. Im 6'5 with large hands so its very difficult for me to "get int here" but i did fins a lighted magnifing lamp invaulable to really get in there. i corrected all the miswires, but it still blew fuses. finally I took Bills advice, disconnected everything, and im still blowing fuses, so ive come to the relization is the power transformer. So im going to order another one and see how that goes. Ive also decided to take a step back and may rewire it again. I found it difficult to get my hands in there so alot of the joints are sloppy and as id like this amp to become my primary home amp, id like to really do it right. the old saying of measure twice and cut is one thing that was running through my head when reviewing all the wiring. at any rate, Id like to thank everyones input so far. its unfortunate its sort ofa lost art that finding someone to look over my shoulder and point things out is just not an option, evern here in nyc. Ill keep you posted.

[Bruce / Mission Amps]

Where are you?
Email me and I'll advise you on what power transformer to buy.
The one you have, I think actually is a silver face Deluxe Reverb clone.
However, it is made by a very high end, reliable magnetics company and I have not seen any bad ones, even though I also read there was a string of failures some time back.

Keep in mind that sometimes a bad transformer is the result of a simple errant wiring and the poor thing never had a chance to survive the dead short.
You must be sure to not recreate any possible reoccurrence.
*********************

added.

I just noticed you are in NYC.
Email me for some advice

[Bruce / Mission Amps]

Not looking for an argument or debate here at all,nor do I ask for your "awe".Our backgrounds and age are quite similar,so I am equally in lack of awe as well.You fired the first shot after I asked for clarification on his description,I fired back,excuse me.I fully understand your concern about the bias issue,but as I pointed out it has no bearing here,this is a cathode biased amp.You know as well as I do when that standby circuit can and cant be used,so lets not re-hash that.Dont know why,but its not the first time I've sensed some animosity from you to one of my replies,but I was merely asking for clarification on his description,obviously that bothered you for some reason,sorry,but I like to be clear before offering a solution.Oh,and by the way,I dont know when I said I was promoting this standby method,just said I used it in this circuit,I dont "promote" anything.So I'll just stop here since this is getting us no closer to helping this guy.Carry on,I'll sit back and learn.

I thought I've read a number of times, (during the time you've been posting here on AMPAGE), that you use the Hi-V secondary center tap standby switch and since there are many novice builders here, I wanted to point out that there are other things to consider when using that method.
To me AMPAGE is about helping out when possible, tossing in some sound
basics and a few tricks here and there.
Sometimes I come across as a "know-it-all" and I don't mean to.
I've said it before and I'll say it again, there are many excellent electronic techs and part timers here that probably know much more about my field then I do!
But, this is all I do anymore.
Regardless of what might come across in my typed text vs the spoken word, my intentions are based on helping out when I can and trying to say nothing when I can add nothing.