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Enzo. Firstly thank you for all the help youve been over the years, about anytime i look for an answer, there you are with one! Youre a legend among my electronics mates down here in Australia!
I have a question regards a MK 3 head with 400BH PA. It makes advertised power, sounds nice but runs hot. The only thing that looks not right is the .05V at Q3-11 emitters. I have .02V at both. Im measuring that across R26 and R60 as the schem reads.The base voltage is about right, around half a volt. Bias string CR13 has the right volts either side of it, everywhere checks out. Except that .02V which i guess just means the drivers may be a tad weak. I really dont think theres much at all wrong.
The owner is running into a single 15 at 8 ohms and it has cut out after a few hours of gig, pilot light flickering which suggests the thermistor is doing its job.
My first reaction when he said he was running an 8ohm load was, that wont hurt the amp at all. But now im not so sure. Im feeling like hes running the thing at clip as its not loud enough with the 8 ohm cab. I reckon if he was running a 4 ohm cab, then he would have it dial'd back somewhat.
It does sag about 5V on the 51V rails at around half output. But makes full power into a static load. Is he asking too much from it?
Cheers! Don from Aus. Oh this was my first post of 11 years!
I have a question regards a MK 3 head with 400BH PA. It makes advertised power, sounds nice but runs hot. The only thing that looks not right is the .05V at Q3-11 emitters. I have .02V at both. Im measuring that across R26 and R60 as the schem reads.The base voltage is about right, around half a volt. Bias string CR13 has the right volts either side of it, everywhere checks out. Except that .02V which i guess just means the drivers may be a tad weak. I really dont think theres much at all wrong.
The owner is running into a single 15 at 8 ohms and it has cut out after a few hours of gig, pilot light flickering which suggests the thermistor is doing its job.
My first reaction when he said he was running an 8ohm load was, that wont hurt the amp at all. But now im not so sure. Im feeling like hes running the thing at clip as its not loud enough with the 8 ohm cab. I reckon if he was running a 4 ohm cab, then he would have it dial'd back somewhat.
It does sag about 5V on the 51V rails at around half output. But makes full power into a static load. Is he asking too much from it?
Cheers! Don from Aus. Oh this was my first post of 11 years!
185F, which ironically translates to a bit over 80 C! Yeah i generally ask guys for their whole rig, but he just landed at the door with the amp. He should be here soon enough with the rest of it. 
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