Transformers - more than meets the eye

hydro

hydro

Prayin' to Cheeses
My friend who is an amp builder/tech has identified a fried-ass output transformer in one of my heads (an old Sovtek).

Anyone here have experience with getting transformers rebuilt? Good? Bad?
Yeah I know it ain't cheap... Just wondering how high the success rate is.
 
Re: Transformers - more than meets the eye

You can pretty much buy a replacement much cheaper than trying to rewind a burnt out one. Also a word of caution, I have heard many techs and reputable ones cry the burnt output transformer story only to find it was a component in the amp that failed.
 
Re: Transformers - more than meets the eye

Burnt output transformer story?
 
Re: Transformers - more than meets the eye

Well I saw it actually, and it did look like it had burnt spots on the paper wrap around the coils. I'll find out, I guess, once the transformer has been replaced.
 
Re: Transformers - more than meets the eye

Yea most likely is in your case. Is the amp a 100 watt or 50 watt. What kind of power tubes, EL34?
 
Re: Transformers - more than meets the eye

50 watt, 6L6 platform.
He did a lot of troubleshooting with me playing through it hot. It does this stairstep volume drop thing when I hit it with a hotter signal going in (boosted with a pedal or just playing hard), after the amp warmed up some. I really hope it is the transformer, because I want it working again, it's a great amp.
 
Re: Transformers - more than meets the eye

There are plenty of off the shelf replacements you can use. Magnetic Components, New Sensor, Hammond, etc.
 
Re: Transformers - more than meets the eye

hydro said:
50 watt, 6L6 platform.
He did a lot of troubleshooting with me playing through it hot. It does this stairstep volume drop thing when I hit it with a hotter signal going in (boosted with a pedal or just playing hard), after the amp warmed up some. I really hope it is the transformer, because I want it working again, it's a great amp.
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If it was fried you'd be getting no output . It may be damaged though from overheating [ viz: burn marks ] and shorting partially in the windings, which means get a replacement.
Well I saw it actually, and it did look like it had burnt spots on the paper wrap around the coils.
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Re: Transformers - more than meets the eye

Did the tech isolate the transformer from the circuit and run tests on it ? Did he isolate it from the circuit and hook in a known-to-be-good transformer ? (easily done on the bench, a test transformer doesn't need to be bolted in to the chasis, just sat alongside the chasis and hooked up with flying leads).
 
Re: Transformers - more than meets the eye

crusty philtrum said:
Did the tech isolate the transformer from the circuit and run tests on it ? Did he isolate it from the circuit and hook in a known-to-be-good transformer ? (easily done on the bench, a test transformer doesn't need to be bolted in to the chasis, just sat alongside the chasis and hooked up with flying leads).
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Yes, he did take it out and test it once he got the amp back home. He found shorts across the different windings. For better or worse, I am having it rewound; we didn't have a spare transformer available at that time although I do have one now. The problem is intermittent but fairly easy to reproduce just by laying some gain on it with a pedal and turning it up about halfway, so I should know once he gets the repaired transformer and I get my hands on it again.
 
Re: Transformers - more than meets the eye

I don't know what's in a Sovtek, but imagine it's as cheap as they could find.

For 18 years, I lived down the street from Mercury Magnetics, and their techs were the best in my area by far. I'd order a MM tranny if the amp is worth upgrading.
 
Re: Transformers - more than meets the eye

Gearjoneser said:
I don't know what's in a Sovtek, but imagine it's as cheap as they could find.

For 18 years, I lived down the street from Mercury Magnetics, and their techs were the best in my area by far. I'd order a MM tranny if the amp is worth upgrading.
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You need correcting.
Sovtek is a brand of vacuum tube owned by Mike Matthews's New Sensor Corporation and manufactured in Saratov, Russia. They are often used in guitar amplification and include versions of the popular 12AX7, EL84, EL34, and 6L6. Many of the vacuum-tube amplifiers in modern production are factory-fitted with Sovtek valves,[SUP][1][/SUP] due to their low noise performance[SUP][citation needed][/SUP] and lower prices than other makes.
In the 1990s Sovtek also manufactured tube amplifiers at factories in St. Petersburg, Saratov, and Novosibirsk.[SUP][2][/SUP] Several models were offered for guitar and bass. These amps were known for their high-quality sound, PCB construction (some of the amps had point to point construction, for example the MIG-60), good reliability and low cost.[SUP][citation needed][/SUP] A decade after production ceased, these amps were considered collectible by some.[SUP][citation needed][/SUP] Sovtek brand speaker cabinets fitted with US made Eminence speakers were also offered. At the same time, Sovtek manufactured variants of several effects pedals already manufactured in New York City, USA by Electro-Harmonix, another company owned by Mike Matthews. Sovtek released versions of the Electro-Harmonix Big Muff and Small Stone pedals. Those pedals, along with the Bass Balls pedal, were later manufactured in both NYC and Russia, under the Electro-Harmonix name.;[SUP][3][/SUP] manufacturing in Russia was later discontinued.
As of 2012 Sovtek was used only as a brand name for vacuum tubes manufactured by the New Sensor Corporation.
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Re: Transformers - more than meets the eye

Bumping this with a happy update - with a rebuilt transformer installed, the MiG 50 is reanimated and ready to crack some skulls. It sounds great. Put in some KT-66 big bottles and my friend added some other upgrades to improve reliability. I am so happy as this is the best sounding amp I have ever had (outside of my Princeton reverb).
 
Re: Transformers - more than meets the eye

GV, what needs correction? Sovtek made amps of average quality, and I doubt they sourced the highest quality transformers.

Thanks for the update, Hydro. Glad you got it sounding better than ever. A friend of mine uses Sovteks, and his have all been upgraded.
 
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Re: Transformers - more than meets the eye

Lol at thread title.

Mercury also makes guitar amp transformers.....more than meets the eye!
 
Re: Transformers - more than meets the eye

there were a handful of handwired mig 60s but i think the majority were pcb. they were cheaply build amps that sounded damn good for the price but they were notoriously unreliable. im not sure where you got that quote but ive seen plenty of them over the years and wouldnt call them well built at all.
 
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