Huge voltage drop on PSU

[KatieandDad]

It should be fine but you don't want to destroy a pair of nice speakers.

You can use anything, cheapo transistor radio speakers (at low volume) just to verify that it's working.

 

[42001]

not good.... only one side gives cracling sound and way too loud....

 

[KatieandDad]

Not good....

If you say "Way too loud" that would point me towards a faulty volume control pot.

You could swap the amplifier boards from L-R just to prove a point. If the problem stays with the same channel then the amp boards are OK.

 

[42001]

can not be... I use a different amp as preamp....

 

[42001]

Do you know the Hiraga 30Watt amp design?

 

[KatieandDad]

Try swapping the input leads.

You need to ascertain where the problem lies.

 

[42001]

I'll try tomorrow.... It's dinner time and it's been enough for one day

Thank you so far! I hope you can help me later on?

Kind regards,
Sjoerd Smits

 

[wintermute]

SjoerdSmits go back and read post number 2 and you will now understand why I asked the question

Tony.

All the resistor across X3 and X4 is doing is acting as part of a CRC filter to reduce ripple slightly.

For testing you can just add a shorting link in place of X3 and another in place of X4.

Once you are happy it is working you can consider what value of resistor you would like to try in those positions.

The current I am referring to is the DC current drawn by the amplifiers from the secondary side of the supply.

 

[42001]

Hi Wintermute,

Yep, get it now! Learning all the time!

Didn't know what you were trying to say with C or CRC....
Thanks!

 

[KatieandDad]

Now you need to find out if the problem is internal to your new build or not - hence swapping over the interconnects.

 

[42001]

Hi KatieandDad,

I measured all the components on both amps. They both measured OK so I got confused. I was expecting to find defective transistors at least. But all seems to be ok using the diode test..... I'm not saying that this test is 100% conclusive, but both the left and right amp measure exactly the same on all components.

So I browsed the internet and found this:

How to Measure DC Offset: 5 steps - wikiHow

Don't know for sure yet, but it would explain the shabby sound on only one channel. My speaker protection unit could have been cutting off the left amp while stil running the right amp. But if the DC offset is very high, that could result in crackling sound couln't it?

I'll try the methode described in that article tomorrow I'll let you know how it turnes out.

Kind regards,
Sjoerd Smits

 

[wintermute]

Hi Wintermute,

Yep, get it now! Learning all the time!

Didn't know what you were trying to say with C or CRC....
Thanks!

Yes I realized that once Katie and Dad nailed it down Easy to forget sometimes that some of the stuff we now take for granted we would have said "whats a CRC" ourselves when starting out!

Tony.

 

[42001]

Hi Tony,

You are so right! But hey, I'm a guy and I'm supposed to be cocky offcourse

I was so confused that I didn't "see" your question the way it was intended. I apologize for that!

Thanks for the lesson

Regards,
Sjoerd

 

[42001]

PS: Tonight I'll set the DC offset while connected to an empty input... Hope to get better results!

Thanks again all!

 

[42001]

Hi There again!

I have a strange problem. It seems that my power supply is having trouble but I can't seem to find what it is. here's what happened:

I accidently swapped pos and neg of the amplifiers. This resulted in a "boom" ofcourse. So I replaced the amps and the diodes on the PSU.

Somehow the new amps do not work. I measured 10VAC on the secondary side of the PSU and the expected 35VCD on the same side. How is this possible? And can this be the reason the amps will not work?

Please help! I'm going out of my mind

Kind regards, Sjoerd

 

[AndrewT]

disconnect the amplifier.

Power up the transformer Alone using a mains bulb tester.

Measure the AC voltage
post your results.

 

[42001]

Hi Andrew,

2 x 25VAC out of the toroid. I guess the toroid is ok. I swapped it to be sure...

 

[AndrewT]

Now add on the bridge rectifier.
Measure the AC at the ~~ connections and measure the "apparent DC" at the +- connections.
report.

 

[42001]

Hi Andrew,

Ac both 25VSC

DC Both 35VDC

Note that DC measurement is on the output of the PSU.

 

[AndrewT]

Now add on the smoothing capacitors.
and measure the AC and DC voltages.