Odd normal vol channel..

[The Captain]

Ill change all coupling caps to .1ufs Mr. Stokes

I have however a serious prob now- the amp keeps blowing fuses. Turn on, pilot light then goes out immediately. The only thing I did prior was to swap out plastic spkr jack for a metal one & wiring checked, all correct. Checked all over for obvious shorts- none. 4 fuses now tried all immediately pop. Im about to throw it in the river now.. what the heck can I do?

And it does exactly same with all tubes pulled.. so a blown PT now I assume!! nothing even touched as far as any filament wiring, checked continuity all along the filament wirings, all read above zero to gnd and same between them.. Im really going crackers now.

[stokes]

Did you ever make that 100watt light bulb current limiter?It will come in handy here.You can use it to diagnose the short without blowing a million fuses in the process.

[Steve Conner]

Don't throw it in the river, sell it to me!

[The Captain]

No I didn't make that limiter Mr.Stokes as MJWB got me up and running checkwise.. I wouldn't be 100% sure using it with HV PT wires without asking/ annoying you friendly lot with Qs again! Ive had a word with Weber (replied asap & with concern- helpful and friendly); he'll send another 'from a different supplier' tho another hefty import duty Ill have to pay.. seems like a common prob then with these Ts: Im surprised he sells them- it doesn't add to his good reputation. And who's to say the replacement won't blow? my confidence has tumbled badly now.. quite frankly Im very pissed off. I should have spent 3x on a Mojo but as many diyers I am on a budget somewhat. There are floods here in Warwickshire, so I can just hurl it out the window if need be..

Would this sort of thing have helped? It seems small enough to go in bttm of cab.. http://cgi.ebay.co.uk/R-F-I-Mains-Fi...QQcmdZViewItem

[Bruce / Mission Amps]

No that RFI filter wouldn't help your problem.
By the way, I'd be pissed off too because it seems like I've seen a few others with blown trannys over the last months.
I wonder if there is some underlining cause or just a coincidence.
Also, did you have this PT "protected" with a 1 amp fuse?

[stokes]

Do you know for sure your PT is blown?To check this disconnect all the secondaries and if the fuse blows with no secondary connections then it is most likely blown.But you also need to find out why it blew.The current limiter is a priceless piece of equipment for basic troubleshooting.It is cheap and easy to make and use.No problem or annoyance to me answering any questions you have Cap'n,and I am sure I speak for most others on this board,we were all in the same place you are right now at one time.For myself,there was no internet to go to,it was just books and if you were lucky enough to know someone in the business as I was,we were pretty much flying by the seat of our pants,so dont hesitate to ask,as you can see there are plenty of people here willing to help.Dont give up,you'll get there.

[The Captain]

Bruce I had a T2AL amp fuse, and a 3A in the mains plug. Mains plug one still ok after 4 or so tries, 2A blows even without tubes. All wiring not touched from when it worked for the 3 weeks or so too.

Mr. Stokes could you run that current limiter past me again, in say Homer Simpson language? The idea of making a box & another bits order put me off iirc; suffice to say as soon as I told Weber they offered a new PT straight up & from a 'different supplier' (a different batch of the same unit tho..??) so they seemed to think its dead Id say, rather than have me fart about checking each wire via emails. So Ill consider the limiter idea but have to thoughrally understand/ go over method 3x before I try.. & with a dangly beard my vision is now compromised too. Replies restore interest/ hope again, cheers Captain.

[stokes]

If you look at the thred titled "Help powering up" I even managed, with some help, to post the diagram.It is a very simple and inexpensive item to make and is extremely useful.If you intend to work on or build amps you will need it anyway.When you build it we can go over step by step how to use it.For now though if you just disconnect all your secondary leads.i.e. the main HV taps to your rectifier and your heater supply you can dismiss the PT as the problem.If the fuse doesnt blow with all the secondaries disconnected your PT is okay.The fact that your mains fuse is not blowing is making me think it is not your PT.The fuse that is blowing I assume is on your B+?If that is the case and it blows with the tubes removed that would indicate a problem with your filter caps.Why do you have a 3amp fuse in the main?Here in the states we would use a 2amp and I think in Eur.it would only require a 1amp,no?

