Topic: Choke Regulated Power Supply

[odyopayl]

I don't know where to put this thread. However, I'm hoping to find answers from our Tube experts and DIY'rs..
My Tube Amp (M99 6L6) choke on the power supply smokin (burned).
I want to replace it with any alternative choke available in the market but Im not sure about the specification?
Is there any computation in getting the correct Choke specs?
the choke is connected to a DC out (I remove the choke and check the voltage across this wires it's 450VDC)
I''m using the amp for more than 5 years already, I'm wondering what causing this choke to overheat? I can't find visually any problem on the components (resistors, diodes, caps etch)
Comments and suggestions are welcome!
Thank you PDVD!  

Below is the porn picture of the amp with the choke encircle in red:

[qguy]

Have you tried contacting the manufacturer for schematics ?

[ATJr.]

I'm wondering what causing this choke to overheat?

current flowing thru the dc resistance of the choke causes heating......you can even replace this choke with a power resistor, just measure the dc resistance and get the equivalent power resistor, nearest standard lower value is fine....

the size of your filter caps says the choke spec is not that critical.....

[odyopayl]

Have you tried contacting the manufacturer for schematics ?

This is something I need to check, thanks qguy. Hoping they can give it.

[odyopayl]

current flowing thru the dc resistance of the choke causes heating......you can even replace this choke with a power resistor, just measure the dc resistance and get the equivalent power resistor, nearest standard lower value is fine....

the size of your filter caps says the choke spec is not that critical.....

Hi Tony, pardon my ignorance, are you saying something to do with the rectifier otr the Power transformer causing this?
I had tried other choke, it's too Big just for test. However, the thing that overheats is the Power Transformer??? Just to make sure, can I substitute a bigger capacitor instead rather than resistor?

[qguy]

if you remove the choke and send it to someone who makes transformers, is it possible for this person to reverse engineer the specs of the choke ?

[ATJr.]

with big capacitors in your, the choke is no big deal.....you can even go without it...

[ATJr.]

Hi Tony, pardon my ignorance, are you saying something to do with the rectifier otr the Power transformer causing this?
I had tried other choke, it's too Big just for test. However, the thing that overheats is the Power Transformer??? Just to make sure, can I substitute a bigger capacitor instead rather than resistor?

heating is inevitable when unit is in operation....the only question is how much...

when you have big capacitors the choke becomes redundant....if not using tube rectification, all the more....

[odyopayl]

if you remove the choke and send it to someone who makes transformers, is it possible for this person to reverse engineer the specs of the choke ?

Yes, but right now I'm thinking of an alternative solution. The Choke structure seems complicated

[odyopayl]

with big capacitors in your, the choke is no big deal.....you can even go without it...

Will check for a good capacitor instead. Thanks for your input TonyT

[ATJr.]

see....you won't miss that choke.....adding caps is also good...

[JojoD818]

Playing the devil's advocate...

The choke was put in there to form a CLC filter to reduce ripple and in turn, hum and noise. Unfortunately, at the expense of some voltage drop but it offers some form of regulation and most of all it increases the psu's overall source impedance forming a barrier between the rectifier and the last filter capacitor thereby reducing the peaks in the diodes on-condition.

Of course no one will miss it if entirely removed except probably for the tubes who's operating points may slightly be affected by the increased supply voltage which would had been dropped by the choke if it were in place.

The earlier proposal of replacing the choke with a power resistor would be a lot more agreeable for it will form a CRC filter instead of the original CLC filter, a lot better than nothing at all.

[ATJr.]

it looks to me that the psu is a cap input type so that the role of the choke is minimal to say the least....it is one of those "nice to have" things in an amp....

[JojoD818]

it sure is, but the reason it burned would probably be caused of smallish gauge wire that would mean a high dcr and in turn cause a fairly noticeable voltage drop under load. tubes are forgiving anyway, and the fact that the psu uses ss diodes says a lot.

[JojoD818]

Why not give him a hv ss regulator instead?

I'm sure he can work that out, if I'm not mistaken, our dear TS is also an engineer.

[JojoD818]

nice, can't help but notice those rikens, auricaps and mcaps...

[odyopayl]

Nice to have both Master JojoD and TonyT inputs here. Now I'm learning a lot.
When I check the circuit I saw Diodes and Capacitors on the circuit. Actually
the voltage across that choke is 450VDC? Let me check Voltage characteristics of the 6L6 tubes. The Data sheet tells that in PP Operation maximum plate voltage is 400V. The resistor or the choke operations
makes sense in dropping the voltage.

[ATJr.]

can't be....no wonder the burn-out....

[JojoD818]

open already?

[juanbote]

Branded ba young amp mo? Ipagawa nyo sir ang choke Kung sira. Pede reverse engineering, at Pwede din taasan wire ampacity. Dalhin mo as akin para Malaman nation Kung ano naging  dahilan bakit nasunog.

Free check up and estimate.

[odyopayl]

Branded ba young amp mo? Ipagawa nyo sir ang choke Kung sira. Pede reverse engineering, at Pwede din taasan wire ampacity. Dalhin mo as akin para Malaman nation Kung ano naging  dahilan bakit nasunog.

Free check up and estimate.

Juanbote thanks for your kind offer. For the meantime I replaced the choke with the exact specs of the choke from the OEM supplier (from our connection to HK). Will check if this will work very wel or need to replace power suply transformer.

[juanbote]

Check the bleeder resistor across the capacitor after the choke if there is one. This can cause choke burnout if it became low resistance due to age and thermal fatigue. The function of this resistor is to discharge the electrolytic capacitor. And this can damage the choke if it has gone low resistance.