Marshall Major Blowing Power Fuse

[cjenrick]

what kind of output transformer is it? Drake? Partridge?

been dying to get the data for this beast, would be willing to rewind for the price of copper (about 20 bucks)

that way you get a cheap OPT and i can start winding those for people,

do you live in the US?

if you have a signal generator or a variac you can try putting ac volts into the secondary and see what you get out of the primaries, be careful to use low volts, like 5 volts on the sec so you do not get hurt with the step up ratio volts which might be 20 to 30 times higher,

Mercury is probably using a layered paper approach as opposed to a nylon bobbin, claiming sonic improvements, as long as the clearance from the first layer to the core is the same with the nylon approach, there will be no difference in sound, if you use the same thickness and type of paper between layers and sections, plus you get a tougher transformer as there is less creepage of HV around the margins due to the nylon flange,

cjenrick@gmail.com

[Leo_Gnardo]

Question: Why does each tap coming off the secondary have two wires: 2 reds wired together, 2 yellows wired together, 2 greens wired together, 2 blacks wired together and a single green to ground??

I'm guessing they bring the winding wires out from each coil, instead of solder splicing flexy leads on and keeping those connections inside the transformer shell. Real old fashioned build style there, with hi voltage leads covered with cambric cloth tubing.

I'm pretty sure the Major's iron is Partridge.

I'm not impressed with Mercury's claims of sonic anything, since I ran across one of their replacement OT's in a blackie Fender Bandmaster. It sounded shattering bright, not at all what you expect from a Bandmaster. The rest of the amp was stock and working correctly.

[Justin Thomas]

Cluster, where are you located? It might make it easier to find someone to help. Maybe (just MAYBE) someone has something suitable locally...

And, is it me, or does this seem like something Hammond might actually make regularly? Or at least something that would work...

Justin

[nsubulysses]

Hammond 1650W might be overkill but should work fine.

Does the major do 2 ohms? 1650W has 4, 8, and 16 ohm taps

[g1]

been dying to get the data for this beast, would be willing to rewind for the price of copper (about 20 bucks)

that way you get a cheap OPT and i can start winding those for people,

do you live in the US?

Now there is a generous offer that will be tough to beat!

[The Dude]

Now there is a generous offer that will be tough to beat!

AMEN!

[The Dude]

If you have a scope, do check the output for ultrasonic parasitic oscillation after replacing the transformer. I recall having one of these myself and have read about others with this problem. The oscillation riding on the audio causes the voltage to exceed transformer ratings and can cause them to fry. I'd hate to see someone go through all of the expense and time replacing an OT only to cook another one.

[cluster]

what kind of output transformer is it? Drake? Partridge?

been dying to get the data for this beast, would be willing to rewind for the price of copper (about 20 bucks)

that way you get a cheap OPT and i can start winding those for people,

do you live in the US?

if you have a signal generator or a variac you can try putting ac volts into the secondary and see what you get out of the primaries, be careful to use low volts, like 5 volts on the sec so you do not get hurt with the step up ratio volts which might be 20 to 30 times higher,

Mercury is probably using a layered paper approach as opposed to a nylon bobbin, claiming sonic improvements, as long as the clearance from the first layer to the core is the same with the nylon approach, there will be no difference in sound, if you use the same thickness and type of paper between layers and sections, plus you get a tougher transformer as there is less creepage of HV around the margins due to the nylon flange,

cjenrick@gmail.com

wow!! thanks so much. I would love to take you up on your offer. I live in Toronto, Canada but would be willing to ship to the US for a rewind. First I need to pull it off the chassis and do that test you mentioned. Will keep u posted. Thanks again.

[cluster]

Cluster, where are you located? It might make it easier to find someone to help. Maybe (just MAYBE) someone has something suitable locally...

And, is it me, or does this seem like something Hammond might actually make regularly? Or at least something that would work...

Justin

Thanks for that info. I'll check with hammond for sure. I've also heard that the MM stuff is very bright and not vintage sounding. Not to mention very over priced.

[cluster]

unfortunately, i don't have a scope. I should get one and learn how to use it though. They sound very useful. I do need to figure things out though since I don't want the repeat situation.

[cluster]

I was taking some resistance readings on the OT this morning and discovered that if I loosened the bellcaps, I would get an "Open" reading on all primaries and if I tightened the bellcaps, I would get my previous readings of 0 ohms on the left and about 30 ohm on the right (to ground). Could anyone please explain this? How do the bellcaps effect the ohms to ground on the primaries?

Also, I was taking resistance measurements across the secondaries at the impedance selector and all my readings gave me 0 ohms. Is this normal? I would expect some resistance across some of these windings. Could this mean that there is a short in the secondary as well?

Thx

Joseph

[Leo_Gnardo]

I was taking some resistance readings on the OT this morning and discovered that if I loosened the bellcaps, I would get an "Open" reading on all primaries and if I tightened the bellcaps, I would get my previous readings of 0 ohms on the left and about 30 ohm on the right (to ground). Could anyone please explain this? How do the bellcaps effect the ohms to ground on the primaries? Thx

Joseph

Could be that your short is to one of the bellcaps. If you can find it and insulate the transformer wire adequately, you could save yourself a couple hundred $$$. So REMOVE the bellcaps and have a look around. Heatshrink tubing and GE RTV cement make dandy insulators. Good luck!

[cluster]

Could be that your short is to one of the bellcaps. If you can find it and insulate the transformer wire adequately, you could save yourself a couple hundred $$$. So REMOVE the bellcaps and have a look around. Heatshrink tubing and GE RTV cement make dandy insulators. Good luck!

Thanks so much Leo. Could you please post links to the insulation you are referring to. It would be a great help.

Also, I was taking resistance measurements across the secondaries at the impedance selector and all my readings gave me 0 ohms. Is this normal? I would expect some resistance across some of these windings. Could this mean that there is a short in the secondary as well?

Thx again,

Joseph

[cluster]

Well, well, well... what do we see here?? Lifted the bell covers and notice some fool at the factory forgot to tuck in the wires properly before fighting the bellcovers and smushed up a primary. Notice the broken insulation. Maybe this baby doesn't need a rewind after all. Now what is the best way to insulate this without de-sodering wires. Suggestion. Thanks again to everyones help.

Joseph

[cluster]

Not sure if you could see this but not only was this primary shorted to ground but it was also cut in the process. Any clue what i need to do? Should i splice a new wire or try to solder the 2 back together? Thoughts? Would want to use the least intrusive method possible. Thx

Joseph