[The Captain]

I know you did Mr.Stokes appreciated so it was- I did read it numerous x too: although its just a few bits I just can't visualise the thing- is yours housed in a case? so then this must be earthed, routed, drilled & a switch/ fuse too etc? also our uk wires are brown L, blue N and green E; yours different iirc; 'female ac outlet' slightly odd for a brit, do you mean a mains wall-plug socket or a 'kettle' type input? ..as you see uncertainty didn't seem fitting for the job. If you had a pic/ photo it'd answer these queries I reckon.. cheers capt

Edit- ok (after hours of head-scratching) is this the idea: basically a box with two mains-type plug sockets and a lead out the back to mains? Amp plugs into one socket, a ..normal household lamp(?).. plugs into other. (If so every time I saw the diagram/ info I've been trying to figure out how a 'light' attatches to the box, assuming it was was a bulb & its socket holder, & an extra socket all somehow mounted in/ or to the top of a box -until just now!) maybe Im still not getting it though.. crikey I think I need a holiday, or an institution..

[stokes]

What you see in the diagram is what it is,just adapt it to your 3 wire set up,one ground,one hot and one neutral.What I used was a double wall type outlet and box,which is standard here in the States.Since the wall outlets are wired in parallel,I just snipped the connection between the two outlets so I now have two independent outlets and rewired them in series.Now to use it for a test I plug the plug you see in the diagram into the wall,the amp under test goes in one of the rewired outlets and a desk lamp with a 100watt bulb gets plugged into the other rewired outlet.You can also use a single outlet and wire a bulb socket in series with it,in other words the bulb socket would take the place of one of the rewired outlets,just plug into the wall and plug the amp into the socket.Now for a quick example of a test.If the bulb stays lit brightly there is a short,if the bulb dims considerably there is no short.Lets say you get a bright bulb,you have a short,you pull one power tube the light stays bright,pull the next,if the bulb dims you have found the problem it is in the second tube or its related circuit.If it stays bright after pulling all the tubes you start disconnecting your filter caps till you find the short.It will save a lot of fuses and the amp can be left on while you poke around to find the short as opposed to having a flash and blowing the fuse.

[The Captain]

Hey Im with you now Mr. Stokes, muchos muchos..
Could I make this as a plywood box do you think? (our uk mains leads have green earth wires Id usually terminate to metal chassis)- if so would wood suffice for terminating.. I mean on the face it seems a bit odd to me, but'd save me arsing about for metal enclosures and faff cutting/ drilling one etc.

[stokes]

I dont see why a wooden enclosure wouldnt work.Dont they sell an outlet box in Britain?Here it is very easy to get a wall outlet box at a home improvement type store,and the outlets themselves are sold as a pair that fit into a "standard" size box.If making a wood box is easier,it will suffice.Our "earth" wire is green as well,but in this case there is no need to connect it to the box it connects to the "third"prong of each outlet,as you can see in the diagram.

[The Captain]

Ah yes of course.. ok Ill pop off to Homebase and see if they do outlet box things. I'll add a photo of it once made to be sure alls ok and go from there.

[stokes]

Homebase?Here it is called Home Depot.If like here the outlets are sold in pairs they are connected somehow in parallel,so you will have to find how they are connected and seperate them so as to wire in series.The ones here are connected at the screw terminals on the side by a solid plate type thing,just snip it on both sides, a quick continuity check with the ohmmeter will tell you they are seperated.

[The Captain]

Well call me old-fashioned, but I knocked this up in 10 mins. From an old 4 way extension, Ive bent/ stripped out the brass links that were paralled for 4 to just 2 now in series.. I think.
The mains pins far right are top gnd, middle (brown) L, and bttm (blue) N. (pic looks like mains gnd connects the top and middle pins! -not so, brown Live tucked under for pin 2).

So Ive got the normal Live pin of 1st outlet now connected to the (normally) Neutral pin of 2nd outlet, and the N pin of first to the normally L of the second; the gnd lugs just kept as was really.. Id really best check this first- thanks Capt.

http://i102.photobucket.com/albums/m...Picture275.jpg