• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Noisy transformer buzzing

I used a washer with the wedge heads .Good info . Any how I will buy flat head screws and give it a shot . I am guessing though the moisture has corroded the internals
 
image.jpg Another day another experiment

So I put individual soft sort of cushions (half an inch)under the 4 legs of the PT . The vibration on the amplifier as well as the humming is gone completely, but the high frequency harmonic sound which @triode17 described is still pretty loud (more worse than an old tube light with an old starter) . So I put a CPU fan on the top of the PT with a speed at 9v . It doesn't seem to make a difference for the sound except the PT is a little more cooler . I can touch it for a good 30 seconds and more with no difficulty

Also discovered the right channel heat sink is Hot . Not too hot but it's definitely not warm . Itss hot . And the left channel heat sink is normal ,not even warm more like room temperature . Which means the right channel heat sink is hot for a reason . There is no load connected to the system . It's just being tested as is . Just kept ON . Sum it up . The right side heat sink is As hot as the transformer temperature with the fan on top


A technician had worked on the system .The things he had to replace were
1- 4new output transistors as they were all Short ( because I myself could not locate the fault so transistors kept shorting every time I put the new ones ) yes i am definitely not qualified

2 - other transistors in the preamp board and left channel pot meter which is linked to the left channel heat sink and one IC 4558

He did mention something in the user Manual that i had given him , couple of things for his notes. he mentioned in one Line that the voltage was very high in left channel and then the rest I could not understand
15191931906412029832539.jpg


So looks like I will have to give it back to him and he will definitely charge me again


Hmm wonder if the transformer is playing around . I mean the day I bought it home from the technicians shop I connected my HPM's and turned it up all the way to test the system at maybe 100wpc or more but nothing went wrong in the system except for a very noisy transformer after 2 hours of high usage .
 
Last edited:
Heat from a heatsink at no-load idle indicates something is loading the power supply, which can result in the transformer warming up. Sounds like problems with the amplifier bias circuitry, or a leaky output transistor, etc.

If it's been worked on, mistakes may have been made.
 
Are you sure it's the amplifier bias circuitry or the output transistors? If it's one of these things over loading the transformer I am going right to the technician tomorrow. In need get this problem resolved as it's happened back in 2013 and the tech dint even look into this after fixing the system . Frustrated
 
Ok I appreciate the effort @DaveVoorhis and to all of you who are helping me out at the moment . Great site . Really bummed but so far that original problems still exist . Either need to find another tech or explain the problem to the present OR I could just use the system as is as long as there no harm to the power transformer in the long run
 
I noticed one thing though , if I play at really loud volumes like peaks of 100 per channel the transformer makes a little lesser noise . It's been running with music for the past 3 hours almost

And if I just keep it ON with no load the PT is more noisy after 2 hours and more hot too . Of course I am using a fan as of now during the playback. But the right channel heat sink got quite hot . Could barely touch it for 5 secs. I am guessing over heating due to the extra current present in the right channel transistors even when it's ON in idle mode
 
Last edited:
Ok , so I have given the system back to the technician. Informed him about the right channel heat sink which gets little more than medium hot with no load no speakers connected to it, just system ON in idle mode .

Also advised him about temperature issue of the PT i.e when the system is kept ON in idle mode , it gets extremely hot after 2 hours . Plus it buzzes at very high harmonics after about 2 hours . Again all in idle mode .

I have a feeling he would call me and say everything is fine and it does not matter if the right channel heat sink (right channel output transistors ) are getting hot on idle mode and the left channel heat sink is barely warm .

In case he does say this , he may add that transformer needs rewinding, cause that's what he said before I collected the set from him last time.

I have 2 questions though
1- what's better ? Rewinding of the coils impregnating the PT at the local place where they restore the transformer ?

OR buying a replacement transformer (which will be difficult )

I want to use the set for the next 20 years minimum at least.

2- I forgot to tell him that the right channel heatsink also gets very hot than the left one on high volume ,like at 100wpc playback . The left heatsink will be like 60% hot but the right one will be like 120% hot . Is that normal on high high volumes ? All this testing was done with the housing cover taken off too.
 
I'd wait to see what the tech says, but it's true that you're unlikely to find a replacement transformer -- at least, outside of another A-9 -- and if you find another A-9, you've probably solved the problem another way. How much does your local rewinder charge?

Transformer rewinding is normally very expensive. On the other hand, quality amplifiers from the same era as your A-9 are relatively plentiful and inexpensive. Unless you're sentimentally attached to it, replacing the unit with something else -- ideally without obvious moisture damage, which may cause more problems in the future -- might be the best option.
 
I don't know how much the local winder charges . Don't have experience on knowing that cost . I have given it to the technician so that incase I agree for rewinding , he will disconnect it from the system him self and refit it back once it is done . He will of course give it to the winding people in some other department for them to do it . Last time he spoke to me about transformer winding , he was very negative about it and Kept saying he can't guarantee what can happen after winding is done. It's like he is cleaning his hands before itself ..

