How to find and install a replacement power transformer for your tube amplifer

BG186 - Tutorial on how to identify a replacement power transformer for about any tube amplifier and how to install it. This video while made about an audio amplifier, would apply to any guitar amp, ham radio receiver or amplifier, about any unit that uses a high voltage power supply transformer.

[@coldfinger459sub0]

Thanks for all your videos and recommended websites for components. The last two years I’ve been practicing with low-voltage amplifiers three solid-state two low-voltage headphone tube amplifiers. I’m about to build my first preamplifier. Then I’ll take a shot at the high-voltage high dollar DIY tube amplifier build. Your knowledge you pass on to us will remain on the Internet forever. 👍

[@materialsguy2002]

Very helpful information for sourcing out new iron, thanks Mark.

[@wa2mo]

Really enjoyed the video... very informative.... I also had Gary from TRS rewind a C-Core transformer from my Ten Tec Titan 425 Linear Amp and it was much cheaper than buying new and he does great work. Keep the videos coming.

[@nigel900]

I’ve upgraded to, and used Mercury Magnetics transformers for several years now, and thought they are expensive, they are superior to almost all others… and they make transformers for EVERYTHING! Great video. 👍🏻

[@danielthomas3057]

The first filter cap should have a tie point to secure the positive lead where it is soldered to the red wire from the 5U4. Looks like a short to chassis could easily happen. Good to see both of these Maggies restored to working condition. I am looking forward to the KT88 build. Have re watched the 807 amp build a few times through. Great work, always love it!

[@normanwalz8636]

Thanks for this video and looking forward to the single ended amp project

[@jp040759]

love your videos. Always look forward to next one.

[@larryshaver3568]

very clean- sounding, that new transformer really did the trick

[@mikeh2599]

Excellent video, takes the mystery out of finding the right transformer

[@srtamplification]

Nice info! Thanks for the knowledge!

[@mobicus1]

Thanks for this useful video! Great stuff!

[@garybevis8691]

Ok, right at the 14:45 mark you make a significant error in sizing, (3-7/16") 7/16" is in fact 5/16" of an inch larger than 1/8" off by a factor of 5 times. Or 3.4375"-3.125"=0.3125" ; 1/16"=0.0625 5/16"=0.3125"(sorry it's the engineer in me). I'm glad you had room on that chassis for the actual difference. It looks great and sounds good too.

[@sonotdown998]

Super helpful video! Also nice D&D T-shirt there at the end.

[@mfr58]

Thanks Mark. Looking forward to the SE KT88. M

[@eduardaguilarpurt1749]

Good work!!

[@HipocratesAG]

Nice save!

[@jonnybeck6723]

Thanx very much... I enjoyed your vid. I have a Fender Hot Rod Deluxe and though it sounds great the power transformer, after about 15 or 20 minutes heats up to a bit more than I'm comfortable with. Can you tell me if there are any guide lines as to how hot is too hot? Thanx in advance and thanx again for a great vid. cheers

[@J_Braz_]

I got a Marshall dsl20 head. It sounded amazing the first couple hours. Then like a idiot I unplugged the speaker cable from the amp while it was on. The amp was on the clean channel with gain around 2, volume around 3. Wasn't playing the guitar. It was unplugged for about 20 seconds before I realized what I had done. Ever since the amp hasn't sounded as good. The tone is fizzy now. No crackling or popping. Didn't smell anything burnt. Could I have damaged the power tubes or OT?

[@THEtechknight]

Hey, what are those blue handled snips? I like the long big handles on those.

[@mstecker]

Why wouldn't you have gone with their number 40-18041? Fits the original size and the specs seem to match - what am I missing? It's line 20 in the spreadsheet.

[@freaksarise]

Hi. When you checked the transformer specs for the high voltage secondary with respect to its current (for plate voltage supply), you showed the tube data sheet for a push-pull config with two power tubes. Do we also have to consider the plates for the preamp tubes and rectifier? I'm in the midst of learning about how to calculate power supply needs based on the tubes in the circuit and this would help. Thank you! Great job always!

[@samuel_towle]

Wait a second. Looking at the transformer schematic @29:30, you used red - red/yellow - red for your B+ windings. From what I see on the diagram, that should be 710 volts across the entire secondary. Shouldn't you have used the red/white - red/yellow - red/white taps which should give you the 610 volts, much closer to the 590 volts (no load) mentioned @3:50 ?

[@bernhardnizynski4403]

WRT the 6BQS, isn't the 92 milliamps plate current for Two tubes? The Hammond transformers can be installed 'upright' or 'lay down' (just take one side cover off). I bought one for my original Vox AC 30!

[@fullwaverecked]

Would this basically pertain to solid-state transformes as well? Thanks!

[@boonedockjourneyman7979]

I am having trouble understanding no-load transformer tests. Every time I try that, the results are useless for predicting performance at even 1/10 load. Are these older transformers different from modern equivalents?

[@westbay5858]

How would you suggest I cover the transformer wires inside ( under the bell covers) after I changed the wires. The sticky shellac like paper was covering the wires which I had to remove to change the wires. I'm not sure what to do. Thanks

[@moodyga40]

Can you measure the current of the HT on the working amp

[@Warclock07]

Hello, Is there a way to find the max. current available of the 6.3 AC heater current since don't know specs? The amp designs for KT88 and I like to use KT120 which needs more current. Thanks

[@littlejohnny1498]

Great video.Good info. Understanding current is my biggest weakness. The values of caps in the power section are confusing. Why does it hurt to raise the uf on caps or add an extra one. Why would it hurt to change an 5f1 champ from 16-8-8 to 22-16-16. I have seen people do it but I have had people say, don't do it.What would be the reason not to do it. Thank you.

