Can you help me identify these burned resistors?

[tubularfluxus]

I have opened my Chinese made amps (I have like 5 of them) and I discovered two burned-looking resistors. The amps work without any problem so far.

# First one - Fatman 182 (rebranded Dared MP-15)
I have the schematic of Dared MP-15 (attached). It's is R12 and the schematic says 51k 2w.
A friend which is assisting me with it recommended to replace it with one that can handle more power. Should I buy then a 51k 5w to replace it?

# Second one - Fatman 252 (rebranded Dared MP-60)
Unluckily I don't have a schematic and seem to not have luck finding one (see below). It's R34. It's pretty brownish so I'm not sure it's recognizable anymore by the color bands.

Can you recognize it? What would you recommend me to do?

# Why I did not manage to find Fatman 252 schematics
Fatman closed down business years ago. TLaudio, which also distributed some Fatman, does not service these amps, only premium Fatman products.
Dared US does not have schematic for MP-60 and told to contact Dared China.
Dared HK says MP-60 is not from them, but a copy from Dared China and they are not authorized to talk to each other (?).
Apparently there was another branch of Dared in mainland China, assembling some variants of these amps. I've tried contacting them, but no success so far.

 

[Eli Duttman]

I read the burned R12 part as 510 Ω/5% (green, brown, brown, gold). Something is "fishy".

 

[realflow100]

Could the 1st brown be red? next to the green? It has a faint red tinge.

 

[as_audio]

Have a look at R11 to compare with R12

 

[Koonw]

For the R12, from the mild burnt seen, it may reached more than 1W, maybe you should check 6N3 tube current see if they're balance or not, and mains supply voltage not >120-130V instead of 115V?

 

[tubularfluxus]

Have a look at R11 to compare with R12

Good call!

R11 looks burned too.

 

[tubularfluxus]

For the R12, from the mild burnt seen, it may reached more than 1W, maybe you should check 6N3 tube current see if they're balance or not, and mains supply voltage not >120-130V instead of 115V?

For a week or two I did use E88CC in place of the 6N3 via an adapter I bought on ebay. May that be the reason? Maybe the E88CC where draining more power?

 

[tubularfluxus]

For the burned R34, I actually have another identical amp with an healthy R34.

Can you help me confirm its value by the color?

I see Yellow - Brown - Red - Gold:
41 x 100 = 4.1k ohm 5%

Or do you think that's a violet?

 

[Parafeed813]

Violet: 4k7.
Sometimes burned resistors still have their nominal value.
Depending on the circuit, you can measure them without taking them out.
R11/12 can be measured as they are, as long as the valves are cold/removed.

 

[as_audio]

For the burned R34, I actually have another identical amp with an healthy R34.

Can you help me confirm its value by the color?

I see Yellow - Brown - Red - Gold:
41 x 100 = 4.1k ohm 5%

Or do you think that's a violet?

This is yel vio or = 47 kOhms

 

[as_audio]

Good call!

R11 looks burned too.

In the diagram it is 51 kOhms, you may want to use two 100 kOhms resistors of this size in parallel.

 

[Koonw]

For a week or two I did use E88CC in place of the 6N3 via an adapter I bought on ebay. May that be the reason? Maybe the E88CC where draining more power?

Yes you're correct ecc88 drained more power, about 300mW more. If so, you can use 3W type res or [URL="http://www.sky-macau.com/Products/Resistors-C2/Page-12/ItemsPerPage-20.html"]this type [/URL]. same size.

 

[Parafeed813]

This is yel vio or = 47 kOhms

You're right, 47k.
My phone didn't show the colours as clear as I see now on my pc.

 

[tubularfluxus]

In the diagram it is 51 kOhms, you may want to use two 100 kOhms resistors of this size in parallel.

Do you mean I should replace both R11 and R12 with 2x 100kOhms 2w resistors in parallel each, so 4x 100kOhms 2w in total?

Or should I replace each R11 and R12 with 1x 51kOhms 3w (2x total)?

 

[tubularfluxus]

Yes you're correct ecc88 drained more power, about 300mW more. If so, you can use 3W type res or [URL="http://www.sky-macau.com/Products/Resistors-C2/Page-12/ItemsPerPage-20.html"]this type [/URL]. same size.

What happens if I buy a 5w untested? Is it the same, but better, or there are specific reason to not increase the wattage too much?

 

[tubularfluxus]

This is yel vio or = 47 kOhms

Ok so for R34 I should buy a 47kOhms. How many watt and which %?

Should I just aim for a generic 5w and 5% or 10%?

 

[Koonw]

What happens if I buy a 5w untested? Is it the same, but better, or there are specific reason to not increase the wattage too much?

If same size and more wattage, it's of course better, but as it doesn't burn as easily, you may lost the fault detection should something go wrong, otherwise sonic wise is not a problem.

 

[tubularfluxus]

If same size and more wattage, it's of course better, but as it doesn't burn as easily, you may lost the fault detection should something go wrong, otherwise sonic wise is not a problem.

How can I find how much current / wattage does a certain tube number drain?

 

[Koonw]

How can I find how much current / wattage does a certain tube number drain?

You measure the voltage across the resistor, divide it by resistance value you got the current, Watt=Voltage x Current. Eg V across 10K is 100V so current = 100/10k=10mA, W=100x0.01=1W.