How do you tell if an amp had a bad OT.
I am always under the assumption that you would get no sound.
I have an old amp that turned extreemly loud and ear piercing highs
also the bass shakes the walls LOL.
Output Transformers
Moderators: pompeiisneaks, Colossal
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David Root
- Posts: 3540
- Joined: Fri Aug 04, 2006 3:00 pm
- Location: Chilliwack BC
Re: Output Transformers
Other than the earpiercing highs, that sounds like a GOOD OT!
Seriously though, do you mean there is now no mid range?
Seriously though, do you mean there is now no mid range?
Re: Output Transformers
Discharge the amp and meter the ot legs for opens and shorts.
Though it is prob ok
Though it is prob ok
My Daughter Build Stone Henge
Re: Output Transformers
A failing output transformer can often be suffering from insulation breakdown which causes a short between a number of windings with high voltage applied.selloutrr wrote:Discharge the amp and meter the ot legs for opens and shorts.
Problems like this aren't easy to diagnose as even static plate voltage may not be enough to cause it to manifest itself but the real-world signals including flyback voltages are.
Re: Output Transformers
sorry i'm not comfortable telling someone i don't personally know is qualified to work with electricity safely to work inside a "live" amp. I'd hate for someone to get hurt! it's not so much the members on here that worry me, most have at least a respect for basic amp safety. it's the fact that these posts can be read without logging in that causes the concern.
If the OT tests good with no voltage... and everything other part of the amp tests "GOOD". take it to a qualified tech or swap out the OT and see if that fixes the issue.
If the OT tests good with no voltage... and everything other part of the amp tests "GOOD". take it to a qualified tech or swap out the OT and see if that fixes the issue.
My Daughter Build Stone Henge
Re: Output Transformers
No-one has told the OP to go and work on a live amp from what I've seen.
You often need a hi-pot test rig to properly diagnose failing OTs since the plate voltage may not be high enough to cause problems without a large signal present.
Whilst you could try to diagnose this in the amp you'd risk your output tubes and possibly the PT if the OT decided to really let go under test, so it's really ill-advised.
Hi-pot tests are designed so you don't kill the test equipment when the item under test fails, whereas amps aren't!
If it looks like the transformer is suspect then change it out and then get it safely tested afterwards if there's a desire to hang on to it either for another project or to re-fit.
You often need a hi-pot test rig to properly diagnose failing OTs since the plate voltage may not be high enough to cause problems without a large signal present.
Whilst you could try to diagnose this in the amp you'd risk your output tubes and possibly the PT if the OT decided to really let go under test, so it's really ill-advised.
Hi-pot tests are designed so you don't kill the test equipment when the item under test fails, whereas amps aren't!
If it looks like the transformer is suspect then change it out and then get it safely tested afterwards if there's a desire to hang on to it either for another project or to re-fit.
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Andy Le Blanc
- Posts: 2582
- Joined: Sat Dec 22, 2007 1:16 am
- Location: central Maine
Re: Output Transformers
look for extreme imbalances in AC/DC and DC leakage thru the lams.
One side might be shorting at a certain signal level.
a standing DC potential where might expect ground, measure safely.
simply cleaning the contact points between the bolts, chassis, and tranny can help.
The old paper in the opt can go, the wire dope insulation can go, and corrosion can frig up the gapping, if it sounds like poo swap it out, try it
for another non- critical build, sell it as vintage or reuse the bell ends.
One side might be shorting at a certain signal level.
a standing DC potential where might expect ground, measure safely.
simply cleaning the contact points between the bolts, chassis, and tranny can help.
The old paper in the opt can go, the wire dope insulation can go, and corrosion can frig up the gapping, if it sounds like poo swap it out, try it
for another non- critical build, sell it as vintage or reuse the bell ends.
lazymaryamps