Well I like my pioneer a-9 too but it's more bulky, bigger in depth and height. I Like the a-7 cause it is slimmer got used to its sound and always wanted to fix it perfectly (I will still use it with the noisy transformer if I have to or until I lose it ). My dads the best . He is like put the pioneer a-9 PT in your a-7
Solved:jump:
 
Last edited:
DaveVoorhis said:
I'd wait to see what the tech says, but it's true that you're unlikely to find a replacement transformer -- at least, outside of another A-9 -- and if you find another A-9, you've probably solved the problem another way. How much does your local rewinder charge?

Transformer rewinding is normally very expensive. On the other hand, quality amplifiers from the same era as your A-9 are relatively plentiful and inexpensive. Unless you're sentimentally attached to it, replacing the unit with something else -- ideally without obvious moisture damage, which may cause more problems in the future -- might be the best option.
Click to expand...
In your first para Are you talking about finding another a-9 or a-7 ? Cause I already own an a-9
 
So the tech called me . He says "your set is ready" I went to pick it up. He got straight to point . He said we tried and it's just fine the way it is . " Don't worry if the right heat sink is getting hot with no load. That s the way it is " . And the transformer he says rewinding of the transformer needs to be done if your really interested and that will cost me anywhere between 60 USD to 75 USD or it could go even more .

He dint charge me .
So I have the system just the way it is when I gave it to him . Right side heat sink which is HOT on no load and very hot with load at high volume levels . And a noisy transformer.Good stuff !

I wonder how long I have for the transformer to die out completely while I just keep using it .
I opened the system as I got home . I saw he has put small aluminum heat sinks for the left channel transistors on the left channel preamp board . They originally don't need a heat sink . I dint know why he put mini heatsinks on them . The transistors are NEC b861. One is green and one is black . I don't even know why he would do that . I uploaded a pic of a spare one I had .
Anyway time to just wish for the best .
 

Attachments

  • IMG_20180420_182039373.jpg
    IMG_20180420_182039373.jpg
    51.7 KB · Views: 13
allanmatters said:
So the tech called me . He says "your set is ready" I went to pick it up. He got straight to point . He said we tried and it's just fine the way it is . " Don't worry if the right heat sink is getting hot with no load. That s the way it is " . And the transformer he says rewinding of the transformer needs to be done if your really interested and that will cost me anywhere between 60 USD to 75 USD or it could go even more .
Click to expand...
That's an excellent price. Transformer rewinding is never cheap, but that sounds like a bargain.
allanmatters said:
I wonder how long I have for the transformer to die out completely while I just keep using it .
Click to expand...
It might last forever, or it might fail in the next ten minutes.
allanmatters said:
I opened the system as I got home . I saw he has put small aluminum heat sinks for the left channel transistors on the left channel preamp board . They originally don't need a heat sink . I dint know why he put mini heatsinks on them . The transistors are NEC b861. One is green and one is black . I don't even know why he would do that .
Click to expand...
Do those transistors run hot?
 
Thanks for your prompt response. Appreciate it.
Excellent price ? If so il do it . It's just that the technician is very negative about doing it . All he has to do is disconnect the transformer and he will give it to the winding people . Once that is done he will reconnect it . Then accordingly il pay him for labour plus the 60usd or 75 USD for the new winding . He just keeps telling me " it's too risky " . He doesn't sound interested in doing the job ?

Yes they do run hot. but they never had heatsinks . They originally don't need mini heat sink s .
 
allanmatters said:
Thanks for your prompt response. Appreciate it.
Excellent price ? If so il do it . It's just that the technician is very negative about doing it . All he has to do is disconnect the transformer and he will give it to the winding people . Once that is done he will reconnect it . Then accordingly il pay him for labour plus the 60usd or 75 USD for the new winding . He just keeps telling me " it's too risky " . He doesn't sound interested in doing the job ?
Click to expand...
There isn't much profit in it for him, and there's a small chance that the rewinder will declare it unfixable and you'll be left with nothing.

You may be happier if you simply replace the amp. Units of similar age, aesthetics, and capability -- but good condition -- are available for roughly the price of rewinding the transformer.
 
That's a great idea . Il have to keep an eye open for one which is working of course. I like the sound if this amp . If I can find a sansui or another Pioneer with similar performance I don't mind buying that as well . Don't really want to buy a non working a-7 again . Plus mine has gone through some rough times external condition is like 6.5/10 rating .

Funny part is I have an a-7 and an a-9 . Both have some issue or the other . The a-9 has a loud popping sound issue and the a-7 has a noisy transformer . Great stuff .;)
 
DaveVoorhis said:
That might be nothing more than a bad solder joint, or -- perhaps at worst -- a failing semiconductor. Likely to be a relatively inexpensive repair, and you wind up with a better amp.
Click to expand...
Yes . Already made a thread here regarding that . I had suspected it was the speaker relays . But I was wrong
 
You must log in or register to reply here.
Back
Top Bottom