Amps

[Crqc]

Hi all, I used to post here a while ago but it looks like things have changed and I had to re register.  So I was out for a wlk with my dog a week ago and came across some bulk trash set out for pickup, inside one of the boxes there was a really nice looking transformer, very clean, nice leads, so I brought it home.  Later that night I was looking at it and it had the same color leads as one of the transformers in my 50W Marshall head.  I was feeling a little bold and remembered reading how guys swap out transformers to make their amps sound better, well you can see where this is going......

I pulled out the transformer that looked like the one I brought home and marked which wire went where and put the one I found in the amp (there was an extra purple wire on the transformer so I taped it off), powered the amp up and nothing happened.  Tried some old tubes I had lying around and still nothing.  I put the original transformer back in (following the wiring that I wrote down when I removed it) and still nothing!  It worked fine before I took it out.  I tried everything, tubes, cables, cleaned the jacks and it still doesn't work.  I think I may have really hosed something up, anyone have any ideas?

Thanks.

[Kazinator]

That is very sad! But it's hard to know where to even begin giving you anything that might be a shred of useful advice. Do you even know the difference between a power supply transformer and output transformer?

Your amp requires troubleshooting by qualified technician with the right equipment, and knowledge of that kind of device.

There are some things you can try, like: Does the indicator lamp on the front panel come on? Are the tubes glowing? Can you try a different cabinet with the amp? Or a different amp with the same cabinet?

Both the transformers in your amp are special to that amp, and cannot simply be replaced by other transformers that have a few wires of the same color. The transformers are fairly complicated, with multiple taps on boths sides, and all those sections of coil have to have the right number of turns.

[Crqc]

I don't really know the difference between the power supply and output, the one I replaced was the bigger one (the one I found looks just like it, same size and everything, I took both transformers out of the amp so I could get a closer look before deciding which one to replace with the one I found). Maybe the purple wire needs to be attached to sometihing?  

I'm not an electrician by any means but I read a lot and can figure stuff out pretty quickly.  I read a lot about swapping out transformers and improving the tone of an amp, I'm guessing I must've missed something but can't figure out why the original transformer doesn't work now.

Anybody familiar with this amp?

[Crqc]

Anyone???

[Jimmyvoyce1]

Hi this is Jim of Voyce Electronics,i couldn't resist this one so here goes.

First of all,bad idea just sticking a transformer in there.It's great that you want to diy and all but the wire colours mean nothing at all.

The original transformer is probably fine as it was out of the amp at the time you switched on with the unknown transformer.Is the amp totally dead? Fuses blown etc?

have you got another amp to test the valves in?

If the transformer you fitted had a short of any kind,it most probably took out your output valves,but sometimes they survive.

Give me a little more info and i might just nail it for you.

Jim

[Crqc]

It didn't power up at all, I tried putting the unknown transformer back in it, this time replacing the one I didn't replace the first time and I noticed a fuse had blown, I put another fuse in and it didn't blow but I guess it might be because I didn't match the wires correctly.  I'll try it again and swap the wires around until it turns on.....

[Kazinator]

---

Crqc wrote:

I don't really know the difference between the power supply and output, the one I replaced was the bigger one (the one I found looks just like it, same size and everything, I took both transformers out of the amp so I could get a closer look before deciding which one to replace with the one I found). Maybe the purple wire needs to be attached to sometihing?  

I'm not an electrician by any means but I read a lot and can figure stuff out pretty quickly.  I read a lot about swapping out transformers and improving the tone of an amp, I'm guessing I must've missed something but can't figure out why the original transformer doesn't work now.

Anybody familiar with this amp?

---

The size of the transformer doesn't mean much. That just means they are built with a simlar or the same iron core. The configuration of the windings could be completely different. That is what you missed. You can't just pull transformers out of the garbage and swap them in just because have the same sized core, or the wires have the same colors.

Your claim that "the original transformer doesn't work now" is not based in sound logic. What doesn't work now is the whole amp. You have not yet isolated the fault to a particular part.  If you make a bad part substitution and the device stops working, it could be because some other part failed (or even more than one part, in different places). So then the device continues not to work even when you put back the correct original part.

There is probably nothing wrong with the original transformer because it was not present in the device when you powered it up with the substitute transformer. There are checks you could run on it to prove this, like taking it out and testing the DC resistance of its windings.  Do you own an electronic multimeter and know how to use it?

You're simply going to have to take this amplifier to a qualified amplifier repair shop.

It is impossible for a qualified electronics person to troubleshoot your amplifier over the Internet. He or she has to open up the sucker and perform various tests, such as checking basic voltages in various places in the circuit, and perhaps looking at signals using  an oscilloscope. (One good thing, by the way, is that the schematics can be found online.)

The amp has lethal high voltages inside, throughout its circuitry, because it is a tube amp. If you keep mucking around inside it without knowing what you're doing, you could end up killling yourself.

[Jimmyvoyce1]

Not sure i follow you there,You put the unknown transformer back in after you had already put the original back in after the fault? Bit confused there lol.

