SS overheating? Can I mod it?

ERiCARDEN · 20th November 2009, 10:07 PM

I'm a fan of the "Eleca EG100-R" Guitar Head. Its the only good sounding amp they produce, the speakers are horrible though.

The distortion is the best I've ever heard. Many musicians ask to use my amp over Peavey and Mesa models. Its great for Metal and Punk.

The problem I have with it though is it over heats. I know that this is the huge complaint everyone has with them.

I don't want something "better" I don't want to switch. I like having a unique amp that has good distortion and looks ugly.

Is there a way to mod it so it doesn't heat?

Could it be the housing? Or electrical?

Easy to fix? Expensive?

Geek · 21st November 2009, 03:22 AM

Hi,

Two common methods to help here are:
- Add a fan.
- Add more heatsink.

Or both.

As for speakers, the best bang for the buck is Weber:
https://taweber.powweb.com/weber/

Cheers!

Enzo · 21st November 2009, 08:21 AM

Does it only overheat while playing? Or if you turn it on and just let it sit there, does it still get hot? Implication being we could back off the idle current level - its bias.

ERiCARDEN · 22nd November 2009, 06:47 PM

it over heats just being turned on. I think it get a little hotter though as I play, but that could just be in my head.

nigelwright7557 · 22nd November 2009, 09:28 PM

Quote:

Originally Posted by ERiCARDEN

it over heats just being turned on. I think it get a little hotter though as I play, but that could just be in my head.

How hot does it get ?
Some amps are designed to run hot coz they have cheap heatsinks.

Silicon can go uptyo 150 degrees C before it dies.

unclejed613 · 22nd November 2009, 09:39 PM

reducing the bias might help.... is it bipolar or MOSFET? MOSFETs have to be run at higher bias currents to reduce crossover distortion and to improve thermal stability. bipolar transistors can be run at lower bias currents at the cost of a bit of crossover distortion. Peavey runs their amps with fixed bias right at cutoff with the idea that the amp is usually going to be run wide open anyway, so no one will ever notice the crossover distortion, and so most of their amps run relatively cool.

nigelwright7557 · 22nd November 2009, 10:02 PM

Quote:

Originally Posted by unclejed613

reducing the bias might help.... is it bipolar or MOSFET? MOSFETs have to be run at higher bias currents to reduce crossover distortion and to improve thermal stability. bipolar transistors can be run at lower bias currents at the cost of a bit of crossover distortion. Peavey runs their amps with fixed bias right at cutoff with the idea that the amp is usually going to be run wide open anyway, so no one will ever notice the crossover distortion, and so most of their amps run relatively cool.

I find with my MOSFET amp designs they usually need about 20mA through the FET to get rid of cross over distortion. Thats 5mV across the 0R22 source resistor.

Take care with the trimmer tho some can be very touchy and before you know it the bias is too big and has blown the MOSFET's.

In my designs I always add a zener across the bias circuit to catch out of range bias voltages.

unclejed613 · 23rd November 2009, 12:12 AM

20mA might get rid of crossover distortion with some FETs, but not all of them. i often see them in home audio and pro audio biased for between 50 and 150mA it depends on the FET, there was a thread here a while back about the proper bias for FETs and what effect it has on thermal stability. for vertical FETS, the Vgs(on) voltage has a negative tempco at low currents, then tere's a point where the tempco is zero, then above that current the tempco is positive. the desirable bias point is with the idle current at or above the zero tempco point. for a lot of FETs, this current is about 2A, but there are some where it's lower. lateral FETs have the zero point at very low currents, so they don't need temperature compensation...

nigelwright7557 · 23rd November 2009, 12:18 AM

The biasing of vertical MOSFETs is quite complex.

I have done lots of research in conjunction with a household iron to heat up the heatsink and tracked the bias current.

I found that I can get away with 20mA in my amps without the bias transistor being connected to the heatsink.

ERiCARDEN · 23rd November 2009, 05:24 PM

I'm pretty sure its Bipolar because these amps are "cheap".

Can I convert it too MOSFET?

20th November 2009, 10:07 PM	#1
ERiCARDEN diyAudio Member Join Date: Nov 2009 Location: Portland, OR	SS overheating? Can I mod it? I'm a fan of the "Eleca EG100-R" Guitar Head. Its the only good sounding amp they produce, the speakers are horrible though. The distortion is the best I've ever heard. Many musicians ask to use my amp over Peavey and Mesa models. Its great for Metal and Punk. The problem I have with it though is it over heats. I know that this is the huge complaint everyone has with them. I don't want something "better" I don't want to switch. I like having a unique amp that has good distortion and looks ugly. Is there a way to mod it so it doesn't heat? Could it be the housing? Or electrical? Easy to fix? Expensive?

23rd November 2009, 12:18 AM	#9
nigelwright7557 diyAudio Member Join Date: Apr 2008 Location: Carlisle, England	The biasing of vertical MOSFETs is quite complex. I have done lots of research in conjunction with a household iron to heat up the heatsink and tracked the bias current. I found that I can get away with 20mA in my amps without the bias transistor being connected to the heatsink. __________________ http://www.murtonpikesystems.co.uk PCBCAD40 pcb design software.

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21st November 2009, 03:22 AM	#2
Geek diyAudio Member Join Date: Sep 2004	Hi, Two common methods to help here are: - Add a fan. - Add more heatsink. Or both. As for speakers, the best bang for the buck is Weber: https://taweber.powweb.com/weber/ Cheers!

21st November 2009, 08:21 AM	#3
Enzo diyAudio Member Join Date: Sep 2004 Location: Lansing, Michigan	Does it only overheat while playing? Or if you turn it on and just let it sit there, does it still get hot? Implication being we could back off the idle current level - its bias.

22nd November 2009, 06:47 PM	#4
ERiCARDEN diyAudio Member Join Date: Nov 2009 Location: Portland, OR	it over heats just being turned on. I think it get a little hotter though as I play, but that could just be in my head.

22nd November 2009, 09:39 PM	#6
unclejed613 diyAudio Member Join Date: Dec 2006	reducing the bias might help.... is it bipolar or MOSFET? MOSFETs have to be run at higher bias currents to reduce crossover distortion and to improve thermal stability. bipolar transistors can be run at lower bias currents at the cost of a bit of crossover distortion. Peavey runs their amps with fixed bias right at cutoff with the idea that the amp is usually going to be run wide open anyway, so no one will ever notice the crossover distortion, and so most of their amps run relatively cool.

23rd November 2009, 12:12 AM	#8
unclejed613 diyAudio Member Join Date: Dec 2006	20mA might get rid of crossover distortion with some FETs, but not all of them. i often see them in home audio and pro audio biased for between 50 and 150mA it depends on the FET, there was a thread here a while back about the proper bias for FETs and what effect it has on thermal stability. for vertical FETS, the Vgs(on) voltage has a negative tempco at low currents, then tere's a point where the tempco is zero, then above that current the tempco is positive. the desirable bias point is with the idle current at or above the zero tempco point. for a lot of FETs, this current is about 2A, but there are some where it's lower. lateral FETs have the zero point at very low currents, so they don't need temperature compensation...

23rd November 2009, 05:24 PM	#10
ERiCARDEN diyAudio Member Join Date: Nov 2009 Location: Portland, OR	I'm pretty sure its Bipolar because these amps are "cheap". Can I convert it too MOSFET?

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