Diagnosing A Power Transformer w/Shorted Turns
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- Опубліковано 14 вер 2021
- This Ashdown Peacemaker 20 really is keeping the peace.
The owner fed it a few fuses before bringing it in.
Unfortunately, the power transformer has failed.
Here's how to know that for sure.
I know I am late to the party and this video is several years old, but I have have one of these amps that was given to me back in 2014 in the same condition - bad power transformer. I contacted Ashdown support and back then they were actually very helpful in providing schematics even separate ones for the transformers. They didn't actually have the replacement part any more so I suspect these were all shipped with a high failure rate on this design.
At the end of the day I was able to successfully repair mine from the info they supplied by buying 2 economical Intek toroid power transformers to replace the faulty one. At the time I think it cost me somewhere in the $75 range total plus my time to install them. I still have the working amp today.
Thanks again for posting these Brad, invaluable info in every one!
Call Ashdown in the UK and ask for Dave Green. Dave is the head of Engineering and has designed several of Ashdown’s amplifiers, he also runs the spares and repairs area. He recently sorted me out for spares on an old Trace Elliot bass combo, top guy!
Bro, the budget was $200 and we're in Australia and the job was years ago.
I never knew Bill Burr had a younger brother who's an amp tech.
I'm funnier than Bill Burr.
HI, when I read the transformer outputs of my Ashdown preamplifier ABM RPM 1 EVO II, I mesure 15v on the 2 1A fuses and 140v on 0,800 mA fuse. On the 0,800 mA fuse it means normally 240v ? Is my transformer bad ? Thank you, good job.
Hey Brad, i had this problem on my last amp build and i solve puting heat shrink on ht primary. Do u know what may cause this? And its possible that a primary still "little bit shorted"? Cause my pt seems more hot than normal, not so hot ( i can stay my hand). what do you think? Thanks for this video.
Gday Diego, it sounds like you may have some internally shorted turns. These are like having a another winding which is shorted out on the secondary. I suggest a replacement for safety.
does anyone know...i don't want to take apart my amp, cause it seems difficult.
what voltage do modern amps run on? I've been thinking they must use an onboard transformer that converts AC to DC then everything in the amp runs on that DC... so... it would be easy to convert any amp to run on battery power and eliminate any need for an inverter, could even run off of lithium ion or Ni Cad because lugging around a lead acid battery is not very convenient.
if anyone knows, let me know!
There are various DC and AC rails in any given amplifier.
Very low end practice amplifiers may have only one set of DC rails, but they'd be bipolar, so it's not practical or trivial to convert for DC usage without designing it that way from the ground up.
Your best bet is to go with a portable amplifier which is designed to run on batteries, as it will have been built with 12V input in mind.
Nice one. Not familiar with these amps. Just out of curiosity, what would the cost of new transformer be vs. the value of the amp?
Also, that face at the end of the video was hilarious. You need to slap that on t-shirt with Champions! across the bottom.
Lacking a schematic and with a shorted PT, he'd have to do a lot of research to find what the secondary voltages should be, then see if any transformers with those specs are on the market. That alone could be 1-2 billable hours of research to be able to even get an estimate for replacing the dead PT. And that makes the estimate that much higher, thanks to Ashdown.
It's hard to get clients to understand that getting prices for X can cost as much as "actual" labor.
Then you have to figure, ok, if the owner sinks a bunch of money into a new PT, what are the odds something else in the amp will die within the next five years?
And the answer with these POS amp is Very High.
Sometimes you just have to cut your losses.
@@PsionicAudio Good point. Also, you have to ask did the transformer just fail, or more likely what failure in the circuit took out the transformer? Which equals more bench time.
For those interested in the topic I would suggest checking out Uncle Doug's channel. He has a couple of great videos on determining power and output transformer requirements. Just search UA-cam for Uncle Doug transformers.
Totally what Psionic Audio said. Thanks for fielding that one while I was sleeping, Lyle!
@bSide Studio, I dare say that loose lamp with the full heater current behind it may have triggered the poor little transformer which was probably JUST up to the job at the best of times anyway.
It looks like there's quite a few secondary windings and that transformer couldn't you buy a transformer that has a separate pair of wires and put three small transformers in it and put your 120-volt primaries together and put the small transformers inside unit consult with an authorized service center before doing
Bro, we're in Australia for starters, 240v primaries. And the budget for this job was about $200 and it was 2 years ago. Not happening.
What's your bench fee?
A link to my current schedule of fees: www.bradsguitargarage.com.au/services-repairs/
@@BradsGuitarGarage thanks so much! I think it's time to raise mine!
Transformer secondaries 6.3V/ 15-0-15V /0-270V. From my experience bad quality 1n4007 and electolytic caps kill the transformers.
From my experience, poor design and cost cutting kills transformers.
Sacrificing transformers to feed the high-current-fuse gods again, sigh....