gen VIII collosus

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caseking

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Joined 2006
#1
Anyone have a schematic for this jewel?One channel works but the other goes onto protection.I replaced all the irfz44"s on that power supply because some were shorted.Now it still goes into protection on that channel.Somebody has obviously done alot of work on the working side.But here is where it gets confusing.On the working side there are small 25 ohm resistors that are in series with one leg of the irfz44's.Howerever in the same location on the non-working the resistors are @ 193 ohms.Being that both sides are almost perfectly symetrical,I dont understand this.Could this be the reason for the fault?Please help if you can
 
#4
The resistors you mean are 220 ohm at my Colossus VIII.
I have boadversion CC or #2 (??)/

Furthermore, both powersupplies are defective, I replaced all MOSFETS IRFZ44 with IRF 1405, but still problems.

I just replace them with IRFZ44 I think...any ideas?

Rob.
 
#5
Bertje said:
The resistors you mean are 220 ohm at my Colossus VIII.
I have boadversion CC or #2 (??)/

Furthermore, both powersupplies are defective, I replaced all MOSFETS IRFZ44 with IRF 1405, but still problems.

I just replace them with IRFZ44 I think...any ideas?

Rob.
Click to expand...

You went abit overboard on your FET selection as you jumped from a 50 amp fet to a 196 amp rated FET. Usually a jump of that magnatude absolutely requires a different gate resistor value. I would look at that right away as it will cause all sorts of power supply issues, such as unstable ops. Usually seen as too much current draw at idle, and or unstabile idle current.:whazzat:

I qoute this from experiance as I have played around with FETs from time to time just to see what could be achieved:smash:

Good luck🙂
 
#6
caseking said:
Anyone have a schematic for this jewel?One channel works but the other goes onto protection.I replaced all the irfz44"s on that power supply because some were shorted.Now it still goes into protection on that channel.Somebody has obviously done alot of work on the working side.But here is where it gets confusing.On the working side there are small 25 ohm resistors that are in series with one leg of the irfz44's.Howerever in the same location on the non-working the resistors are @ 193 ohms.Being that both sides are almost perfectly symetrical,I dont understand this.Could this be the reason for the fault?Please help if you can
Click to expand...

If your power supply has been repaired then you should :
1. check for dc output on the channel in question. DC out then start ohming out the entire channel.
2. if theres no DC out on that channel then go back to the power supply and check the protection circuitry comparator.

That should get you thru the amp "without" a schematic. I have some docs for this brand but not the exact model you have.

Best of luck 🙂
 
#7
OK thanks, I checked the datasheets of the IRFZ44 and IRF1405, and they are very different indeed. I changed them with the originals back again.
The MOSFet driver seems to be ok, without the IRF's mounted there is a nice squarewave at the gates.

The bottomplate is white with a big black spot (5").....😀 and 5 IRFZ44 where broken in pieces...nice amps anyway.😎
 
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