I thought you had made a note of the wire colours of the 1987x transformer.If so,i would stick to that rather than changing things.

When a fuse blows,it basically means a higher than normal electric current has rampaged through your amp,Mainly the output valves and surrounding components.

If you are not familiar with using a meter to check the parts then it is probably time to get a tech in.

[JorisBlack]

I have the feeling you have no idea what you're doing. Messing with a guitar amplifier without knowing what you're doing is one of the worst ideas ever, so find a tech guy who can help you.

[omni]

So the amp worked before?  You tried to fix something that was not broke?  NO!!!!!

[Crqc]

Yes it worked before but I've read about guys swapping stuff to make it better and I found a transformer, figured it would be a way to improve it.

Last night I took all of the transformers out and put them back in according to the diagrams I drew, this time I soldered them in instead of twisting the wires and taping them like I have been doing (my soldering skills are not too good) and this time the amp powered up for a second, there was a pop, smoke and it went dead.  The fuse was blown and the wires at the tube socket was burnt, is it because I didn't bias the tubes again?

[omni]

That thing could have come from a stove.. I have feeling you are just fucking with us.

[Pepi]

B

[Crqc]

No I am not f***ing with anyone, and while I have no idea where it came from, it does look a lot like a transformer used in an amp.  Thanks for contributing.  Anyone else have any useful advice?

[Wyatt]

---

Crqc wrote:

No I am not f***ing with anyone, and while I have no idea where it came from, it does look a lot like a transformer used in an amp.  Thanks for contributing.  Anyone else have any useful advice?

---

I gotta admit, to me it seems like a troll thread, and that's why I haven't contributed. And I think if you step back and look at what you said, you'll see why others don't believe you.

You randomly found a discarded transformer and wired it into your Marshall?  You have no idea of the source of the trasnformer? You have no idea of the function of the transformer? Power transformer? Audio transformer? Step-down transformer? Output transformer? Yet, you felt you knew enough to go in and remove the told trasnformer and solder in the new transformer? Around dangerous votlages?

That requires a big leap of faith on my part...yet for the sake of having trust in my fellow man, I'll now make that leap. If you aren't trolling, you were entirely unprepared and unsuited to install the new transformer.

Without know the transformer used or how you wired it, I don't know the extent of the damage. You may have just  simply wired the original back incorrectly, you may just need to replace the HT fuse, or you may have absolutely f***ed up a massive amount of your amp. Either way, this is way above your head and impossible for someone to diagnose online.

The bet and most solid advice I can give and find tech with a good reputation, take him the amp AND the transformer (so he can deduce it's purpose an any harm it may have done) and expect $35-75 in bench fees just for the diagnosis. I would expect the total repair to cost anywhere from $35-250...PLUS parts.

Then I want you to head over here...

http://www.classictone.net/

And click through as many spec sheets as it takes to understand that the variety and use and application of transformers is quite wide, even when limited to guitar amplifiers. ou can't jus mix and match, with power transformers, you need to get the correct HT voltage and the current heater current for the application, with output transformers, you need to have the correct primary impednace according to what tube type you use (and how many) and what secondary speaker load you want to use.

Good luck.

[Kazinator]

♪　Song time!　♪

Transformers: they're more than meets the eye!

The fact'ry bots wind their bobbins to all kinds of specs, don't substitute ...

Now your amp is gone!

[HKSblade2]

Bad idea all around. I bet the power supply diodes are now shorted. Feel lucky if that is all the damage done.

Transformers are specific in design and not very interchangeable.

Lesson learned. Take that amp to a certified tech.

[JorisBlack]

---

omni wrote:

That thing could have come from a stove.. I have feeling you are just fucking with us.

---

I totally agree, although one can never underestimate stupidity

[Crqc]

Update:

A few days after my last post I wired the new found transformer in and it blew a fuse.  I then put a jumper across the fuse holder and went to bring it up slowly on a variac that I made a few months ago.  Unfortunately I didn't realize that I had left the variac set full up so when I flipped the switch there was a blinding flash and that was the last I remember.

Apparantly I was holding onto the edge of the chassis when I flipped the switch and took a pretty big shock that threw me to the floor and knocked me out cold, as well as setting the amp and the workbench on fire.  Luckily it knocked the power out upstairs and my roommate came down to see what had happened.  She grabbed a fire extinguisher and was able to get the fire out (the amp is ruined as is the bench and a lot of my tools), and called 911 to get me to the ER.  Suffered a pretty bad concussion, burns on my hand and arm plus singed hair on my face.

The Dr. there told me I should consider taking a beginner electronics course or maybe even think about doing something safer.  LOL

[Steve2112]

That above post didn't help the troll accusations. You've violated just about every single basic rule of electronics. How is it possible?

You killed the amp AND nearly killed yourself? Saved by your rommate with a fire extinguisher? The best trolls of the old HCAF couldn't have done any better.

kudos!