[@joseislanio8910]

If you're using a rectifier tube, a bigger capacitor will draw more current, and for more time, during first charge up, when you turn on the amp. That would damage the tube. If you're using solid state rectification, it's not really an issue. My champ uses 100, 47 and 47 uF. It's dead silent, no hum at all, unless with single coils.

[@victortrinidad5588]

Do you know where I can get a Heathkit power transformer # 54-93 for my AA 151.i did not see this listing on the Classic Tone

[@xiclateespada5258]

can you help me to choose the transformer for the fu19 amplifier 110xv 200v 3.15v 6.3v

[@ghazalco50]

I need a rule for winding audio transformers because I am designing a valve amplifier, I searched a lot on the Internet and did not get a result, thanks

[@kolarkaraudioresearch]

Nice to see I'm from India I make hifi and guitar output transformer and tube amp to

[@johnmiller9219]

when speaking of voltage please designate AC or DC would be a big help

[@mfowler8808]

Wondering why you used the 710vct HT rather then the 610vc HT. I would have used the lower HT taps for EL84's.

[@videolabguy]

That's how I read the transformer too. The B+ is now much higher than before. Calculated 504 volts vs the original calculated 417 volts. B+ = ((VCT * √2) / 2)

[@larryshaver3568]

is that amp from an Imperial? i had one i think i mentioned in another comment

[@danielthomas3057]

The first transformer 40-18035 would have been shy on current for the rectifier fillament, 5v @2 amps. A 5U4 requires 3 amps.

[@danielthomas3057]

A 5U4 filament draws 3 amps @ 5 volts. The first transformer choice would have been short by 1 amp.

[@OIE82]

I wish someone would have captured all that data before classictone went out of business. Spreadsheets are much easier to filter than a webpage listing.

[@jimcatanzaro7808]

I can’t my transformer for my voice of Music 1428 any help would be helpful

[@jeffcotton526]

The measurement difference is actually 5/16" on the mounting center length of the 40-18029 transformer. But we're not spring chickens anymore and are able to make goofy math mistakes. 3-1/8 to 3-7/16" is an additional 5/16".

[@VikasG007]

Hi I am from india and I have Delta Company "BMB 20" Power Transformer Cum Vibrator Transformer which have one side black, green, yellow wire or 2 sleev with copper enimal and other side 2 red, White 2 sleeve with copper enimal and 1 center tap copper enimal. Can you please tell me how I will connect it with EZ80 tube.

[@kirkopperman9753]

Is there anyway you can send me a picture of the wiring for the transformer for a GXT 100 Crate Qual Triode Combo Amp!?’ Pleeeeeeeaaaaaasssseee!

[@strikingitrich2009]

Hey, update, on October 26, 2018, just got an email from Gary Brown that he's now retired and TRS is closed. Got another rebuilder you can -recommend? -

[@Steven9675]

Classic tone still in business?

[@hermanman5685]

If bassman 300 pro convert 120v to 240v ?

[@russellesimonetta3835]

Save those cut offs. The classic tone and heyboers are the best in guitar amps. Mercury mags are high priced and in the snake oil category.

[@Rick_Erickson]

Seems that many like to dis on Mercury. I have been using them for a long time now. Their prices may seem high, but their quality is very good and they carry a full 10 year warranty in case you do have a problem. I had an amp come in with a Mercury PT that I had installed exactly 10 years earlier. By some fluke it had an intermittent issue between two windings. By the time I got it on my bench it was technically past the warranty period. They replaced it for free. I don't necessarily sell them as "tone improvements, but in the case of a Vietnam made Ampeg SVT, the difference in tone from the stock OT to the Mercury was astounding. They have never steered me wrong on a transformer recommendation. I do occasionally use Hammond transformers. Their Drop-In line works very well and is probably a good choice for a DIY home builder. It seems Classic Tone has gone under now. Maybe they should have charged more.

[@larryshaver3568]

i'm putting a Belton socket or 2 in my 8600

[@lego40404]

Mark, Thats the same PT you used for the SE 807, Uncle Doug has a nice turorial here kzbin.info/www/bejne/gJnFe2aaa7WbaK8 explaining how to choose a PT. I'm slowly chipping away at building your 807 amp

[@johnc8910]

You can avoid the hassles of an incorrect 5 volt winding by replacing the power rectifier with solid state diodes especially with a transformer with a lower secondary HV rating.

[@johnsweda2999]

Why can't you un-pot the transformer and see if it's repairable. The guy at valve wizard is he the same guy who manufactures and owns do you know the great little valve company amplifiers

[@Blueglow]

Its not a potted transformer. You could unwind it but on these old ones, they typically take a full rewind and the coating on the wires chips off as you unwind them. Would be way more time and money than simply replacing it.

[@johnsweda2999]

Blueglow Electronics I just wondered because sometimes I don't know what the results are on this transformer but a dead primary could be broken connection usually happens might be just broken at the terminal end to the wire.

[@mcsniper77]

Could the orange wire "Shield Wire" possibly cause a ground loop? I just bought a brand new Hammond 290BBX and the eyelet for the shield makes the bottom cover sit funny. www.dropbox.com/s/9elukoabidoj4k2/100_0489.JPG?dl=0 Are they all like this? Is it a bad idea to remove it If bolted to shinny steel?